AttachmentsClassLoader fails when calling setURLStreamHandlerFactory

• A clear description of the issue

AttachmentsClassLoader blindly attempts to set a custom URLStreamHandlerFactory by calling URL.setURLStreamHandlerFactory. The problem with this approach is the method can be called at most once in a given Java Virtual Machine, so an error is thrown if a factory has already been set elsewhere, e.g. by Tomcat during integration testing.

For JDK8 this can be solved with using a decorator and reflection (example). As of Java 9 you can use SPI to provide handlers.

• Any logs or stack traces that you can provide (use a site like https://pastebin.com for larger logs)

e.g. when TransactionBuilder.toSignedTransaction is called:

java.lang.Error: factory already defined
        at java.net.URL.setURLStreamHandlerFactory(URL.java:1112) ~[na:1.8.0_181]
        at net.corda.core.serialization.internal.AttachmentsClassLoader.<clinit>(AttachmentsClassLoader.kt:45) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.serialization.internal.AttachmentsClassLoaderBuilder$build$2.apply(AttachmentsClassLoader.kt:146) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.serialization.internal.AttachmentsClassLoaderBuilder$build$2.apply(AttachmentsClassLoader.kt:136) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at java.util.HashMap.computeIfAbsent(HashMap.java:1127) ~[na:1.8.0_181]
        at java.util.Collections$SynchronizedMap.computeIfAbsent(Collections.java:2672) ~[na:1.8.0_181]
        at net.corda.core.serialization.internal.AttachmentsClassLoaderBuilder.build(AttachmentsClassLoader.kt:145) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.serialization.internal.AttachmentsClassLoaderBuilder.withAttachmentsClassloaderContext(AttachmentsClassLoader.kt:153) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.transactions.LedgerTransaction.verifyInternal$core(LedgerTransaction.kt:135) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.transactions.LedgerTransaction.verify(LedgerTransaction.kt:121) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.transactions.TransactionBuilder.addMissingDependency(TransactionBuilder.kt:181) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.transactions.TransactionBuilder.toWireTransactionWithContext$core(TransactionBuilder.kt:168) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.transactions.TransactionBuilder.toWireTransactionWithContext$core$default(TransactionBuilder.kt:136) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.transactions.TransactionBuilder.toWireTransaction(TransactionBuilder.kt:133) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.transactions.TransactionBuilder.toSignedTransaction(TransactionBuilder.kt:701) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.node.ServiceHub$DefaultImpls.signInitialTransaction(ServiceHub.kt:228) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.core.node.ServiceHub$DefaultImpls.signInitialTransaction(ServiceHub.kt:242) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.node.services.api.ServiceHubInternal$DefaultImpls.signInitialTransaction(ServiceHubInternal.kt) ~[corda-node-4.0-SNAPSHOT.jar:na]
        at net.corda.node.internal.AbstractNode$ServiceHubInternalImpl.signInitialTransaction(AbstractNode.kt:994) ~[corda-node-4.0-SNAPSHOT.jar:na]
        at net.corda.core.node.ServiceHub$DefaultImpls.signInitialTransaction(ServiceHub.kt:251) ~[corda-core-4.0-SNAPSHOT.jar:na]
        at net.corda.node.services.api.ServiceHubInternal$DefaultImpls.signInitialTransaction(ServiceHubInternal.kt) ~[corda-node-4.0-SNAPSHOT.jar:na]
        at net.corda.node.internal.AbstractNode$ServiceHubInternalImpl.signInitialTransaction(AbstractNode.kt:994) ~[corda-node-4.0-SNAPSHOT.jar:na]

same error when calling TransactionBuilder.verify

java.lang.Error: factory already defined
	at java.net.URL.setURLStreamHandlerFactory(URL.java:1112) ~[na:1.8.0_181]
	at net.corda.core.serialization.internal.AttachmentsClassLoader.<clinit>(AttachmentsClassLoader.kt:45) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.serialization.internal.AttachmentsClassLoaderBuilder$build$2.apply(AttachmentsClassLoader.kt:146) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.serialization.internal.AttachmentsClassLoaderBuilder$build$2.apply(AttachmentsClassLoader.kt:136) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at java.util.HashMap.computeIfAbsent(HashMap.java:1127) ~[na:1.8.0_181]
	at java.util.Collections$SynchronizedMap.computeIfAbsent(Collections.java:2672) ~[na:1.8.0_181]
	at net.corda.core.serialization.internal.AttachmentsClassLoaderBuilder.build(AttachmentsClassLoader.kt:145) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.serialization.internal.AttachmentsClassLoaderBuilder.withAttachmentsClassloaderContext(AttachmentsClassLoader.kt:153) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.transactions.LedgerTransaction.verifyInternal$core(LedgerTransaction.kt:135) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.transactions.LedgerTransaction.verify(LedgerTransaction.kt:121) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.transactions.TransactionBuilder.addMissingDependency(TransactionBuilder.kt:181) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.transactions.TransactionBuilder.toWireTransactionWithContext$core(TransactionBuilder.kt:168) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.transactions.TransactionBuilder.toWireTransactionWithContext$core$default(TransactionBuilder.kt:136) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.transactions.TransactionBuilder.toWireTransaction(TransactionBuilder.kt:133) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.transactions.TransactionBuilder.toLedgerTransaction(TransactionBuilder.kt:483) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at net.corda.core.transactions.TransactionBuilder.verify(TransactionBuilder.kt:491) ~[corda-core-4.0-SNAPSHOT.jar:na]
	at mypackage.yo.workflow.YoFlow.call(YoWorkflow.kt:73) ~[cordapp-workflow-0.19-SNAPSHOT.jar:na]
	at mypackage.yo.workflow.YoFlow.call(YoWorkflow.kt:41) ~[cordapp-workflow-0.19-SNAPSHOT.jar:na]

• The version/tag/release or commit hash it occurred on

https://github.com/corda/corda/commit/2d043828a0de2903102dd2a17776d82d8b39f933

[mikehearn]

Is the actual problem here that the driver API is putting too much stuff onto the node classpath? The URL stream handler factory thing is a very unfortunate part of the Java API but nonetheless, the node JVM process is our domain - roaming tomcats are dangerous, and so should be shot and have their heads mounted on the walls.

I recall someone mentioning that the driver works in a weird way and just adds everything in the host JVM onto the node classpath, which isn’t how things would work in production at all. I’m not sure why it works that way for tests, but I wonder if that’s the real issue here.

We can merge this as a temporary workaround but we should mark it as to be removed as part of cleanup.

[joeldudley]

Fixed - thanks @manosbatsis