In this tutorial we will see the migration of a web application made in struts to spring mvc. Struts to Spring migration we will do step by step. Here I will share you step by step approach to migrate application from Struts to Spring using annotations.

Step 1: Replace struts libraries with spring libraries.

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: Change made to web.xml file for struts to spring migration

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>springApp</display-name>

<servlet>

<servlet-name>springApp</servlet-name>

<servlet-class>

org.springframework.web.servlet.DispatcherServlet

</servlet-class>

<load-on-startup>1</load-on-startup>

</servlet>

<servlet-mapping>

<servlet-name>springApp</servlet-name>

<url-pattern>/</url-pattern>

</servlet-mapping>

</web-app>

Step 3: Replace config files for struts to spring migration

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

In Struts application 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> <span style="font-family: Times New Roman;"><span style="white-space: normal;">

</span></span>

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".

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.

For other three Steps see the reference