自定义MVC之登录实例

最新推荐文章于 2024-08-19 20:26:27 发布

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最新推荐文章于 2024-08-19 20:26:27 发布

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分类专栏： java 文章标签：自定义MVC

本文链接：https://blog.youkuaiyun.com/pang_ping/article/details/73369329

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本文介绍了一种基于Servlet的简单MVC模式实现方法，通过自定义Servlet进行路由分发，实现了请求与处理类之间的解耦。具体步骤包括定义一个总控Servlet、使用配置文件映射请求与处理类的关系，并通过反射机制实例化处理类。

步骤：

1、定义个servlet（ActionServlet）控制所有的*.do请求
2、获得请求路径（request.getRequestURI()）,截取到后面的请求名(cname)
3、在webinf下创建一个config.properties文件，保存一个键值对，根据不同的请求得到其对应的Class，同时创建好对应的处理类
4、在servlet的init方法中加载配置文件
Properties config=new Properties();
String path=this.getServletContext.getRealPath();//得到其绝对路径
path=path+"/WEB-INF/config.properties";
config.load(new FileInputStream(path));//加载到内存中来
this.getServletContext.setAttribute("config",config);//存入到application中
5、到dopost方法中取出application中的数据,结合前面取到的请求名得到其对应的类名
Properties config=(Properties)this.getServletContext.getAttribute("config");
String className=config.getProperty(cname);
6、将"/WEB-INF/config.properties"存入到web.xml文件中,并通过代码取出
String sname=this.getServletContext().getInitParameter("config");
7、根据取出来的类名(全路径名)，实例化对象
Class.forName(classname).newInstance();
8、新建一个接口(Action)，声明方法execute();将所有的实现类继承action接口
9、将Class.forName返回的对象统一为转换为Action,再统一的调用execute()方法(多态)
10、修改接口的方法execute(),让其带参数(request,response),其所有的继承类对应的做修改，保证能从ActionServlet传送到对应页面
11、将Action存入到一个池中，步骤：先在init方法中建立一个池(Properties)，再在dopost方法中判断，以保证每一个类只会被实例化一次

jsp页面代码：

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>My JSP 'login.jsp' starting page</title>
    
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">    
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->

  </head>
  
  <body>
  	<h1>登录</h1>
    <form action="login.do" method="post">
		用户名：<input type="text" name="uname"/><br/>    	
		密码：<input type="password" name="upass"/><br/>    	
		<input type="submit" value="登录"/><br/>    	
    </form>
  </body>
</html>

配置文件：

<?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">
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  
  
  <!-- 配置总的Servlet -->
  <servlet>
  	<servlet-name>totalServlet</servlet-name>
  	<servlet-class>com.zking.servlet.TotalServlet</servlet-class>
  </servlet>
  
  <servlet-mapping>
  	<servlet-name>totalServlet</servlet-name>
	<url-pattern>*.do</url-pattern>  
  </servlet-mapping>
  
</web-app>

Java代码：

package com.zking.servlet;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.Reader;
import java.util.Properties;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class TotalServlet extends HttpServlet{
	
	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		doPost(req, resp);
	}
	
	
	@Override
	public void init(ServletConfig config) throws ServletException {
		try {
			//3.加载配置文件config.properties
			Properties properties=new Properties();
			Properties propertiesObject=new Properties();
			//3.1获取服务器的路径
			String serverPath=config.getServletContext().getRealPath("/");
			FileInputStream fis=new FileInputStream(serverPath+"WEB-INF/config.properties");
			properties.load(fis);
			
			//将properties存放到application中
			config.getServletContext().setAttribute("properties", properties);
			config.getServletContext().setAttribute("propertiesObject", propertiesObject);
			
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	
	
	
	
	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		
		//1.获取请求路径
		String uri=req.getRequestURI();
		
		//2.截取
		//2.1获取最后一个斜杠的位置
		int lastXiePosition=uri.lastIndexOf("/");
		//2.2获取最后一个点的位置
		int lastPointPosition=uri.lastIndexOf(".");
		uri=uri.substring(lastXiePosition+1, lastPointPosition);
		System.out.println("请求路径："+uri);
		
		//从application中获取properties
		Properties properties=(Properties) req.getSession().getServletContext().getAttribute("properties");
		
		//3.2根据键获取值
		String className=properties.getProperty(uri);
		System.out.println("获取到相对应的全限定名为:"+className);
		
		Properties propertiesObject=(Properties) req.getSession().getServletContext().getAttribute("propertiesObject");
		
		TotalDo total=(TotalDo) propertiesObject.get(className);
		
		//3.3 根据类的全限定名 来 实例化 该对象
		try {
			if(total==null){
				System.out.println("初始化对象");
				total=(TotalDo)Class.forName(className).newInstance();
				//必须存放
				propertiesObject.put(className, total);
			}
			total.execute(req,resp);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

package com.zking.servlet;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public interface TotalDo {
	public void execute(HttpServletRequest req, HttpServletResponse resp);
}

package com.zking.servlet;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginDO implements TotalDo{
	public void execute(HttpServletRequest req, HttpServletResponse resp){
		System.out.println("执行登录的业务逻辑");
		System.out.println(req.getParameter("uname"));
		System.out.println(req.getParameter("upass"));
	}
}