ConcurrentModification exception because of javax.validation exception

Question

I am facing this weird issue where the api is throwing concurrent modification exception because of javax.validation issue.

    java.util.ConcurrentModificationException: null
    at java.util.HashMap$HashIterator.nextNode(HashMap.java:1445) ~[na:1.8.0_265]
    at java.util.HashMap$ValueIterator.next(HashMap.java:1474) ~[na:1.8.0_265]
    at org.eclipse.persistence.jpa.PersistenceProvider.isLoadedWithReference(PersistenceProvider.java:464) ~[eclipselink-2.6.1.jar:2.6.1.v20150916-55dc7c3]
    at javax.persistence.Persistence$PersistenceUtilImpl.isLoaded(Persistence.java:154) ~[javax.persistence-2.1.0.jar:2.1.0]
    at org.hibernate.validator.internal.engine.resolver.JPATraversableResolver.isReachable(JPATraversableResolver.java:56) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.resolver.DefaultTraversableResolver.isReachable(DefaultTraversableResolver.java:130) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.resolver.SingleThreadCachedTraversableResolver.isReachable(SingleThreadCachedTraversableResolver.java:46) ~[bean-validator-2.2.0.jar:5.0.0.Final] [1 skipped]
    at org.hibernate.validator.internal.engine.ValidatorImpl.isReachable(ValidatorImpl.java:1307) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.isValidationRequired(ValidatorImpl.java:1292) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    ... 49 common frames omitted
Wrapped by: javax.validation.ValidationException: HV000041: Call to TraversableResolver.isReachable() threw an exception.
    at org.hibernate.validator.internal.engine.ValidatorImpl.isReachable(ValidatorImpl.java:1316) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.isValidationRequired(ValidatorImpl.java:1292) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateConstraint(ValidatorImpl.java:475) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateConstraintsForDefaultGroup(ValidatorImpl.java:424) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateConstraintsForCurrentGroup(ValidatorImpl.java:388) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateInContext(ValidatorImpl.java:340) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateCascadedConstraint(ValidatorImpl.java:635) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateCascadedConstraints(ValidatorImpl.java:524) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateInContext(ValidatorImpl.java:349) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateCascadedConstraint(ValidatorImpl.java:635) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateCascadedConstraints(ValidatorImpl.java:524) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateParametersInContext(ValidatorImpl.java:916) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateParameters(ValidatorImpl.java:240) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateParameters(ValidatorImpl.java:198) ~[bean-validator-2.2.0.jar:5.0.0.Final]
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1095) [webapp-runner.jar:na] [28 skipped]
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:672) [webapp-runner.jar:na]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1502) [webapp-runner.jar:na]
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1458) [webapp-runner.jar:na]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_265]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_265]
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [webapp-runner.jar:na]
    at java.lang.Thread.run(Thread.java:748) [na:1.8.0_265]

The stack trace doesn't say anything about which validation in the bean is causing the issue.

Answer 1

Clearly Exception stack trace is saying that Concurrent modification exception is occuring in hashmap. Concurrent modification exception can happen if you use Iterators while traversing map values or API which are not thread safe like the Generic Hashmap object. Try using concurrent hashmap and your problem should be resolved.

Answer 2

It looks like the stacktrace is being formatted in an idiosyncratic way by ... something.

The normal way to display it is to display the primary exception first, followed by the cause (or wrapped) exception chain. But what you have shown us has the wrapped exception followed by the exception that is wrapping it.

So that means that the ConcurrentModificationException is causing the ValidationException ... not the other way around.

Unfortunately, this doesn't explain what is actually going on.