Builder Pattern

bytekin provides a fluent Builder API for constructing transformers programmatically.

Basic Usage

BytekinTransformer transformer = new BytekinTransformer.Builder(MyHooks.class)
    .build();

Using Mappings

Apply name mappings during builder construction:

BytekinTransformer transformer = new BytekinTransformer.Builder(MyHooks.class)
    .mapping(new CustomMappingProvider())
    .build();

Adding Programmatic Transformations

Mix annotation-based and programmatic configurations:

BytekinTransformer transformer = new BytekinTransformer.Builder(AnnotationHooks.class)
    .inject("com.example.Extra", new Injection(...))
    .invoke("com.example.Another", new Invocation(...))
    .build();

Multiple Hook Classes

BytekinTransformer transformer = new BytekinTransformer.Builder(
    LoggingHooks.class,
    SecurityHooks.class,
    PerformanceHooks.class
)
.mapping(myMappings)
.build();

Builder Methods

mapping(IMappingProvider)

Set a mapping provider for class/method name translation.

inject(String, Injection)

Add injection transformation programmatically.

invoke(String, Invocation)

Add invocation transformation programmatically.

redirect(String, RedirectData)

Add redirect transformation programmatically.

modifyConstant(String, ConstantModification)

Add constant modification programmatically.

modifyVariable(String, VariableModification)

Add variable modification programmatically.

build()

Build and return the transformer. This method:

1. Scans all hook classes
2. Extracts annotations
3. Adds programmatic transformations
4. Creates internal transformer map
5. Returns ready-to-use transformer

Best Practices

1. Build once: Create transformers during initialization
2. Reuse: Use the same transformer for multiple transformations
3. Combine patterns: Mix annotations and programmatic API
4. Document configuration: Comment why specific transformations are applied

Performance Tips

// Good: Build once
BytekinTransformer transformer = new BytekinTransformer.Builder(Hooks.class).build();

for (String className : classes) {
    byte[] transformed = transformer.transform(className, bytecode);
}

// Bad: Building multiple times
for (String className : classes) {
    BytekinTransformer transformer = new BytekinTransformer.Builder(Hooks.class).build();
    byte[] transformed = transformer.transform(className, bytecode);
}

Next Steps

• Learn Advanced Usage
• Review Best Practices