Lombok 使用小結

Lombok 使用小結

• Lombok 簡介
• Lombok 安裝
• Lombok 使用
  • API
  • 示例
• 示例源碼
• 引用和引申

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）。它通過注釋實現這一目的。通過在開發環境中實現 Lombok，開發人員可以節省構建諸如 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 支持 Lombok 方式如下：

（1）Intellij 設置支持注解處理

點擊 File > Settings > Build > Annotation Processors

勾選 Enable annotation processing

（2）安裝插件

點擊 Settings > Plugins > Browse repositories

查找 Lombok Plugin 并進行安裝

重啟 IntelliJ IDEA

（3）將 lombok 添加到 pom 文件

<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

@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

@NonNull Lombok 代碼：

@Getter @Setter @NonNull
private List<Person> members;

等價于 Java 源碼：

@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 Lombok 代碼：

@ToString(callSuper=true,exclude="someExcludedField")
public class Foo extends Bar {private boolean someBoolean = true;private String someStringField;private float someExcludedField;
}

等價于 Java 源碼：

public class Foo extends Bar {private boolean someBoolean = true;private String someStringField;private float someExcludedField;@java.lang.Overridepublic java.lang.String toString() {return "Foo(super=" + super.toString() +", someBoolean=" + someBoolean +", someStringField=" + someStringField + ")";}
}

@EqualsAndHashCode

@EqualsAndHashCode Lombok 代碼：

@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;
}

等價于 Java 源碼：

public class Person extends SentientBeing {enum Gender {/*public static final*/ Male /* = new Gender() */,/*public static final*/ Female /* = new Gender() */;}@NonNullprivate String name;@NonNullprivate Gender gender;private String ssn;private String address;private String city;private String state;private String zip;@java.lang.Overridepublic 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.Overridepublic 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 Lombok 代碼：

@Data(staticConstructor="of")
public class Company {private final Person founder;private String name;private List<Person> employees;
}

等價于 Java 源碼：

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.Overridepublic 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.Overridepublic 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.Overridepublic java.lang.String toString() {return "Company(founder=" + founder + ", name=" + name + ", employees=" + employees + ")";}
}

@Cleanup

@Cleanup Lombok 代碼：

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();}
}

等價于 Java 源碼：

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

@Synchronized Lombok 代碼：

private DateFormat format = new SimpleDateFormat("MM-dd-YYYY");@Synchronized
public String synchronizedFormat(Date date) {return format.format(date);
}

等價于 Java 源碼：

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 Lombok 代碼：

@SneakyThrows
public void testSneakyThrows() {throw new IllegalAccessException();
}

等價于 Java 源碼：

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)

示例源碼

完整示例：源碼

引用和引申

引申

• JavaStack

參考

• Lombok 官網
• Lombok Github
• IntelliJ IDEA - Lombok Plugin