Classes and Interfaces

Reference documentation for bytekin classes and interfaces.

Core Classes

BytekinTransformer

Main transformer class for bytecode manipulation.

Methods:

• byte[] transform(String className, byte[] bytes, int api) - Transform class bytecode
• byte[] transform(String className, byte[] bytes) - Transform (default API)

Builder:

• new BytekinTransformer.Builder(Class<?>... classes) - Create builder

CallbackInfo

Data structure for controlling transformation behavior.

Fields:

• boolean cancelled - Skip original code execution
• Object returnValue - Custom return value
• Object[] modifyArgs - Modified method arguments

Methods:

• static CallbackInfo empty() - Create empty callback
• CallbackInfo(boolean cancelled, Object returnValue, Object[] modifyArgs) - Constructor

Builder Class

BytekinTransformer.Builder

Fluent builder for constructing transformers.

Constructors:

• Builder(Class<?>... classes) - Initialize with hook classes

Methods:

• Builder mapping(IMappingProvider) - Set mapping provider
• Builder inject(String, Injection) - Add injection
• Builder invoke(String, Invocation) - Add invocation
• Builder redirect(String, RedirectData) - Add redirect
• Builder modifyConstant(String, ConstantModification) - Add constant modification
• Builder modifyVariable(String, VariableModification) - Add variable modification
• BytekinTransformer build() - Build transformer

Data Classes

Injection

Represents an injection point.

Purpose: Store injection configuration data.

Invocation

Represents an invocation point.

Purpose: Store invocation configuration data.

RedirectData

Represents a redirect target.

Purpose: Store redirect configuration data.

ConstantModification

Represents a constant modification.

Purpose: Store constant modification data.

VariableModification

Represents a variable modification.

Purpose: Store variable modification data.

Interfaces

IMappingProvider

Interface for name mapping.

Methods:

• String getClassName(String name) - Map class name
• String getMethodName(String className, String methodName, String descriptor) - Map method name
• String getFieldName(String className, String fieldName) - Map field name

Implementation Examples

EmptyMappingProvider - No-op mapping (returns unchanged names)

Custom Mapping:

public class CustomMapping implements IMappingProvider {
    @Override
    public String getClassName(String name) {
        // Custom mapping logic
        return name;
    }
    
    @Override
    public String getMethodName(String className, String methodName, String descriptor) {
        // Custom mapping logic
        return methodName;
    }
    
    @Override
    public String getFieldName(String className, String fieldName) {
        // Custom mapping logic
        return fieldName;
    }
}

Utility Classes

DescriptorParser

Parse and validate method descriptors.

Methods:

• static String parseDescriptor(String desc) - Parse descriptor format

BytecodeManipulator

Low-level bytecode utilities.

Purpose: Internal utilities for bytecode manipulation.

Inheritance Hierarchy

Object
├── BytekinTransformer
│   └── BytekinTransformer.Builder
├── CallbackInfo
├── Injection
├── Invocation
├── RedirectData
├── ConstantModification
└── VariableModification

Interface Implementations

IMappingProvider
├── EmptyMappingProvider
└── (Custom implementations)

Next Steps

• Review API Reference
• Check Annotations
• Explore Examples