Project Lombok - @Data Annotation Example

In this post, I will show you how to reduce boilerplate code for the below methods using @Data annotation.
  1. getters for all fields
  2. setters for all non-final fields,
  3. toString method
  4. equals and hashCode implementations that involve the fields of the class
  5. constructor that initializes all final fields

@Data Annotation Overview

@Data is a convenient shortcut annotation that bundles the features of @ToString, @EqualsAndHashCode, @Getter / @Setter, and @RequiredArgsConstructor together.

Project Lombok Maven

Create a simple maven project using - How to Create a Simple Maven Project in Eclipse article.
Add the below dependency in your maven project pom.xml file:
<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.4</version>
    <scope>provided</scope>
</dependency>

Adding the Lombok Plugin in IDE (Eclipse)

Follow below steps to install Lombok in eclipse for Windows:
  • Downloaded jar from https://projectlombok.org/download or use the jar which is downloaded from your maven build.
  • Execute command in terminal: java -jar lombok.jar
  • This command will open window as shown in the picture below, install and quit the installer and restart eclipse.

Without Project Lombok

package net.javaguides.lombok;

import java.time.LocalDate;

public class User {
    private long id;
    private String firstName;
    private String lastName;
    private int age;
    private LocalDate createdDate;
    private LocalDate updatedDate;
    private String gender;
    public User(long id, String firstName, String lastName, int age, LocalDate createdDate, LocalDate updatedDate,
        String gender) {
        super();
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = age;
        this.createdDate = createdDate;
        this.updatedDate = updatedDate;
        this.gender = gender;
    }
    public long getId() {
        return id;
    }
    public String getFirstName() {
        return firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public int getAge() {
        return age;
    }
    public LocalDate getCreatedDate() {
        return createdDate;
    }
    public LocalDate getUpdatedDate() {
        return updatedDate;
    }
    public String getGender() {
        return gender;
    }
    public void setId(long id) {
        this.id = id;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public void setCreatedDate(LocalDate createdDate) {
        this.createdDate = createdDate;
    }
    public void setUpdatedDate(LocalDate updatedDate) {
        this.updatedDate = updatedDate;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + age;
        result = prime * result + ((createdDate == null) ? 0 : createdDate.hashCode());
        result = prime * result + ((firstName == null) ? 0 : firstName.hashCode());
        result = prime * result + ((gender == null) ? 0 : gender.hashCode());
        result = prime * result + (int)(id ^ (id >>> 32));
        result = prime * result + ((lastName == null) ? 0 : lastName.hashCode());
        result = prime * result + ((updatedDate == null) ? 0 : updatedDate.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;
        User other = (User) obj;
        if (age != other.age)
            return false;
        if (createdDate == null) {
            if (other.createdDate != null)
                return false;
        } else if (!createdDate.equals(other.createdDate))
            return false;
        if (firstName == null) {
            if (other.firstName != null)
                return false;
        } else if (!firstName.equals(other.firstName))
            return false;
        if (gender == null) {
            if (other.gender != null)
                return false;
        } else if (!gender.equals(other.gender))
            return false;
        if (id != other.id)
            return false;
        if (lastName == null) {
            if (other.lastName != null)
                return false;
        } else if (!lastName.equals(other.lastName))
            return false;
        if (updatedDate == null) {
            if (other.updatedDate != null)
                return false;
        } else if (!updatedDate.equals(other.updatedDate))
            return false;
        return true;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", age=" + age +
            ", createdDate=" + createdDate + ", updatedDate=" + updatedDate + ", gender=" + gender + "]";
    }
}

With Project Lombok

With Project Lombok, we can remove all of these methods here. Just with @Data annotation in Project Lombok.
package net.javaguides.lombok.data;

import java.time.LocalDate;

import lombok.Data;

/**
 * @Data is a convenient shortcut annotation that bundles the features of 
 * @ToString, @EqualsAndHashCode, @Getter / @Setter and @RequiredArgsConstructor together.
 */

@Data
public class UserLombokModel {
    private long id;
    private String firstName;
    private String lastName;
    private int age;
    private LocalDate createdDate;
    private LocalDate updatedDate;
    private String gender;
}

Testing

As you installed Lombok plugin in eclipse so we can test using main() method:
package net.javaguides.lombok.data;

import java.time.LocalDate;

public class LombokTest {
    public static void main(String[] args) {
        UserLombokModel lombokModel = new UserLombokModel();

        // test setter methods
        lombokModel.setId(100 L);
        lombokModel.setFirstName("Ramesh");
        lombokModel.setLastName("Fadatare");
        lombokModel.setAge(28);
        lombokModel.setGender("Male");
        lombokModel.setCreatedDate(LocalDate.now());
        lombokModel.setUpdatedDate(LocalDate.now());

        UserLombokModel lombokModel2 = new UserLombokModel();

        lombokModel2.setId(100 L);
        lombokModel2.setFirstName("Ramesh");
        lombokModel2.setLastName("Fadatare");
        lombokModel2.setAge(28);
        lombokModel2.setGender("Male");
        lombokModel2.setCreatedDate(LocalDate.now());
        lombokModel2.setUpdatedDate(LocalDate.now());

        // equals method
        System.out.println(lombokModel.equals(lombokModel2));

        // hashCode method
        System.out.println(lombokModel.hashCode());
        System.out.println(lombokModel2.hashCode());

        // toString method
        System.out.println(lombokModel.toString());
    }
}

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