jvmbuilder's Introduction

JvmBuilder

A source code generator for Kotlin data classes to automatically create a Builder class.

How to use JvmBuilder

When annotating a Kotlin data class with @JvmBuilder

@JvmBuilder
data class Test(val foo: Int = 1, val bar: String)

The following class is generated

// Code auto-generated by JvmBuilder. Do not edit.
package com.example

import kotlin.Int
import kotlin.String

class JvmBuilder_Test {
    private var foo: Int? = null

    private var bar: String? = null

    fun foo(foo: Int): JvmBuilder_Test {
        this.foo = foo
        return this
    }

    fun bar(bar: String): JvmBuilder_Test {
        this.bar = bar
        return this
    }

    fun build(): Test {
        var result = com.example.Test(bar = this.bar!!)
        result = result.copy(foo = this.foo ?: result.foo)
        return result
    }
}

This provides a Builder class that can be used in Java to create your Kotlin Test data class using the default values and following a Builder Pattern.

The following Java code generates a Test instance with foo = 1 (taking the 1 from the default Kotlin constructor) and bar = "bar".

new Jvm_Builder().bar("bar").build()

Gradle

Gradle users should add the dependencies in their build.gradle file:

dependencies {
  implementation "io.github.jffiorillo:jvmbuilder-annotations:<latest_version>"
  kapt "io.github.jffiorillo:jvmbuilder:<latest_version>"
}

Maven

Maven users should add the dependencies in their pom.xml file:

<dependency>
  <groupId>io.github.jffiorillo</groupId>
  <artifactId>jvmbuilder-annotations</artifactId>
  <version>{latest_version}</version>
</dependency>
<dependency>
  <groupId>io.github.jffiorillo</groupId>
  <artifactId>jvmbuilder</artifactId>
  <version>{latest_version}</version>
  <scope>provided</scope>
</dependency>

Benefit

In order to have a good Kotlin interoperability with Java, you can use this tool to generate automatically generate Builders for your data classes that are accessible from Java consumers.
The time of executing the annotation processor is really slow because uses the kotlin-metadata instead of reflection.

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