First Step to Lombok Annotations

1. Overview

Do you feel bored of writing the same boilerplate and repetitive code in Java again and again ?

So this is what Lombok Project was made for, it helps you to prevent bothering yourself from writing this ugly repetitive code, and instead replace it with some meaningful annotations, so you will end up with a clean and good looking source code. 🙂

In this article, i will show you how to use Lombok with some basic examples.

2. Setup Lombok

1. To be able to use Lombok in your project, add the following dependency to your pom.xml.

<dependency>
	<groupId>org.projectlombok</groupId>
	<artifactId>lombok</artifactId>
	<optional>true</optional>
	<version>1.16.20</version>
</dependency>

2. And add the Lombok plugin to your IDE to be able to deal with Lombok annotations.

• Lombok plugin for IntelliJ IDEA : projectlombok.org/setup/intellij
• Lombok plugin for Eclipse and STS : projectlombok.org/setup/eclipse

Visit Project Lombok official website for other IDEs.

3. Use Lombok

3.1. @NonNull

Adding @NonNull on the parameter of a method generates a null check statement for these parameter.

With Lombok :

public class NonNullHelloWorld {

    public void doSomething(@NonNull String input) {
        input.length();
    }
}

Without Lombok :

public class NonNullHelloWorld {

    public void doSomething(String input) {
	
        if (input == null) {
            throw new NullPointerException("input");
        }
        input.length();
    }
}

3.2. @Getter and @Setter

Add @Getter and/or @Setter to an attribute to generate getter and setter for it.

With Lombok :

public class GetterSetterHelloWorld {

    @Getter @Setter
    private String firstAttribute;
    
    @Getter
    private String secondAttribute;
}

Without Lombok :

public class GetterSetterHelloWorld {

	private String firstAttribute;
	private String secondAttribute;

    public String getFirstAttribute() { ... }
    public void setFirstAttribute(String firstAttribute) { ... }
    public String getSecondAttribute() { ... }
}

3.3. @ToString

Use @ToString to generate under the hood the toString() method for your classes.

With Lombok :

@ToString
public class ToStringHelloWorld {

    private String firstAttribute;

}

Without Lombok :

public class ToStringHelloWorld {

    private String firstAttribute;

    public String toString() {
        return "ToStringHelloWorld(firstAttribute=" + this.firstAttribute + ")";
    }
}

There is also @EqualsAndHashCode that do exactly the same but with equals() and hashCode() methods.

3.4. @Data

the @Data annotation is equivalent to the @Getter, @Setter, @ToString and @EqualsAndHashCode together, it generates getters, setters, toString, equals and hashCode methods for your classes.

With Lombok :

@Data
public class DataHelloWorld {

    private String firstAttribute;
    private String secondAttribute;

}

Without Lombok :

public class DataHelloWorld {

    private String firstAttribute;
    private String secondAttribute;

    public String getFirstAttribute() {
        //...
    }
    public String getSecondAttribute() {
        //...
    }
    public void setFirstAttribute(String firstAttribute) {
        //...
    }
    public void setSecondAttribute(String secondAttribute) {
        //...
    }
    public boolean equals(Object o) {
        // ...
    }
    public int hashCode() {
        //...
    }
    public String toString() {
       //...
    }
}

3.5. @Value

The @Value is similar to @Data, the main difference between them is @Value generates an immutable class.

With Lombok :

@Value
public class ValueHelloWorld {

    private String firstAttribute;
    private String secondAttribute;

}

Without Lombok :

public final class ValueHelloWorld {

    private final String firstAttribute;
    private final String secondAttribute;

    public ValueHelloWorld(String firstAttribute, String secondAttribute) {
        this.firstAttribute = firstAttribute;
        this.secondAttribute = secondAttribute;
    }
    public String getFirstAttribute() {
        //...
    }
    public String getSecondAttribute() {
        //...
    }
    public boolean equals(Object o) {
       //...
    }
    public int hashCode() {
        //...
    }
    public String toString() {
        //...
    }
}

3.6. @Log and @Slf4j

The @Log, @Slf4j and @CommonsLog annotations add a Logger to your class.

With Lombok :

@Slf4j
public class Slf4jHelloWorld {

    public void doSomething() {
        log.info("This is a message from Lombok @Slf4j");
    }
}

Without Lombok :

public class Slf4jHelloWorld {

    private static final Logger log = LoggerFactory.getLogger(Slf4jHelloWorld.class);

    public void doSomething() {
        log.info("This is a message from Lombok @Slf4j");
    }
}

3.7. @Cleanup

Add @Cleanup to your resources to make sure that they will be cleaned up properly in a finally block.

With Lombok :

public class CleanupHelloWorld {

    public void doSomething() throws IOException {
        @Cleanup OutputStream out = new FileOutputStream("file");
        out.write(1);
        out.write(2);
    }
}

Without Lombok :

public class CleanupHelloWorld {

    public void doSomething() throws IOException {
        FileOutputStream out = new FileOutputStream("file");
        try {
            out.write(1);
            out.write(2);
        } finally {
            if (out != null) {
                out.close();
            }
        }
    }
}

You can visit Project Lombok website for more annotations.

Find the source code of this example on GitHub.

 

4. Conclusion

Project Lombok is a powerful tool that saves time and prevents developers from dealing with boilerplate code.

If for some reason you felt not comfortable with the Lombok ( probably not 🙂 ), you can Delombok your source code to a version without Lombok annotations.