unpackr

unpackr is a lightweight Java library for dynamically invoking methods or accessing fields using structured data, such as DTOs or composite contexts.

It provides a flexible mechanism to map deeply nested object fields and method calls into method parameters, enabling powerful and efficient unpacking logic via reflection or bytecode generation (ASM).

Getting Started

To install it, you will need:

• java 11+
• Maven/Gradle

Features

• Declarative access to nested fields and methods
• Automatic unpacking of composite objects into method arguments
• Bytecode-based (ASM) and reflection-based implementations
• Optional method arguments support
• Minimal dependencies

Installing

Gradle dependency

dependencies {
    implementation group: 'com.github.romanqed', name: 'unpackr', version: '1.0.1'
    implementation group: 'com.github.romanqed', name: 'unpackr-asm', version: '1.0.1'
    // OR
    implementation group: 'com.github.romanqed', name: 'unpackr-reflect', version: '1.0.1'
}

Maven dependency

<dependencies>
    <dependency>
        <groupId>com.github.romanqed</groupId>
        <artifactId>unpackr</artifactId>
        <version>1.0.1</version>
    </dependency>
    <dependency>
        <groupId>com.github.romanqed</groupId>
        <artifactId>unpackr-asm</artifactId>
        <version>1.0.1</version>
    </dependency>
    <!-- OR -->
    <dependency>
        <groupId>com.github.romanqed</groupId>
        <artifactId>unpackr-reflect</artifactId>
        <version>1.0.1</version>
    </dependency>
</dependencies>

Examples

Suppose you have a class hierarchy like this:

class Ctx {
    Rq getRq();
    Rp getRp();
}

class Rq {
    Map<String, Object> getRqProps();
}

class Rp {
    Map<String, Object> getRpProps();
}

And a method to invoke:

interface Handler { 
    void handle(Object rqProp, Object rpProp);
}

You can create an unpacker using the ASM implementation like this:

var unpacker = new AsmUnpacker(new DefineClassLoader());
var first = MemberAccess.of()
        .of(Ctx.class)
        .of(Ctx.class.getMethod("getRq"))
        .of(Rq.class.getMethod("getRqProps"))
        .of(Map.class.getMethod("get", Object.class), "rqProp")
        .build();

var second = MemberAccess.of()
        .of(Ctx.class)
        .of(Ctx.class.getMethod("getRp"))
        .of(Rp.class.getMethod("getRpProps"))
        .of(Map.class.getMethod("get", Object.class), "rpProp")
        .build();

var target = Handler.class.getMethod("handle", Object.class, Object.class);

var fn = unpacker.unpack(Ctx.class, target, first, second);
...
fn.invoke(handlerInstance, ctxInstance);

Built With

• Gradle - Dependency management
• ASM - Generation of dynamic proxies
• jfunc - Functional interfaces

Authors

• RomanQed - Main work

See also the list of contributors who participated in this project.

License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details