Helios

Helios is a developer tool designed to improve the usability of the Builder pattern in Java.

Installing

You can use the features listed below by installing the plugin from the IntelliJ marketplace which you can find here.

Features

RequiredMethod annotation

The @RequiredMethod annotation should be added to the build() (or equivalent) method in your builder pattern. This annotation will ensure that the methods specified in the value are called before the build method allowing you to provide a compile-time error if a required method is not called.

This improves the usability of the builder pattern as you no longer have to compile, and then run, your code to find out that you have missed a required method call.

Example

public class ExampleBuilder {
    
    private String name = null;
    private int age = -1;
    
    public ExampleBuilder() {}
    
    @RequiredMethod({"name", "age"})
    public ExampleBuilder build() {
        assert name != null;
        assert age != -1;
        
        return new ExampleBuilder();
    }
    
    public ExampleBuilder name(@NotNull String name) {
        assert name != null;
        
        this.name = name;
        return this;
    }
    
    public ExampleBuilder someUnimportantMethod() {
        return this;
    }
    
    public ExampleBuilder age(int age) {
        assert age > 0;
        
        this.age = age;
        return this;
    }
}

public class MainClass {
    
    public static void main(String[] args) {
        // This would be highlighted as an error as the `name()` method has not been called
        new ExampleBuilder()
                .age(10)
                .build();
        
        // This would not be highlighted as all required methods have been called
        new ExampleBuilder()
                .age(10)
                .name("Test")
                .build();
    }
    
}

Getting Started

Note: if you want the syntax highlighting to work you need to install the IntelliJ plugin.

You can use the Helios library by adding the following to your build.gradle file repositories block:

repositories {
    maven {
        url 'https://maven.envyware.co.uk'
    }
}

And then adding the following to your dependencies block:

dependencies {
    implementation 'uk.co.envyware:helios:1.4-SNAPSHOT'
}