把系统从Struts2 迁移到 Spring MVC六大步总结

基于struts的系统迁移到SpringMVC架构上来，共分六部曲，让系统一部一部迁移过来，本文讲的知识点以Struts2 to Spring4，但是针对其他应用场景也是可以参考的。

Step 1: 替换基本的框架库。

Firstly while migrating from struts to spring we have to replace our struts related libraries with spring libraries in lib folder.

I have mentioned basic libraries of both struts and spring for your clarification.

Struts basic libraries :

1. struts.jar
2. struts-legacy.jar
3. etc.. 

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Spring basic libraries :

1. standard.jar
2. org.springframework.asm-4.0.1.RELEASE-A.jar
3. org.springframework.beans-4.0.1.RELEASE-A.jar
4. org.springframework.context-4.0.1.RELEASE-A.jar
5. org.springframework.core-4.0.1.RELEASE-A.jar
6. org.springframework.expression-4.0.1.RELEASE-A.jar
7. org.springframework.web.servlet-4.0.1.RELEASE-A.jar
8. org.springframework.web-4.0.1.RELEASE-A.jar
9. etc..

Step 2: 修改web.xml配置文件

In this step we have to remove Action filter dispatcher for the web.xml and add Spring dipatcher servlet as Front controller
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In Strut application web.xml look like as follows

<?xml version="1.0" encoding="UTF-8"?>  
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">  
  <display-name>Struts2MyFirstApp</display-name>  
  <filter>  
        <filter-name>struts2</filter-name>  
        <filter-class>  
            org.apache.struts2.dispatcher.FilterDispatcher  
        </filter-class>  
    </filter>  

<filter-mapping>  
        <filter-name>struts2</filter-name>  
        <url-pattern>/*</url-pattern>  
    </filter-mapping>  
    <welcome-file-list>  
        <welcome-file>Login.jsp</welcome-file>  
    </welcome-file-list>  
</web-app>

In Spring application web.xml look like as follows

<?xml version="1.0" encoding="UTF-8"?>  
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">  
  <display-name>dispatcher</display-name>  
  <servlet>  
    <servlet-name>dispatcher</servlet-name>  
    <servlet-class>  
            org.springframework.web.servlet.DispatcherServlet  
        </servlet-class>  
    <load-on-startup>1</load-on-startup>  
  </servlet>  
  <servlet-mapping>  
    <servlet-name>dispatcher</servlet-name>  
    <url-pattern>/</url-pattern>  
  </servlet-mapping>  
</web-app>

Step 3: 替换Struts本身的配置文件

Now replace all struts configuration files to spring configuration file as follows

In Struts applivation struts configuration file-

<?xml version="1.0" encoding="UTF-8" ?>  
<!DOCTYPE struts PUBLIC  
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"  
    "http://struts.apache.org/dtds/struts-2.0.dtd">  
   
<struts>  
    <constant name="struts.enable.DynamicMethodInvocation" value="false" />  
    <constant name="struts.devMode" value="false" />  
    <constant name="struts.custom.i18n.resources" value="myapp" />  
   
    <package name="default" extends="struts-default" namespace="/">  
        <action name="login" class="com.geekonjavaonjava.struts2.login.LoginAction">  
            <result name="success">Welcome.jsp</result>  
            <result name="error">Login.jsp</result>  
        </action>  
    </package>  
</struts>  

In Spring application spring configuration file as follows

<?xml version="1.0" encoding="UTF-8"?>    
<beans xmlns="http://www.springframework.org/schema/beans"    
     xmlns:context="http://www.springframework.org/schema/context"    
     xmlns:p="http://www.springframework.org/schema/p"      
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    
     xsi:schemaLocation="http://www.springframework.org/schema/beans    
    http://www.springframework.org/schema/beans/spring-beans-4.0.xsd    
    http://www.springframework.org/schema/context    
    http://www.springframework.org/schema/context/spring-context-4.0.xsd">    
        
     <context:component-scan base-package="com.geekonjavaonjava.spring.login.controller" />    
        
     <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">    
        <property name="prefix">    
          <value>/WEB-INF/views/</value>    
        </property>    
        <property name="suffix">    
          <value>.jsp</value>    
        </property>    
      </bean>    
</beans>

Here, <context:component-scan> tag is used, so that spring will load all the components from given package i.e. " com.geekonjavaonjava.spring.login.controller".

Use this in Struts2 : Get value of struts property tag into jsp variable

We can use different view resolver, here I have used InternalResourceViewResolver. In which prefix and suffix are used to resolve the view by prefixing and suffixing values to the object returned by ModelAndView in action class.

Step 4: 修改JSP文件

While migration an application from struts to spring we need to change in jsp file as following

Firstly replace all tlds-

<%@ taglib uri="http://struts.apache.org/tags-bean" prefix="bean" %>  
<%@ taglib uri="http://struts.apache.org/tags-html" prefix="html" %>  
<%@ taglib uri="http://struts.apache.org/tags-logic" prefix="logic" %>  
<%@ taglib uri="http://struts.apache.org/tags-tiles" prefix="tiles" %>

Replace these with following spring taglib's :

<%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>  
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags"%>

In Struts :

<html:form action="/addLogin" method="post">

In Spring :

<form:form method="POST" commandName="loginForm" name="loginForm" action="login.do"> 

Here commandName is going to map with corresponding formbean for that jsp. Next we will see, how action is getting called with spring 4 annotations.

Step 5: 修改Action 类文件

Now following changes need to be done in action classes for struts to spring migration using annotations-

Struts Action:

package com.geekonjavaonjava.struts2.login;  
  
import com.opensymphony.xwork2.ActionSupport;  
  
/** 
 * @author geekonjava 
 * 
 */  
@SuppressWarnings("serial")  
public class LoginAction  extends ActionSupport{  
 private String username;  
    private String password;  
      
 public String execute() {  
     
        if (this.username.equals("geekonjava")   
                && this.password.equals("sweety")) {  
            return "success";  
        } else {  
         addActionError(getText("error.login"));  
            return "error";  
        }  
    }  
  
 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;  
 }  
   
}

Spring action

package com.geekonjavaonjava.spring.login.controller;  
  
import org.springframework.stereotype.Controller;  
import org.springframework.ui.ModelMap;  
import org.springframework.web.bind.annotation.RequestMapping;  
import org.springframework.web.bind.annotation.RequestMethod;  
  
/** 
 * @author GeekOnJava 
 * 
 */  
@Controller  
public class LoginController {  
   
 @RequestMapping(value="/login.do", method = RequestMethod.GET)  
 public String doLogin(ModelMap model, LoginForm loginForn) {  
 if (this.username.equals("geekonjava")   
                && this.password.equals("sweety")) {  
            model.addAttribute("message", "Login Success");  
        } else {  
            model.addAttribute("message", "Login Failure");  
        }  
         return "home";  
   
 }  
}

Step 6: 修改前端验证机制

In struts JSP file validation changes as follows

<% ActionErrors actionErrors = (ActionErrors)request.getAttribute("org.apache.struts.action.ERROR"); %>

In Spring JSP file as follows-

<form:errors path="*" cssClass="error" /> 

参考链接

---

• 把系统从Struts2 迁移到 Spring MVC六大步总结
• SpringBoot系列——i18n国际化
• SpringMVC：Struts2区别、搭建应用、流程处理、核心控制器
• Spring MVC国际化（i18n）和本地化（L10n）示例
• Spring 国际化遇到的坑 No message found under code ‘xxx.xxxx‘ for locale ‘zh_CN‘
• 项目整理：springmvc国际化配置messageSource（以中英文为例）
• Spring核心——MessageSource实现国际化
• springMVC访问静态资源——js、css、img等资源访问不到
• springmvc将后台的数据展示到jsp页面
• Model、ModelMap和ModelAndView的使用详解
• SpringMVC原理分析 | 数据处理：ModelAndView