引入了 struts2-spring-plugins 包后 Spring 就会管理你的 Action

Struts2 与 Spring 结合，使用 Spring 来管理 Action 实例，在项目中引入了struts2-spring-plugin-2.2.1.jar 包。然后想到的是既然是要用 Spring 来管理 Action 实例，就得在 struts.xml 里加上：

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

或者是在 struts.properties 里加上一条属性：

struts.objectFactory = spring

OK，这也没问题，然而有次在某个测试项目中想暂时不用 Spring 来管理 Bean，于是把上面的配置去了，也把 web.xml 中的相关 Spring 的 ContextLoaderListener 也格啦。容器启动的时候却发现：

INFO: Initializing Struts-Spring integration...
Jan 20, 2011 7:32:08 PM org.apache.struts2.spring.StrutsSpringObjectFactory <init>
SEVERE: ********** FATAL ERROR STARTING UP STRUTS-SPRING INTEGRATION **********
Looks like the Spring listener was not configured for your web app!
Nothing will work until WebApplicationContextUtils returns a valid ApplicationContext.
You might need to add the following to web.xml:
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>
Jan 20, 2011 7:32:08 PM org.apache.catalina.core.StandardContext filterStart
SEVERE: Exception starting filter action2
java.lang.NullPointerException
 at com.opensymphony.xwork2.spring.SpringObjectFactory.getClassInstance(SpringObjectFactory.java:189)
 at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.verifyResultType(XmlConfigurationProvider.java:479)
 at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addResultTypes(XmlConfigurationProvider.java:450)
 at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:407)
 at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:239)
 at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:111)
 at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reload(DefaultConfiguration.java:152)
 at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:52)
 at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:395)
 at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:452)
 at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:201)

本文原始链接 http://unmi.cc/struts2-spring-plugins-action/, 来自 隔叶黄莺 Unmi Blog

难道 Struts2 默认就是用 Spring 来管理 Bean 吗？也不对啊，Struts2 并不依赖 Spring 啊。原来是在 struts2-spring-plugin-2.2.1.jar 中的 struts-plugin.xml 中是这样的配置：

< struts >
    < bean type = "com.opensymphony.xwork2.ObjectFactory" name = "spring" class = "org.apache.struts2.spring.StrutsSpringObjectFactory" />

    <!--  Make the Spring object factory the automatic default -->
    < constant name = "struts.objectFactory" value = "spring" />

    < constant name = "struts.class.reloading.watchList" value = "" />
    < constant name = "struts.class.reloading.acceptClasses" value = "" />
    < constant name = "struts.class.reloading.reloadConfig" value = "false" />

    < package name = "spring-default" >
        < interceptors >
            < interceptor name = "autowiring" class = "com.opensymphony.xwork2.spring.interceptor.ActionAutowiringInterceptor" />
            < interceptor name = "sessionAutowiring" class = "sessionAutowiring" class = "org.apache.struts2.spring.interceptor.SessionContextAutowiringInterceptor" />
        </ interceptors >
    </ package >
</ struts >

看到里面的 <constant name="struts.objectFactory" value="spring" />，只要引入了 struts2-spring-plugin 插件包就启作用了，原来我们自己在 struts.xml 或是 struts.properties 中的设置的该属性完全是多此一举，要知道 spring 这个 objectfactory 也是在这里边声明的啊。只要引入了 struts2-spring 插件包即可，最好还是从 strtus.xml 或 struts.properties 中把该项目配置拿掉。

 

同时也多请留意下里面配置的其他几个属性，肯定蕴藏着不少学问的。