（三）首页处理

完成功能：登陆后直接进入index.jsp界面

1、导入index.jsp页面

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
　　
    <jsp:forward page="/index"></jsp:forward>   //在web.xml
</body>
</html>
package com.louis.web.servlet;

import java.io.IOException;
import java.lang.reflect.Method;

import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 通用servlet
 */

public class BaseServlet extends HttpServlet {
    @Override
    public  void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        try {
            //1获取子类,创建子类或调用子类的时候，this代表的是子类对象
            Class clazz = this.getClass();
            System.out.println(this);
            
            //2获取请求方法
            String m = request.getParameter("method");
            
            //如果方法为空。默认为index。于是每个servlet都要又index()
            if(m==null) {
                m = "index";
            }
            System.out.println(m);
            //3获取方法对象
            Method method = clazz.getDeclaredMethod(m, HttpServletRequest.class,HttpServletResponse.class);
            
            //4让方法执行,返回值为请求转发的路径
            String s = (String)method.invoke(this, request,response);
            
            //5判断s是否为空
            if(s!=null) {
                request.getRequestDispatcher(s).forward(request, response);
            }
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            throw new RuntimeException();
        } 
        
    }
    
    public String index(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        return null;
    }

}
package com.louis.web.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 和首页相关的servlet
 */
public class IndexServlet extends BaseServlet {
    public String index(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 去数据库中查询最新商品和热门商品，将他们放入request域中请求转发
        return "/jsp/index.jsp";
    }
}
说明：
1、url中不带方法即可进入首页，所以在BaseServlet中要加一个判断条件，如果没有method方法就调用index函数
2、IndexServlet中的index重写了BaseServlet中的index方法

 

 

问题：<jsp:forward>能自动请求么？

参考：https://jingyan.baidu.com/article/b7001fe19210fb0e7282dd3a.html

 

posted on 2017-10-07 13:13  Michael2397  阅读(229)  评论(0)  编辑  收藏  举报

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