Java – webtarget and thread safety

My understanding is that Jersey's webtargets are thread safe and can be called at the same time, but I have a concurrent bug The following code works normally in a thread, but when I call it at the same time, I get an NPE

public static final MultivaluedMap<String,Object> ACCEPT_GZIP =
                new MultivaluedHashMap<>(hashMap("Accept-Encoding","gzip"));

webTarget.path("my_web_service/path")
                .request(MediaType.APPLICATION_JSON_TYPE)
                .headers(ACCEPT_GZIP)
                .post(entity(symbols.keySet(),APPLICATION_JSON_TYPE),new GenericType<List<MyPojo>>(){});

Stack trace:

javax.ws.rs.ProcessingException
at org.glassfish.jersey.client.ClientRuntime.invoke(ClientRuntime.java:255)
at org.glassfish.jersey.client.JerseyInvocation$3.call(JerseyInvocation.java:705)
at org.glassfish.jersey.internal.Errors.process(Errors.java:315)
at org.glassfish.jersey.internal.Errors.process(Errors.java:297)
at org.glassfish.jersey.internal.Errors.process(Errors.java:228)
at org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:424)
at org.glassfish.jersey.client.JerseyInvocation.invoke(JerseyInvocation.java:701)
at org.glassfish.jersey.client.JerseyInvocation$Builder.method(JerseyInvocation.java:446)
at org.glassfish.jersey.client.JerseyInvocation$Builder.post(JerseyInvocation.java:343)
at com.assylias.xxx.ws.xx.getLastDates(xx.java:107)
at com.assylias.xxx.ws.xx.lambda$main$5(xx.java:87)
at com.assylias.xxx.ws.xx$$Lambda$34/231311211.accept(UnkNown Source)
at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1359)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)
at java.util.stream.ForEachOps$ForEachTask.compute(ForEachOps.java:290)
at java.util.concurrent.CountedCompleter.exec(CountedCompleter.java:731)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:902)
at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1689)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1644)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)

Caused by: java.lang.NullPointerException
at java.util.LinkedList$ListItr.next(LinkedList.java:893)
at jersey.repackaged.com.google.common.collect.TransformedIterator.next(TransformedIterator.java:48)
at org.glassfish.jersey.filter.LoggingFilter.printPrefixedHeaders(LoggingFilter.java:190)
at org.glassfish.jersey.filter.LoggingFilter.filter(LoggingFilter.java:230)
at org.glassfish.jersey.client.ClientFilteringStages$RequestFilteringStage.apply(ClientFilteringStages.java:110)
at org.glassfish.jersey.client.ClientFilteringStages$RequestFilteringStage.apply(ClientFilteringStages.java:98)
at org.glassfish.jersey.process.internal.Stages.process(Stages.java:171)
at org.glassfish.jersey.client.ClientRuntime.invoke(ClientRuntime.java:246)
... 21 more

Solution

The problem is that multivaluedmaps is not thread safe, and Jersey's recorder seems to use titles in a thread unsafe manner, so it shares a common static final multivalued map < string, Object > accept_ Gzip is not a good idea The header should be recreated for each request:

webTarget.path("my_web_service/path")
                .request(MediaType.APPLICATION_JSON_TYPE)
                .header("Accept-Encoding","gzip")
                .post(entity(symbols.keySet(),new GenericType<List<MyPojo>>(){});