HttpServletRequestWrapper的用法

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HttpServletRequestWrapper 是HttpServletRequest的装饰器。

代码实例如下：

新建 TestRequestWrapper.java

package com.demo;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class TestRequestWrapper extends HttpServletRequestWrapper {

private String param = "";

public TestRequestWrapper(HttpServletRequest request, String param) {

        //装饰器模式的写法，必须将被装饰的对象初始化到装饰类中，详细用法请参照java设计模式
       super(request);
       this.param = param;
   }

   //覆写getParameter方法
   @Override
   public String getParameter(String name) {
       return param;
   }
}

新建过滤器类TestFilte

package com.demo;

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.http.HttpServletRequest;

public class TestFilter implements Filter {
   private FilterConfig filterConfig;
   @Override
   public void init(FilterConfig filterConfig) throws ServletException {
       // TODO Auto-generated method stub
       this.filterConfig = filterConfig;

   }

   @Override
   public void doFilter(ServletRequest request, ServletResponse response,
           FilterChain chain) throws IOException, ServletException {
       // TODO Auto-generated method stub

TestRequestWrapper requestwrapper = new TestRequestWrapper((HttpServletRequest)request,"我就是个参数");

//对自定义装饰器初始化后，继续发关原先的请求，不过将ServletRequest request 改为自定义装饰器的对像requestwrapper

   chain.doFilter(requestwrapper, response);
   }

   @Override
   public void destroy() {
       // TODO Auto-generated method stub

   }

}

新建 servlet类 ServletSessionTest.,java

package com.demo;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.catalina.Session;

/**
* Servlet implementation class ServletSessionTest
*/
public class ServletSessionTest extends HttpServlet {
   private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public ServletSessionTest() {
        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

     //此处request是自定义装饰器类的对像。getParameter为覆写后的方法，str的什是我就是个参数
   String str = request.getParameter("id");
   if(str.equals("1")){
           request.getSession().setAttribute("aa", "sssss");
   }else if(str.equals("2")){
           request.getSession().setAttribute("bbb", "bbb");

   }else if(str.equals("3")){
           request.getSession().removeAttribute("bbb");
   }else if(str.equals("4")){
       request.getSession().invalidate();
   }
   }

   /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
   protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       // TODO Auto-generated method stub
   }

}

web.xml配置

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">
<display-name>demo</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>
<listener>
    <listener-class>com.demo.HttpSessionListenerTest</listener-class>
</listener>
<filter>
   <filter-name>TestFilter</filter-name>
   <filter-class>com.demo.TestFilter</filter-class>

</filter>
<filter-mapping>
    <filter-name>TestFilter</filter-name>
    <url-pattern>/*</url-pattern>
</filter-mapping>
<servlet>
    <description></description>
    <display-name>ServletSessionTest</display-name>
    <servlet-name>ServletSessionTest</servlet-name>
    <servlet-class>com.demo.ServletSessionTest</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>ServletSessionTest</servlet-name>
    <url-pattern>/ServletSessionTest</url-pattern>
</servlet-mapping>
   <session-config>
         <session-timeout>1</session-timeout>
   </session-config>
</web-app>

访问地址：

localhost:8080/demo/ServletSessionTest?id=1

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