[ovirt-devel] Removing boilerplate code in engine

[Mike Kolesnik]

Hi, 

I recently introduced 2 changes for removing boilerplate code:

1. http://gerrit.ovirt.org/29414 - Fluent syntax for writing validations
2. http://gerrit.ovirt.org/29617 - Wrapper for locks to use with try-with-resources

By removing boilerplate code we're making the code less error prone and easier to read (and maintain).
I've already sent some simple refactors to use these new styles of writing,
but more work is necessary to apply to the whole project.

I urge all engine developers that need to write such code to use the new styles of writing.

Below are examples for each change.

1. When expecting a negative outcome, instead of using:
  return getVds() == null
      ? new ValidationResult(VdcBllMessages.ACTION_TYPE_FAILED_HOST_NOT_EXIST)
      : ValidationResult.VALID;

use:
  return ValidationResult.failWith(VdcBllMessages.ACTION_TYPE_FAILED_HOST_NOT_EXIST)
      .when(getVds() == null);


When expecting a positive outcome, instead of using:
  return FeatureSupported.nonVmNetwork(getDataCenter().getcompatibility_version())
      ? ValidationResult.VALID
      : new ValidationResult(VdcBllMessages.NON_VM_NETWORK_NOT_SUPPORTED_FOR_POOL_LEVEL);

use: 
  return ValidationResult.failWith(VdcBllMessages.NON_VM_NETWORK_NOT_SUPPORTED_FOR_POOL_LEVEL)
      .unless(FeatureSupported.nonVmNetwork(getDataCenter().getcompatibility_version()));


2. To lock a block of code, instead of using [1]:
  lock.lock();
  try {
      // Thread safe code
  } finally {
      lock.unlock();
  }

use:
  try (AutoCloseableLock l = new AutoCloseableLock(lock)) {
      // Thread safe code
  }

[1] This is best used with locks from java.util.concurrent.locks package.
    For regular thread safe blocks it's best to use the standard synchronized block.

Regards,
Mike