An easy-to-use Framework to find and handle differences between Java objects.

To learn how to use Java Object Diff, please have a look at the short starter guide.

Java Object Diff is currently used to...

• Generate Facebook-like activity streams
• Visualize the differences between two object versions
• Automatically resolve conflicts on concurrent database writes
• Detect and persist only properties that actually changed

Even though none one of the above solutions comes out-of-the-box, this framework made them very easy to realize.

• Generates a graph of your object, allowing you to build powerful visitors to extract and modify exactly what you want.
• Works with every kind of object, even those you can't modify.
• Can be configured entirely from the outside. No annotations needed. (Although they exist and make it much more convenient.)
• Properties can be grouped into categories, to easily compare or merge specific groups of properties.

Although I successfully use this framework in a rather complex project for quite a while now, I'm sure there are still many edge cases, that I didn't even think about. Fortunately, the simple API makes it easy for you, to test it on your own set of objects, to see if it works for you.

• Performance has not been a hight priority so far, so there is still some room for improvement.
• Object comparison is very strict. Objects with different types cannot be compared, even when they share the same interface.
• It should be possible to apply the annotations to fields and not only to methods, to allow for some advanced merging techniques.
• It would be great to integrate a text-based diff algorithm for regular Strings.
• Some out-out-of-the-box Mergers would be nice (e.g. LeftToRightMerger, NonConflictingMerger, etc.)
• Could use more documentation and tests.

• Array handling is not implemented properly yet.
• Map keys are currently not compared via introspection and only used to identify map values.