很多人在刚开始学习struts的时候，都搞不清struts的执行流程和底层的原理，本人开始也是，但是通过深入的学习，也试着自己来写一个模拟struts的框架，下面是我自己写的一个模拟struts2的框架。
首先先写一个登陆页面：
login.jsp
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>login</title>
</head>
<body>
<form action="login.action" method="post">
用户名：<input type="text" name="username"/><br/>
密 码：<input type="password" name="password"/><br/>
<input type="submit" value="提交"/>
</form>
</body>
</html>
然后我们编写一个Servlet来处理所有以.action结尾的请求,因为这是一个MVC框架，我们的请求action以及结果视图都应在配置文件中配置，以达到解耦的目的，配置文件mystruts.xml在后面给出：
在读取配置文件时，我们需要对读取的配置信息进行保存，所以我们需要创建保存配置文件的两个实体类ActionMapping和Result类，在这里我们还需要导入dom4j这个jar包以读取配置文件：
Result.java
package org.wp.action;
/**
* 定义Result
* 保存配置的Result节点的信息
*/
public final class Result {
private String name ;//result的名称
private String url ; //result的跳转页面
private Boolean redirect ;//是否重定向
public Result(){}
public Result(String name, String url, Boolean redirect) {
this.name = name;
this.url = url;
this.redirect = redirect;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getUrl() {
return url;
}
public void setUrl(String url) {
this.url = url;
}
public Boolean getRedirect() {
return redirect;
}
public void setRedirect(Boolean redirect) {
this.redirect = redirect;
}
}
ActionMapping.java
package org.wp.action;
import java.util.HashMap;
import java.util.Map;
/**
* 定义ActionMapping
* 保存配置文件中的信息
*/
public final class ActionMapping {
private String name ; //action名称
private String className ; //权限定类名
//action对应的Result
private Map<String,Result> results = new HashMap<String, Result>();
public String getName() {
return name;
}
public ActionMapping() {
}
public ActionMapping(String name, String className) {
this.name = name;
this.className = className;
}
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;
}
}
ActionServlet.java
package org.wp.servlet;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Iterator;
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 org.wp.action.ActionMapping;
import org.wp.action.Result;
/** 核心控制器 拦截所有以.action结尾的请求 **/
public class ActionServlet extends HttpServlet {
// mappings保存所有从配置文件mystruts.xml读取的信息 key:提交的请求名，value:请求名对应的action信息
private Map<String,ActionMapping> mappings = new HashMap<String, ActionMapping>();
@SuppressWarnings("unchecked")
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//获得表单提交的所有请求参数名
Enumeration<String> en = request.getParameterNames();
//获得请求的uri 如:/MyStruts/login.action
String uri = request.getRequestURI();
//获得上下文路径 /MyStruts
String contextPath = request.getContextPath();
//通过字符串截取获得请求的action名称 即：login
String actionName = uri.substring(contextPath.length()+1,uri.lastIndexOf("."));
//通过请求的action名,获得对应的映射信息
ActionMapping mapping = mappings.get(actionName);
String className = null ;
try {
//获得对应的
className = mapping.getClassName();
} catch (Exception e) {
throw new RuntimeException("请求的action找不到");
}
Object obj = instance(className);
//获得该类的所有方法
Method[] methods = obj.getClass().getMethods();
setValue(en,methods,obj,request);
Method m = null ;
try {
m = obj.getClass().getMethod("execute",null);
String s = (String) m.invoke(obj, null);
if(s!=null){
//取得结果试图
Result r = mapping.getResults().get(s);
//判断是否是重定向
if(r.getRedirect()){
response.sendRedirect(request.getContextPath()+r.getUrl());
}else{
request.getRequestDispatcher(r.getUrl()).forward(request, response);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 通过反射为对应的Action中的属性赋值
* @param en
* @param methods
* @param obj
* @param req
*/
private void setValue(Enumeration<String> en, Method[] methods,Object obj,HttpServletRequest req) {
while (en.hasMoreElements()) {
String name = en.nextElement();
String name_ = name.substring(0,1).toUpperCase().concat(name.substring(1));
for (Method m : methods) {
if(m.getName().startsWith("set")){
String n = m.getName().substring(3);
if(n.equals(name_)){
try {
String value = req.getParameter(name);
m.invoke(obj,value);
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}
}
/**
* 通过反射初始化对应的处理类
* @param className
* @return Object
*/
private Object instance(String className) {
try {
return Class.forName(className).newInstance();
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request, response);
}
/**
* 初始化ActionServlet时，就读取指定的配置文件
*/
public void init(ServletConfig config) throws ServletException {
//获得配置文件的名字
String configName = config.getInitParameter("configName");
String[] names = configName.split(",");
for (String name : names) {
readXML(name);
}
}
/**
* 读取指定的配置文件
* @param name
*/
@SuppressWarnings("unchecked")
private void readXML(String name) {
//加载配置文件
InputStream is = this.getClass().getClassLoader().getResourceAsStream(name);
SAXReader read = new SAXReader();
try {
//通过dom4j读取配置文件
Document document = read.read(is);
//得到根元素
Element root = document.getRootElement();
//得到actions元素
Element actions = root.element("actions");
//迭代action元素
Iterator<Element> it = actions.elementIterator("action");
while(it.hasNext()){
Element action = it.next();
//封装action属性
ActionMapping mapping = new ActionMapping(
action.attributeValue("name"),action.attributeValue("class"));
//迭代result元素
Iterator<Element> results = action.elementIterator("result");
while(results.hasNext()){
Element result = results.next();
//封装result属性
Result res = new Result(result.attributeValue("name"),
result.getText(),Boolean.valueOf(result.attributeValue("redirect")));
mapping.getResults().put(res.getName(),res);
}
//保存配置信息
mappings.put(mapping.getName(),mapping);
}
} catch (DocumentException e) {
e.printStackTrace();
}
}
}
写好核心控制器之后，在web.xml中部署该ActionServlet:
<?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>org.wp.servlet.ActionServlet</servlet-class>
<init-param>
<param-name>configName</param-name>
<param-value>mystruts.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>ActionServlet</servlet-name>
<url-pattern>*.action</url-pattern>
</servlet-mapping>
</web-app>
然后定义Action接口：
package org.wp.action;
/**
* 定义Action接口
*/
public interface Action {
//定义结果试图常量
public static final String SUCCESS = "success" ;
public static final String INPUT = "input" ;
public static final String ERROR = "error" ;
public static final String LOGIN = "login" ;
/**
* 定义execute方法
* @return String
* @throws Exception
*/
public String execute() throws Exception;
}
提供一个实现了Action接口的实现类ActionSupport：
package org.wp.action;
/**
* 定义ActionSupport并实现Action接口
*
*/
public class ActionSupport implements Action {
/**
* 实现execute方法，并返回SUCCESS试图
*/
public String execute() throws Exception {
return SUCCESS;
}
}
然后编写自己的Action类LoginAction来处理登陆：
package entity;
package org.wp.action;
public class LoginAction extends ActionSupport {
private String username ;//接收与表单域名称相同的参数值
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 execute() throws Exception {
if(username.equals("admin")&&password.equals("admin"))
return SUCCESS;
else
return INPUT ;
}
}
然后在mystruts.xml对请求和视图进行配置：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mystruts[
<!ELEMENT mystruts (actions*)>
<!ELEMENT actions (action*)>
<!ELEMENT action (result*)>
<!ATTLIST action name CDATA #REQUIRED class CDATA #REQUIRED>
<!ATTLIST result name CDATA #REQUIRED redirect (true|false) "true">
]>
<mystruts>
<actions>
<action name="login" class="org.wp.action.LoginAction">
<result name="success">/register.jsp</result>
<result name="input">/index.jsp</result>
</action>
</actions>
</mystruts>
这样一个自定义的struts框架就完成了，看看也不是很复杂吧！然后我们通过访问http://localhost:8080/MyStruts/login.jsp 提交后ActionServlet就会进行拦截，然后就会去mystruts.xml中去找到与提交的action名相同的对应的Action处理类，通过执行execute方法来跳转到相应的视图。