Lombok-入门篇

电玩女神 2023-01-10 14:31 238阅读 0赞

随着编程以及各种框架的发展，大大提供了开发的简洁和便利性。在开发过程中，我们经常要定义各种Bean，在Bean中会出现大量的getter、setter方法，有时还会重写toString等方法，比如：

  1. /**
  2.  * @author javaerui
  3.  * @Description:
  4.  * @date 2021/1/22
  5.  */
  6. public class User {
  8.     public User() {
  9.     }
  11.     public User(String name, long id, Integer age, boolean vip, Boolean svip) {
  12.         this.name = name;
  13.         this.id = id;
  14.         this.age = age;
  15.         this.vip = vip;
  16.         this.svip = svip;
  17.     }
  19.     private String name;
  21.     private long id;
  23.     private Integer age;
  25.     private boolean vip;
  27.     private Boolean svip;
  29.     public String getName() {
  30.         return name;
  31.     }
  33.     public void setName(String name) {
  34.         this.name = name;
  35.     }
  37.     public long getId() {
  38.         return id;
  39.     }
  41.     public void setId(long id) {
  42.         this.id = id;
  43.     }
  45.     public Integer getAge() {
  46.         return age;
  47.     }
  49.     public void setAge(Integer age) {
  50.         this.age = age;
  51.     }
  53.     public boolean isVip() {
  54.         return vip;
  55.     }
  57.     public void setVip(boolean vip) {
  58.         this.vip = vip;
  59.     }
  61.     public Boolean getSvip() {
  62.         return svip;
  63.     }
  65.     public void setSvip(Boolean svip) {
  66.         this.svip = svip;
  67.     }
  69.     @Override
  70.     public String toString() {
  71.         return "User{" +
  72.                 "name='" + name + '\'' +
  73.                 ", id=" + id +
  74.                 ", age=" + age +
  75.                 ", vip=" + vip +
  76.                 ", svip=" + svip +
  77.                 '}';
  78.     }
  79. }

大量的方法重置着整个类，让这个类看上去失去了很多美观性。于是，Lombok诞生了，我们只需要编写Bean的属性，然后使用Lombok提供的注解便能够完成getter、setter等方法的添加。对于JVM来说，它是只能够识别class字节码的，而我们程序员一般编写的java源码需要先编译成class字节码才能够被JVM识别并运行，所以Lombok是对class字节码做了文章，在.java文件的源码级别使用Lombok提供的注解，Lombok会在类编译成.class字节码的时候根据特定注解对类添加特定的方法，比如：

  1. /**
  2.  * @author javaerui
  3.  * @Description:
  4.  * @date 2021/1/22
  5.  */
  6. @NoArgsConstructor
  7. @AllArgsConstructor
  8. @Getter
  9. @Setter
  10. @ToString
  11. public class User {
  13.     private String name;
  15.     private long id;
  17.     private Integer age;
  19.     private boolean vip;
  21.     private Boolean svip;
  23. }

编译User.java后，用IDEA打开编译生成的User.class内容：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. public class User {
  7.     private String name;
  8.     private long id;
  9.     private Integer age;
  10.     private boolean vip;
  11.     private Boolean svip;
  13.     public User() {
  14.     }
  16.     public User(String name, long id, Integer age, boolean vip, Boolean svip) {
  17.         this.name = name;
  18.         this.id = id;
  19.         this.age = age;
  20.         this.vip = vip;
  21.         this.svip = svip;
  22.     }
  24.     public String getName() {
  25.         return this.name;
  26.     }
  28.     public void setName(String name) {
  29.         this.name = name;
  30.     }
  32.     public long getId() {
  33.         return this.id;
  34.     }
  36.     public void setId(long id) {
  37.         this.id = id;
  38.     }
  40.     public Integer getAge() {
  41.         return this.age;
  42.     }
  44.     public void setAge(Integer age) {
  45.         this.age = age;
  46.     }
  48.     public boolean isVip() {
  49.         return this.vip;
  50.     }
  52.     public void setVip(boolean vip) {
  53.         this.vip = vip;
  54.     }
  56.     public Boolean getSvip() {
  57.         return this.svip;
  58.     }
  60.     public void setSvip(Boolean svip) {
  61.         this.svip = svip;
  62.     }
  64.     public String toString() {
  65.         return "User{name='" + this.name + '\'' + ", id=" + this.id + ", age=" + this.age + ", vip=" + this.vip + ", svip=" + this.svip + '}';
  66.     }
  67. }

对User类使用了Lombok提供的注解后，类的内容实质上和上面没有使用Lombok的效果是一样的。从源码层对比两个类，使用Lombok注解后，看上去更加简洁明了了。

█ 简单使用

（1）IDEA安装Lombok插件：

watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl81MDUxODI3MQ_size_16_color_FFFFFF_t_70

watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3dlaXhpbl81MDUxODI3MQ_size_16_color_FFFFFF_t_70 1

（2）引入依赖：

  1. <dependency>
  2.     <groupId>org.projectlombok</groupId>
  3.     <artifactId>lombok</artifactId>
  4.     <version>1.18.16</version>
  5.     <scope>provided</scope>
  6. </dependency>

（3）以User类为例，查看Lombok提供的注解所对应的方法。

  1. public class User {
  3.     private String name;
  5.     private long id;
  7.     private Integer age;
  9.     private boolean vip;
  11.     private Boolean svip;
  13. }
  • @Getter

对Bean的属性构建标准getter方法。

源码：

  1. @Getter
  2. public class User {
  4.     private String name;
  6.     private long id;
  8.     private Integer age;
  10.     private boolean vip;
  12.     private Boolean svip;
  14. }

编译后：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. public class User {
  7.     private String name;
  8.     private long id;
  9.     private Integer age;
  10.     private boolean vip;
  11.     private Boolean svip;
  13.     public User() {
  14.     }
  16.     public String getName() {
  17.         return this.name;
  18.     }
  20.     public long getId() {
  21.         return this.id;
  22.     }
  24.     public Integer getAge() {
  25.         return this.age;
  26.     }
  28.     public boolean isVip() {
  29.         return this.vip;
  30.     }
  32.     public Boolean getSvip() {
  33.         return this.svip;
  34.     }
  35. }
  • @Setter

对属性构建set方法。

源码：

  1. @Setter
  2. public class User {
  4.     private String name;
  6.     private long id;
  8.     private Integer age;
  10.     private boolean vip;
  12.     private Boolean svip;
  14. }

编译后：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. public class User {
  7.     private String name;
  8.     private long id;
  9.     private Integer age;
  10.     private boolean vip;
  11.     private Boolean svip;
  13.     public User() {
  14.     }
  16.     public void setName(String name) {
  17.         this.name = name;
  18.     }
  20.     public void setId(long id) {
  21.         this.id = id;
  22.     }
  24.     public void setAge(Integer age) {
  25.         this.age = age;
  26.     }
  28.     public void setVip(boolean vip) {
  29.         this.vip = vip;
  30.     }
  32.     public void setSvip(Boolean svip) {
  33.         this.svip = svip;
  34.     }
  35. }
  • @ToString

重写toString方法。

源码：

  1. @ToString
  2. public class User {
  4.     private String name;
  6.     private long id;
  8.     private Integer age;
  10.     private boolean vip;
  12.     private Boolean svip;
  14. }

编译后：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. public class User {
  7.     private String name;
  8.     private long id;
  9.     private Integer age;
  10.     private boolean vip;
  11.     private Boolean svip;
  13.     public User() {
  14.     }
  16.     public String toString() {
  17.         return "User(name=" + this.name + ", id=" + this.id + ", age=" + this.age + ", vip=" + this.vip + ", svip=" + this.svip + ")";
  18.     }
  19. }
  • @EqualsAndHashCode

重写equals与hashcode方法。

源码：

  1. @EqualsAndHashCode
  2. public class User {
  4.     private String name;
  6.     private long id;
  8.     private Integer age;
  10.     private boolean vip;
  12.     private Boolean svip;
  14. }

编译后，从下面的方法可以看出，Lombok重写的方法会比较所有属性：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. public class User {
  7.     private String name;
  8.     private long id;
  9.     private Integer age;
  10.     private boolean vip;
  11.     private Boolean svip;
  13.     public User() {
  14.     }
  16.     public boolean equals(Object o) {
  17.         if (o == this) {
  18.             return true;
  19.         } else if (!(o instanceof User)) {
  20.             return false;
  21.         } else {
  22.             User other = (User)o;
  23.             if (!other.canEqual(this)) {
  24.                 return false;
  25.             } else if (this.id != other.id) {
  26.                 return false;
  27.             } else if (this.vip != other.vip) {
  28.                 return false;
  29.             } else {
  30.                 label52: {
  31.                     Object this$age = this.age;
  32.                     Object other$age = other.age;
  33.                     if (this$age == null) {
  34.                         if (other$age == null) {
  35.                             break label52;
  36.                         }
  37.                     } else if (this$age.equals(other$age)) {
  38.                         break label52;
  39.                     }
  41.                     return false;
  42.                 }
  44.                 Object this$svip = this.svip;
  45.                 Object other$svip = other.svip;
  46.                 if (this$svip == null) {
  47.                     if (other$svip != null) {
  48.                         return false;
  49.                     }
  50.                 } else if (!this$svip.equals(other$svip)) {
  51.                     return false;
  52.                 }
  54.                 Object this$name = this.name;
  55.                 Object other$name = other.name;
  56.                 if (this$name == null) {
  57.                     if (other$name != null) {
  58.                         return false;
  59.                     }
  60.                 } else if (!this$name.equals(other$name)) {
  61.                     return false;
  62.                 }
  64.                 return true;
  65.             }
  66.         }
  67.     }
  69.     protected boolean canEqual(Object other) {
  70.         return other instanceof User;
  71.     }
  73.     public int hashCode() {
  74.         int PRIME = true;
  75.         int result = 1;
  76.         long $id = this.id;
  77.         int result = result * 59 + (int)($id >>> 32 ^ $id);
  78.         result = result * 59 + (this.vip ? 79 : 97);
  79.         Object $age = this.age;
  80.         result = result * 59 + ($age == null ? 43 : $age.hashCode());
  81.         Object $svip = this.svip;
  82.         result = result * 59 + ($svip == null ? 43 : $svip.hashCode());
  83.         Object $name = this.name;
  84.         result = result * 59 + ($name == null ? 43 : $name.hashCode());
  85.         return result;
  86.     }
  87. }
  • @AllArgsConstructor、@NoArgsConstructor

@AllArgsConstructor构建全参构造器，@NoArgsConstructor构建无参构造器。

源码：

  1. @AllArgsConstructor
  2. @NoArgsConstructor
  3. public class User {
  5.     private String name;
  7.     private long id;
  9.     private Integer age;
  11.     private boolean vip;
  13.     private Boolean svip;
  15. }

编译后：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. public class User {
  7.     private String name;
  8.     private long id;
  9.     private Integer age;
  10.     private boolean vip;
  11.     private Boolean svip;
  13.     public User(String name, long id, Integer age, boolean vip, Boolean svip) {
  14.         this.name = name;
  15.         this.id = id;
  16.         this.age = age;
  17.         this.vip = vip;
  18.         this.svip = svip;
  19.     }
  21.     public User() {
  22.     }
  23. }
  • @Builder

对Bean构建Builder构建者模式。

源码：

  1. @Builder
  2. public class User {
  4.     private String name;
  6.     private long id;
  8.     private Integer age;
  10.     private boolean vip;
  12.     private Boolean svip;
  14. }

编译后：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. public class User {
  7.     private String name;
  8.     private long id;
  9.     private Integer age;
  10.     private boolean vip;
  11.     private Boolean svip;
  13.     User(String name, long id, Integer age, boolean vip, Boolean svip) {
  14.         this.name = name;
  15.         this.id = id;
  16.         this.age = age;
  17.         this.vip = vip;
  18.         this.svip = svip;
  19.     }
  21.     public static User.UserBuilder builder() {
  22.         return new User.UserBuilder();
  23.     }
  25.     public static class UserBuilder {
  26.         private String name;
  27.         private long id;
  28.         private Integer age;
  29.         private boolean vip;
  30.         private Boolean svip;
  32.         UserBuilder() {
  33.         }
  35.         public User.UserBuilder name(String name) {
  36.             this.name = name;
  37.             return this;
  38.         }
  40.         public User.UserBuilder id(long id) {
  41.             this.id = id;
  42.             return this;
  43.         }
  45.         public User.UserBuilder age(Integer age) {
  46.             this.age = age;
  47.             return this;
  48.         }
  50.         public User.UserBuilder vip(boolean vip) {
  51.             this.vip = vip;
  52.             return this;
  53.         }
  55.         public User.UserBuilder svip(Boolean svip) {
  56.             this.svip = svip;
  57.             return this;
  58.         }
  60.         public User build() {
  61.             return new User(this.name, this.id, this.age, this.vip, this.svip);
  62.         }
  64.         public String toString() {
  65.             return "User.UserBuilder(name=" + this.name + ", id=" + this.id + ", age=" + this.age + ", vip=" + this.vip + ", svip=" + this.svip + ")";
  66.         }
  67.     }
  68. }
  • @Cleanup

用于局部变量，会调用变量的close方法来关闭资源。@Cleanup标记的局部变量，必须具有close方法。

源码：

  1. public void method() throws IOException {
  2.     @Cleanup FileOutputStream fileOutputStream = new FileOutputStream("E:\\Downloads\\java.txt");
  3.     fileOutputStream.write("Hello World".getBytes());
  4. }

编译后：

  1. public void method() throws IOException {
  2.     FileOutputStream fileOutputStream = new FileOutputStream("E:\\Downloads\\java.txt");
  4.     try {
  5.         fileOutputStream.write("Hello World".getBytes());
  6.     } finally {
  7.         if (Collections.singletonList(fileOutputStream).get(0) != null) {
  8.             fileOutputStream.close();
  9.         }
  11.     }
  13. }
  • @NonNull

非空检查，当设置的值为空时，会抛异常。

  1. public void setName(@NonNull String name) {
  2.     this.name = name;
  3. }

调用，对name进行赋值为null：

  1. User user = new User();
  2. user.setName(null);

抛异常：

20210124180253286.png

  • @RequiredArgsConstructor

对标记了@NonNull的属性构建有参构造器。

源码：

  1. @RequiredArgsConstructor
  2. public class User {
  4.     @NonNull
  5.     private String name;
  7.     private long id;
  9.     private Integer age;
  11.     @NonNull
  12.     private boolean vip;
  14.     private Boolean svip;
  16. }

编译后，从这里可以看出@NonNull标注的字段会加非空判断：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. import lombok.NonNull;
  8. public class User {
  9.     @NonNull
  10.     private String name;
  11.     private long id;
  12.     private Integer age;
  13.     @NonNull
  14.     private boolean vip;
  15.     private Boolean svip;
  17.     public User(@NonNull String name, @NonNull boolean vip) {
  18.         if (name == null) {
  19.             throw new NullPointerException("name is marked non-null but is null");
  20.         } else {
  21.             this.name = name;
  22.             this.vip = vip;
  23.         }
  24.     }
  25. }
  • @Data

作用是@Getter、@Setter、@ToString、@EqualsAndHashCode、@RequiredArgsConstructor的聚合。

源码：

  1. @Data
  2. public class User {
  4.     private String name;
  6.     private long id;
  8.     private Integer age;
  10.     private boolean vip;
  12.     private Boolean svip;
  14. }

编译后：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. import java.util.List;
  7. import lombok.NonNull;
  9. public class User {
  10.     @NonNull
  11.     private String name;
  12.     private long id;
  13.     private Integer age;
  14.     private boolean vip;
  15.     private Boolean svip;
  16.     private List<String> list;
  18.     public User(@NonNull String name) {
  19.         if (name == null) {
  20.             throw new NullPointerException("name is marked non-null but is null");
  21.         } else {
  22.             this.name = name;
  23.         }
  24.     }
  26.     @NonNull
  27.     public String getName() {
  28.         return this.name;
  29.     }
  31.     public long getId() {
  32.         return this.id;
  33.     }
  35.     public Integer getAge() {
  36.         return this.age;
  37.     }
  39.     public boolean isVip() {
  40.         return this.vip;
  41.     }
  43.     public Boolean getSvip() {
  44.         return this.svip;
  45.     }
  47.     public List<String> getList() {
  48.         return this.list;
  49.     }
  51.     public void setName(@NonNull String name) {
  52.         if (name == null) {
  53.             throw new NullPointerException("name is marked non-null but is null");
  54.         } else {
  55.             this.name = name;
  56.         }
  57.     }
  59.     public void setId(long id) {
  60.         this.id = id;
  61.     }
  63.     public void setAge(Integer age) {
  64.         this.age = age;
  65.     }
  67.     public void setVip(boolean vip) {
  68.         this.vip = vip;
  69.     }
  71.     public void setSvip(Boolean svip) {
  72.         this.svip = svip;
  73.     }
  75.     public void setList(List<String> list) {
  76.         this.list = list;
  77.     }
  79.     public boolean equals(Object o) {
  80.         if (o == this) {
  81.             return true;
  82.         } else if (!(o instanceof User)) {
  83.             return false;
  84.         } else {
  85.             User other = (User)o;
  86.             if (!other.canEqual(this)) {
  87.                 return false;
  88.             } else if (this.getId() != other.getId()) {
  89.                 return false;
  90.             } else if (this.isVip() != other.isVip()) {
  91.                 return false;
  92.             } else {
  93.                 label64: {
  94.                     Object this$age = this.getAge();
  95.                     Object other$age = other.getAge();
  96.                     if (this$age == null) {
  97.                         if (other$age == null) {
  98.                             break label64;
  99.                         }
  100.                     } else if (this$age.equals(other$age)) {
  101.                         break label64;
  102.                     }
  104.                     return false;
  105.                 }
  107.                 label57: {
  108.                     Object this$svip = this.getSvip();
  109.                     Object other$svip = other.getSvip();
  110.                     if (this$svip == null) {
  111.                         if (other$svip == null) {
  112.                             break label57;
  113.                         }
  114.                     } else if (this$svip.equals(other$svip)) {
  115.                         break label57;
  116.                     }
  118.                     return false;
  119.                 }
  121.                 Object this$name = this.getName();
  122.                 Object other$name = other.getName();
  123.                 if (this$name == null) {
  124.                     if (other$name != null) {
  125.                         return false;
  126.                     }
  127.                 } else if (!this$name.equals(other$name)) {
  128.                     return false;
  129.                 }
  131.                 Object this$list = this.getList();
  132.                 Object other$list = other.getList();
  133.                 if (this$list == null) {
  134.                     if (other$list != null) {
  135.                         return false;
  136.                     }
  137.                 } else if (!this$list.equals(other$list)) {
  138.                     return false;
  139.                 }
  141.                 return true;
  142.             }
  143.         }
  144.     }
  146.     protected boolean canEqual(Object other) {
  147.         return other instanceof User;
  148.     }
  150.     public int hashCode() {
  151.         int PRIME = true;
  152.         int result = 1;
  153.         long $id = this.getId();
  154.         int result = result * 59 + (int)($id >>> 32 ^ $id);
  155.         result = result * 59 + (this.isVip() ? 79 : 97);
  156.         Object $age = this.getAge();
  157.         result = result * 59 + ($age == null ? 43 : $age.hashCode());
  158.         Object $svip = this.getSvip();
  159.         result = result * 59 + ($svip == null ? 43 : $svip.hashCode());
  160.         Object $name = this.getName();
  161.         result = result * 59 + ($name == null ? 43 : $name.hashCode());
  162.         Object $list = this.getList();
  163.         result = result * 59 + ($list == null ? 43 : $list.hashCode());
  164.         return result;
  165.     }
  167.     public String toString() {
  168.         return "User(name=" + this.getName() + ", id=" + this.getId() + ", age=" + this.getAge() + ", vip=" + this.isVip() + ", svip=" + this.getSvip() + ", list=" + this.getList() + ")";
  169.     }
  170. }
  • @SneakyThrows

标记方法抛出的异常。

源码：

  1. @SneakyThrows(IOException.class)
  2. public void method() {
  3.     FileOutputStream fileOutputStream = new FileOutputStream("E:\\Downloads\\java.txt");
  4.     fileOutputStream.write("Hello World".getBytes());
  5. }

编译后：

  1. public void method() {
  2.     try {
  3.         FileOutputStream fileOutputStream = new FileOutputStream("E:\\Downloads\\java.txt");
  4.         fileOutputStream.write("Hello World".getBytes());
  5.     } catch (IOException var2) {
  6.         throw var2;
  7.     }
  8. }
  • @Synchronized

对方法体进行同步操作。

源码：

  1. @Synchronized
  2. public void method() throws IOException{
  3.     FileOutputStream fileOutputStream = new FileOutputStream("E:\\Downloads\\java.txt");
  4.     fileOutputStream.write("Hello World".getBytes());
  5. }

编译后：

  1. private final Object $lock = new Object[0];
  3. public void method() throws IOException {
  4.     synchronized(this.$lock) {
  5.         FileOutputStream fileOutputStream = new FileOutputStream("E:\\Downloads\\java.txt");
  6.         fileOutputStream.write("Hello World".getBytes());
  7.     }
  8. }
  • @Value

构建一个final修饰的类，并提供全参构造器，getter方法，重新equals、hashcode、toString方法。

源码：

  1. @Value
  2. public class User {
  4.     private String name;
  6.     private long id;
  8.     private Integer age;
  10.     private boolean vip;
  12.     private Boolean svip;
  14. }

编译后：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. public final class User {
  7.     private final String name;
  8.     private final long id;
  9.     private final Integer age;
  10.     private final boolean vip;
  11.     private final Boolean svip;
  13.     public User(String name, long id, Integer age, boolean vip, Boolean svip) {
  14.         this.name = name;
  15.         this.id = id;
  16.         this.age = age;
  17.         this.vip = vip;
  18.         this.svip = svip;
  19.     }
  21.     public String getName() {
  22.         return this.name;
  23.     }
  25.     public long getId() {
  26.         return this.id;
  27.     }
  29.     public Integer getAge() {
  30.         return this.age;
  31.     }
  33.     public boolean isVip() {
  34.         return this.vip;
  35.     }
  37.     public Boolean getSvip() {
  38.         return this.svip;
  39.     }
  41.     public boolean equals(Object o) {
  42.         if (o == this) {
  43.             return true;
  44.         } else if (!(o instanceof User)) {
  45.             return false;
  46.         } else {
  47.             User other = (User)o;
  48.             if (this.getId() != other.getId()) {
  49.                 return false;
  50.             } else if (this.isVip() != other.isVip()) {
  51.                 return false;
  52.             } else {
  53.                 label49: {
  54.                     Object this$age = this.getAge();
  55.                     Object other$age = other.getAge();
  56.                     if (this$age == null) {
  57.                         if (other$age == null) {
  58.                             break label49;
  59.                         }
  60.                     } else if (this$age.equals(other$age)) {
  61.                         break label49;
  62.                     }
  64.                     return false;
  65.                 }
  67.                 Object this$svip = this.getSvip();
  68.                 Object other$svip = other.getSvip();
  69.                 if (this$svip == null) {
  70.                     if (other$svip != null) {
  71.                         return false;
  72.                     }
  73.                 } else if (!this$svip.equals(other$svip)) {
  74.                     return false;
  75.                 }
  77.                 Object this$name = this.getName();
  78.                 Object other$name = other.getName();
  79.                 if (this$name == null) {
  80.                     if (other$name != null) {
  81.                         return false;
  82.                     }
  83.                 } else if (!this$name.equals(other$name)) {
  84.                     return false;
  85.                 }
  87.                 return true;
  88.             }
  89.         }
  90.     }
  92.     public int hashCode() {
  93.         int PRIME = true;
  94.         int result = 1;
  95.         long $id = this.getId();
  96.         int result = result * 59 + (int)($id >>> 32 ^ $id);
  97.         result = result * 59 + (this.isVip() ? 79 : 97);
  98.         Object $age = this.getAge();
  99.         result = result * 59 + ($age == null ? 43 : $age.hashCode());
  100.         Object $svip = this.getSvip();
  101.         result = result * 59 + ($svip == null ? 43 : $svip.hashCode());
  102.         Object $name = this.getName();
  103.         result = result * 59 + ($name == null ? 43 : $name.hashCode());
  104.         return result;
  105.     }
  107.     public String toString() {
  108.         return "User(name=" + this.getName() + ", id=" + this.getId() + ", age=" + this.getAge() + ", vip=" + this.isVip() + ", svip=" + this.getSvip() + ")";
  109.     }
  110. }
  • @With

构建一个withXX的方法，实现将参数比较，如果是相等，返回当前对象，如果不等，创建新的对象。@With标记的类必须提供一个全参构造器，否则无法编译通过（为什么呢？看完编译后的源码就清楚了）。

源码：

  1. @AllArgsConstructor
  2. @With
  3. public class User {
  5.     private String name;
  7.     public User(String name) {
  8.         this.name = name;
  9.     }
  11.     private long id;
  13.     private Integer age;
  15.     private boolean vip;
  17.     private Boolean svip;
  19. }

编译后：

  1. //
  2. // Source code recreated from a .class file by IntelliJ IDEA
  3. // (powered by Fernflower decompiler)
  4. //
  6. public class User {
  7.     private String name;
  8.     private long id;
  9.     private Integer age;
  10.     private boolean vip;
  11.     private Boolean svip;
  13.     public User(String name) {
  14.         this.name = name;
  15.     }
  17.     public User(String name, long id, Integer age, boolean vip, Boolean svip) {
  18.         this.name = name;
  19.         this.id = id;
  20.         this.age = age;
  21.         this.vip = vip;
  22.         this.svip = svip;
  23.     }
  25.     public User withName(String name) {
  26.         // 通过new User的全参构造器创建对象的，所以必须提供一个全参构造器
  27.         return this.name == name ? this : new User(name, this.id, this.age, this.vip, this.svip);
  28.     }
  30.     public User withId(long id) {
  31.         return this.id == id ? this : new User(this.name, id, this.age, this.vip, this.svip);
  32.     }
  34.     public User withAge(Integer age) {
  35.         return this.age == age ? this : new User(this.name, this.id, age, this.vip, this.svip);
  36.     }
  38.     public User withVip(boolean vip) {
  39.         return this.vip == vip ? this : new User(this.name, this.id, this.age, vip, this.svip);
  40.     }
  42.     public User withSvip(Boolean svip) {
  43.         return this.svip == svip ? this : new User(this.name, this.id, this.age, this.vip, svip);
  44.     }
  45. }
  • var、val

声明局部变量。

源码：

  1. public void method() {
  2.     var x = 10;
  3.     val y = 1.1;
  4.     var list = new ArrayList<>();
  5.     list.add("hello world");
  6. }

编译后：

  1. public void method() {
  2.     int x = true;
  3.     double y = 1.1D;
  4.     ArrayList<Object> list = new ArrayList();
  5.     list.add("hello world");
  6. }
  • @CommonsLog

日志相关，构建log字段，类型为org.apache.commons.logging.Log。使用的时候要引入相对应的日志依赖。

源码：

  1. @CommonsLog
  2. public class User {
  4. }

编译后：

  1. public class User {
  3.     private static final org.apache.commons.logging.Log log = 
  4.             org.apache.commons.logging.LogFactory.getLog(User.class);
  6. }
  • @Flogger、@JBossLog、@Log、@Log4j、@Log4j2、@Slf4j、@XSlf4j

和@CommonsLog一样都是日志相关，区别是Log类型不同。

@Flogger：

private static final com.google.common.flogger.FluentLogger log = com.google.common.flogger.FluentLogger.forEnclosingClass();

@JBossLog：

private static final org.jboss.logging.Logger log = org.jboss.logging.Logger.getLogger(User.class);

@Log：

private static final java.util.logging.Logger log = java.util.logging.Logger.getLogger(User.class.getName());

@Log4j：

private static final org.apache.log4j.Logger log = org.apache.log4j.Logger.getLogger(User.class);

@Log4j2：

private static final org.apache.logging.log4j.Logger log = org.apache.logging.log4j.LogManager.getLogger(User.class);

@Slf4j：

private static final org.slf4j.Logger log = org.slf4j.LoggerFactory.getLogger(User.class);

@XSlf4j：

private static final org.slf4j.ext.XLogger log = org.slf4j.ext.XLoggerFactory.getXLogger(User.class);

关于Lombok的详细介绍，请戳《Lombok-高级篇》

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