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。。

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。。

巴特西

Servlet开发（3）

Servlet开发

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