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 {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//取得访问的URIString 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 ="/del_success.jsp";//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);}@Overrideprotected 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 {@Overridepublic 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";}}
删除用户DelUserAction
package com.liang.servlet;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class DelUserAction implements Action {@Overridepublic 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";}}
修改用户ModifyUserAction
package com.liang.servlet;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class ModifyUserAction implements Action {@Overridepublic 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";}}
查询用户QueryUserAction
package com.liang.servlet;import java.util.List;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class QueryUserAction implements Action {@Overridepublic 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";}}
我们再对比看一下我们封装之后的TestServlet
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 {@Overrideprotected void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//取得访问的URIString 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AddUserActionif ("/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);}@Overrideprotected void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request,response);}}
通过对比，我们可以发现简单了很多，但是实现的道理基本一样，仍然是将path截取出来，做相应的判断，进入对应的分支，New一个刚写的Action，New谁调谁，但是此时仅仅是完成了功能，系统并不灵活，IF...ELSE并没有去掉，扩展性不好，不能适用需求。
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
