Re: Rest ws: how to return an empty List avoiding java.lang.IndexOutOfBoundsException

Sergey Beryozkin Fri, 17 May 2013 04:20:54 -0700

On 17/05/13 11:52, eanbiso wrote:

I'm resting an original SOAP ws so what is important to me is to ensure the 
same behavior.

What happens when you return 'null' on the WS path ?

I've seen that returning null, no exception server side occurs and mine 
"RestExceptionHandler", that implements ResponseHandler, 
ExceptionMapper<Exception>, is not called.
So probably "an empty body and HTTP status 204" is a good response for me.
How can I obtain this returning an empty list?

This is not possible actually with an empty List. The runtime checks ifthe response entity is null, if it is then it returns a message with nobody. It can't deduce that an empty List means no message body, giventhat in case of XML it will be wrapped in the empty XML payload whichstill represents a non-empty HTTP response body.

However if I wanted to wrap a List<Integer> into a bean, how should I proceed?


Something like this:

@XmlRootElement
public class NetworkIds {
  List<Integer> ids;
}

Cheers, Sergey

Thanks a lot,

Andrea

Date: Fri, 17 May 2013 03:36:12 -0700
From: [email protected]
To: [email protected]
Subject: Re: Rest ws: how to return an empty List<Integer> avoiding 
java.lang.IndexOutOfBoundsException



        Hi

Please see comments below,

On 17/05/13 11:04, eanbiso wrote:

Hi all,

I have a problem with rest endPoint that return an empty list.

I have a ws interface like this:

      @GET

      @Produces("multipart/form-data;type=text/xml")

      @Path("/GetNetworkIDsManagedBy/{controller}")

      public List<Integer> GetNetworkIDsManagedBy(

                        @PathParam("controller") int controller);

If in the implementor I return an empty list:

      @Override

      public List<Integer> GetNetworkIDsManagedBy(int controller) {

          List<Integer> temp = new ArrayList<Integer>();

          return temp;

this exception occurs:

java.lang.IndexOutOfBoundsException: Index: 0, Size: 0

        at java.util.ArrayList.RangeCheck(Unknown Source)

        at java.util.ArrayList.get(Unknown Source)

at

org.apache.cxf.jaxrs.ext.MessageContextImpl.convertToAttachments(MessageContextImpl.java:185)

at

org.apache.cxf.jaxrs.ext.MessageContextImpl.put(MessageContextImpl.java:159)

at

org.apache.cxf.jaxrs.impl.tl.ThreadLocalMessageContext.put(ThreadLocalMessageContext.java:83)

at

org.apache.cxf.jaxrs.provider.MultipartProvider.writeTo(MultipartProvider.java:245)

at

org.apache.cxf.jaxrs.interceptor.JAXRSOutInterceptor.serializeMessage(JAXRSOutInterceptor.java:257)

at

org.apache.cxf.jaxrs.interceptor.JAXRSOutInterceptor.processResponse(JAXRSOutInterceptor.java:144)

at

org.apache.cxf.jaxrs.interceptor.JAXRSOutInterceptor.handleMessage(JAXRSOutInterceptor.java:83)

at

org.apache.cxf.phase.PhaseInterceptorChain.doIntercept(PhaseInterceptorChain.java:263)

at

org.apache.cxf.interceptor.OutgoingChainInterceptor.handleMessage(OutgoingChainInterceptor.java:77)

at

org.apache.cxf.phase.PhaseInterceptorChain.doIntercept(PhaseInterceptorChain.java:263)

at

org.apache.cxf.transport.ChainInitiationObserver.onMessage(ChainInitiationObserver.java:123)

at

org.apache.cxf.transport.http_jetty.JettyHTTPDestination.serviceRequest(JettyHTTPDestination.java:323)

at

org.apache.cxf.transport.http_jetty.JettyHTTPDestination.doService(JettyHTTPDestination.java:289)

at

org.apache.cxf.transport.http_jetty.JettyHTTPHandler.handle(JettyHTTPHandler.java:72)

at

org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:942)

at

org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:878)

at

org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)

at

org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:250)

at

org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:110)

        at org.eclipse.jetty.server.Server.handle(Server.java:349)

at

org.eclipse.jetty.server.HttpConnection.handleRequest(HttpConnection.java:441)

at

org.eclipse.jetty.server.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:919)

        at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:582)

        at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:218)

at

org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:52)

at

org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:586)

at

org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:44)

at

org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:598)

at

org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:533)

        at java.lang.Thread.run(Unknown Source)

However, if I return null instead of the empty list, no exception occurs and

the client receive the response.


In this case it has to be an empty body and HTTP status 204 - is what

the client is seeing when you return null.

I'd like to get the same behavior, returning an empty list.

Is it possible and how?

Do I use wrong annotations?



What exactly do you expect when you return an empty List<Integer> ?

Empty body & 204 ? Or actually a proper multipart/form-data payload

response with the root part containing some XML ?


FYI, JAXB provider will not handle List<Integer>, you will need to wrap

it into a bean or if you prefer returning List - then wrap Integer into

a bean


Cheers, Sergey

Thanks a lot,

Andrea

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