Java-8 mixin interface code generator
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Java-8 mix-in interface code generator

##Latest release Maven Central

[Release notes on github] (


In Maven:


##Background The arrival of default interfaces in Java 8 opens the door to "mix-in" interfaces - a form of multiple inheritance.

For example:

public class A implements MixinB, MixinC {

In Java 8 it's possible that class A, despite having 0 implementation, is actually a useful class because MixinB and MixinC have default method implementations.

##What interface-it does

The interface-it library uses reflection to auto-generate Java code for mix-in classes that delegate to static methods.


This can be useful in unit tests, because libraries like Mockito and AssertJ use a lot of static methods. With a generated mix-in, you can replace static methods by inherited methods.

It's also useful for refactoring legacy code. You can replace static calls with calls to a mix-in interface - reducing the coupling in the design because the mix-in can be overridden (and mocked in unit tests).

Anywhere that you use static imports, you might want to consider generating a mix-in interface instead.

##How to use interface-it

Many of you may just need to copy and paste a source file from the examples and adjust it to the needs of your project. There are delegate interfaces for AssertJ, Mockito, and JUnit Assert which you can use in your own unit tests. A unit test class which implements some of these is DelegateMethodGeneratorTest.

If you want to generate mix-ins which wrap other static classes, such as in your own legacy code, you can build the jar file from source using mvn clean package or you can just download it or use a dependency manager to fetch it for you.

Once you have the binary, you run the jar file, providing a classpath which allows loading the class you want to wrap (and any classes it needs to load for its method signatures) and the appropriate command-line arguments. An example .bat file is provided to show how this is done.

Or, use a custom ANT task.

Or, create your own UI using the ClassCodeGenerator API. Here's [an example usage of the API] ( "an example usage of the API").

Requires Java 8 (or higher)

For Mockito, consider using extended-mockito, which contains mixins generated by interface-it.

##Command-line flags

-v > Write version number.
-n > Name of the target interface (ex: "MyMixin")
-d > Directory which will contain the generated file (default value is ".")
-c > Fully qualified delegate class name (ex: "java.lang.Math")
-p > The package name for the target interface (ex: "org.example")
-s > File path of either a .jar or .zip file or a single source file ending in .java or .txt containing source code to be used to recover argument names lost during compilation
-i > Ignore all deprecated methods. Default behavior is to wrap each deprecated method and deprecate the wrapping method.
-P > Simple name of the mixin to generate for the superclass of the delegate class. If present, 2 mixins will be generated - one for the delegate class and one for its parent, and the mixin for the delegate will extend the mixin for the delegate's parent class.

###Complementary project(s)

##Acknowledgments Inspired by the following articles:

I thought that using mockito-java8 would be a good idea, but mockito-java8 was not keeping up with the latest Mockito versions, so it seemed better to make a tool that allows you to use whatever version you want of Mockito, AssertJ or whatever static classes for which you may want to make mix-ins.

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##Disclaimer Not affiliated in any way with the Australian company