POST request to Struts2 with REST plugin not receiving response

Question

I have a struts2 application which uses the struts2-rest-plugin v.2.2.3.

Everything is working great when it comes to the routing of the requests to the actions and its methods and I'm also using ModelDriven to specify the object to serialise when using extensions like JSON and XML.

The problem I'm having is that when I send a POST or PUT request to the struts layer I just get an empty response.

I am sending a POST request to the action like so: http://localhost:8080/alert-settings!update.json. I have a breakpoint in that method and it gets called and the code runs and completes. I have a feeling the issue might be that I am trying to use the ModelDriven interface to send me back the response and for some reason the rest-plugin doesn't like this but I don't know why it would behave like that.

Is there a known issue with receiving responses from POST requests while using the rest plugin? I have looked everywhere and can't find anything about it really.

Any help appreciated and I can provide any more details on request.

Answer 1

I encountered the same issue. Have you tried to set in the struts.xml file:

struts.rest.content.restrictToGET = false

See the last setting on the rest plugin docs

Answer 2

I actually figured out that it was a line in the rest plugin causing this:

// don't return any content for PUT, DELETE, and POST where there are no errors
if (!hasErrors && !"get".equalsIgnoreCase(ServletActionContext.getRequest().getMethod())) {
  target = null;
}

This is in org.apache.struts2.rest.RestActionInvocation in the selectTarget() method. I find this to be quite annoying as it doesn't really follow the REST architecture, id like the option to be able to return response objects for POST, DELETE and PUT requests in some cases.

I worked around this by extending RestActionProxyFactory and RestActionInvocation and specifying the use of this in my struts xml like so:

<bean type="com.opensymphony.xwork2.ActionProxyFactory" name="restOverride" class="uk.co.ratedpeople.tp.rest.RPRestActionProxyFactory" />
<constant name="struts.actionProxyFactory" value="restOverride" />

This allows me to use the struts plugin throughout while returning object on POST requests.

RestActionProxyFactory

public class RPRestActionProxyFactory extends RestActionProxyFactory {

    @Override
    public ActionProxy createActionProxy(String namespace, String actionName, String methodName, Map extraContext, boolean executeResult, boolean cleanupContext) {
        if (namespace.startsWith(this.namespace)) {
            ActionInvocation inv = new RPRestActionInvocation(extraContext, true);
            container.inject(inv);
            return createActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);
        } else {
            return super.createActionProxy(namespace, actionName, methodName, extraContext, executeResult, cleanupContext);
        }
    }

}

RestActionInvocation

public class RPRestActionInvocation extends RestActionInvocation {

    public RPRestActionInvocation(Map extraContext, boolean pushAction) {
        super(extraContext, pushAction);
    }

    @SuppressWarnings("unchecked")
    @Override
    protected void selectTarget() {

        // Select target (content to return)
        Throwable e = (Throwable)stack.findValue("exception");
        if (e != null) {

            // Exception
            target = e;
            hasErrors = true;

        } else if (action instanceof ValidationAware && ((ValidationAware)action).hasErrors()) {

            // Error messages
            ValidationAware validationAwareAction = ((ValidationAware)action);

            Map errors = new HashMap();
            if (validationAwareAction.getActionErrors().size() > 0) {
                errors.put("actionErrors", validationAwareAction.getActionErrors());
            }
            if (validationAwareAction.getFieldErrors().size() > 0) {
                errors.put("fieldErrors", validationAwareAction.getFieldErrors());
            }
            target = errors;
            hasErrors = true;

        } else if (action instanceof ModelDriven) {

            // Model
            target = ((ModelDriven)action).getModel();

        } else {
            target = action;
        }

        // don't return any content for PUT, DELETE, and POST where there are no errors
//      if (!hasErrors && !"get".equalsIgnoreCase(ServletActionContext.getRequest().getMethod())) {
//          target = null;
//      }
    }

}

Answer 3

I've used struts actions with mixed result types in the past, returning json, xml, and tiles for instance. I'm not sure if it's the recommended way to do it but it requires some configuration using struts.xml even though conventions are being used. Maybe you've already done this, not sure there isn't enough info provided to tell.

Struts.xml settings:

<constant name="struts.convention.default.parent.package" value="restful"/>

<package name="restful"  extends="rest-default, struts-default, json-default">
    <result-types>
        <result-type name="tiles" class="org.apache.struts2.views.tiles.TilesResult" />
        <result-type name="json" class="com.googlecode.jsonplugin.JSONResult"/>
    </result-types>

    ....
</package>

I have setup the extra result types to be used on specific actions later. In the action class you can then setup your result types by action or method.

Action Class:

@Results({
    @Result(name = "JsonSuccess", type = "json"),
    @Result(name = "success", type = "tiles", location = "/tickets.tiles")
})

public class EventController extends RestActionSupport implements ModelDriven<EventBean>{
     ...
}

Something else to note about json results, I've noticed that when I have a serializable object being returned as a result, if that object contains other complex objects with a getter/setter that returns the embedded object, I will often receive an empty result or no result. I often end up writing json wrapper objects to use for my json results with getters/setters that only return java types (String, int, Boolean, etc) and not the embedded objects. I think that've solved this using delegate getters/setters but I'll have to go back and look at some old code.