Lombok 簡介
Lombok 是一種 Java 實用工具,可用來幫助開發人員消除 Java 的冗長,尤其是對于簡單的 Java 對象(POJO)。它通過注釋實作這一目的。通過在開發環境中實作 Lombok,開發人員可以節省建構諸如
hashCode()
和
equals()
、
getter / setter
這樣的方法以及以往用來分類各種 accessor 和 mutator 的大量時間。
Lombok 安裝
使 IntelliJ IDEA 支援 Lombok 方式如下:
- Intellij 設定支援注解處理
點選 File > Settings > Build > Annotation Processors
勾選 Enable annotation processing
- 安裝插件
點選 Settings > Plugins > Browse repositories
查找 Lombok Plugin 并進行安裝
重新開機 IntelliJ IDEA
- 将 lombok 添加到 pom 檔案
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.8</version>
</dependency>
Lombok 使用
API
Lombok 提供注解API 來修飾指定的類:
@Getter and @Setter
Lombok 代碼:
@Getter @Setter private boolean employed = true;
@Setter(AccessLevel.PROTECTED) private String name;
等價于 Java 源碼:
private boolean employed = true;
private String name;
public boolean isEmployed() {
return employed;
}
public void setEmployed(final boolean employed) {
this.employed = employed;
}
protected void setName(final String name) {
this.name = name;
}
@NonNull
@Getter @Setter @NonNull
private List<Person> members;
@NonNull
private List<Person> members;
public Family(@NonNull final List<Person> members) {
if (members == null) throw new java.lang.NullPointerException("members");
this.members = members;
}
@NonNull
public List<Person> getMembers() {
return members;
}
public void setMembers(@NonNull final List<Person> members) {
if (members == null) throw new java.lang.NullPointerException("members");
this.members = members;
}
@ToString
@ToString(callSuper=true,exclude="someExcludedField")
public class Foo extends Bar {
private boolean someBoolean = true;
private String someStringField;
private float someExcludedField;
}
public class Foo extends Bar {
private boolean someBoolean = true;
private String someStringField;
private float someExcludedField;
@java.lang.Override
public java.lang.String toString() {
return "Foo(super=" + super.toString() +
", someBoolean=" + someBoolean +
", someStringField=" + someStringField + ")";
}
}
@EqualsAndHashCode
@EqualsAndHashCode(callSuper=true,exclude={"address","city","state","zip"})
public class Person extends SentientBeing {
enum Gender { Male, Female }
@NonNull private String name;
@NonNull private Gender gender;
private String ssn;
private String address;
private String city;
private String state;
private String zip;
}
public class Person extends SentientBeing {
enum Gender {
/*public static final*/ Male /* = new Gender() */,
/*public static final*/ Female /* = new Gender() */;
}
@NonNull
private String name;
@NonNull
private Gender gender;
private String ssn;
private String address;
private String city;
private String state;
private String zip;
@java.lang.Override
public boolean equals(final java.lang.Object o) {
if (o == this) return true;
if (o == null) return false;
if (o.getClass() != this.getClass()) return false;
if (!super.equals(o)) return false;
final Person other = (Person)o;
if (this.name == null ? other.name != null : !this.name.equals(other.name)) return false;
if (this.gender == null ? other.gender != null : !this.gender.equals(other.gender)) return false;
if (this.ssn == null ? other.ssn != null : !this.ssn.equals(other.ssn)) return false;
return true;
}
@java.lang.Override
public int hashCode() {
final int PRIME = 31;
int result = 1;
result = result * PRIME + super.hashCode();
result = result * PRIME + (this.name == null ? 0 : this.name.hashCode());
result = result * PRIME + (this.gender == null ? 0 : this.gender.hashCode());
result = result * PRIME + (this.ssn == null ? 0 : this.ssn.hashCode());
return result;
}
}
@Data
@Data(staticConstructor="of")
public class Company {
private final Person founder;
private String name;
private List<Person> employees;
}
public class Company {
private final Person founder;
private String name;
private List<Person> employees;
private Company(final Person founder) {
this.founder = founder;
}
public static Company of(final Person founder) {
return new Company(founder);
}
public Person getFounder() {
return founder;
}
public String getName() {
return name;
}
public void setName(final String name) {
this.name = name;
}
public List<Person> getEmployees() {
return employees;
}
public void setEmployees(final List<Person> employees) {
this.employees = employees;
}
@java.lang.Override
public boolean equals(final java.lang.Object o) {
if (o == this) return true;
if (o == null) return false;
if (o.getClass() != this.getClass()) return false;
final Company other = (Company)o;
if (this.founder == null ? other.founder != null : !this.founder.equals(other.founder)) return false;
if (this.name == null ? other.name != null : !this.name.equals(other.name)) return false;
if (this.employees == null ? other.employees != null : !this.employees.equals(other.employees)) return false;
return true;
}
@java.lang.Override
public int hashCode() {
final int PRIME = 31;
int result = 1;
result = result * PRIME + (this.founder == null ? 0 : this.founder.hashCode());
result = result * PRIME + (this.name == null ? 0 : this.name.hashCode());
result = result * PRIME + (this.employees == null ? 0 : this.employees.hashCode());
return result;
}
@java.lang.Override
public java.lang.String toString() {
return "Company(founder=" + founder + ", name=" + name + ", employees=" + employees + ")";
}
}
@Cleanup
public void testCleanUp() {
try {
@Cleanup ByteArrayOutputStream baos = new ByteArrayOutputStream();
baos.write(new byte[] {'Y','e','s'});
System.out.println(baos.toString());
} catch (IOException e) {
e.printStackTrace();
}
}
public void testCleanUp() {
try {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
try {
baos.write(new byte[]{'Y', 'e', 's'});
System.out.println(baos.toString());
} finally {
baos.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
@Synchronized
private DateFormat format = new SimpleDateFormat("MM-dd-YYYY");
@Synchronized
public String synchronizedFormat(Date date) {
return format.format(date);
}
private final java.lang.Object $lock = new java.lang.Object[0];
private DateFormat format = new SimpleDateFormat("MM-dd-YYYY");
public String synchronizedFormat(Date date) {
synchronized ($lock) {
return format.format(date);
}
}
@SneakyThrows
@SneakyThrows
public void testSneakyThrows() {
throw new IllegalAccessException();
}
public void testSneakyThrows() {
try {
throw new IllegalAccessException();
} catch (java.lang.Throwable $ex) {
throw lombok.Lombok.sneakyThrow($ex);
}
}
示例
使用 Lombok 定義一個 Java Bean
import lombok.Data;
import lombok.ToString;
@Data
@ToString(exclude = "age")
public class Person {
private String name;
private Integer age;
private String sex;
}
測試
Person person = new Person();
person.setName("張三");
person.setAge(20);
person.setSex("男");
System.out.println(person.toString());
// output: Person(name=張三, sex=男)
資料
Lombok 官網|
Lombok Github IntelliJ IDEA - Lombok Plugin