简介

为了减少写一些 get/set/toString 方法,让项目代码更加整洁,提高开发效率,发现大家都开始采用 Lombok 这个工具。Lombok 是一个 Java 类库,它会自动插入编辑器和构建工具,用于帮助开发人员消除 Java 中冗长样板代码。而我们开发人员所要做的,仅仅是添加几个 Lombok 中的注解,就可以替换掉原来的多行 get/set/toString 方法代码,既简洁也易于维护。下面我们就来看看,如何安装并使用这一工具。

安装 Lombok

日常开发中,相信大多数人现在使用的都是 IDEA 这个 Java 神器了,如果你还在使用 Eclipse 或者 MyEclipse 等工具,那强烈推荐你去体验一把 IDEA,相信你一用上它就会爱上他它的强大!下面我就一在 IDEA 中使用 Lombok 为例,看看如何安装并使用它。

在先前 IDEA 的版本中,Lombok 是需要通过插件来安装的,安装方法如下:依次进入File -> Settings -> Plugins,然后搜索 Lombok ,最后进行安装即可。而在新版本的 IDEA 中,Lombok 已经被集成到 IDEA 中,我们不用再去安装它就可以直接使用,可以说是十分方便了。

  • 老版本 IDEA 安装 Lombok

img

  • 新版本中集成了 Lombok

img

以上就是 Lombok 的安装过程了,是不是十分简单?那接下来我们就来看看,如何在我们的项目中使用 Lombok!

Lombok 使用

现在大家进行项目管理时用的工具大多应该都是 Maven,所以我们直接在需要使用 Lombok 的项目中加入 Lombok 编译支持,也就是在 pom.xml 文件中加入以下依赖。

<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>

导入相关依赖之后,接下来就是具体使用过程了。

具体使用

在需要的实体类中引入相关注解即可,只不过注解不同它们所对应的功能也不同,而且同一个注解可能在不同位置的功能也不一样。如下图;

img

常用注解

@Data

注解在 上:给类的所有属性提供 getset 方法,此外还有 equals、canEqual、hashCode、toString 方法以及 默认参数为空的构造方法

  • 使用前
package com.cunyu.user.entity;

public class User {
private Long id;
private String name;
private Integer age;
private String email;

public User() {
}

public Long getId() {
return this.id;
}

public String getName() {
return this.name;
}

public Integer getAge() {
return this.age;
}

public String getEmail() {
return this.email;
}

public void setId(final Long id) {
this.id = id;
}

public void setName(final String name) {
this.name = name;
}

public void setAge(final Integer age) {
this.age = age;
}

public void setEmail(final String email) {
this.email = email;
}

public boolean equals(final Object o) {
if (o == this) {
return true;
} else if (!(o instanceof User)) {
return false;
} else {
User other = (User)o;
if (!other.canEqual(this)) {
return false;
} else {
label59: {
Object this$id = this.getId();
Object other$id = other.getId();
if (this$id == null) {
if (other$id == null) {
break label59;
}
} else if (this$id.equals(other$id)) {
break label59;
}

return false;
}

Object this$age = this.getAge();
Object other$age = other.getAge();
if (this$age == null) {
if (other$age != null) {
return false;
}
} else if (!this$age.equals(other$age)) {
return false;
}

Object this$name = this.getName();
Object other$name = other.getName();
if (this$name == null) {
if (other$name != null) {
return false;
}
} else if (!this$name.equals(other$name)) {
return false;
}

Object this$email = this.getEmail();
Object other$email = other.getEmail();
if (this$email == null) {
if (other$email != null) {
return false;
}
} else if (!this$email.equals(other$email)) {
return false;
}

return true;
}
}
}

protected boolean canEqual(final Object other) {
return other instanceof User;
}

public int hashCode() {
int PRIME = true;
int result = 1;
Object $id = this.getId();
int result = result * 59 + ($id == null ? 43 : $id.hashCode());
Object $age = this.getAge();
result = result * 59 + ($age == null ? 43 : $age.hashCode());
Object $name = this.getName();
result = result * 59 + ($name == null ? 43 : $name.hashCode());
Object $email = this.getEmail();
result = result * 59 + ($email == null ? 43 : $email.hashCode());
return result;
}

public String toString() {
Long var10000 = this.getId();
return "User(id=" + var10000 + ", name=" + this.getName() + ", age=" + this.getAge() + ", email=" + this.getEmail() + ")";
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.Data;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

@Data
public class User {
private Long id;
private String name;
private Integer age;
private String email;
}

@Setter

注解在 上:为该类所有属性均提供 set 方法,同时提供 默认构造方法

  • 使用前
package com.cunyu.user.entity;

public class User {
private Long id;
private String name;
private Integer age;
private String email;

public User() {
}

public void setId(final Long id) {
this.id = id;
}

public void setName(final String name) {
this.name = name;
}

public void setAge(final Integer age) {
this.age = age;
}

public void setEmail(final String email) {
this.email = email;
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.Setter;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

@Setter
public class User {
private Long id;
private String name;
private Integer age;
private String email;
}

注解在 属性 上:为该属性提供 set 方法,同时提供 默认构造方法

  • 使用前
package com.cunyu.user.entity;

public class User {
private Long id;
private String name;
private Integer age;
private String email;

public User() {
}

public void setId(final Long id) {
this.id = id;
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.Setter;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

public class User {
@Setter
private Long id;
private String name;
private Integer age;
private String email;
}

@Getter

注解在 上:为该类所有属性均提供 get 方法,同时提供 默认构造方法

  • 使用前
package com.cunyu.user.entity;

public class User {
private Long id;
private String name;
private Integer age;
private String email;

public User() {
}

public Long getId() {
return this.id;
}

public String getName() {
return this.name;
}

public Integer getAge() {
return this.age;
}

public String getEmail() {
return this.email;
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.Getter;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

@Getter
public class User {
private Long id;
private String name;
private Integer age;
private String email;
}

注解在 属性 上:为该属性提供 get 方法,同时提供 默认构造方法

  • 使用前
package com.cunyu.user.entity;

public class User {
private Long id;
private String name;
private Integer age;
private String email;

public User() {
}

public Long getId() {
return this.id;
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.Getter;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

public class User {
@Getter
private Long id;
private String name;
private Integer age;
private String email;
}

@ToString

注解在 上:生成所有参数的 toString() 方法,同时提供 默认构造方法

  • 使用前
package com.cunyu.user.entity;

public class User {
private Long id;
private String name;
private Integer age;
private String email;

public User() {
}

public String toString() {
return "User(id=" + this.id + ", name=" + this.name + ", age=" + this.age + ", email=" + this.email + ")";
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.ToString;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

@ToString
public class User {
private Long id;
private String name;
private Integer age;
private String email;
}

@Value

注解在 上:生成 get 方法,以及 equals、hashCode、toString 方法,同时提供 含所有参数的构造方法

  • 使用前
package com.cunyu.user.entity;

public final class User {
private final Long id;
private final String name;
private final Integer age;
private final String email;

public User(final Long id, final String name, final Integer age, final String email) {
this.id = id;
this.name = name;
this.age = age;
this.email = email;
}

public Long getId() {
return this.id;
}

public String getName() {
return this.name;
}

public Integer getAge() {
return this.age;
}

public String getEmail() {
return this.email;
}

public boolean equals(final Object o) {
if (o == this) {
return true;
} else if (!(o instanceof User)) {
return false;
} else {
User other;
label56: {
other = (User)o;
Object this$id = this.getId();
Object other$id = other.getId();
if (this$id == null) {
if (other$id == null) {
break label56;
}
} else if (this$id.equals(other$id)) {
break label56;
}

return false;
}

label49: {
Object this$age = this.getAge();
Object other$age = other.getAge();
if (this$age == null) {
if (other$age == null) {
break label49;
}
} else if (this$age.equals(other$age)) {
break label49;
}

return false;
}

Object this$name = this.getName();
Object other$name = other.getName();
if (this$name == null) {
if (other$name != null) {
return false;
}
} else if (!this$name.equals(other$name)) {
return false;
}

Object this$email = this.getEmail();
Object other$email = other.getEmail();
if (this$email == null) {
if (other$email != null) {
return false;
}
} else if (!this$email.equals(other$email)) {
return false;
}

return true;
}
}

public int hashCode() {
int PRIME = true;
int result = 1;
Object $id = this.getId();
int result = result * 59 + ($id == null ? 43 : $id.hashCode());
Object $age = this.getAge();
result = result * 59 + ($age == null ? 43 : $age.hashCode());
Object $name = this.getName();
result = result * 59 + ($name == null ? 43 : $name.hashCode());
Object $email = this.getEmail();
result = result * 59 + ($email == null ? 43 : $email.hashCode());
return result;
}

public String toString() {
Long var10000 = this.getId();
return "User(id=" + var10000 + ", name=" + this.getName() + ", age=" + this.getAge() + ", email=" + this.getEmail() + ")";
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.Value;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

@Value
public class User {
private Long id;
private String name;
private Integer age;
private String email;
}

@AllArgsConstructor

注解在 上:为类提供一个 全参构造方法,但此时不再提供默认构造方法;

  • 使用前
package com.cunyu.user.entity;

public class User {
private Long id;
private String name;
private Integer age;
private String email;

public User(final Long id, final String name, final Integer age, final String email) {
this.id = id;
this.name = name;
this.age = age;
this.email = email;
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.AllArgsConstructor;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

@AllArgsConstructor
public class User {
private Long id;
private String name;
private Integer age;
private String email;
}

@NoArgsConstructor

注解在 上:为类提供一个 无参构造方法

  • 使用前
package com.cunyu.user.entity;

public class User {
private Long id;
private String name;
private Integer age;
private String email;

public User() {
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.NoArgsConstructor;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

@NoArgsConstructor
public class User {
private Long id;
private String name;
private Integer age;
private String email;
}

@RequiredArgsConstructor

注解在 上:使用类中所有带 @NonNull 注解的或带有 final 修饰的成员变量生成对应构造方法;

  • 使用前
package com.cunyu.user.entity;

import lombok.NonNull;

public class User {
@NonNull
private Long id;
private String name;
private Integer age;
@NonNull
private String email;

public User(@NonNull final Long id, @NonNull final String email) {
if (id == null) {
throw new NullPointerException("id is marked non-null but is null");
} else if (email == null) {
throw new NullPointerException("email is marked non-null but is null");
} else {
this.id = id;
this.email = email;
}
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.RequiredArgsConstructor;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

@RequiredArgsConstructor
public class User {
@NonNull
private Long id;
private String name;
private Integer age;
@NonNull
private String email;
}

@NonNull

注解在 属性 上,自动生成一个关于该参数的非空检查,若参数为 null,则抛出一个空指针异常,同时提供 默认构造方法,具体用法可以参照上面的例子;

@EqualsAndHashCode

注解在 上,生成 equals、canEquals、hasnCode 方法,同时会生成默认构造方法;

  • 使用前
//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by FernFlower decompiler)
//

package com.cunyu.user.entity;

public class User {
private Long id;
private String name;
private Integer age;
private String email;

public User() {
}

public boolean equals(final Object o) {
if (o == this) {
return true;
} else if (!(o instanceof User)) {
return false;
} else {
User other = (User)o;
if (!other.canEqual(this)) {
return false;
} else {
label59: {
Object this$id = this.id;
Object other$id = other.id;
if (this$id == null) {
if (other$id == null) {
break label59;
}
} else if (this$id.equals(other$id)) {
break label59;
}

return false;
}

Object this$age = this.age;
Object other$age = other.age;
if (this$age == null) {
if (other$age != null) {
return false;
}
} else if (!this$age.equals(other$age)) {
return false;
}

Object this$name = this.name;
Object other$name = other.name;
if (this$name == null) {
if (other$name != null) {
return false;
}
} else if (!this$name.equals(other$name)) {
return false;
}

Object this$email = this.email;
Object other$email = other.email;
if (this$email == null) {
if (other$email != null) {
return false;
}
} else if (!this$email.equals(other$email)) {
return false;
}

return true;
}
}
}

protected boolean canEqual(final Object other) {
return other instanceof User;
}

public int hashCode() {
int PRIME = true;
int result = 1;
Object $id = this.id;
int result = result * 59 + ($id == null ? 43 : $id.hashCode());
Object $age = this.age;
result = result * 59 + ($age == null ? 43 : $age.hashCode());
Object $name = this.name;
result = result * 59 + ($name == null ? 43 : $name.hashCode());
Object $email = this.email;
result = result * 59 + ($email == null ? 43 : $email.hashCode());
return result;
}
}
  • 使用后
package com.cunyu.user.entity;

import lombok.EqualsAndHashCode;

/**
* Created with IntelliJ IDEA.
*
* @author : zhangliang
* @version : 1.0
* @project : User
* @package : com.cunyu.user.entity
* @className : User
* @createTime : 2021/8/6 17:14
* @description : 用户实体类
*/

@EqualsAndHashCode
public class User {
private Long id;
private String name;
private Integer age;
private String email;
}

@Cleanup

注解在 局部变量 前,保证该变量代表的资源使用后自动关闭,默认调用资源的 close() 方法,若该资源有其它关闭方法,可用 @Cleanup("方法名") 来指定要调用的方法,同时提供 默认构造方法;

  • 使用前
import java.io.*;

public class CleanupExample {
public static void main(String[] args) throws IOException {
InputStream in = new FileInputStream(args[0]);
try {
OutputStream out = new FileOutputStream(args[1]);
try {
byte[] b = new byte[10000];
while (true) {
int r = in.read(b);
if (r == -1) break;
out.write(b, 0, r);
}
} finally {
if (out != null) {
out.close();
}
}
} finally {
if (in != null) {
in.close();
}
}
}
}
  • 使用后
import lombok.Cleanup;
import java.io.*;

public class CleanupExample {
public static void main(String[] args) throws IOException {
@Cleanup InputStream in = new FileInputStream(args[0]);
@Cleanup OutputStream out = new FileOutputStream(args[1]);
byte[] b = new byte[10000];
while (true) {
int r = in.read(b);
if (r == -1) break;
out.write(b, 0, r);
}
}
}

@Synchronized

注解在 类方法 或 实例方法:效果与 synchronized 关键字相同,区别在于锁对象不同,对于类方法和实例方法,synchronized 关键字的锁对象分别是 类的 **class** 对象和 **this** 对象,而 @Synchronized 的锁对象分别是 私有静态 **final** 对象 **lock** 和 私有 **final** 对象 **lock**,也可以自己指定锁对象,同时提供默认构造方法;

  • 使用前
public class SynchronizedExample {
private static final Object $LOCK = new Object[0];
private final Object $lock = new Object[0];
private final Object readLock = new Object();

public static void hello() {
synchronized($LOCK) {
System.out.println("world");
}
}

public int answerToLife() {
synchronized($lock) {
return 42;
}
}

public void foo() {
synchronized(readLock) {
System.out.println("bar");
}
}
}
  • 使用后
import lombok.Synchronized;

public class SynchronizedExample {
private final Object readLock = new Object();

@Synchronized
public static void hello() {
System.out.println("world");
}

@Synchronized
public int answerToLife() {
return 42;
}

@Synchronized("readLock")
public void foo() {
System.out.println("bar");
}
}

@SneakyThrows

注解在 方法 上:将方法中的代码用 try-catch 语句包裹,捕获异常并在 catch 中用 Lombok.sneakyThrow(e) 将异常抛出,还可以用 @SneakyThrows(Exception.class) 的形式指定抛出异常类型,同时提供 默认构造方法

  • 使用前
import lombok.Lombok;

public class SneakyThrowsExample implements Runnable {
public String utf8ToString(byte[] bytes) {
try {
return new String(bytes, "UTF-8");
} catch (UnsupportedEncodingException e) {
throw Lombok.sneakyThrow(e);
}
}

public void run() {
try {
throw new Throwable();
} catch (Throwable t) {
throw Lombok.sneakyThrow(t);
}
}
}
  • 使用后
import lombok.SneakyThrows;

public class SneakyThrowsExample implements Runnable {
@SneakyThrows(UnsupportedEncodingException.class)
public String utf8ToString(byte[] bytes) {
return new String(bytes, "UTF-8");
}

@SneakyThrows
public void run() {
throw new Throwable();
}
}

@Log

注解在 上:主要用于我们记录日志信息,同时提供 默认构造方法。它封装了多个主流 Log 库,主要有如下几个;

  • @Log

  • @Slf4j

  • Log4j

  • Log4j2

总结

以上就是关于 Lombok 的相关使用小技巧了,如果你还没有使用过它,那就赶紧去试试吧!

最后,创作不易,如果你觉得我的文章对你有所帮助,那就来个一键三连吧!

参考资料

  1. https://projectlombok.org/features/all
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