Fix warnings in ClientVersion when amqp-client is relocated

[astei]

Proposed Changes

This pull request fixes spurious warnings emitted by the com.rabbitmq.client.impl.ClientVersion class when amqp-client is relocated. This problem happens because the key com.rabbitmq.client.version is rewritten to use a different prefix by whatever produces the uberjar (maven-shade-plugin or Gradle Shadow, for instance), but the rabbitmq-amqp-client.properties key is not rewritten.

In order to prevent this rewriting, the property key is now stored in a char[] and we create a String from it. This is unusual, but required if we want to retain backwards-compatibility. Doing so allows us to defeat the rewriting done during relocation.

This behavior has been broken for a while: prior to bd1d73f, the version returned could be null.

This issue fixes #436.

While we're here, I also fixed a typo in the exception message thrown by getVersionFromPropertyFile().

Types of Changes

What types of changes does your code introduce to this project?
Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes issue Spurious warnings emitted by ClientVersion when the library is relocated #436)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (correction or otherwise)
• Cosmetics (whitespace, appearance)

Checklist

• I have read the CONTRIBUTING.md document
• I have signed the CA (see https://cla.pivotal.io/sign/rabbitmq)
• All tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in related repositories

[michaelklishin]

@astei may I ask you to clarify how instantiating a string from a character array addresses this? I’m afraid I haven’t used Gradle Shadow.

[astei]

@michaelklishin A very good question to ask!

Gradle Shadow uses ASM for relocating classes. By default, ASM remaps just Class<?> and Handle. Gradle Shadow adds mappings for String.

Obviously, char[] is not remapped in either case, so we can use it to avoid this mapping step.