老师，这个异常怎么解决

老师，这个异常怎么解决

15:57:43,254  INFO ClassPathXmlApplicationContext:578 - Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@58c1670b: startup date [Wed Sep 19 15:57:43 CST 2018]; root of context hierarchy
15:57:43,443  INFO XmlBeanDefinitionReader:317 - Loading XML bean definitions from class path resource [applicationContext.xml]
15:57:44,666  WARN ClassPathXmlApplicationContext:546 - Exception encountered during context initialization - cancelling refresh attempt: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'product' defined in class path resource [applicationContext.xml]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanExpressionException: Expression parsing failed; nested exception is org.springframework.expression.spel.SpelEvaluationException: EL1001E:(pos 0): Type conversion problem, cannot convert from com.imooc.ioc.demo4.Category to java.lang.String

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'product' defined in class path resource [applicationContext.xml]: Initialization of bean failed; nested exception is org.springframework.beans.factory.BeanExpressionException: Expression parsing failed; nested exception is org.springframework.expression.spel.SpelEvaluationException: EL1001E:(pos 0): Type conversion problem, cannot convert from com.imooc.ioc.demo4.Category to java.lang.String

	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:553)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
	at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772)
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839)
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
	at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
	at com.imooc.ioc.demo4.SpringDemo4.demo3(SpringDemo4.java:24)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:389)
	at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:115)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$6(TestMethodTestDescriptor.java:167)
	at org.junit.jupiter.engine.execution.ThrowableCollector.execute(ThrowableCollector.java:40)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:163)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:110)
	at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:57)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.lambda$execute$3(HierarchicalTestExecutor.java:83)
	at org.junit.platform.engine.support.hierarchical.SingleTestExecutor.executeSafely(SingleTestExecutor.java:66)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:77)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.lambda$null$2(HierarchicalTestExecutor.java:92)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
	at java.util.Iterator.forEachRemaining(Iterator.java:116)
	at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.lambda$execute$3(HierarchicalTestExecutor.java:92)
	at org.junit.platform.engine.support.hierarchical.SingleTestExecutor.executeSafely(SingleTestExecutor.java:66)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:77)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.lambda$null$2(HierarchicalTestExecutor.java:92)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
	at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:175)
	at java.util.Iterator.forEachRemaining(Iterator.java:116)
	at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.lambda$execute$3(HierarchicalTestExecutor.java:92)
	at org.junit.platform.engine.support.hierarchical.SingleTestExecutor.executeSafely(SingleTestExecutor.java:66)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:77)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:51)
	at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:43)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:170)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:154)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:90)
	at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:74)
	at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
	at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
	at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)
Caused by: org.springframework.beans.factory.BeanExpressionException: Expression parsing failed; nested exception is org.springframework.expression.spel.SpelEvaluationException: EL1001E:(pos 0): Type conversion problem, cannot convert from com.imooc.ioc.demo4.Category to java.lang.String
	at org.springframework.context.expression.StandardBeanExpressionResolver.evaluate(StandardBeanExpressionResolver.java:164)
	at org.springframework.beans.factory.support.AbstractBeanFactory.evaluateBeanDefinitionString(AbstractBeanFactory.java:1413)
	at org.springframework.beans.factory.support.BeanDefinitionValueResolver.doEvaluate(BeanDefinitionValueResolver.java:255)
	at org.springframework.beans.factory.support.BeanDefinitionValueResolver.evaluate(BeanDefinitionValueResolver.java:214)
	at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:186)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1481)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1226)
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543)
	... 62 more
Caused by: org.springframework.expression.spel.SpelEvaluationException: EL1001E:(pos 0): Type conversion problem, cannot convert from com.imooc.ioc.demo4.Category to java.lang.String
	at org.springframework.expression.spel.support.StandardTypeConverter.convertValue(StandardTypeConverter.java:78)
	at org.springframework.expression.common.ExpressionUtils.convertTypedValue(ExpressionUtils.java:53)
	at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:301)
	at org.springframework.expression.common.CompositeStringExpression.getValue(CompositeStringExpression.java:89)
	at org.springframework.expression.common.CompositeStringExpression.getValue(CompositeStringExpression.java:42)
	at org.springframework.context.expression.StandardBeanExpressionResolver.evaluate(StandardBeanExpressionResolver.java:161)
	... 69 more
Caused by: org.springframework.core.convert.ConverterNotFoundException: No converter found capable of converting from type [com.imooc.ioc.demo4.Category] to type [java.lang.String]
	at org.springframework.core.convert.support.GenericConversionService.handleConverterNotFound(GenericConversionService.java:313)
	at org.springframework.core.convert.support.GenericConversionService.convert(GenericConversionService.java:195)
	at org.springframework.expression.spel.support.StandardTypeConverter.convertValue(StandardTypeConverter.java:74)
	... 74 more


Process finished with exit code -1
<?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:p="http://www.springframework.org/schema/p"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
    <!--<bean id="userService" class="com.imooc.ioc.demo1.UserServiceImp1">-->

    <!--</bean>-->

    <!--<bean id="bean1" class="com.imooc.ioc.demo2.Bean1"/>-->
    <!--<bean id="bean2" class="com.imooc.ioc.demo2.Bean2Factory" factory-method="createBean2"/>-->
    <!--<bean id="bean3Factory" class="com.imooc.ioc.demo2.Bean3Factory"/>-->
    <!--<bean id="bean3" factory-bean="bean3Factory" factory-method="createBean3"/>-->
    <!---->
    <!--<bean id="person" class="com.imooc.ioc.demo3.Person" scope="prototype"/>-->
    <!--<bean id="man" class="com.imooc.ioc.demo3.Man" scope="singleton" init-method="setup" destroy-method="teardown">-->
    <!--<property name="name" value="张三"/>-->
    <!--</bean>-->
    <!--<bean class="com.imooc.ioc.demo3.SpringBeanPostProcessor"/>-->

    <!--<bean id="userDao" class="com.imooc.ioc.demo3.UserDaoImp1"/>-->
    <bean id="user" class="com.imooc.ioc.demo4.User">
        <constructor-arg name="name" value="张三"/>
        <constructor-arg name="age" value="23"/>
    </bean>

    <!--<bean id="person" class="com.imooc.ioc.demo4.Person">-->
    <!--<property name="name" value="李四"/>-->
    <!--<property name="age" value="23"/>-->
    <!--<property name="cat" ref="cat"/>-->
    <!--</bean>-->

    <!--<bean id="cat" class="com.imooc.ioc.demo4.Cat">-->
    <!--<property name="name" value="kitty"></property>-->
    <!--</bean>-->
    <!--bean的p名称空间的属性注入-->
    <bean id="person" class="com.imooc.ioc.demo4.Person" p:name="小黄" p:age="23" p:cat-ref="cat">

    </bean>

    <bean id="cat" class="com.imooc.ioc.demo4.Cat" p:name="大黄">

    </bean>

    <!--bean的SpEL名称空间的属性注入-->
    <bean id="category" class="com.imooc.ioc.demo4.Category">
        <property name="name" value="#{'服装'}"/>
    </bean>

    <bean id="product" class="com.imooc.ioc.demo4.Product">
        <property name="name" value="#{'男装'}"/>
        <property name="price" value="#{199.00}"/>
        <property name="category" value="#{category}"/>
    </bean>

</beans>
@Test
public void demo3() {
    ApplicationContext applicationContext = new ClassPathXmlApplicationContext("applicationContext.xml");
    Product product = (Product) applicationContext.getBean("product");
    System.out.println(product);
}
广州麻辣牛杂档 2018-09-19
源自：Spring Bean管理   4-5 SpEL的属性注入
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1回答
chrismorgen 2018-09-19 17:08:08

建议你学会看报错提示，如下图所示，根据报错提示，你可以根据老师的源码核进行核对，内容指向applicationContext文件和Product类，祝学习愉快~

http://img1.sycdn.imooc.com//climg/5ba2110d00017be606570125.jpg

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老师，实现接口的类的实例调用他类中的方法时，其实调用的都是他的实现类中的方法？

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这个value的作用是什么啊

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