J2EE 第三周(03.19-03.25)

package com.ljq.servlet;  
  
import java.io.IOException;  
  
import javax.servlet.Filter;  
import javax.servlet.FilterChain;  
import javax.servlet.FilterConfig;  
import javax.servlet.ServletContext;  
import javax.servlet.ServletException;  
import javax.servlet.ServletRequest;  
import javax.servlet.ServletResponse;  
import javax.servlet.http.HttpServletRequest;  
  
public class LogFilter implements Filter {  
    // FilterConfig可用于访问Filter的配置信息  
    private FilterConfig config;  
  
    // 实现初始化方法  
    public void init(FilterConfig config) {  
        this.config = config;  
    }  
  
    // 实现销毁方法  
    public void destroy() {  
        this.config = null;  
    }  
  
    // 执行过滤的核心方法  
    public void doFilter(ServletRequest request, ServletResponse response,  
            FilterChain chain) throws IOException, ServletException {  
        // ---------下面代码用于对用户请求执行预处理---------  
        // 获取ServletContext对象，用于记录日志  
        ServletContext context = this.config.getServletContext();  
        long before = System.currentTimeMillis();  
        System.out.println("开始过滤...");  
        // 将请求转换成HttpServletRequest请求  
        HttpServletRequest hrequest = (HttpServletRequest) request;  
        // 记录日志  
        context.log("Filter已经截获到用户的请求地址： " + hrequest.getServletPath());  
        // Filter只是链式处理，请求依然放行到目的地址  
        chain.doFilter(request, response);  
          
        // ---------下面代码用于对服务器响应执行后处理---------  
        long after = System.currentTimeMillis();  
        // 记录日志  
        context.log("过滤结束");  
        // 再次记录日志  
        context.log("请求被定位到" + hrequest.getRequestURI() + "所花的时间为: "  
                + (after - before));  
    }  
  
}  

<?xml version="1.0" encoding="UTF-8"?>  
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"  
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"  
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee   
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">  
    <filter>  
        <filter-name>LogFilter</filter-name>  
        <filter-class>com.ljq.servlet.LogFilter</filter-class>  
    </filter>  
  
    <filter-mapping>  
        <filter-name>LogFilter</filter-name>  
        <url-pattern>/*</url-pattern>  
    </filter-mapping>  
  
    <welcome-file-list>  
        <welcome-file>index.jsp</welcome-file>  
    </welcome-file-list>  
</web-app>  

package com.yl.servlet;  
  
import java.io.IOException;  
import java.io.PrintWriter;  
import java.util.Date;  
  
import javax.servlet.AsyncContext;  
import javax.servlet.ServletException;  
import javax.servlet.annotation.WebServlet;  
import javax.servlet.http.HttpServlet;  
import javax.servlet.http.HttpServletRequest;  
import javax.servlet.http.HttpServletResponse;  
/** 
 * Servlet组件异步处理请求特性的演示小程序 
 *  
 * @author LYYL 
 * 
 */  
//通过注解的方式配置,支持异步处理请求  
@WebServlet(name="servlet", urlPatterns={"/asyncServlet"}, asyncSupported=true)  
public class AsyncServlet extends HttpServlet{  
  
    @Override  
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)  
            throws ServletException, IOException {  
        processRequest(req, resp);  
    }  
  
    @Override  
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)  
            throws ServletException, IOException {  
        processRequest(req, resp);  
    }  
      
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)  
            throws ServletException, IOException{  
        response.setContentType("text/html;charset=UTF-8");  
        PrintWriter pw = response.getWriter();  
        pw.println("进入Servlet的时间是：" + new Date() + ".");  
        pw.flush();  
          
        //在子线程中执行业务逻辑，并由其负责输出响应，主线程退出  
        AsyncContext act = request.startAsync();  
        //创建一个模拟业务逻辑执行的线程  
        Executor ec = new Executor(act);  
        Thread td = new Thread(ec);  
        td.start();  
          
        pw.println("<br>");  
        pw.println("结束Servlet的时间是： " + new Date() + ".");  
        pw.flush();   
    }  
    /** 
     * 内部类，模拟线程执行的业务逻辑 
     *  
     * @author LYYL 
     * 
     */  
    public class Executor implements Runnable{  
        private AsyncContext act = null;  
          
        /** 
         * @param act 
         */  
        public Executor(AsyncContext act) {  
            this.act = act;  
        }  
  
        @Override  
        public void run() {  
            try {  
                Thread.sleep(3000);  
                PrintWriter pw = act.getResponse().getWriter();  
                pw.println("<br>");  
                pw.println("业务执行完的时间是： " + new Date() + ".");  
                pw.flush();  
                act.complete();  
                pw.close();  
            } catch (InterruptedException e) {  
                // TODO Auto-generated catch block  
                e.printStackTrace();  
            } catch (IOException e) {  
                // TODO Auto-generated catch block  
                e.printStackTrace();  
            }  
        }  
          
    }  
}