夜譚struts的運行原理

談起MVC設計模式，不得不說說struts。作爲經典的SSH框架之一的struts以獨具匠心的攔截器和公用servlet設計樣式讓人耳目一新，今天我要和大家一起探討的是關於以公共、唯一的servlet爲基礎，多個操作action爲核心的MVC設計框架。

下面是我模擬struts的運行原理寫的一個程序，希望對大家有用！

首先跟大家分享框架結構圖：

第一步，容器管理的框架ActionServlet初始化獲取ActionConfig.xml配置文件

第二步，創建ActionMappingManager映射文件管理器，將配置信息以ActionMapping的格式保存在ActionMappingManager裏

第三步，ActionServlet獲取*.jsp文件的提交，到ActionMappingManager裏面查找相對應的ActionMapping

第四步，通過ActionManager實例化Action對象

第五步，調用該對象進行邏輯處理，並返回Action

第六步，操作完畢後返回ActionServlet，再跳轉到響應的*.jsp

 

看完結構圖，由我帶大家瀏覽一下設計流程：

1、首先創建一個Web Project

2、然後需要導入一個解析XML文件的jar包dom4j-1.6.1.jar

3、需要在src下寫一個名叫ActionConfig.dtd文件，這個文件用於規範ActionConfig.XML配置文件

<!ELEMENT ActionConfig (actions)>
<!ELEMENT actions (action*)>
<!ELEMENT action (result*)>
<!ATTLIST action
	name CDATA #REQUIRED
	class CDATA #REQUIRED
>
<!ELEMENT result (#PCDATA)>
<!ATTLIST result
	name CDATA #IMPLIED
	redirect (true|false) "false">

4、下面就開始寫各個類

    a、統一的ActionServlet類

package com.huan.frame;

import java.io.IOException;

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 ActionServlet extends HttpServlet {
	private ActionMappingManager manager;
	@Override
	public void init(ServletConfig config) throws ServletException {
		// TODO Auto-generated method stub
		String configStr = config.getInitParameter("config");
		String[] files;
		//判斷是否配置初始化參數
		if(configStr == null || configStr.isEmpty())
			files = new String[]{"ActionConfig.xml"};
		else
			files = configStr.split(",");
		System.out.println("映射管理器運行");
		manager = new ActionMappingManager(files);
	}

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		doPost(req, resp);
	}

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		try {
			ActionMapping mapping = getActionMapping(request);
			if(mapping == null)
				throw new Exception("doPost裏mapping沒有值！");
			ActionSuport action = ActionManager.createAction(mapping.getClassName());
			if(action == null)
				throw new Exception("doPost裏action對象未生成！");
			String isSuceess = action.execute(request, response);
			
			System.out.println(mapping.getResult(isSuceess).getPath());
			if(mapping.getResult(isSuceess).isRedirect())
				response.sendRedirect(mapping.getResult(isSuceess).getPath());
			else
				request.getRequestDispatcher(mapping.getResult(isSuceess).getPath()).forward(request, response);
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public ActionMapping getActionMapping(HttpServletRequest request){
		//獲取請求的uri
		String uri = request.getRequestURI();
		//獲取上下文路徑
		String contextPath = request.getContextPath();
		//截取上下文路徑以後的部分
		String actionPath = uri.substring(contextPath.length());
		//獲取action名稱
		String actionName = actionPath.substring(1,actionPath.lastIndexOf('.')).trim();
		return manager.getActionMappingByName(actionName);
	}
	
}

    b、規範接口ActionSuport類

package com.huan.frame;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.*;

public interface ActionSuport {
	//action需要實現的接口
		public String execute(HttpServletRequest request,HttpServletResponse response)
							throws ServletException,IOException;
}

    c、映射文件ActionMapping類和返回結果Result類

package com.huan.frame;

import java.util.*;

public class ActionMapping {
	private String name;
	private String className;
	private Map<String,Result> results = new HashMap<String,Result>();
	public ActionMapping() {
		super();
	}
	public ActionMapping(String name, String className,
			Map<String, Result> results) {
		super();
		this.name = name;
		this.className = className;
		this.results = results;
	}
	
	public void addResult(String key,Result value){
		results.put(key, value);
	}
	public Result getResult(String name){
		return results.get(name);
	}
	
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getClassName() {
		return className;
	}
	public void setClassName(String className) {
		this.className = className;
	}
	public Map<String, Result> getResults() {
		return results;
	}
	public void setResults(Map<String, Result> results) {
		this.results = results;
	}
}

package com.huan.frame;

public class Result {
	private String name;
	private boolean isRedirect;
	private String path;
	public Result() {
		super();
	}
	public Result(String name, boolean isRedirect, String path) {
		super();
		this.name = name;
		this.isRedirect = isRedirect;
		this.path = path;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public boolean isRedirect() {
		return isRedirect;
	}
	public void setRedirect(boolean isRedirect) {
		this.isRedirect = isRedirect;
	}
	public String getPath() {
		return path;
	}
	public void setPath(String path) {
		this.path = path;
	}
}

    d、映射文件實例化ActionManager類

package com.huan.frame;

public class ActionManager {
	public static ActionSuport createAction(String className){
		try {
			return (ActionSuport)Class.forName(className).newInstance();
		} catch (InstantiationException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (IllegalAccessException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return null;
	}
}

    e、映射文件管理器ActionMappingManager類

package com.huan.frame;

import java.io.*;
import java.util.*;

import org.dom4j.*;
import org.dom4j.io.SAXReader;

public class ActionMappingManager {
	private static Map<String,ActionMapping> actionMappings = new HashMap<String,ActionMapping>();
	
	public ActionMappingManager(String[] files){
		try {
			if(files == null || files.length == 0)
				throw new Exception("配置文件爲空！");
			for (String file : files) {
				read(file);
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	private void read(String file){
		try {
			if(file == null || file.isEmpty())
				throw new Exception("文件不能爲空！");
			//加上“/”和文件名，系統將在src下面找該文件
			InputStream is = getClass().getResourceAsStream("/" + file);
			if(is == null)	throw new Exception("沒有找到" + file + "文件！");
			Document doc = new SAXReader().read(is);
			if(doc == null)	throw new Exception("文件解析失敗！");
			Element root = doc.getRootElement();
			Iterator<Element> actionsIt = root.elementIterator("actions");
			Element actions = actionsIt.next();
			Iterator<Element> actionIt = actions.elementIterator("action");
			ActionMapping mapping = null;
			Element node = null;
			Iterator<Element> resultIt = null;
			String resultStr,redirectStr,pathStr;
			Result result;
			System.out.println("進入讀取循環");
			while(actionIt.hasNext()){
				node = actionIt.next();
				mapping = new ActionMapping();
				mapping.setName(node.attributeValue("name"));
				mapping.setClassName(node.attributeValue("class"));
				resultIt = node.elementIterator("result");
				System.out.println("action循環");
				while(resultIt.hasNext()){
					node = resultIt.next();
					resultStr = node.attributeValue("name");
					redirectStr = node.attributeValue("redirect");
					pathStr = node.getText();
					result = new Result();
					if(resultStr == null || resultStr.isEmpty()){
						result.setName("success");
						if(redirectStr == null || redirectStr.isEmpty() || redirectStr.equals("false"))
							result.setRedirect(false);
						else
							result.setRedirect(true);
						result.setPath(pathStr);
					}else{
						result.setName(resultStr);
						if(redirectStr == null || redirectStr.isEmpty() || redirectStr.equals("false"))
							result.setRedirect(false);
						else
							result.setRedirect(true);
						result.setPath(pathStr);
					}
					System.out.println("result循環");
					mapping.addResult(resultStr, result);
				}
				actionMappings.put(mapping.getName(), mapping);
				System.out.println("加載配置文件完畢！");
			}
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	public ActionMapping getActionMappingByName(String name){
		ActionMapping mapping = null;
		try {
			if(actionMappings.isEmpty()) throw new Exception("映射管理沒有數據！");
			mapping = actionMappings.get(name);
			if(mapping == null) throw new Exception("映射爲空！");
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		return mapping;
	}
}

5、寫完各個類之後就是打包，右鍵點擊項目export，保存爲JAR file文件即可！

 

瀏覽完設計流程，就讓我們測試一下我們的MVC框架吧，let's go！

1、創建一個Web Project項目，導入咱們剛剛寫好的包，還要導入dom4j-1.6.1.jar，別忘了！

2、在web.xml文件裏配置框架的servlet

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" 
	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_3_0.xsd">
  <display-name></display-name>	
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
  
  <servlet>
  	<servlet-name>servlet</servlet-name>
  	<servlet-class>com.huan.frame.ActionServlet</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>servlet</servlet-name>
  	<url-pattern>*.action</url-pattern>
  </servlet-mapping>
  
</web-app>

3、創建一個dao層，寫一個虛擬數據庫

package com.huan.test;

import java.util.*;

import com.huan.entity.User;

public class UserDaoImp {
	private static List<User> list = new ArrayList<User>();
	//虛擬數據庫
	static{
		list.add(new User("111","aaa"));
		list.add(new User("222","bbb"));
		list.add(new User("333","ccc"));
	}
	
	public User getUserByName(String name){
		Iterator<User> it = list.iterator();
		User user = null;
		while(it.hasNext()){
			user = it.next();
			if(user.getName().equals(name))
			return user;
		}
		return null;
	}
}

4、創建頁面

<%@ 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>
<form action="LoginAction.action" method="post">
	用戶名:<input type="text" name="username"/>
	密碼:<input type="password" name="password"/>
	<input type="submit" value="提交"/>
</form>
</body>
</html>

5、創建Action

package com.huan.test;

import java.io.IOException;

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

import com.huan.entity.User;
import com.huan.frame.ActionSuport;

public class LoginAction implements ActionSuport {
	private UserDaoImp user = new UserDaoImp();
	@Override
	public String execute(HttpServletRequest request, HttpServletResponse arg1)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		request.setCharacterEncoding("UTF-8");
		String name = request.getParameter("username");
		String pwd = request.getParameter("password");
		User u = user.getUserByName(name);
		if(u == null){
			request.setAttribute("msg", "找不到該用戶！");
		}else if(!u.getPwd().equals(pwd)){
			request.setAttribute("msg", "密碼錯誤！");
		}else{
			return "success";
		}
		return "error";
	}

}

6、在src下創建ActionConfig.xml配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE ActionConfig[
<!ELEMENT ActionConfig (actions)>
<!ELEMENT actions (action*)>
<!ELEMENT action (result*)>
<!ATTLIST action
	name CDATA #REQUIRED
	class CDATA #REQUIRED
>
<!ELEMENT result (#PCDATA)>
<!ATTLIST result
	name CDATA #IMPLIED
	redirect (true|false) "false">
]>

<ActionConfig>
	<actions>
		<action name="LoginAction" class="com.huan.test.LoginAction">
			<result name="success">index.jsp</result>
		</action>
	</actions>
</ActionConfig>	

當你順利的跳轉到index.jsp界面的時候，就說明自定義MVC框架沒問題！

今天的struts運行原理就跟大家探討到這裏，想交流的朋友請留言或私信。