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
        
    }

}

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
        
    }

}

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
        
    }
}

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>

启动登录------>注销

运行结果

至此ok了。。