Project Lombok is a Java library that automatically plugs into projects and generates common boilerplate code like getters, setters, equals, hashCode and toString methods through annotations. This reduces code verbosity and speeds up development. The document discusses how to add Lombok dependencies to Maven and Gradle projects, and demonstrates how annotations like @Getter, @Setter, @ToString, @EqualsAndHashCode, @NoArgsConstructor and @Builder can be used to generate these common methods automatically. Potential downsides are that Lombok relies on non-public APIs so compiler upgrades could break code, and it cannot detect constructors of superclasses.

1. Project Lombok in Java
Krzysztof Czajkowski
krzysztof.czajkowski@softwarehut.com

2. public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
private LocalDateTime birthDate;
private List<Superhero> friends;
private List<Superhero> enemies;
}

4. public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
private LocalDateTime birthDate;
private List<Superhero> friends;
private List<Superhero> enemies;
public Superhero() {
}
}

7. public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
private LocalDateTime birthDate;
private List<Superhero> friends;
private List<Superhero> enemies;
private City birthPlace;
private Planet homePlanet;
private City residenceCity;
private Nature nature;
}

10. Can we do it easier?

11. public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
private LocalDateTime birthDate;
private List<Superhero> friends;
private List<Superhero> enemies;
}

12. @Data
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
private LocalDateTime birthDate;
private List<Superhero> friends;
private List<Superhero> enemies;
}

13. @Data
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
private LocalDateTime birthDate;
private List<Superhero> friends;
private List<Superhero> enemies;
private City birthPlace;
private Planet homePlanet;
private City residenceCity;
private Nature nature;
}

14. How to add Lombok to your project?

15. Maven
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.6</version>
</dependency>

16. Gradle
Version < 2.12
dependencies {
provided "org.projectlombok:lombok:1.16.16"
}
Version >= 2.12
dependencies {
compileOnly "org.projectlombok:lombok:1.16.16"
}

17. Annotation processing
lombok.core.AnnotationProcessor extends AbstractProcessor

18. Getter and Setter

19. Getter and Setter
@Getter
@Setter
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
}

20. Getter and Setter
@Getter
public class Superhero {
@Setter
private String firstName;
@Setter
private String lastName;
@Setter
private String name;
private String superpower;
}

21. NonNull

22. NonNull
@Getter
@Setter
public class Superhero {
private String firstName;
private String lastName;
private String name;
@NonNull
private String superpower;
}

23. NonNull
public void setSuperpower(@NonNull String superpower) {
if(superpower == null) {
throw new NullPointerException("superpower");
} else {
this.superpower = superpower;
}
}

24. EqualsAndHashCode
@EqualsAndHashCode
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
}

25. EqualsAndHashCode
@EqualsAndHashCode(of = {"name"})
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
}

26. EqualsAndHashCode
public int hashCode() {
boolean PRIME = true;
byte result = 1;
String $name = this.name;
int result1 = result * 59 + ($name ==
null?43:$name.hashCode());
return result1;
}

27. EqualsAndHashCode
@EqualsAndHashCode(exclude = {„superpower"})
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
}

28. EqualsAndHashCodepublic int hashCode() {
boolean PRIME = true;
byte result = 1;
String $firstName = this.firstName;
int result1 = result * 59 + ($firstName ==
null?43:$firstName.hashCode());
String $lastName = this.lastName;
result1 = result1 * 59 + ($lastName ==
null?43:$lastName.hashCode());
String $name = this.name;
result1 = result1 * 59 + ($name ==
null?43:$name.hashCode());
return result1;

29. ToString
@ToString(of = {"name", "superpower"})
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
}

30. ToString
public String toString() {
return "Superhero(name=" + this.name +
", superpower=" + this.superpower + ")";
}

31. Generate constructors

32. NoArgsConstructor

33. NoArgsConstructor
@NoArgsConstructor
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
}

34. AllArgsConstructor

35. AllArgsConstructor
@AllArgsConstructor
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
}

36. AllArgsConstructor
@ConstructorProperties({"firstName", "lastName",
"name", "superpower"})
public Superhero(String firstName, String lastName,
String name, String superpower) {
this.firstName = firstName;
this.lastName = lastName;
this.name = name;
this.superpower = superpower;
}

37. RequiredArgsConstructor

38. RequiredArgsConstructor
@RequiredArgsConstructor
public class Superhero {
private final int counter;
@NonNull
private String firstName;
private String lastName;
private String name;
private String superpower;
}

39. RequiredArgsConstructor
@ConstructorProperties({"counter", "firstName"})
public Superhero(int counter, @NonNull String
firstName) {
if(firstName == null) {
throw new NullPointerException("firstName");
} else {
this.counter = counter;
this.firstName = firstName;
}
}

40. Data
@Data
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
}

41. Combined annotations
@RequiredArgsConstructor @ToString
@Getter
public class Superhero {
@Setter
private String firstName;
@Setter
private String lastName;
@NonNull @Setter
private String name;
private String superpower;
}

42. Log
@Log
public class Superhero {
public void doSomething() {
log.log(Level.INFO, "Doing something");
}
}

43. Log
public class Superhero {
private static final Logger log =
Logger.getLogger(Superhero.class.getName());
public Superhero() {
}
public void doSomething() {
log.log(Level.INFO, "Doing something");
}
}

44. Log
maj 31, 2017 8:55:24 AM com.sh.lombok.superhero.model.Superhero
doSomething
INFO: Doing something

45. Builder
@Builder
@ToString
public class Superhero {
private String firstName;
private String lastName;
private String name;
private String superpower;
}

46. Builder
public static void main(String[] args) {
Superhero batman = Superhero.builder()
.firstName("Bruce")
.lastName("Wayne")
.name("Batman")
.superpower("")
.build();
log.log(Level.INFO, batman.toString());
}

47. Builder
INFO: Superhero(firstName=Bruce, lastName=Wayne, name=Batman,
superpower=)

48. Delombok
<plugin>
<groupId>org.projectlombok</groupId>
<artifactId>lombok-maven-plugin</artifactId>
<version>1.16.16.0</version>
<executions>
<execution>
<phase>generate-sources</phase>
<goals>
<goal>delombok</goal>
</goals>
</execution>
</executions>
</plugin>

49. Delombok
@java.lang.SuppressWarnings("all")
@javax.annotation.Generated("lombok")
public Nature getNature() {
return this.nature;
}
@java.lang.SuppressWarnings("all")
@javax.annotation.Generated("lombok")
public void setFirstName(final String firstName) {
this.firstName = firstName;
}

50. Pros
•Less code
•More readable classes
•Faster development

51. Cons?
•Can’t detect constructor of superclass
•Using non-public API - upgrading
compiler may break your code

52. Project Lombok
• https://projectlombok.org/

53. The End