Bermuda is a modular framework for making powerful Javac compiler plugins.

One of the primary goals of Project Transparent is providing Java developers with less boilerplate and more free-roam tooling.
We have provided many different tools working with Javac, but this is the first to truly break new ground.

An issue with Javac is how unextensible it is, until Java 1.6.
That is when Javac plugins were introduced, which allowed users to plug directly into Javac's stages for analysis.
...But you don't have just the ability to analyze.

Bermuda offers the ability to change the output of a compile cycle with either AST manipulation or bytecode injection.

Simple

Bermuda is quite simple to setup, as the Plugin class it provides comes with a few helpers for transforming/visiting Javac's output.

import org.transparent.bermuda.Plugin;

public class MyPlugin extends Plugin {
    public MyPlugin() {
        // Javac uses a plugin name to identify names from console arguments.
        super("myplugin");
    }

    @Override
    public void apply() {
        // Register a transformer.
        // Transformers take in a value and return a value.
        // Modules come with their own transformers, such as 'TreeTransformer' from 'ast'.
        register(new MyTransformer());
    }
}

Note: You will need to create a services file for com.sun.source.util.Plugin so that Javac can locate your plugin class, you will also need to specify your plugin in the command-line arguments when compiling.

Modular

However you want to use it, there's a method available:

• core — The primary module, contains all the base classes required for Bermuda to function. This is required for any plugin.
• ast   — The AST module contains an extensive, clean wrapper for Javac's AST that allows easier manipulation and creation of types.
• asm   — The ASM module contains small tools that allow you to directly modify Javac's bytecode output.

Powerful

To best illustrate the flexibility of certain modules, we've provided a few code snippets.

AST

// todo

ASM

public class DeprecationAlerter extends ByteTransformer {
    @Override
    public byte[] transform(byte[] bytes) {
        // Utilize ASM's Tree API for easy, programmatic extensions.
        return modify(bytes, clazz -> {
            if (Annotations.isAnnotated(clazz, Deprecated.class)) {
                clazz.methods.forEach(method -> {
                    final InsnList list = method.instructions;
                    // Injects the following statement into every method in this class:
                    // System.err.println("This class is deprecated!");
                    list.insert(new FieldInsnNode(Opcodes.GETSTATIC, "java/lang/System", "err", "Ljava/io/PrintStream;"));
                    list.insert(new LdcInsnNode("This class is deprecated!"));
                    list.insert(new MethodInsnNode(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false));
                });
            }
        });
    }
}