自定义一个MVC框架

构建基于MVC模式的框架，必须要满足MVC模式的结构要求。下面我们就以用户登录的业务为例，按照MVC模式进行程序设计。使用MVC框架开发登录程序的结构如图所示。

如果希望按照图所示的程序结构实现登录功能，需要哪些步骤呢？

 

可参考的步骤如下。

(1)将所有的请求发送到控制器（基于Servlet API实现），并且系统中最好只有一个控制器负责接收请求。

(2)定义一个Action接口，用于代表请求的处理，并实现具体请求的处理，如登录。

(3)控制器根据请求的路径判断由哪个Action执行操作。

(4) Action调用模型，完成业务操作，获取操作的结果，最后将结果返回给视图（页面）。

具体代码参考如下：

1) ===============Action接口======================

package com.obtk.actions;public interface Action {String SUCCESS="success";String INPUT="input";/** * 处理请求 * @return */String excute();}

2) =============一般父类ActionSupport===================

package com.obtk.actions;public class ActionSupport implements Action {public String excute() {return this.SUCCESS;}}

3)  ============后端控制器LoginAction=====================

package com.obtk.actions;public class LoginAction extends ActionSupport {private String userName;private String passWord;public String getUserName() {return userName;}public void setUserName(String userName) {this.userName = userName;}public String getPassWord() {return passWord;}public void setPassWord(String passWord) {this.passWord = passWord;}public String excute() {if(userName.equals("jack") && passWord.equals("123")){return SUCCESS;}else{return "input";}}}

4) ==================配置文件mystruts.xml===================

<!DOCTYPE mystruts[<!ELEMENT mystruts (package)><!ELEMENT package (action*)><!ELEMENT action (result*)><!ELEMENT result (#PCDATA)><!ATTLIST action name CDATA #REQUIRED                 class CDATA #REQUIRED><!ATTLIST result name CDATA #IMPLIED                 redirect (true|false) "false">                 ]><mystruts><package><action name="Login" class="com.obtk.actions.LoginAction"><result name="success">index.jsp</result><result name="input" redirect="true">Login.jsp</result></action><action name="Register" class="com.obtk.actions.RegisterAction"><result  name="success">Login.jsp</result><result name="input" redirect="true">Register.jsp</result></action></package></mystruts>

5)  ========================ActionMapping(用于保存mystruts.xml信息)=================

package com.obtk.entity;import java.util.Map;public class ActionMapping {private String actionName;private String className;private Map<String, Result> resultMap;public String getActionName() {return actionName;}public void setActionName(String actionName) {this.actionName = actionName;}public String getClassName() {return className;}public void setClassName(String className) {this.className = className;}public Map<String, Result> getResultMap() {return resultMap;}public void setResultMap(Map<String, Result> resultMap) {this.resultMap = resultMap;}}

6)  ========================Result(也用于保存mystruts.xml信息)=================

package com.obtk.entity;public class Result {private String name;private String isRedirect;private String url;public String getName() {return name;}public void setName(String name) {this.name = name;}public String getIsRedirect() {return isRedirect;}public void setIsRedirect(String isRedirect) {this.isRedirect = isRedirect;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}}

7)  ================ActionServlet(前端核心控制器)======================

package com.obtk.servlets;import java.io.IOException;import java.io.InputStream;import java.io.PrintWriter;import java.lang.reflect.Method;import java.util.Enumeration;import java.util.HashMap;import java.util.List;import java.util.Map;import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.dom4j.Document;import org.dom4j.DocumentException;import org.dom4j.Element;import org.dom4j.io.SAXReader;import com.obtk.entity.ActionMapping;import com.obtk.entity.Result;public class ActionServlet extends HttpServlet {private Map<String, ActionMapping> actionMap=new HashMap<String, ActionMapping>();public void init(ServletConfig config) throws ServletException {String configXml=config.getInitParameter("configName");SAXReader reader=new SAXReader();InputStream input=this.getClass().getClassLoader().getResourceAsStream(configXml);try {//1.获得文档对象Document doc=reader.read(input);//2.获得根元素Element root=doc.getRootElement();Element packageEle=root.element("package");List<Element> actionEleList=packageEle.elements("action");Element actionEle=null;ActionMapping oneAction=null;for(int i=0;i<actionEleList.size();i++){oneAction=new ActionMapping();actionEle=actionEleList.get(i);oneAction.setActionName(actionEle.attributeValue("name"));oneAction.setClassName(actionEle.attributeValue("class"));List<Element> resultEleList=actionEle.elements("result");Map<String,Result> resultMap=new HashMap<String, Result>();Result oneReuslt=null;Element resultEle=null;for(int j=0;j<resultEleList.size();j++){oneReuslt=new Result();resultEle=resultEleList.get(j);oneReuslt.setName(resultEle.attributeValue("name"));oneReuslt.setIsRedirect(resultEle.attributeValue("redirect"));oneReuslt.setUrl(resultEle.getText());resultMap.put(oneReuslt.getName(), oneReuslt);}oneAction.setResultMap(resultMap);actionMap.put(oneAction.getActionName(), oneAction);}} catch (DocumentException e) {e.printStackTrace();}}public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doPost(request,response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String requestUrl=request.getRequestURI();System.out.println("url:"+requestUrl);///mystruts/Login.do 得到action名称String actionName=requestUrl.substring(requestUrl.lastIndexOf('/')+1, requestUrl.lastIndexOf('.'));System.out.println("action:"+actionName);//获得某个action的配置ActionMapping theMapp=actionMap.get(actionName);//得到类的具体路径String claName=theMapp.getClassName();try {Class theCla=Class.forName(claName);Object theObj=theCla.newInstance();//获得所有表单名称Enumeration<String> params=request.getParameterNames();//通过反射执行类的set方法，设置表单参数setParamValues(theCla,theObj,params,request);//得到处理业务逻辑的方法对象Method finalMethod=theCla.getDeclaredMethod("excute", null);//执行方法，返回要跳转的地址String url=(String)finalMethod.invoke(theObj, null);Map<String, Result> resultMap=theMapp.getResultMap();Result theResult=resultMap.get(url); //从map对象里面找到最终要跳转的url//找到要跳转的具体jspString jspName=theResult.getUrl();request.getRequestDispatcher(jspName).forward(request, response);} catch (Exception e) {e.printStackTrace();} }/** * 通过反射设置表单参数值 * @param theCla * @param theObj * @param params * @param request */void setParamValues(Class theCla,Object theObj,Enumeration<String> params,HttpServletRequest request){String theParam="";Method theSetMeth=null;String methName="";while(params.hasMoreElements()){theParam=params.nextElement();methName="set"+theParam.substring(0, 1).toUpperCase()+theParam.substring(1);try {theSetMeth=theCla.getDeclaredMethod(methName, new Class[]{String.class});theSetMeth.invoke(theObj, request.getParameter(theParam));} catch (Exception e) {e.printStackTrace();} }}}

8) ================web.xml=======================

<?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">    <servlet>    <servlet-name>ActionServlet</servlet-name>    <servlet-class>com.obtk.servlets.ActionServlet</servlet-class>    <init-param>  <param-name>configName</param-name>  <param-value>config/mystruts.xml</param-value>      </init-param>    <load-on-startup>1</load-on-startup>  </servlet>  <servlet-mapping>    <servlet-name>ActionServlet</servlet-name>    <url-pattern>*.do</url-pattern>  </servlet-mapping>    <welcome-file-list>    <welcome-file>Login.jsp</welcome-file>  </welcome-file-list></web-app>

9)  =======================Login.jsp================

<%@ 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>登录</title><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0"> <style type="text/css">#show{ border: 2px solid blue; width:400px;}#err{ color: red;}</style>   </head>  <body><div id="show"><form action="Login.do" method="post"><div id="err">${requestScope.errMsg }</div><table border="1px" cellpadding="0"><tr><td>请输入用户名:</td><td><input type="text" name="userName" /></td></tr><tr><td>请输入密码:</td><td><input type="password" name="passWord" /></td></tr><tr><td colspan="2"><input type="submit" value="提交" /></td></tr></table></form></div></body></html>

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