Introduction
In this blog we will get started with Lombok in Java.
Lombok is a java library that helps you reduce boilerplate code for mainly Java classes.
When you define a class, you need to write getter and setters, constructors and methods like
equals(), hashcode() and toString().
If your class have many fields you will have lot of getter and setters.
To improve code readability we can use Lombok annotations.
In the below example we can see code which does not use Lombok Annotations.
It has getter and setters, constructor and methods like equals(), hashcode() and toString().
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package demolombok;
import java.util.Objects;
public class Employee {
private int empid;
private String empname;
private int salary;
public Employee(int empid, String empname, int salary) {
this.empid = empid;
this.empname = empname;
this.salary = salary;
}
public int getEmpid() {
return empid;
}
public void setEmpid(int empid) {
this.empid = empid;
}
public String getEmpname() {
return empname;
}
public void setEmpname(String empname) {
this.empname = empname;
}
public int getSalary() {
return salary;
}
public void setSalary(int salary) {
this.salary = salary;
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Employee employee = (Employee) o;
return empid == employee.empid && salary == employee.salary && Objects.equals(empname, employee.empname);
}
@Override
public int hashCode() {
return Objects.hash(empid, empname, salary);
}
@Override
public String toString() {
return "Employee{" +
"empid=" + empid +
", empname='" + empname + '\'' +
", salary=" + salary +
'}';
}
}
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You can see that above code has lot of boilerplate code.
We can reduce this by using Lombok Annotations.
Using Lombok
To get started with lombok, we need to add following maven dependency.
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<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.32</version>
</dependency>
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After using lombok, below code become concise.
Code is reduced only while viewing.
This keeps code small,clean and readable.
During compilation, bytecode is injected with all boilerplate code.
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package demolombok;
import lombok.*;
@Getter
@Setter
@AllArgsConstructor
@ToString
@EqualsAndHashCode
public class Employee {
private int empid;
private String empname;
private int salary;
}
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package demolombok;
public class App {
public static void main(String[] args) {
Employee employee = new Employee(1,"Harish",20000);
System.out.println(employee.getEmpid());
System.out.println(employee.toString());
System.out.println(employee.hashCode());
//1
//Employee(empid=1, empname=Harish, salary=20000)
//-2139197279
}
}
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Lombok Annotations
Below is the brief detail about each annotation.
@NonNull: This will add non-null validation on fields, method parameters or constructor arguments.
@Getter and @Setter: This will generate getter and setter methods for the class.
@ToString : This will generate toString() method for the class.
@EqualsAndHashCode : This will generate equals and hashcode methods for the given class
@NoArgsConstructor: This will generate no argument constructor for the class.
@AllArgsConstructor: This will generate all argument constructor for the class.
@RequiredArgsConstructor: This will generate constructor
using those fields which are final or @NotNull annotated.
@Data: This will combine @Getter,@Setter,@ToString,@EqualsAndHashCode and @RequiredArgsConstructor
together.
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package demolombok;
import lombok.*;
@Data
public class Employee {
private final int empid;
private final String empname;
private final int salary;
}
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package demolombok;
public class App {
public static void main(String[] args) {
Employee employee = new Employee(1,"Harish",20000);
System.out.println(employee.getEmpid());
System.out.println(employee.toString());
System.out.println(employee.hashCode());
//1
//Employee(empid=1, empname=Harish, salary=20000)
//-2139197279
}
}
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Conclusion
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Lombok annotations reduce boilerplate code.
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It improves readability of code.
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Makes life easier for developers.
I hope this guide to Lombok in Java was useful!!!