Java + Lombok

By Daniel Padua

Published in Programming

May 05, 2019

3 min read

Learn to add and configure lombok in your favorite IDE to boost java development

Intro

I always heard comments from other developers things like: “Java is a very verbose language”, or Hello World line count comparison between Java vs Other X Language. And I also think that this is true, when you develop pure Java (without extensions, libs and plugins) compared to other modern languages, the developer ends up writing more to reach the goal. However, since some time ago, we have a lib called lombok that helps you simplify (a lot) the life of those who develop with java.

Features

Lombok is a lib that provides a collection of annotations that eases some repetitive java tasks (such as, getters and setters creation). Besides of being dependency of your project, it connects in your IDE making it understand the annotations, so it requires a certain configuration. In this guide I’ll show how to configure it on eclipse, intellij idea and also vscode. If you don’t know how to work with java with vscode take a look at here.

The github repository with the sample classes can be found at: https://github.com/danielpadua/lombok-examples

Requirements

Java JDK 8 or higher
Eclipse or IntelliJ IDEA or vscode

IDE configuration

Use the sections below according to the IDE you are using:

Eclipse

Download latest lombok.jar at: https://projectlombok.org/download, store this file in some directory of your choice (e.g.: your user’s home folder). From this moment on, there are two ways of configuring eclipse:

Run the lombok.jar. It will open a window that will search in all folders of your machine looking for IDEs and if it finds eclipse it will display a checkbox to enable. So, click install and it will be done, as the image below:

If method 1 didn’t work or didn’t found any IDE, we will do the same work jar does under the hood but manually. Open the eclipse.ini file located under the configuration directory of the eclipse that you use, and edit it as below:

-javaagent:${full_path}/lombok.jar

We are just adding the full path of lombok’s jar as eclipse’s initialisation argument, and this will make it understands lombok. Lombok’s jar does exactly the same thing, but it copies the jar inside of eclipse installation folder and writes eclipse.ini automatically.

IntelliJ IDEA

It’s really simple enable Lombok support in IntelliJ IDEA, to do so, open plugin installation section and install the highlighted plugin:

Restart IntelliJ IDEA and Lombok support will be enabled.

vscode

Search for lombok at the extensions tab:

Install the Gabriel Basilio Brito’s extension, which is recommended by lombok: https://projectlombok.org/setup/vscode. Restart vscode:

Project

First we need to create a java spring-boot project, so:

To create a java spring-boot in eclipse follow this guide: here.
To create a java spring-boot in intellij idea follow this guide: here.
To create a java spring-boot in vscode follow this guide: here.

After creating the project, use the sections below depending on the build-tool that you are using:

Maven

Add lombok’s dependency in pom.xml:

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.6</version>
    <scope>provided</scope>
</dependency>

You may need to force maven import update on your IDE.

Gradle

Add lombok’s depedency in build.gradle file:

repositories {
  mavenCentral()
}

dependencies {
  compileOnly ‘org.projectlombok:lombok:1.18.6’
  annotationProcessor ‘org.projectlombok:lombok:1.18.6’
}

Usage

Now let’s explore what lombok has to offer for us to reduce boilerplate code:

Getters, Setters, Constructors, ToString, Equals e HashCode

To enable getter in all fields of your class, annotate above your class name: @Getter.

To enable setter in all fields of your class, annotate above your class name: @Setter.

To create a constructor with all fields as input parameter, annotate above your class name: @AllArgsConstructor, without parameters: @NoArgsConstrutor, with required fields (or non-null): @RequiredArgsConstructor

To implement default toString() use: @ToString,

To implement default equals() and hashCode() use: @EqualsAndHashCode

The @Data annotation above class is a shortcut to: @ToString, @EqualsAndHashCode, @Getter, @Setter and @RequiredArgsConstructor together.

Without lombok:

package br.com.danielpadua.lombok_examples;

public class Dog {
    private Integer id;
    private String name;
    private String breed;

    public Dog(Integer id, String name, String breed) {
        this.id = id;
        this.name = name;
        this.breed = breed;
    }

    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getBreed() {
        return breed;
    }
    public void setBreed(String breed) {
        this.breed = breed;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((breed == null) ? 0 : breed.hashCode());
        result = prime * result + ((id == null) ? 0 : id.hashCode());
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        Dog other = (Dog) obj;
        if (breed == null) {
            if (other.breed != null)
                return false;
        } else if (!breed.equals(other.breed))
            return false;
        if (id == null) {
            if (other.id != null)
                return false;
        } else if (!id.equals(other.id))
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "Dog [id=" + id + ", name=" + name + ", breed=" + breed + "]";
    }
}

With lombok:

package br.com.danielpadua.lombok_examples;

import lombok.Data;
import lombok.NonNull;

@Data
public class Dog {
    @NonNull
    private Integer id;
    @NonNull
    private String name;
    @NonNull
    private String breed;
}

Immutable classes

Use the annotation: @Value above the class, to make it immutable

Without lombok:

package br.com.danielpadua.lombok_examples;

public class DogCreateRequest {
    private final String name;
    private final String breed;

    public DogCreateRequest(final String name, final String breed) {
        this.name = name;
        this.breed = breed;
    }

    public String getName() {
        return name;
    }

    public String getBreed() {
        return breed;
    }

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((breed == null) ? 0 : breed.hashCode());
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        return result;
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        DogCreateRequest other = (DogCreateRequest) obj;
        if (breed == null) {
            if (other.breed != null)
                return false;
        } else if (!breed.equals(other.breed))
            return false;
        if (name == null) {
            if (other.name != null)
                return false;
        } else if (!name.equals(other.name))
            return false;
        return true;
    }

    @Override
    public String toString() {
        return "DogCreateRequest [name=" + name + ", breed=" + breed + "]";
    }
}

With lombok:

package br.com.danielpadua.lombok_examples;

import lombok.Value;

@Value
public class DogCreateRequest {
    String name;
    String breed;
}

Builder pattern

Use the annotation: @Builder above the class to create the builder pattern

Without lombok:

package br.com.danielpadua.lombok_examples;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;

public class Kennel {
    private Integer id;
    private String name;
    private Set<Dog> dogs;

    public Kennel(Integer id, String name, Set<Dog> dogs) {
        this.id = id;
        this.name = name;
        this.dogs = dogs;
    }

    public static KennelBuilder builder() {
        return new KennelBuilder();
    }

    public static class KennelBuilder {
        private Integer id;
        private String name;
        private HashSet<Dog> dogs;

        KennelBuilder() {
        }

        public KennelBuilder id(Integer id) {
            this.id = id;
            return this;
        }

        public KennelBuilder name(String name) {
            this.name = name;
            return this;
        }

        public KennelBuilder dog(Dog dog) {
            if (this.dogs == null) {
                this.dogs = new HashSet<Dog>();
            }
            this.dogs.add(dog);
            return this;
        }

        public KennelBuilder dogs(Collection<? extends Dog> dogs) {
            if (this.dogs == null) {
                this.dogs = new HashSet<Dog>();
            }
            this.dogs.addAll(dogs);
            return this;
        }

        public KennelBuilder clearDogs() {
            if (this.dogs != null) {
                this.dogs.clear();
            }
            return this;
        }

        public Kennel build() {
            Set<Dog> dogs = Collections.unmodifiableSet(this.dogs);
            return new Kennel(this.id, this.name, dogs);
        }

        @Override
        public String toString() {
            return "KennelBuilder [id=" + id + ", name=" + name + ", dogs=" + dogs + "]";
        }
    }
}

With lombok:

package br.com.danielpadua.lombok_examples;

import java.util.Set;
import lombok.Builder;
import lombok.Singular;

@Builder
public class Kennel {
    private Integer id;
    private String name;
    @Singular
    private Set<Dog> dogs;
}

Logging

Slf4j is one of the supported log interfaces, take a look at: https://projectlombok.org/features/log to see all the supported

Without lombok:

package br.com.danielpadua.lombok_examples;

public class App
{
    private static final org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(App.class);

    public static void main( String[] args )
    {
        log.info( "Hello World!" );
    }
}

With lombok:

package br.com.danielpadua.lombok_examples;

import lombok.extern.slf4j.Slf4j;

@Slf4j
public class App {

    public static void main(String... args) {
        log.info("Hello world");
    }
}

Conclusion

Despite the setup and configuration time spent, lombok was developed aimed to boost productivity of java developers. I’ve been using this lib for some time and I’m not thinking of stopping using it!

See you soon!