Lombok: A Collection of @Annotations You Must Know

Lombok #

One of the Java libraries that makes long source code concise using annotations.

Types of Lombok Annotations #

@NotNull #

Specifies that a field's value cannot be null.

@Getter #

Generates a getter method for the field. @Getter(lazy=true): Calculates the value once on the first getter call, then caches and uses that value (to use it only once on the first call, rather than every time the getter is called). AccessLevel can be specified.

@Setter #

Generates a setter method for the field. AccessLevel can be specified.

@NoArgsConstructor #

Generates a default constructor with no parameters.

@RequiredArgsConstructor #

Generates a constructor for uninitialized final fields and fields annotated with @NotNull.

@AllArgsConstructor #

Generates a constructor with all fields.

ToString #

Generates a toString() method. Removes unnecessary properties using the exclude attribute, e.g., @ToString(exclude ="value").

@EqualsAndHashCode #

Generates equals() and hashCode() methods. The exclude attribute can be used.

@Data #

@Getter + @Setter + @RequiredArgsConstructor + @ToString + @EqualsAndHashCode

@Value #

An annotation that signifies immutability. Member fields annotated with @Value become constants with a private access modifier and final (since they are final, setters cannot exist).

@Log #

Can automatically generate a Logger. Automatically creates a log field and assigns a logger object with the class name to it.

@Builder #

Automatically generates a Builder. When using the @Singular annotation, elements can be added one by one.

@Builder + @Singular Example #

// 선언
@Builder
public class Movie {
	private String title;
    @Singular
    private List<String> actress;
}

// 사용 예제
// movie(title="삼진그룹 영어토익반", actress= ["고아성", "이솜", "박혜수"])
Movie movie = Movie.builder()
				.title("삼진그룹 영어토익반")
                .actress("고아성")
                .actress("이솜")
                .actress("박혜수")
                .build();

toString(): A method that converts an object's values into a string and returns it. equals(): An equality comparison operator (compares whether the contents of two objects are the same). hashCode(): An identity comparison operator (compares whether two objects are the same).