Java開発においてとても便利なLombokを説明します。

1. Lombok
2017-07-20
onozaty

2. Lombok?
• Java (
)
•
• getter/setter
• equals, hashCode
• toString
•

3. Lombok?
•
@Getter
@Setter
public class Customer {
private int id;
private String name;
}
public class Customer {
private int id;
private String name;
public int getId() {
return this.id;
}
public String getName() {
return this.name;
}
public void setId(final int id) {
this.id = id;
}
public void setName(final String name) {
this.name = name;
}
}

4. Lombok?
• IDE IDE

5. • Lombok
( )
• IDE
• Eclipse Lombok jar
Eclipse
( )

6. @Getter, @Setter
• getter/setter
• (
)
• (
public)
• final setter (
)

7. @Getter, @Setter
public class GetterSetterExample {
//
@Getter
@Setter
private int id;
//
@Setter(AccessLevel.PROTECTED)
private String name;
}
public class GetterSetterExample {
private int id;
private String name;
public int getId() {
return this.id;
}
public void setId(final int id) {
this.id = id;
}
protected void setName(final String name) {
this.name = name;
}
}

8. @ToString
•
toString
•

9. @ToString
@ToString
public class ToStringExample {
private int id;
private String name;
public String getName() {
return name;
}
}
// exclude
@ToString(exclude = "name")
class ToStringExample2 {
private int id;
private String name;
}
public class ToStringExample {
private int id;
private String name;
public String getName() {
return name;
}
@Override
public String toString() {
return "ToStringExample(id=" + this.id
+ ", name=" + this.getName() + ")";
}
}
class ToStringExample2 {
private int id;
private String name;
@Override
public String toString() {
return "ToStringExample2(id="
+ this.id + ")";
}
}

10. @EqualsAndHashCode
• equals hashCode
•
•
Lombok

11. @EqualsAndHashCode
@EqualsAndHashCode
public class EqualsAndHashCodeExample
{
private int id;
private String name;
}
//
@EqualsAndHashCode(exclude = "age")
class EqualsAndHashCodeExample2 {
private int id;
private String name;
private int age;
}
public class EqualsAndHashCodeExample {
private int id;
private String name;
@Override
public boolean equals(final Object o) { … }
@Override
public int hashCode() { … }
}
public class EqualsAndHashCodeExample2 {
private int id;
private String name;
private int age;
// age
@Override
public boolean equals(final Object o) { … }
@Override
public int hashCode() { … }
}

12. @AllArgsConstructor,
@NoArgsConstructor,
@RequiredArgsConstructor
•
• @AllArgsConstructor
• @NoArgsConstructor
• @RequiredArgsConstructor final
(final
)

13. @AllArgsConstructor,
@NoArgsConstructor,
@RequiredArgsConstructor
@AllArgsConstructor
@NoArgsConstructor
public class ConstructorExample {
private int id;
private String name;
}
@RequiredArgsConstructor
class ConstructorExample2 {
private final int id;
private String name;
}
public class ConstructorExample {
private int id;
private String name;
public ConstructorExample(
final int id, final String name) {
this.id = id;
this.name = name;
}
public ConstructorExample() {
}
}
class ConstructorExample2 {
private final int id;
private String name;
public ConstructorExample2(final int id) {
this.id = id;
}
}

14. @Data
•
• @ToString
• @EqualsAndHashCode
• @Getter
• @Setter
• @RequiredArgsConstructor
•

15. @Data
@Data
public class DataExample {
private final int id;
private String name;
}
public class DataExample {
private final int id;
private String name;
public DataExample(final int id) {
this.id = id;
}
public int getId() {
return this.id;
}
public String getName() {
return this.name;
}
public void setName(final String name) {
this.name = name;
}
@Override
public boolean equals(final Object o) { … }
@Override
public int hashCode() { … }
@Override
public String toString() { … }
}

16. @Value
• final
• @ToString
• @EqualsAndHashCode
• @Getter
• @RequiredArgsConstructor
• Immutable

17. @Value
@Value
public class ValueExample {
private int id;
private String name;
}
public final class ValueExample {
private final int id;
private final String name;
public ValueExample(
final int id, final String name) {
this.id = id;
this.name = name;
}
public int getId() {
return this.id;
}
public String getName() {
return this.name;
}
@Override
public boolean equals(final Object o) { … }
@Override
public int hashCode() { … }
@Override
public String toString() { … }
}

18. @Builder
• Builder (GoF Effective
Java ) Builder
• Builder

19. @Builder
public static void main(String[] args) {
// Builder ( )
Customer customer = new Customer(
"Taro",
"Yamada",
"Tokyo",
Arrays.asList("A", "B"));
System.out.println(customer);
}
@AllArgsConstructor
@ToString
class Customer {
private String firstName;
private String lastName;
private String city;
private List<String> tags;
}
public static void main(String[] args) {
// Builder
Customer customer = Customer.builder()
.firstName("Taro")
.lastName("Yamada")
.city("Tokyo")
.tag("A")
.tag("B")
.build();
System.out.println(customer);
}
@Builder
@ToString
class Customer {
private String firstName;
private String lastName;
private String city;
@Singular
private List<String> tags;
}

20. @Slf4j
• log static Logger
• Slf4j Apache commons log(@Log)
• Logger

21. @Slf4j
@Slf4j
public class LogExample {
public static void main(String[] args) {
log.info("main.");
}
}
public class LogExample {
private static final org.slf4j.Logger log =
org.slf4j.LoggerFactory.getLogger(LogExample.class);
public static void main(String[] args) {
log.info("main.");
}
}

22. @NonNull
• null
(null
NullPointerException )
• Objects.requireNonNull

23. @NonNull
@RequiredArgsConstructor
public class NonNullExample {
@NonNull
private String name;
public void printLength(
@NonNull String message) {
System.out.println(
message.length());
}
}
public class NonNullExample {
@NonNull
private String name;
public void printLength(
@NonNull String message) {
if (message == null) {
throw new NullPointerException("message");
}
System.out.println(message.length());
}
public NonNullExample(
@NonNull final String name) {
if (name == null) {
throw new NullPointerException("name");
}
this.name = name;
}
}

24. val
•
• Scala val

25. val
public static void main(String[] args) {
val list = new ArrayList<String>();
list.add("a");
list.add("b");
val item = list.get(0);
System.out.println(item);
}
public static void main(String[] args) {
final ArrayList<String> list =
new ArrayList<String>();
list.add("a");
list.add("b");
final String item = list.get(0);
System.out.println(item);
}

26. @Cleanup
•
( )
close
• try/finally
• close

27. @Cleanup
public static void main(String[] args) throws IOException {
Path filePath = Paths.get(args[0]);
@Cleanup BufferedReader reader = Files.newBufferedReader(filePath);
System.out.println(reader.readLine());
}
public static void main(String[] args) throws IOException {
Path filePath = Paths.get(args[0]);
BufferedReader reader = Files.newBufferedReader(filePath);
try {
System.out.println(reader.readLine());
} finally {
if (Collections.singletonList(reader).get(0) != null) {
reader.close();
}
}
}

28. @Synchronized
• synchronized
• static
Lock
• Lock

29. @Synchronized
public class SynchronizedExample {
@Synchronized
public static void hello() {
System.out.println("hello");
}
@Synchronized
public void bye() {
System.out.println("bye");
}
}
public class SynchronizedExample {
private static final Object $LOCK = new Object[0];
private final Object $lock = new Object[0];
public static void hello() {
synchronized (SynchronizedExample.$LOCK) {
System.out.println("hello");
}
}
public void bye() {
synchronized (this.$lock) {
System.out.println("bye");
}
}
}

30. @SneakyThrows
• (
)
•
•
• https://github.com/rzwitserloot/lombok/blob/master/src/core/
lombok/Lombok.java#L49
• Lombok
Lombok jar

31. @SneakyThrows
public class SneakyThrowsExample {
@SneakyThrows
public static void main(String[] args) {
throw new Exception();
}
}
public class SneakyThrowsExample {
public static void main(String[] args) {
try {
throw new Exception();
} catch (final Throwable $ex) {
throw Lombok.sneakyThrow($ex);
}
}
}

32. delombok
• delombok Lombok
• delombok
• https://projectlombok.org/features/delombok
> java -jar lombok.jar delombok src -d src-delomboked

33. • Lombok
onMethd onParam
• https://projectlombok.org/features/experimental/onX

34. Lombok
•
•
• getter/setter
•
• equals hashCode

35. Lombok
•
• Lombok
• Lombok
Lombok
• val @Cleanup @SneakyThrows
(Lombok
)

36. •
Lombok
• https://projectlombok.org/features/all