Servlet开发（3）

Servlet开发

Servlet过滤器：

主要是对访问主页的用户进行过滤，通过登录系统进入的用户可以看到主页内容，在session中存在currentuser。

可以对此进行判断：

 package com.java1234.web;
 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;
 import javax.servlet.http.HttpSession;

 public class Loginfilter implements Filter {

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

     } 

     @Override
     public void doFilter(ServletRequest ServletRequest, ServletResponse ServletResponse, FilterChain FilterChain)
             throws IOException, ServletException {
         // TODO Auto-generated method stub
         HttpServletRequest request=(HttpServletRequest)ServletRequest;//将ServletRequest强制转化为HttpServetRequest
         HttpSession session=request.getSession();//获取sessin(如果用户登录就存在session)
         Object o=session.getAttribute("currentUser");//获取currentUser对象
         String path=request.getServletPath();//获取登录路径
         if(o == null && path.indexOf("login")< 0){
             /*服务器内部跳转 - -> 没有登录不能能访问主页*/
             request.getRequestDispatcher("Login.jsp").forward(ServletRequest, ServletResponse);
         }else{
              FilterChain.doFilter(ServletRequest,ServletResponse);
         }
     }

     @Override
     public void init(FilterConfig arg0) throws ServletException {
         // TODO Auto-generated method stub

     }

 }

Loginfilter.java

配置类似于 Servlet ：

 </web-app>
 <filter>
        <filter-name>Loginfilter</filter-name>
        <filter-class>com.java1234.web.Loginfilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>Loginfilter</filter-name>
        <url-pattern>/login</url-pattern>
    </filter-mapping>
 </web-app>

Servlet监听器：

监听web事件；如application，session,request。

写一个监听session的例子：

首先当用户登录时，设置session值，这时候会添加属性，监听到。。。

其次注销的时候，删除session值，这时候是删除属性，监听到。。

so

代码如下:

 package com.java1234.listener;

 import javax.servlet.http.HttpSessionAttributeListener;
 import javax.servlet.http.HttpSessionBindingEvent;

 public class SessionAttributeListener implements HttpSessionAttributeListener{

     @Override
     public void attributeAdded(HttpSessionBindingEvent HttpSessionBindingEvent) {
         // TODO Auto-generated method stub
          System.out.println("添加的属性名："+HttpSessionBindingEvent.getName()+"属性值:"+HttpSessionBindingEvent.getValue());
     }

     @Override
     public void attributeRemoved(HttpSessionBindingEvent HttpSessionBindingEvent) {
         // TODO Auto-generated method stub
         System.out.println("删除的属性名："+HttpSessionBindingEvent.getName()+"属性值 :"+HttpSessionBindingEvent.getValue());
     }

     @Override
     public void attributeReplaced(HttpSessionBindingEvent arg0) {
         // TODO Auto-generated method stub

     }

 }

SessionAttributeListener.java

退出登录的java代码：

 package com.java1234.web;
 import java.io.IOException;
 import java.io.PrintWriter;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 public class LogoutServlet extends HttpServlet{

     /**
      *
      */
     private static final long serialVersionUID = 1L;
     @Override
     protected void doGet(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         // TODO Auto-generated method stub
         this.doPost(request,response);
     }

     @Override
     protected void doPost(HttpServletRequest request, HttpServletResponse response)
             throws ServletException, IOException {
         // TODO Auto-generated method stub
     //清除session
         request.getSession().invalidate();
         response.sendRedirect("Login.jsp");
     }
     @Override
     public void destroy() {
         // TODO Auto-generated method stub

     }
     @Override
     public void init() throws ServletException {
         // TODO Auto-generated method stub

     }
 }

LogoutServlet.java

配置web.xml

  <!-- 添加监听器 -->
   <listener>
   <listener-class>
       com.java1234.listener.SessionAttributeListener
   </listener-class>
   </listener>
   <!-- 设置logout的servlet -->
      <servlet>
          <servlet-name>LogoutServlet</servlet-name>
          <servlet-class>com.java1234.web.LogoutServlet</servlet-class>
      </servlet>
      <servlet-mapping>
          <servlet-name>LogoutServlet</servlet-name>
          <url-pattern>/logout</url-pattern>
      </servlet-mapping>

web.xml

启动登录------>注销

运行结果

至此ok了。。