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Overview

The Spring plugin

It works by overriding the Struts ObjectFactory to enhance the creation of core framework objects. When an object is to be created, it uses the class attribute in the Struts configuration to correspond to the id attribute in the Spring configuration. If not found, the class will try to be created as usual, then be autowired by Spring. In the case of Actions, Spring 2's bean scope feature can be used to scope an Action instance to the session, application, or a custom scope, providing advanced customization above the default per-request scoping.

Features

• Allow Actions, Interceptors, and Results to be created by Spring
• Struts-created objects can be autowired by Spring after creation
• Provides two interceptors that autowire actions, if not using the Spring ObjectFactory

Usage

To enable Spring integration, simply include struts2-spring-plugin-x-x-x.jar in your application.

If you are using more than one object factory, (for example, by including both the Spring and Plexus plugins in your application,) you will need to set the struts.objectFactory property in struts.properties or in one of several XML files via Constant Configuration:

struts.objectFactory = spring

<struts>
  <constant name="struts.objectFactory" value="spring" />
  ... 
</struts>

Autowiring

The framework enables "autowiring" by default. (Autowiring means to look for objects defined in Spring with the same name as your object property). To change the wiring mode, modify the spring.autowire property.

struts.objectFactory.spring.autoWire = type

The autowire property can be set to several options.

By default, the framework will at least try to use Spring to create all its objects. If the object cannot be created by Spring, then the framework will create the object itself.

Enabling Spring integration for other application objects is a two-step process.

• Configure the Spring listener

...

<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

• Register your objects via the Spring configuration

...

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans default-autowire="autodetect">
    <bean id="personManager" class="com.acme.PersonManager"/>
    ...
</beans>

...

Since the Spring integration uses a standard Listener, it can be configured to support configuration files other than applicationContext.xml. Adding the following to your web.xml will cause Spring's ApplicationContext to be inititalized from all files matching the given pattern:

...

<!-- Context Configuration locations for Spring XML files -->
<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/applicationContext-*.xml,classpath*:applicationContext-*.xml</param-value>
</context-param>

See the Spring documentation for a full description of this parameter.

Initializing Actions from Spring

Normally, in struts.xml you specify the class for each Action. When using the default SpringObjectFactory, the framework will ask Spring to create the Action and wire up dependencies as specified by the default auto-wire behavior.

However, sometimes you might want the bean to be completely managed by Spring. This is useful, for example, if you wish to apply more complex AOP or Spring-enabled technologies, such as Acegi, to your beans. To do this, all you have to do is configure the bean in your Spring applicationContext.xml and then change the class attribute from your Action in the struts.xml to use the bean name defined in Spring instead of the class name.

Your struts.xml file would then have the Action class attributes changed.

...

<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
    <include file="struts-default.xml"/>

    <package name="default" extends="struts-default">
        <action name="foo" class="com.acme.Foo">
            <result>foo.ftl</result>
        </action>
    </package>

    <package name="secure" namespace="/secure" extends="default">
        <action name="bar" class="bar">
            <result>bar.ftl</result>
        </action>
    </package>
</struts>

The Spring plugin

Where you have a Spring bean defined in your applicationContext.xml named "bar". Note that the com.acme.Foo Action did not need to be changed, because it can be autowired.

A typical spring configuration for bar could look as following.

...

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans default-autowire="autodetect">
    <bean id="bar" class="com.my.BarClass" singleton="false"/>
    ...
</beans>

To use session-scoped components with Spring and Struts, see the Spring Session Components Workarounds analysis.

Settings

The following settings can be customized. See the developer guide.

Installation

This plugin can be installed by copying the plugin jar into your application's /WEB-INF/lib directory. No other files need to be copied or created.