Dependency Injection in Struts2 Accessing Session

2019-01-03 06:54发布

站内问答 / Java
1154 2 5

Recently I needed to use DI in Struts2. I know it uses it's own DI implementation like Guice but not Guice, as far as I couldn't find some annotations suitable to set the scope for injected beans. To be short, I created a bean

//@Repository
//@Scope("session")
public class Session {

    private Map<String, Object> map = new HashMap<>();

    public Map<String, Object> getMap() {
        return map;
    }

    public void setMap(Map<String, Object> map) {
        this.map = map;
    }
}

I have commented the annotations used with Spring beans. I was successfully created the same bean via spring DI and set the scope in which my objects were injected. Now, I want to do the same with Struts2 and DI. For this purpose I created the bean definition in struts.xml

<bean name="session" class="jspbean.struts.Session" scope="session"/>

and simple action to get that bean created and injected into my action

public class DefaultAction extends ActionSupport {

    private Session session;

    //  @Autowired
    @Inject("session")
    public void setSession(Session session) {
        this.session = session;
    }

    public Session getSession() {
        return session;
    }

    private Map<String, String> myMap = new HashMap<String, String>();

    public Map<String, String> getMyMap() {
        return myMap;
    }

    public void setMyMap(Map<String, String> myMap) {
        this.myMap = myMap;
    }

    @Override
    public String execute() throws Exception {
        //populate my bean with sample data
        myMap.put("q1", "Question1");
        myMap.put("q2", "Question2");
        session.getMap().put("myMap", myMap);
        return SUCCESS;
    }
}

in the JSP I use simple iterator over session bean

<s:iterator value="session.map['myMap']">
  <s:textfield name="myMap['%{key}']" value="%{value}" theme="simple" size="10" /><br>
</s:iterator>

Now, when I'm running this smple application I've got the exception

Stacktraces
Unable to instantiate Action, jspbean.struts.DefaultAction, defined for '' in namespace '/'java.lang.IllegalStateException: Scope strategy not set. Please call Container.setScopeStrategy().

    com.opensymphony.xwork2.DefaultActionInvocation.createAction(DefaultActionInvocation.java:316)
    com.opensymphony.xwork2.DefaultActionInvocation.init(DefaultActionInvocation.java:397)
    com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:194)
    org.apache.struts2.impl.StrutsActionProxy.prepare(StrutsActionProxy.java:63)
    org.apache.struts2.impl.StrutsActionProxyFactory.createActionProxy(StrutsActionProxyFactory.java:39)
    com.opensymphony.xwork2.DefaultActionProxyFactory.createActionProxy(DefaultActionProxyFactory.java:58)
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:536)
    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
    org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    java.lang.Thread.run(Unknown Source)


java.lang.RuntimeException: java.lang.IllegalStateException: Scope strategy not set. Please call Container.setScopeStrategy().

    com.opensymphony.xwork2.inject.ContainerImpl$MethodInjector.inject(ContainerImpl.java:301)
    com.opensymphony.xwork2.inject.ContainerImpl.inject(ContainerImpl.java:492)
    com.opensymphony.xwork2.inject.ContainerImpl$6.call(ContainerImpl.java:530)
    com.opensymphony.xwork2.inject.ContainerImpl$6.call(ContainerImpl.java:528)
    com.opensymphony.xwork2.inject.ContainerImpl.callInContext(ContainerImpl.java:584)
    com.opensymphony.xwork2.inject.ContainerImpl.inject(ContainerImpl.java:528)
    com.opensymphony.xwork2.ObjectFactory.injectInternalBeans(ObjectFactory.java:139)
    com.opensymphony.xwork2.spring.SpringObjectFactory.autoWireBean(SpringObjectFactory.java:208)
    com.opensymphony.xwork2.spring.SpringObjectFactory.buildBean(SpringObjectFactory.java:183)
    com.opensymphony.xwork2.spring.SpringObjectFactory.buildBean(SpringObjectFactory.java:154)
    com.opensymphony.xwork2.ObjectFactory.buildBean(ObjectFactory.java:151)
    com.opensymphony.xwork2.ObjectFactory.buildAction(ObjectFactory.java:121)
    com.opensymphony.xwork2.DefaultActionInvocation.createAction(DefaultActionInvocation.java:297)
    com.opensymphony.xwork2.DefaultActionInvocation.init(DefaultActionInvocation.java:397)
    com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:194)
    org.apache.struts2.impl.StrutsActionProxy.prepare(StrutsActionProxy.java:63)
    org.apache.struts2.impl.StrutsActionProxyFactory.createActionProxy(StrutsActionProxyFactory.java:39)
    com.opensymphony.xwork2.DefaultActionProxyFactory.createActionProxy(DefaultActionProxyFactory.java:58)
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:536)
    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
    org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    java.lang.Thread.run(Unknown Source)


java.lang.IllegalStateException: Scope strategy not set. Please call Container.setScopeStrategy().

    com.opensymphony.xwork2.inject.InternalContext.getScopeStrategy(InternalContext.java:53)
    com.opensymphony.xwork2.inject.Scope$5$1.create(Scope.java:130)
    com.opensymphony.xwork2.inject.ContainerImpl$ParameterInjector.inject(ContainerImpl.java:469)
    com.opensymphony.xwork2.inject.ContainerImpl.getParameters(ContainerImpl.java:484)
    com.opensymphony.xwork2.inject.ContainerImpl.access$000(ContainerImpl.java:34)
    com.opensymphony.xwork2.inject.ContainerImpl$MethodInjector.inject(ContainerImpl.java:299)
    com.opensymphony.xwork2.inject.ContainerImpl.inject(ContainerImpl.java:492)
    com.opensymphony.xwork2.inject.ContainerImpl$6.call(ContainerImpl.java:530)
    com.opensymphony.xwork2.inject.ContainerImpl$6.call(ContainerImpl.java:528)
    com.opensymphony.xwork2.inject.ContainerImpl.callInContext(ContainerImpl.java:584)
    com.opensymphony.xwork2.inject.ContainerImpl.inject(ContainerImpl.java:528)
    com.opensymphony.xwork2.ObjectFactory.injectInternalBeans(ObjectFactory.java:139)
    com.opensymphony.xwork2.spring.SpringObjectFactory.autoWireBean(SpringObjectFactory.java:208)
    com.opensymphony.xwork2.spring.SpringObjectFactory.buildBean(SpringObjectFactory.java:183)
    com.opensymphony.xwork2.spring.SpringObjectFactory.buildBean(SpringObjectFactory.java:154)
    com.opensymphony.xwork2.ObjectFactory.buildBean(ObjectFactory.java:151)
    com.opensymphony.xwork2.ObjectFactory.buildAction(ObjectFactory.java:121)
    com.opensymphony.xwork2.DefaultActionInvocation.createAction(DefaultActionInvocation.java:297)
    com.opensymphony.xwork2.DefaultActionInvocation.init(DefaultActionInvocation.java:397)
    com.opensymphony.xwork2.DefaultActionProxy.prepare(DefaultActionProxy.java:194)
    org.apache.struts2.impl.StrutsActionProxy.prepare(StrutsActionProxy.java:63)
    org.apache.struts2.impl.StrutsActionProxyFactory.createActionProxy(StrutsActionProxyFactory.java:39)
    com.opensymphony.xwork2.DefaultActionProxyFactory.createActionProxy(DefaultActionProxyFactory.java:58)
    org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:536)
    org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
    org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)
    org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
    org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
    java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    java.lang.Thread.run(Unknown Source)

The exception says that I need to set the scope strategy. So, my question is what is this scope strategy and how it could be implemented in my simple application. Also, there is annotation @Scoped, how this annotations to apply in my case?

My example references:

  1. bean configuration

2条回答
The star\"
2楼-- · 2019-01-03 07:35

I believe Luiggi's comment is correct. The "@Inject" needs to be on the field value itself, not on the setter.

 @Inject("session")
 private Session session;

As long as you've got the "session" bean defined in struts.xml or registered it with the Struts container it should be able to find it and inject it. From your explanation that seems to be the case.

For some more specific information check this Discussion on the Struts User list: Struts user question on built-in DI

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女痞
3楼-- · 2019-01-03 07:36

Let's start from looking what is a Scope.Strategy by looking at the docs. It says

Pluggable scoping strategy. Enables users to provide custom implementations of request, session, and wizard scopes. Implement and pass to Container.setScopeStrategy(com.opensymphony.xwork2.inject.Scope.Strategy)

Ok, assume I want to implement session scope. Then I need to know the place where I could implement it. The framework has it's extension points where where you could plug your extensions or simply extend the default implementation and provide your own custom implementations. This is easy done via looking at the BeanSelectionProvider. Then analyzing the stacktraces I decided the best point would be to extend the DefaultActionProxyFactory. Extending it requires to extend the DefaultActionProxy also.

public class MyActionProxyFactory extends DefaultActionProxyFactory {

    public MyActionProxyFactory() {
        super();
    }

    @Override
    public ActionProxy createActionProxy(ActionInvocation inv, String namespace, String actionName, String methodName, boolean executeResult, boolean cleanupContext) {

        MyActionProxy proxy = new MyActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);
        container.inject(proxy);
        container.setScopeStrategy(new MyScopeStrategy());
        proxy.prepare();
        return proxy;
    }
}

public class MyActionProxy extends DefaultActionProxy {

    protected MyActionProxy(ActionInvocation inv, String namespace, String actionName, String methodName, boolean executeResult, boolean cleanupContext) {
        super(inv, namespace, actionName, methodName, executeResult, cleanupContext);
    }

    @Override
    protected void prepare() {
        super.prepare();
    }
}

public class MyScopeStrategy implements Scope.Strategy {

    @Override
    public <T> T findInRequest(Class<T> type, String name, Callable<? extends T> factory) throws Exception {
        return null;
    }

    @Override
    public <T> T findInSession(Class<T> type, String name, Callable<? extends T> factory) throws Exception {

        ActionContext context = ActionContext.getContext();
        SessionMap<String, T> sessionMap = (SessionMap<String, T>) context.getSession();

        if (sessionMap == null) {
            sessionMap = new SessionMap<String, T>(ServletActionContext.getRequest());
            context.setSession((Map<String, Object>) sessionMap);
        }

        T obj = sessionMap.get(name);

        if (obj == null) {
            obj = factory.call();
            sessionMap.put(name, obj);
        }
        return obj;
    }

    @Override
    public <T> T findInWizard(Class<T> type, String name, Callable<? extends T> factory) throws Exception {
        return null;
    }
}

In the configuration file struts.xml you should set the property

<constant name="struts.actionProxyFactory" value="jspbean.struts.factory.MyActionProxyFactory"/>

That's all you need to inject a bean Session with the session scope. Similar implementations could be done for other scopes. Notice, that other scopes like singlton (used by default), thread, and default seems don't require such pluggable extension. And the last word is about @Scoped annotation. It's not used if you provide the beans via xml configuration. But if you supply the ContainerBuilder with the bean in any other way it's able to find annotation on it and set the corresponding scope.

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