测试了好久，一会能显示页面空值，有值了就不跳转页面了

测试了好久，一会能显示页面空值，有值了就不跳转页面了

数据都是可以正常获取的，到了跳转页面的时候就出错了。

我的WEB的版本选的是4.0 ，控制台显示不符合，这个之前也是一样选择的，也没啥问题

一会控制台显示DispatcherServlet- Completed 404 NOT_FOUND

还显示过现在这样的：FTL stack trace ("~" means nesting-related):


配置都是按照之前的配来着


相关截图：

http://img1.sycdn.imooc.com//climg/60a292b7097d48cf11780791.jpg

相关代码：控制台输出

​[http-nio-80-exec-1] 2021-05-17 23:57:36,555 DEBUG o.m.s.SqlSessionUtils - Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@52595a3e]
[http-nio-80-exec-1] 2021-05-17 23:57:36,555 DEBUG o.m.s.SqlSessionUtils - Transaction synchronization closing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@52595a3e]
[http-nio-80-exec-1] 2021-05-17 23:57:36,800 DEBUG o.s.w.s.v.f.FreeMarkerView - View name '/index', model {categoryList=[Category{categoryId=1, categoryName='前端'}, Category{categoryId=2, categoryName='后端'}, Category{categoryId=3, categoryName='测试'}, Category{categoryId=4, categoryName='产品'}]}
[http-nio-80-exec-1] 2021-05-17 23:57:36,805 DEBUG o.s.w.s.v.f.FreeMarkerView - Rendering [/index.ftl]
17-May-2021 23:57:36.916 严重 [http-nio-80-exec-1] freemarker.log._JULLoggerFactory$JULLogger.error Error executing FreeMarker template
	FreeMarker template error:
	The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

	----
	FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
	----

	Java stack trace (for programmers):
	----
	freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...]
		at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
		at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:481)
		at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:401)
		at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:370)
		at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
		at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
		at freemarker.core.Environment.visit(Environment.java:383)
		at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:321)
		at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271)
		at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244)
		at freemarker.core.Environment.visitIteratorBlock(Environment.java:657)
		at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108)
		at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94)
		at freemarker.core.Environment.visit(Environment.java:347)
		at freemarker.core.Environment.visit(Environment.java:353)
		at freemarker.core.Environment.process(Environment.java:326)
		at freemarker.template.Template.process(Template.java:383)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:391)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:304)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:255)
		at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:179)
		at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
		at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
		at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
		at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
		at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
		at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
		at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
		at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
		at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
		at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
		at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
		at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
		at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)
		at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
		at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
		at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:698)
		at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
		at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:353)
		at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)
		at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
		at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
		at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1629)
		at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
		at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
		at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
		at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
		at java.lang.Thread.run(Thread.java:748)
17-May-2021 23:57:36.939 严重 [http-nio-80-exec-2] freemarker.log._JULLoggerFactory$JULLogger.error Error executing FreeMarker template
	FreeMarker template error:
	The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

	----
	FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
	----

	Java stack trace (for programmers):
	----
	freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...]
		at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
		at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:481)
		at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:401)
[http-nio-80-exec-2] 2021-05-17 23:57:36,932 DEBUG o.s.w.s.DispatcherServlet - GET "/", parameters={}
[http-nio-80-exec-2] 2021-05-17 23:57:36,933 DEBUG o.s.w.s.m.m.a.RequestMappingHandlerMapping - Mapped to com.roan.reader.controller.BookController#showCategory()
我要被运行了
[http-nio-80-exec-2] 2021-05-17 23:57:36,933 DEBUG o.m.s.SqlSessionUtils - Creating a new SqlSession
[http-nio-80-exec-2] 2021-05-17 23:57:36,933 DEBUG o.m.s.SqlSessionUtils - Registering transaction synchronization for SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3dcc9f6]
[http-nio-80-exec-2] 2021-05-17 23:57:36,934 DEBUG o.s.j.d.DataSourceUtils - Fetching JDBC Connection from DataSource
[http-nio-80-exec-2] 2021-05-17 23:57:36,934 DEBUG o.m.s.t.SpringManagedTransaction - JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@6348c40f] will be managed by Spring
[http-nio-80-exec-2] 2021-05-17 23:57:36,935 DEBUG c.r.r.m.C.selectList - ==>  Preparing: SELECT category_id,category_name FROM category
[http-nio-80-exec-2] 2021-05-17 23:57:36,935 DEBUG c.r.r.m.C.selectList - ==> Parameters: 
[http-nio-80-exec-2] 2021-05-17 23:57:36,937 DEBUG c.r.r.m.C.selectList - <==      Total: 4
[http-nio-80-exec-2] 2021-05-17 23:57:36,938 DEBUG o.m.s.SqlSessionUtils - Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3dcc9f6]
[http-nio-80-exec-2] 2021-05-17 23:57:36,938 DEBUG o.m.s.SqlSessionUtils - Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3dcc9f6]
[http-nio-80-exec-2] 2021-05-17 23:57:36,938 DEBUG o.m.s.SqlSessionUtils - Transaction synchronization closing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@3dcc9f6]
[http-nio-80-exec-2] 2021-05-17 23:57:36,938 DEBUG o.s.w.s.v.f.FreeMarkerView - View name '/index', model {categoryList=[Category{categoryId=1, categoryName='前端'}, Category{categoryId=2, categoryName='后端'}, Category{categoryId=3, categoryName='测试'}, Category{categoryId=4, categoryName='产品'}]}
[http-nio-80-exec-2] 2021-05-17 23:57:36,938 DEBUG o.s.w.s.v.f.FreeMarkerView - Rendering [/index.ftl]
[http-nio-80-exec-1] 2021-05-17 23:57:36,931 DEBUG o.s.w.s.DispatcherServlet - Error rendering view [org.springframework.web.servlet.view.freemarker.FreeMarkerView: name '/index'; URL [/index.ftl]]
freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
----
	at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
	at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:481)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:401)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:370)
	at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
	at freemarker.core.Environment.visit(Environment.java:383)
	at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:321)
	at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271)
	at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244)
	at freemarker.core.Environment.visitIteratorBlock(Environment.java:657)
	at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108)
	at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94)
	at freemarker.core.Environment.visit(Environment.java:347)
	at freemarker.core.Environment.visit(Environment.java:353)
	at freemarker.core.Environment.process(Environment.java:326)
	at freemarker.template.Template.process(Template.java:383)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:391)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:304)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:255)
	at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:179)
	at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:698)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:353)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1629)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)
[http-nio-80-exec-1] 2021-05-17 23:57:36,941 DEBUG o.s.w.s.DispatcherServlet - Failed to complete request: freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
----
[http-nio-80-exec-2] 2021-05-17 23:57:36,951 DEBUG o.s.w.s.DispatcherServlet - Error rendering view [org.springframework.web.servlet.view.freemarker.FreeMarkerView: name '/index'; URL [/index.ftl]]
freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
		at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:370)
		at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
		at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
		at freemarker.core.Environment.visit(Environment.java:383)
		at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:321)
		at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271)
		at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244)
		at freemarker.core.Environment.visitIteratorBlock(Environment.java:657)
		at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108)
		at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94)
		at freemarker.core.Environment.visit(Environment.java:347)
		at freemarker.core.Environment.visit(Environment.java:353)
		at freemarker.core.Environment.process(Environment.java:326)
		at freemarker.template.Template.process(Template.java:383)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:391)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:304)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:255)
		at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:179)
		at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
		at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
		at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
		at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
		at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
		at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
		at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
		at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
		at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
		at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
		at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
		at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
		at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)
		at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
		at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
		at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:698)
		at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
		at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:353)
		at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)
		at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
		at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
		at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1629)
		at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
		at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
		at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
		at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
		at java.lang.Thread.run(Thread.java:748)
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
----
	at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
	at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:481)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:401)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:370)
	at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
	at freemarker.core.Environment.visit(Environment.java:383)
	at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:321)
	at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271)
	at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244)
	at freemarker.core.Environment.visitIteratorBlock(Environment.java:657)
	at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108)
	at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94)
	at freemarker.core.Environment.visit(Environment.java:347)
	at freemarker.core.Environment.visit(Environment.java:353)
	at freemarker.core.Environment.process(Environment.java:326)
	at freemarker.template.Template.process(Template.java:383)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:391)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:304)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:255)
	at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:179)
	at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:698)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:353)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1629)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)
[http-nio-80-exec-2] 2021-05-17 23:57:36,964 DEBUG o.s.w.s.DispatcherServlet - Failed to complete request: freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
----
[http-nio-80-exec-3] 2021-05-17 23:57:38,270 DEBUG o.s.w.s.DispatcherServlet - GET "/", parameters={}
[http-nio-80-exec-3] 2021-05-17 23:57:38,271 DEBUG o.s.w.s.m.m.a.RequestMappingHandlerMapping - Mapped to com.roan.reader.controller.BookController#showCategory()
我要被运行了
[http-nio-80-exec-3] 2021-05-17 23:57:38,271 DEBUG o.m.s.SqlSessionUtils - Creating a new SqlSession
[http-nio-80-exec-3] 2021-05-17 23:57:38,271 DEBUG o.m.s.SqlSessionUtils - Registering transaction synchronization for SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@616c0b9a]
[http-nio-80-exec-3] 2021-05-17 23:57:38,272 DEBUG o.s.j.d.DataSourceUtils - Fetching JDBC Connection from DataSource
[http-nio-80-exec-3] 2021-05-17 23:57:38,273 DEBUG o.m.s.t.SpringManagedTransaction - JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@6348c40f] will be managed by Spring
[http-nio-80-exec-3] 2021-05-17 23:57:38,275 DEBUG c.r.r.m.C.selectList - ==>  Preparing: SELECT category_id,category_name FROM category
[http-nio-80-exec-3] 2021-05-17 23:57:38,276 DEBUG c.r.r.m.C.selectList - ==> Parameters: 
[http-nio-80-exec-3] 2021-05-17 23:57:38,279 DEBUG c.r.r.m.C.selectList - <==      Total: 4
[http-nio-80-exec-3] 2021-05-17 23:57:38,279 DEBUG o.m.s.SqlSessionUtils - Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@616c0b9a]
[http-nio-80-exec-3] 2021-05-17 23:57:38,279 DEBUG o.m.s.SqlSessionUtils - Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@616c0b9a]
[http-nio-80-exec-3] 2021-05-17 23:57:38,279 DEBUG o.m.s.SqlSessionUtils - Transaction synchronization closing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@616c0b9a]
[http-nio-80-exec-3] 2021-05-17 23:57:38,282 DEBUG o.s.w.s.v.f.FreeMarkerView - View name '/index', model {categoryList=[Category{categoryId=1, categoryName='前端'}, Category{categoryId=2, categoryName='后端'}, Category{categoryId=3, categoryName='测试'}, Category{categoryId=4, categoryName='产品'}]}
[http-nio-80-exec-3] 2021-05-17 23:57:38,282 DEBUG o.s.w.s.v.f.FreeMarkerView - Rendering [/index.ftl]
[http-nio-80-exec-3] 2021-05-17 23:57:38,286 DEBUG o.s.w.s.DispatcherServlet - Error rendering view [org.springframework.web.servlet.view.freemarker.FreeMarkerView: name '/index'; URL [/index.ftl]]
freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
----
	at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
	at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:481)
17-May-2021 23:57:38.282 严重 [http-nio-80-exec-3] freemarker.log._JULLoggerFactory$JULLogger.error Error executing FreeMarker template
	FreeMarker template error:
	The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

	----
	FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
	----

	Java stack trace (for programmers):
	----
	freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...]
		at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
		at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:481)
		at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:401)
		at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:370)
		at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
		at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
		at freemarker.core.Environment.visit(Environment.java:383)
		at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:321)
		at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271)
		at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244)
		at freemarker.core.Environment.visitIteratorBlock(Environment.java:657)
		at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108)
		at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94)
		at freemarker.core.Environment.visit(Environment.java:347)
		at freemarker.core.Environment.visit(Environment.java:353)
		at freemarker.core.Environment.process(Environment.java:326)
		at freemarker.template.Template.process(Template.java:383)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:391)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:304)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:255)
		at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:179)
		at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
		at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
		at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
		at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
		at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
		at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
		at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
		at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:401)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:370)
	at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
	at freemarker.core.Environment.visit(Environment.java:383)
	at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:321)
	at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271)
	at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244)
	at freemarker.core.Environment.visitIteratorBlock(Environment.java:657)
	at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108)
	at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94)
	at freemarker.core.Environment.visit(Environment.java:347)
	at freemarker.core.Environment.visit(Environment.java:353)
	at freemarker.core.Environment.process(Environment.java:326)
	at freemarker.template.Template.process(Template.java:383)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:391)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:304)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:255)
	at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:179)
	at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
		at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
		at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
		at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
		at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
		at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)
		at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
		at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
		at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:698)
		at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
		at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:353)
		at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)
		at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
		at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
		at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1629)
		at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
		at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:698)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:353)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1629)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)
[http-nio-80-exec-3] 2021-05-17 23:57:38,287 DEBUG o.s.w.s.DispatcherServlet - Failed to complete request: freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
----
		at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
		at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
		at java.lang.Thread.run(Thread.java:748)
[http-nio-80-exec-4] 2021-05-17 23:57:45,626 DEBUG o.s.w.s.DispatcherServlet - GET "/", parameters={}
[http-nio-80-exec-4] 2021-05-17 23:57:45,626 DEBUG o.s.w.s.m.m.a.RequestMappingHandlerMapping - Mapped to com.roan.reader.controller.BookController#showCategory()
我要被运行了
[http-nio-80-exec-4] 2021-05-17 23:57:45,627 DEBUG o.m.s.SqlSessionUtils - Creating a new SqlSession
[http-nio-80-exec-4] 2021-05-17 23:57:45,627 DEBUG o.m.s.SqlSessionUtils - Registering transaction synchronization for SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@24f7b217]
[http-nio-80-exec-4] 2021-05-17 23:57:45,628 DEBUG o.s.j.d.DataSourceUtils - Fetching JDBC Connection from DataSource
[http-nio-80-exec-4] 2021-05-17 23:57:45,629 DEBUG o.m.s.t.SpringManagedTransaction - JDBC Connection [com.mysql.cj.jdbc.ConnectionImpl@6348c40f] will be managed by Spring
[http-nio-80-exec-4] 2021-05-17 23:57:45,630 DEBUG c.r.r.m.C.selectList - ==>  Preparing: SELECT category_id,category_name FROM category
[http-nio-80-exec-4] 2021-05-17 23:57:45,631 DEBUG c.r.r.m.C.selectList - ==> Parameters: 
[http-nio-80-exec-4] 2021-05-17 23:57:45,635 DEBUG c.r.r.m.C.selectList - <==      Total: 4
[http-nio-80-exec-4] 2021-05-17 23:57:45,636 DEBUG o.m.s.SqlSessionUtils - Releasing transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@24f7b217]
[http-nio-80-exec-4] 2021-05-17 23:57:45,636 DEBUG o.m.s.SqlSessionUtils - Transaction synchronization deregistering SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@24f7b217]
[http-nio-80-exec-4] 2021-05-17 23:57:45,636 DEBUG o.m.s.SqlSessionUtils - Transaction synchronization closing SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@24f7b217]
[http-nio-80-exec-4] 2021-05-17 23:57:45,637 DEBUG o.s.w.s.v.f.FreeMarkerView - View name '/index', model {categoryList=[Category{categoryId=1, categoryName='前端'}, Category{categoryId=2, categoryName='后端'}, Category{categoryId=3, categoryName='测试'}, Category{categoryId=4, categoryName='产品'}]}
[http-nio-80-exec-4] 2021-05-17 23:57:45,639 DEBUG o.s.w.s.v.f.FreeMarkerView - Rendering [/index.ftl]
17-May-2021 23:57:45.684 严重 [http-nio-80-exec-4] freemarker.log._JULLoggerFactory$JULLogger.error Error executing FreeMarker template
	FreeMarker template error:
	The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

	----
	FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
	----

	Java stack trace (for programmers):
	----
	freemarker.core.InvalidReferenceException: [... Exception message was already printed; see it above ...]
		at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
		at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:481)
		at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:401)
		at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:370)
		at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
		at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
		at freemarker.core.Environment.visit(Environment.java:383)
		at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:321)
		at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271)
		at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244)
		at freemarker.core.Environment.visitIteratorBlock(Environment.java:657)
		at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108)
		at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94)
		at freemarker.core.Environment.visit(Environment.java:347)
		at freemarker.core.Environment.visit(Environment.java:353)
		at freemarker.core.Environment.process(Environment.java:326)
		at freemarker.template.Template.process(Template.java:383)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:391)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:304)
		at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:255)
		at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:179)
		at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
		at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
		at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
		at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
[http-nio-80-exec-4] 2021-05-17 23:57:45,689 DEBUG o.s.w.s.DispatcherServlet - Error rendering view [org.springframework.web.servlet.view.freemarker.FreeMarkerView: name '/index'; URL [/index.ftl]]
freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
----
	at freemarker.core.InvalidReferenceException.getInstance(InvalidReferenceException.java:134)
	at freemarker.core.EvalUtil.coerceModelToTextualCommon(EvalUtil.java:481)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:401)
	at freemarker.core.EvalUtil.coerceModelToStringOrMarkup(EvalUtil.java:370)
	at freemarker.core.DollarVariable.calculateInterpolatedStringOrMarkup(DollarVariable.java:100)
	at freemarker.core.DollarVariable.accept(DollarVariable.java:63)
	at freemarker.core.Environment.visit(Environment.java:383)
	at freemarker.core.IteratorBlock$IterationContext.executedNestedContentForCollOrSeqListing(IteratorBlock.java:321)
	at freemarker.core.IteratorBlock$IterationContext.executeNestedContent(IteratorBlock.java:271)
	at freemarker.core.IteratorBlock$IterationContext.accept(IteratorBlock.java:244)
	at freemarker.core.Environment.visitIteratorBlock(Environment.java:657)
	at freemarker.core.IteratorBlock.acceptWithResult(IteratorBlock.java:108)
	at freemarker.core.IteratorBlock.accept(IteratorBlock.java:94)
	at freemarker.core.Environment.visit(Environment.java:347)
	at freemarker.core.Environment.visit(Environment.java:353)
	at freemarker.core.Environment.process(Environment.java:326)
	at freemarker.template.Template.process(Template.java:383)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.processTemplate(FreeMarkerView.java:391)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.doRender(FreeMarkerView.java:304)
	at org.springframework.web.servlet.view.freemarker.FreeMarkerView.renderMergedTemplateModel(FreeMarkerView.java:255)
	at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:179)
	at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:316)
	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1373)
	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1118)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1057)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
	at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:698)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:353)
	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1629)
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Thread.java:748)
[http-nio-80-exec-4] 2021-05-17 23:57:45,690 DEBUG o.s.w.s.DispatcherServlet - Failed to complete request: freemarker.core.InvalidReferenceException: The following has evaluated to null or missing:
==> category.categoryId  [in template "index.ftl" at line 193, column 61]

----
Tip: It's the step after the last dot that caused this error, not those before it.
----
		at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
		at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
		at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
		at javax.servlet.http.HttpServlet.service(HttpServlet.java:626)
		at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
		at javax.servlet.http.HttpServlet.service(HttpServlet.java:733)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
		at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
		at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
		at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
		at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
		at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:97)
		at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:544)
		at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:143)
		at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
		at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:698)
		at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:78)
		at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:353)
		at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:616)
		at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
		at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:831)
		at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1629)
		at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
		at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
		at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
		at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
		at java.lang.Thread.run(Thread.java:748)
Tip: If the failing expression is known to legally refer to something that's sometimes null or missing, either specify a default value like myOptionalVar!myDefault, or use <#if myOptionalVar??>when-present<#else>when-missing</#if>. (These only cover the last step of the expression; to cover the whole expression, use parenthesis: (myOptionalVar.foo)!myDefault, (myOptionalVar.foo)??
----

----
FTL stack trace ("~" means nesting-related):
	- Failed at: ${category.categoryId}  [in template "index.ftl" at line 193, column 59]
----

相关代码：index.jsp

<!DOCTYPE html>
<html lang="en"><head>
    <meta charset="UTF-8">
    <title>慕课书评网</title>
    <meta name="viewport" content="width=device-width,initial-scale=1.0, maximum-scale=1.0,user-scalable=no">
    <link rel="stylesheet" href="./resources/bootstrap/bootstrap.css">
    <link rel="stylesheet" href="./resources/raty/lib/jquery.raty.css">
    <script src="./resources/jquery.3.3.1.min.js"></script>
    <script src="./resources/bootstrap/bootstrap.min.js"></script>
    <script src="./resources/art-template.js"></script>
   <script src="./resources/raty/lib/jquery.raty.js"></script>
    <style>
        .highlight {
            color: #ff0000 !important;
        }
        a:active{
            text-decoration: none!important;
        }
    </style>
    

    <style>
        .container {
            padding: 0px;
            margin: 0px;
        }

        .row {
            padding: 0px;
            margin: 0px;
        }

        .col- * {
            padding: 0px;
        }
    </style>
    <#--定义模板-->
    <script type="text/html" id="tpl">
        <a href="/book/{{bookId}}" style="color: inherit">
            <div class="row mt-2 book">
                <div class="col-4 mb-2 pr-2">
                    <img class="img-fluid" src="{{cover}}">
                </div>
                <div class="col-8  mb-2 pl-0">
                    <h5 class="text-truncate">{{bookName}}</h5>

                    <div class="mb-2 bg-light small  p-2 w-100 text-truncate">{{author}}</div>


                    <div class="mb-2 w-100">{{subTitle}}</div>

                    <p>
                        <span class="stars" data-score="{{evaluationScore}}" title="gorgeous"></span>
                        <span class="mt-2 ml-2">{{evaluationScore}}</span>
                        <span class="mt-2 ml-2">{{evaluationQuantity}}人已评</span>
                    </p>
                </div>
            </div>
        </a>

        <hr>
    </script>

    <script>
        $.fn.raty.defaults.path ="./resources/raty/lib/images";
        //loadMore()加载更多数据
        //isReset参数设置为true,代表从第一页开始查询,否则按nextPage查询后续页
        function loadMore(isReset){
            if(isReset == true){
                $("#bookList").html("");
                $("#nextPage").val(1);
            }
            var nextPage = $("#nextPage").val();
            var categoryId= $("#categoryId").val();
            var order = $("#order").val();

            $.ajax({
                url : "/books" ,
                data : {p:nextPage,"categoryId":categoryId , "order":order},
                type : "get" ,
                dataType : "json" ,
                success : function(json){
                    console.info(json);
                    var list = json.records;
                    for(var i = 0 ; i < list.length ; i++){
                        var book = json.records[i];
                        // var html = "<li>" + book.bookName + "</li>";
                        //将数据结合tpl模板,生成html
                        var html = template("tpl" , book);
                        console.info(html);
                        $("#bookList").append(html);
                    }
                    //显示星型评价组件
                    $(".stars").raty({readOnly:true});

                    //判断是否到最后一页
                    if(json.current < json.pages){
                        $("#nextPage").val(parseInt(json.current) + 1);
                        $("#btnMore").show();
                        $("#divNoMore").hide();
                    }else{
                        $("#btnMore").hide();
                        $("#divNoMore").show();
                    }
                }
            })
        }
        $(function(){
            /*$.ajax({
                url : "/books" ,
                data : {p:1},
                type : "get" ,
                dataType : "json" ,
                success : function(json){
                    console.info(json);
                    var list = json.records;
                    for(var i = 0 ; i < list.length ; i++){
                        var book = json.records[i];
                        // var html = "<li>" + book.bookName + "</li>";
                        //将数据结合tpl模板,生成html
                        var html = template("tpl" , book);
                        console.info(html);
                        $("#bookList").append(html);
                    }
                    //显示星型评价组件
                    $(".stars").raty({readOnly:true});
                }
            })*/
            loadMore(true);
        })

        //绑定加载更多按钮单击事件
        $(function(){
            $("#btnMore").click(function(){
                loadMore();
            })

            $(".category").click(function () {
                $(".category").removeClass("highlight");
                $(".category").addClass("text-black-50");
                $(this).addClass("highlight");
                var categoryId = $(this).data("category");
                $("#categoryId").val(categoryId);
                loadMore(true);
            })

            $(".order").click(function(){
                $(".order").removeClass("highlight");
                $(".order").addClass("text-black-50");
                $(this).addClass("highlight");
                var order = $(this).data("order");
                $("#order").val(order);
                loadMore(true);
            })
        })
    </script>
</head>
<body>

<div class="container">
    <nav class="navbar navbar-light bg-white shadow mr-auto">
        <ul class="nav">
            <li class="nav-item">
                <a href="/">
                    <img src="https://m.imooc.com/static/wap/static/common/img/logo2.png" class="mt-1" style="width: 100px">
                </a>
            </li>

        </ul>
            <#if loginMember??>
                <h6 class="mt-1">
                    <img style="width: 2rem;margin-top: -5px" class="mr-1" src="./images/user_icon.png">${loginMember.nickname}
                </h6>
            <#else>
                <a href="/login.html" class="btn btn-light btn-sm">
                    <img style="width: 2rem;margin-top: -5px" class="mr-1" src="./images/user_icon.png">登录
                </a>
            </#if>

    </nav>
    <div class="row mt-2">



        <div class="col-8 mt-2">
            <h4>热评好书推荐</h4>
        </div>

        <div class="col-8 mt-2">
                <span data-category="-1" style="cursor: pointer" class="highlight  font-weight-bold category">全部</span>
                |
                <#list categoryList as category>
                <a style="cursor: pointer" data-category="${category.categoryId}" class="text-black-50 font-weight-bold category">${category.categoryName}</a>
                <#--<#if category_has_next>|</#if>-->|
                </#list>
                    

        </div>

        <div class="col-8 mt-2">
            <span data-order="quantity" style="cursor: pointer" class="order highlight  font-weight-bold mr-3">按热度</span>

            <span data-order="score" style="cursor: pointer" class="order text-black-50 mr-3 font-weight-bold">按评分</span>
        </div>
    </div>
    <div class="d-none">
        <input type="hidden" id="nextPage" value="2">
        <input type="hidden" id="categoryId" value="-1">
        <input type="hidden" id="order" value="quantity">
    </div>

    <div id="bookList">
    


    </div>
    <button type="button" id="btnMore" data-next-page="1" class="mb-5 btn btn-outline-primary btn-lg btn-block">
        点击加载更多...
    </button>
    <div id="divNoMore" class="text-center text-black-50 mb-5" style="display: none;">没有其他数据了</div>
</div>

</body></html>

相关代码：BookController

package com.roan.reader.controller;

import com.roan.reader.entity.Category;
import com.roan.reader.service.CategoryService;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.servlet.ModelAndView;

import javax.annotation.Resource;
import java.util.List;

/**
 * @author Administrator
 */
@Controller
public class BookController {
    @Resource
    private CategoryService categoryService;

    /**
     *  获取图书别类数据
     * @return 将需跳转的URL和数据发送
     */
    @GetMapping("/")
    public ModelAndView showCategory() {
        System.out.println("我要被运行了");
        ModelAndView modelAndView = new ModelAndView("/index");
        List<Category> categoryList = categoryService.selectAll();
        modelAndView.addObject("categoryList",categoryList);
        return modelAndView;
    }

}

相关代码：applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:task="http://www.springframework.org/schema/task"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        https://www.springframework.org/schema/mvc/spring-mvc.xsd
         http://www.springframework.org/schema/task
        https://www.springframework.org/schema/task/spring-task.xsd
        http://www.springframework.org/schema/tx
        https://www.springframework.org/schema/tx/spring-tx.xsd
        http://www.springframework.org/schema/context
        https://www.springframework.org/schema/context/spring-context.xsd">
    <!--开启Spring IoC容器注解形式开发-->
    <context:component-scan base-package="com.roan.reader"/>
    <!--开启Spring MVC注解形式开发-->
    <mvc:annotation-driven>
        <mvc:message-converters>
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <property name="supportedMediaTypes">
                    <!--响应，解决中文乱码-->
                    <list><value>text/html;charset=utf-8</value></list>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>
    <!--静态资源排除-->
    <mvc:default-servlet-handler/>

    <!--Spring MVC 配置FreeMarker模板引起-->
    <bean id="ViewResolver" class="org.springframework.web.servlet.view.freemarker.FreeMarkerViewResolver">
        <!--解决响应输出乱码问题-->
        <property name="contentType" value="text/html;charset=utf-8"/>
        <!--指定Freemarker模板的文件扩展名-->
        <property name="suffix" value=".ftl"/>
    </bean>
    <!--配置FreeMarker模板引擎参数-->
    <bean id="freemarkerConfig" class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">
        <!--设置FreeMarker模板保存路径-->
        <property name="templateLoaderPath" value="/WEB-INF/ftl"/>
        <property name="freemarkerSettings">
            <!--设置Freemarker脚本与数据渲染是的字符集-->
            <props><prop key="defaultEncoding">UTF-8</prop>
            <!--<prop key="classic_compatible">true</prop>--></props>
        </property>
    </bean>

    <!--Spring 与 MyBatis整合-->
    <!--2. 设置数据源-->
    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="com.mysql.cj.jdbc.Driver"/>
        <property name="url"
                  value="jdbc:mysql://localhost:3306/imooc_reader?useSSL=false&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=Asia/Shanghai"/>
        <property name="username" value="root"/>
        <property name="password" value="123456"/>
        <property name="initialSize" value="5"/>
        <property name="maxActive" value="20"/>
    </bean>
    <!--3. SqlSessionFactoryBean 用于根据配置信息创建SqlSessionFactory，不再需要自己编码创建-->
    <!--原生MyBatis 创建<bean id="sessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">-->
    <bean id="sessionFactory" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
        <!--关联数据源-->
        <property name="dataSource" ref="dataSource"/>
        <!--代表用于存储SQL语句的mapper.xml文件的路径-->
        <property name="mapperLocations" value="classpath:mappers/*.xml"/>
        <!--用于指定MyBatis配置文件的地址-->
        <property name="configLocation" value="classpath:mybatis-config.xml"/>
    </bean>

    <!--4. 配置Mapper扫描器-->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.roan.reader.mapper"/>
    </bean>

    <!--声明式事务-->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource"/>
    </bean>
    <!--声明式事务开启注解开发-->
    <tx:annotation-driven/>
</beans>

相关代码：web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <!--DispatcherServlet 是Spring MVC最核心的对象，拦截Http请求，并根据对应的URL分配与之对应的Controller方法，完成请求-->
    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!--加载applicationContext配置文件-->
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:applicationContext*.xml</param-value>
        </init-param>
        <!--在WEB应用启动时自动加载Spring IOC容器，并创建DispatcherServlet对象-->
        <load-on-startup>0</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

    <!--请求 POST 解决中文乱码-->
    <filter>
        <filter-name>characterFilter</filter-name>
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
        <init-param>
            <param-name>encoding</param-name>
            <param-value>UTF-8</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>characterFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>
大吉他 2021-05-18
源自：SSM开发社交网站   4-1 显示图书类别
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1回答
好帮手慕小班 2021-05-18 11:58:29

同学你好，根据贴出的报错信息，在ftl页面category属性展示有误

http://img1.sycdn.imooc.com//climg/60a33ac7091c433408510156.jpg

但是测试贴出代码，在index.ftl页面中，这里是可以正常输出的，比如

http://img1.sycdn.imooc.com//climg/60a33a7709f5df0d04100167.jpg

如上所示，ftl页面中的代码并没有问题，可能是在Controller中对应的showCategory查询有误，没有查出具体的数据，同学可以尝试检查一下，是否正确查出了对应数据，比如

http://img1.sycdn.imooc.com//climg/60a33b5e0910dc0109820320.jpg

另外，根据同学的描述，出现跳转页面就出现问题，是404问题吗，还麻烦具体描述一下。

祝学习愉快！

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  • 提问者 大吉他 #1

    那是不是我的脚本js. css路径引用出现问题，需要向外跳出两个路径，但是在index. ftl页面引用只用了一个小数点

    2021-05-18 12:01:38
  • 好帮手慕小班 回复 提问者 大吉他 #2

    同学你好，现在并不能定位同学的问题，在同学的项目中，当不跳转页面时，只有这个报错信息吗

    http://img1.sycdn.imooc.com//climg/60a36fb20900643504680068.jpg

    如果是，此时同学可以排查一下，是不是查询到的数据有问题，不能正常展示导致的。

    祝学习愉快！

    2021-05-18 15:42:14
  • 提问者 大吉他 回复 好帮手慕小班 #3

    控制台也有显示查询到的数据，都是正常的，如果是数据没有或者有一场，那界面应该能跳转到index. ftl界面吧，现在页面也不会跳转，也不能进去调试页面界面，等我回去改下路径再试一次

    2021-05-18 15:59:35
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