【SSH进阶之路】一步步重构MVC实现Struts框架——封装业务逻辑和跳转路径（四）

目录：

      【SSH进阶之路】Struts基本原理 + 实现简单登录（二）

      【SSH进阶之路】一步步重构MVC实现Struts框架——从一个简单MVC开始（三）

      【SSH进阶之路】一步步重构MVC实现Struts框架——封装业务逻辑和跳转路径（四）

      【SSH进阶之路】一步步重构MVC实现Struts框架——彻底去掉逻辑判断（五）

      【SSH进阶之路】一步步重构MVC实现Struts框架——完善转向页面，大功告成（六）

       Struts的第二篇博客【SSH进阶之路】Struts基本原理 + 实现简单登录（二），我们介绍了MVC和Struts的基本理论，上篇博客【SSH进阶之路】一步步重构MVC实现Struts框架——从一个简单MVC开始（三），我们实现了一个MVC模型，这篇博客我们解决一下上篇博客留下的第一个问题：封装业务逻辑和跳转路径。

       我们先回顾一下上篇博客中的TestServlet的代码：

package com.liang.servlet;

import java.io.IOException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * 使用servlet做相关的控制，转向多个（V）视图
 * @author liang
 *
 */
public class TestServlet extends HttpServlet {

	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//取得访问的URI
		String reqeuestURI = request.getRequestURI();
		System.out.println(reqeuestURI);
		//截取URI，获得路径
		String path = reqeuestURI.substring(reqeuestURI.indexOf("/",1), reqeuestURI.indexOf("."));
		System.out.println(path);
		//获得表单数据
		String username = request.getParameter("username");
		
		UserManager userManager = new UserManager();
		
		String forward ="";
		//根据url执行相关的功能
		//等于添加，调用添加方法，添加成功转到添加页面
		if("/servlet/addUser".equals(path)){
			//调用添加的业务逻辑
			userManager.add(username);
			forward ="/add_success.jsp";
			//删除，调用删除方法，删除成功转到删除
		}else if("/servlet/delUser".equals(path)){
			//调用删除的业务逻辑
			userManager.del(username);
			forward ="/servlet/delUser";
		//修改，调用修改方法，修改成功转到修改页面
		}else if("/servlet/modifyUser".equals(path)){
			//调用修改的业务逻辑
			userManager.modify(username);
			forward ="/modify_success.jsp";
		//查询，调用查询方法，查询成功转到查询成功页面
		}else if("/servlet/queryUser".equals(path)){
			//调用查询的业务逻辑
			List userList = userManager.query(username);
			request.setAttribute("userList", userList);
			forward ="/query_success.jsp";
		}else{
			throw new RuntimeException("请求失败");
		}
		//统一完成转向
		request.getRequestDispatcher(forward).forward(request, response);
	}

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request,response);
	}

}

       从TestServlet中我们发现，它就是一个简单的Servlet，它是Struts的前端控制器，负责把所有的URL截取下来，通过IF语句根据URL的不同执行相关的功能，并且添加，删除，修改和查询各自有各自的业务逻辑和跳转路径，我们可以各自的业务逻辑和跳转路径封装成不同的类，并抽象出一个公共接口，如下所示：

下面，我们看一下接口和实现类的代码：

接口Action

package com.liang.servlet;

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

public interface Action {
	
	public String execute(HttpServletRequest req, HttpServletResponse resp)
	throws Exception;
}

添加用户AddUserAction

package com.liang.servlet;

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

public class AddUserAction implements Action {

	@Override
	public String execute(HttpServletRequest req, HttpServletResponse resp)
			throws Exception {
		//获取参数
		String username = req.getParameter("username");
		
		UserManager userManager = new UserManager();
		//调用业务逻辑
		userManager.add(username);
		//返回跳转页面
		return "/add_success.jsp";
	}

}

package com.liang.servlet;

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

public class DelUserAction implements Action {

	@Override
	public String execute(HttpServletRequest req, HttpServletResponse resp)
			throws Exception {
<span style="white-space:pre">		</span>//获取参数
		String username = req.getParameter("username");
		
		UserManager userManager = new UserManager();
		//调用业务逻辑
		userManager.del(username);
		//返回跳转页面
		return "/del_success.jsp";
	}

}

package com.liang.servlet;

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

public class ModifyUserAction implements Action {

	@Override
	public String execute(HttpServletRequest req, HttpServletResponse resp)
			throws Exception {
		//获取参数
		String username = req.getParameter("username");

		//调用业务逻辑
		UserManager userManager = new UserManager();

		userManager.modify(username);
		//返回跳转页面
		return "/modify_success.jsp";
	}

}

package com.liang.servlet;

import java.util.List;

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

public class QueryUserAction implements Action {

	@Override
	public String execute(HttpServletRequest req, HttpServletResponse resp)
			throws Exception {
		//获取参数
		String username = req.getParameter("username");
		
		//调用业务逻辑
		UserManager userManager = new UserManager();

		List userList = userManager.query(username);
		req.setAttribute("userList", userList);
	
		userManager.query(username);
		//返回跳转页面
		return "/query_success.jsp";
	}

}

package com.liang.servlet;

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

import com.liang.action.Action;
import com.liang.action.AddUserAction;
import com.liang.action.DelUserAction;
import com.liang.action.ModifyUserAction;
import com.liang.action.QueryUserAction;
/**
 * 使用servlet做相关的控制，转向多个（V）视图
 * @author liang
 *
 */
public class TestServlet extends HttpServlet {

	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//取得访问的URI
		String reqeuestURI = request.getRequestURI();
		System.out.println(reqeuestURI);
		//截取URI，获得路径
		String path = reqeuestURI.substring(reqeuestURI.indexOf("/",1), reqeuestURI.indexOf("."));
		System.out.println(path);
		
		Action action = null;
		//等于添加，调用AddUserAction
		if ("/servlet/addUser".equals(path)) {
			action = new AddUserAction();
		//等于删除，调用DelUserAction
		}else if ("/servlet/delUser".equals(path)) {
			action = new DelUserAction();
		//等于修改，调用ModifyUserAction
		}else if ("/servlet/modifyUser".equals(path)) {
			action = new ModifyUserAction();
		//等于查询，调用QueryUserAction
		}else if ("/servlet/queryUser".equals(path)) {
			action = new QueryUserAction();
		}else {
			throw new RuntimeException("请求失败");
		}
		String forward = null;
		//返回不同的转向页面
		try {
			forward = action.execute(request, response);
		} catch (Exception e) {
			e.printStackTrace();
		}
		//根据路径,统一完成转向
		request.getRequestDispatcher(forward).forward(request, response);
	}

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request,response);
	}

}

      下篇博客【SSH进阶之路】一步步重构MVC实现Struts框架——彻底去掉判断逻辑（五），我们解决第二个问题：IF...ElSE的问题。

       源码下载