过滤指定servlet的顺序

为什么过滤指定servlet的filter不是按filter-mapping里的先后顺序执行？第一个filter是过滤指定servlet，但是是最后才被执行？

xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
    id="WebApp_ID" version="3.1">
    <display-name>Filter</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.htm</welcome-file>
        <welcome-file>default.jsp</welcome-file>
    </welcome-file-list>
      
    <servlet>
    <servlet-name>testservlet</servlet-name>
    <servlet-class>pers.hyu.filter.TestServlet</servlet-class>
    </servlet>
     
    <servlet-mapping>
    <servlet-name>testservlet</servlet-name>
    <url-pattern>/test</url-pattern>
    </servlet-mapping>
      
    <filter>
        <filter-name>first_filter</filter-name>
        <filter-class>pers.hyu.filter.FirstFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>first_filter</filter-name>
        <servlet-name>testservlet</servlet-name>
 
        <!-- 
        <url-pattern>*.jsp</url-pattern>
        <url-pattern>*.html</url-pattern>
         -->
    </filter-mapping>
     
    <filter>
        <filter-name>charset</filter-name>
        <filter-class>pers.hyu.filter.CharertFilter</filter-class>
        <init-param>
            <param-name>charertSet</param-name>
            <param-value>GBK</param-value>
        </init-param>
    </filter>
    <filter-mapping>
        <filter-name>charset</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
     
     <filter>
    <filter-name>annotatoin</filter-name>
    <filter-class>pers.hyu.filter.AnnotatoinFilter</filter-class>
    </filter>
    <filter-mapping>
    <filter-name>annotatoin</filter-name>
    <url-pattern>/*</url-pattern>
    </filter-mapping>
     
     
     
</web-app>

3个filter

package pers.hyu.filter;
 
import java.io.IOException;
 
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
//@WebFilter(filterName = "filterF", urlPatterns="/*")
public class FirstFilter implements Filter{
 
    @Override
    public void destroy() {
        // TODO Auto-generated method stub
         
    }
 
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        // TODO Auto-generated method stub
        response.getWriter().println("AAA----This is the first filter!!!");
        chain.doFilter(request, response);
        System.out.println("AAAAAA!");
 
         
    }
 
    @Override
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub
         
    }
 
}

package pers.hyu.filter;
 
import java.io.IOException;
 
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
//@WebFilter(filterName = "filterC",urlPatterns="/*")
public class CharertFilter implements Filter {
 
    private String c;
    @Override
    public void destroy() {
        // TODO Auto-generated method stub
 
    }
 
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        // TODO Auto-generated method stub
         
        response.setContentType("text/html;charset=" + c);
        //System.out.println(c);
        response.getWriter().println("BBBB ----- This is the charet filter!!!");
        chain.doFilter(request, response);
        System.out.println("BBB");
 
    }
 
    @Override
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub
        c = arg0.getInitParameter("charertSet");
    }
 
}

package pers.hyu.filter;
 
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
 
/**
 * Servlet Filter implementation class AnnotatoinFilter
 */
//@WebFilter(filterName = "filterA",urlPatterns="/*")
public class AnnotatoinFilter implements Filter {
 
    /**
     * Default constructor. 
     */
    public AnnotatoinFilter() {
        // TODO Auto-generated constructor stub
    }
 
    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
        //System.out.println("Destory ");
    }
 
    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        // TODO Auto-generated method stub
        // place your code here
        response.getWriter().println("CCC ---- This is the annotation filter!!!");
        // pass the request along the filter chain
        chain.doFilter(request, response);
        System.out.println("ccc");
    }
 
    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
        //System.out.println("Init ");
    }
 
}

要过滤的servlet

package pers.hyu.filter;
 
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
/**
 * Servlet implementation class TestServlet
 */
//@WebServlet("/test")
public class TestServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
        
    /**
     * @see HttpServlet#HttpServlet()
     */
    public TestServlet() {
        super();
        // TODO Auto-generated constructor stub
    }
 
    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        response.getWriter().append("Served at: ").append(request.getContextPath());
    }
 
}

weixin_慕勒8187086 2020-03-26

源自：过滤器 2-8 过滤链

收起

2回答

好帮手慕小尤 2020-03-26 10:09:10

同学你好，过滤器的顺序由 web.xml 文件中 <filter-mapping>的顺序决定，从上到下的顺序来执行的。同学在filter-mapping设置地址（url-pattern）即可，可通过设置的地址进行过滤。不需要设置servlet-name。修改后代码如下所示：

如果解答了同学的疑问，望采纳~祝学习愉快~

收起回答

提问者 weixin_慕勒8187086 #1

你好，和输出语句放在doFilter前后没有关系。 doFilter前面有输出到页面的语句。你看xml的配置，filter-mapping 里的filter顺序是 firstFilter， charertfilter, annotationfilter，即AAA， bbb，ccc 。第一个firstfilter 是过滤指定的Servlet，执行顺序就变成了bbb ccc aaa，如果不过滤指定servlet 则是按照filter-mapping的顺序执行。可以看我之前回复的贴图

2020-03-26 11:18:09
好帮手慕小尤回复提问者 weixin_慕勒8187086 #2

同学你好，是老师理解错误，已修改上次回答，请同学查看，给您的学习带来不便，深感抱歉！祝学习愉快！

2020-03-26 14:56:39