Tomcat fails to start with "factory already defined" error if two integration test harnesses start spring boot as part of the same maven multi-module build (JVM instance)

[jamiecramb]

We use spring boot as a way to run an embedded tomcat / spring app inside of a JBehave integration test harness.

When in a multi-module maven reactor build we have noticed that if there are 2 modules with integration tests (and therefore 2 tomcat instances embedded within spring boot apps) that the second module will fail to run even though it runs fine if the module is built by itself.

I have tracked the problem down to the org.apache.catalina.webresources.TomcatURLStreamHandlerFactory calling URL.setURLStreamHandlerFactory(..) for each spring boot app startup; all after the first call in the same JVM will fail with a "factory already defined" Error being thrown.

The workaround has been to clone and override the org.apache.catalina.webresources.TomcatURLStreamHandlerFactory private constructor so that it wraps the call to URL.setURLStreamHandlerFactory(..) in a try/catch which ignores the "factory already defined" Error.

I have created a sample multi-module maven build to demonstrate the issue:
spring-boot-tomcat-chain-issue.zip. Note that the README.txt explains how to apply the workaround which is off by default.

[wilkinsona]

I don't think this really has anything to do with Spring Boot.

TomcatURLStreamHandlerFactory uses a static to ensure that setURLStreamHandlerFactory is only called once. If setURLStreamHandlerFactory is being called multiple times by TomcatURLStreamHandlerFactory, there must be multiple class loaders in the same JVM, each of which has loaded TomcatURLStreamHandlerFactory. That's something that is out of the control of Spring Boot and Tomcat.

I'm not familiar with JBehave, but I would recommend looking at its class loading to see if it can be configured so that it doesn't load the same classes multiple times with different class loaders.

[bakersemail]

Have the same problem reported here.

[snicoll]

@bakersemail I am not sure I got that. Saying you have the same problem on a closed issue is not a great way to get support. As @wilkinsona indicated in the comment above yours, there is not much we can do here. If you're looking for help, please ask on StackOverflow.