1.背景

    ServletContext,是一个全局的储存信息的空间，服务器开始建立，服务器关闭销毁。request，每次请求一个；session，一个会话一个；而servletContext，所有用户共用一个。

    ServletContext维护着一个服务器中的一个特定URL名字空间（比如，/myapplication）下的所有Servlet，Filter，JSP，JavaBean等Web部件的集合。

    也就是说Servlet和Filter并不是由Spring ApplicationContext维护的，所以使用autowire注解来进行注入会产生问题。

一般都是通过下面这个方法解决

WebApplicationContext springContext = WebApplicationContextUtils.getWebApplicationContext(servletContextEvent.getServletContext());

  

2.准备工作

准备一个由Spring ApplicationContext维护Bean，分别在Listener、Filter和Servlet中调用其中的方法。

 

import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.stereotype.Component;@Component("springBean")public class SpringBean {    private static final Logger logger = LoggerFactory.getLogger(SpringBean.class);    public void listener() {        logger.info("listener use spring bean");    }    public void servlet() {        logger.info("servlet use spring bean");    }    public void filter() {        logger.info("filter use spring bean");    }}

 

 

 

2.Listener

1.web.xml

    
        
     
      com.gqshao.spring.listener.MyListener
     
    

 

 

 

2.MyListener

package com.gqshao.spring.listener;import com.gqshao.spring.bean.SpringBean;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.web.context.WebApplicationContext;import org.springframework.web.context.support.WebApplicationContextUtils;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;/** * 功能说明：测试自定义Listener使用spring使用注解定义的bean */public class MyListener implements ServletContextListener {    private static final Logger logger = LoggerFactory.getLogger(MyListener.class);    @Override    public void contextInitialized(ServletContextEvent event) {        WebApplicationContext springContext = WebApplicationContextUtils.getWebApplicationContext(event.getServletContext());        SpringBean bean = (SpringBean) springContext.getBean("springBean");        bean.listener();    }    @Override    public void contextDestroyed(ServletContextEvent sce) {        logger.info("MyListener contextDestroyed");    }}

 

 

3.Filter

针对Filter，Spring提供了DelegatingFilterProxy解决

 

1.web.xml

    
        
     
      MyFilter
         
     
      org.springframework.web.filter.DelegatingFilterProxy
         
             
      
       targetBeanName
              
      
       myFilter
          
     
    
        
     
      MyFilter
         
     
      /*
         
     
      REQUEST
         
     
      FORWARD
     
    

 

2.applicationContext.xml

 

3.MyFilter

package com.gqshao.spring.filter;import com.gqshao.spring.bean.SpringBean;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.beans.factory.annotation.Autowired;import javax.servlet.*;import java.io.IOException;public class MyFilter implements Filter {    private static final Logger logger = LoggerFactory.getLogger(MyFilter.class);    @Autowired    private SpringBean springBean;    @Override    public void init(FilterConfig filterConfig) throws ServletException {        logger.info("MyFilter init");    }    @Override    public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException, ServletException {        springBean.filter();        filterChain.doFilter(request, response);    }    @Override    public void destroy() {        logger.info("MyFilter destroy");    }}

 

3.Servlet

Servlet我们仿照Spring对Filter的处理写一个DelegatingServletProxy这样的代理Servlet

 

1.web.xml

    
        
     
      myServlet
         
     
      com.gqshao.spring.servlet.DelegatingServletProxy
     
    
        
     
      myServlet
         
     
      /testservlet
     
    

 

2.DelegatingServletProxy

package com.gqshao.spring.servlet;import org.springframework.web.context.WebApplicationContext;import org.springframework.web.context.support.WebApplicationContextUtils;import javax.servlet.*;import java.io.IOException;public class DelegatingServletProxy extends GenericServlet {    private String targetBean;    private Servlet proxy;    @Override    public void service(ServletRequest request, ServletResponse response) throws ServletException,            IOException {        proxy.service(request, response);    }    @Override    public void init() throws ServletException {        this.targetBean = getServletName();        setServletBean();        proxy.init(getServletConfig());    }    private void setServletBean() {        WebApplicationContext wac = WebApplicationContextUtils.getRequiredWebApplicationContext(getServletContext());        this.proxy = (Servlet) wac.getBean(targetBean);    }}

 

3.MyServlet

package com.gqshao.spring.servlet;import com.gqshao.spring.bean.SpringBean;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;import java.io.PrintWriter;@Componentpublic class MyServlet extends HttpServlet {    @Autowired    private SpringBean springBean;    public void service(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        springBean.servlet();        PrintWriter out = response.getWriter();        out.println("
Hello World
");        out.flush();        out.close();    }}

 

4.说明

MyServlet使用Spring ApplicationContext来维护，通过@Component来定义

DelegatingServletProxy 通过web.xml文件中servlet-name中的值在Spring ApplicationContext中查找MyServlet，注意名称一致。