Lombok: The Java Plugin that Substantially Reduces Boilerplate

Nov 24th, 2020

java bean

Java's Required Boilerplate Code

Java is notorious for the huge amount of boilerplate code required for simple things, especially everyday Java POJO beans.

POJO

POJO is an acronym for 'Plain Old Java Object'.

These objects typically exist to store or transport data. We sometimes call these objects beans.

Typical POJO Bean Boilerplate Code

Let's look at a real-world example, a user bean:


public class User{

  private Long id;
  private String username;
  private String email;
  private String name;

}

This POJO has four fields:

  • id
  • username
  • email
  • name

Let's look at the typical code we would need for this POJO bean.

Setters

Setters are methods that allow us to assign values to bean properties.


public void setName(String name){
  this.name = name;
}

Getters

Getters are methods that allow us to retrieve values from our POJO beans.


public String getName(){
  return this.name;
}

Constructors

Constructors are methods that allow use to construct new instances of a Java object with given data.

Default No-Args Constructor

In Java, the default constructor is one that takes no arguments, and creates an empty default bean.

If you don't define any constructors, the compiler will automatically create the default constructor.


public User(){

}
All-Args Constructor

In Java, the all-args constructor takes an argument for every field in the bean.


public User(Long id, String username, String email, String name){
  this.id = id;
  this.username;
  this.email = email;
  this.name = name;
}
Required-Args Constructor

You can define a required-args constuctor if you only need a few properties at initialization.


public User(Long id){
  this.id = id;
}

Lombok

Enter Lombok, a Java build plugin that generates all this code at compile time, reducing the countless hours required to engineer all this boilerplate code for our POJO beans. Lombok is configured by adding annotations to your POJO beans.

Lombok does many useful things, but we will only focus on the types of boilerplate defined above.

Adding Lombok to a Project

For maven, add this to your pom.xml


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

For gradle, add this to your build.gradle file


providedCompile group: 'org.projectlombok', name: 'lombok'

Lombok Annotations

@Setter

The @Setter annotation auto-generates a setter for a POJO bean field


private String name;

public void setName(String name){
  this.name = name;
}

becomes


@Setter
private String name;
@Getter

The @Getter annotation auto-generates a getter for a POJO bean field


private String name;

public String getName(){
  return this.name;
}

becomes


@Getter
private String name;
@Data

The @Data annotation auto-generates a setter and getter for every POJO bean field.


public class Bean {

  private String stringField;

  public String getStringField(){
    return this.stringField;
  }

  public void setStringField(String stringField) {
    this.stringField = stringField;
  }

}

becomes


@Data
public class Bean {

  private String stringField;

}
@AllArgsConstructor

The @AllArgsConstructor annotration automatically generates an all-args constructor


public class Bean {

  private String stringField;

  public Bean(String stringField) {
    this.stringField = stringField;
  }

}

becomes


@AllArgsConstructor
public class Bean {
   
  private String stringField;

}
@NoArgsConstructor

Similar to @AllArgsConstructor, @NoArgsConstructor generates a default constructor.

Note that you will only need this if you have defined a different constructor, this is because the Java compiler automatically generates the no-args constructor when no constructor is defined.

Conclusion

Java requires a lot of boilerplate code for our very common everyday POJO beans. Lombok is a java build plugin that generates boilerplate code at compile-time.

By switching multiple lines of code with single annotations, Lombok is sure to save you much time. If you are not using Lombok now, it is about time to start.

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