Lombok的功能是什么

发布时间：2021-10-14 10:02:59 作者：iii
来源：亿速云阅读：135

本篇内容主要讲解“Lombok的功能是什么”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“Lombok的功能是什么”吧!

什么是 lombok

Lombok项目是一个Java库，工具库，它会自动在编辑器或构建工具中生成代码，从而使你的Java代码更简洁。不用在给每一个变量生成get和set等方法，还会生成一个功能齐全的Builder，已经自动化日志记录变量，以及更多

常用注解

@Setter
@Getter
@Builder
@RequiredArgsConstructor 生成一个该类的构造方法，禁止无参数构造
@ToString 重写该类的 toString()方法
@EqualsAndHashCode 重写该类的equals() 和 hashCode() 方法
@NoArgsConstructor
@AllArgsConstructor
@Data 等同于 @Setter @Getter @RequiredArgsConstructor @ToString @EqualsAndHashCode 注解之和
@Slf4j

写一个简单的类使用这个类来详细的的看一下 Lombok 帮我们做了什么

package lombok;
public class UserData {
    private String name;
    private int age;
    private boolean good;
}

这个类很简单代码中没有构造函数、没有get set 方法使用 javap 工具来看一下

javap 是 jdk 自带的反编译工具、这里先不关心生成的字节码只看方法

// javap UserData.class
Compiled from "UserData.java"
public class lombok.UserData {
  public lombok.UserData();
}

JDK当检测到没有默认构造器时，自动生成一个 public 的无参数默认构造器

使用 @Getter

在类 UserData 上增加注解 @Getter

Compiled from "UserData.java"
public class lombok.UserData {
  public lombok.UserData();
  public java.lang.String getName();
  public int getAge();
  public boolean isGood();
}

反编译后看到使用驼峰命名方式增加 get 变量方法需要注意 boolean 类型使用的 is 方法

使用 @Setter

Compiled from "UserData.java"
public class lombok.UserData {
  public lombok.UserData();
  public void setName(java.lang.String);
  public void setAge(int);
  public void setGood(boolean);
}

反编译后增加 set 变量方法

使用 @RequiredArgsConstructor

Compiled from "UserData.java"
public class lombok.UserData {
  public lombok.UserData();
}

反编译后可以看到和没有注解是一样的生成一个无参数构造函数

使用 @ToString

public class lombok.UserData {
  public lombok.UserData();
  public java.lang.String toString();
}

反编译后可以看到增加 toString 方法这里的toString和原生的是有区别的

System.out.println(new UserData().toString());
// 原生toString输出
lombok.UserData@60e53b93 每次生成引用地址会变化
// @ToString输出
UserData(name=null, age=0, good=false)

使用 @EqualsAndHashCode

Compiled from "UserData.java"
public class lombok.UserData {
  public lombok.UserData();
  public boolean equals(java.lang.Object);
  protected boolean canEqual(java.lang.Object);
  public int hashCode();
}

反编译后可以看到增加 equals canEqual hashCode 三个方法

和原生对比下输出

public static void main(String[] args) {
        UserData userData = new UserData();
        System.out.println(userData.equals(new UserData()));
        System.out.println(userData.canEqual(new UserData()));
        System.out.println(userData.hashCode());
    }
// 原生输出
false
// 没有 canEqual 方法
1625635731
// @EqualsAndHashCode 输出
true
true
355159

通过上面的输出对比明显加注解后的结果和原生的equals 不一样，建议_谨慎使用_

可以使用 Idea 反编译下看看生成的代码逻辑这里就不展示了有兴趣的可以自己试下

增加 @Data 注解

来看一下这个懒人注解也是用的最广泛的注解 @Data

Compiled from "UserData.java"
public class lombok.UserData {
  public lombok.UserData();
  public java.lang.String getName();
  public int getAge();
  public boolean isGood();
  public void setName(java.lang.String);
  public void setAge(int);
  public void setGood(boolean);
  public boolean equals(java.lang.Object);
  protected boolean canEqual(java.lang.Object);
  public int hashCode();
  public java.lang.String toString();
}

反编译后可以看出它是 @Getter @Setter @EqualsAndHashCode @ToString 的集合体

这里还是建议谨慎使用主要是 @EqualsAndHashCode 注解生成的代码会影响 equal 的判断

使用 @NoArgsConstructor

Compiled from "UserData.java"
public class lombok.UserData {
  public lombok.UserData();
}

反编译后可以看到和使用 @RequiredArgsConstructor 和没有注解一样的

使用 @AllArgsConstructor

Compiled from "UserData.java"
public class lombok.UserData {
  public lombok.UserData(java.lang.String, int, boolean);
}

反编译后看出没有无参数构造函数增加一个全参数构造函数

使用 @Builder

编译后多了一个内部类 UserData$UserDataBuilder.class
Compiled from "UserData.java"
public class lombok.UserData$UserDataBuilder {
  lombok.UserData$UserDataBuilder();
  public lombok.UserData$UserDataBuilder name(java.lang.String);
  public lombok.UserData$UserDataBuilder age(int);
  public lombok.UserData$UserDataBuilder good(boolean);
  public lombok.UserData build();
  public java.lang.String toString();
}

Compiled from "UserData.java"
public class lombok.UserData {
  lombok.UserData(java.lang.String, int, boolean);
  public static lombok.UserData$UserDataBuilder builder();
}

生成了一个全参数构造函数和一个 builder 方法

参考

https://projectlombok.org/

javap -verbose UserData

Classfile /***/classes/lombok/UserData.class
  Last modified 2021-4-13; size 1975 bytes
  MD5 checksum 3fe9c971d14ecbcecdc5be0c02e7907e
  Compiled from "UserData.java"
public class lombok.UserData
  minor version: 0
  major version: 52 // 便衣使用的JDK版本  
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool: // 常量池
   #1 = Methodref          #22.#66        // java/lang/Object."<init>":()V
   #2 = Fieldref           #5.#67         // lombok/UserData.name:Ljava/lang/String;
   #3 = Fieldref           #5.#68         // lombok/UserData.age:I
   #4 = Fieldref           #5.#69         // lombok/UserData.good:Z
   #5 = Class              #70            // lombok/UserData
   #6 = Methodref          #5.#71         // lombok/UserData.canEqual:(Ljava/lang/Object;)Z
   #7 = Methodref          #5.#72         // lombok/UserData.getName:()Ljava/lang/String;
   #8 = Methodref          #22.#73        // java/lang/Object.equals:(Ljava/lang/Object;)Z
   #9 = Methodref          #5.#74         // lombok/UserData.getAge:()I
  #10 = Methodref          #5.#75         // lombok/UserData.isGood:()Z
  #11 = Methodref          #22.#76        // java/lang/Object.hashCode:()I
  #12 = Class              #77            // java/lang/StringBuilder
  #13 = Methodref          #12.#66        // java/lang/StringBuilder."<init>":()V
  #14 = String             #78            // UserData(name=
  #15 = Methodref          #12.#79        // java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #16 = String             #80            // , age=
  #17 = Methodref          #12.#81        // java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;
  #18 = String             #82            // , good=
  #19 = Methodref          #12.#83        // java/lang/StringBuilder.append:(Z)Ljava/lang/StringBuilder;
  #20 = String             #84            // )
  #21 = Methodref          #12.#85        // java/lang/StringBuilder.toString:()Ljava/lang/String;
  #22 = Class              #86            // java/lang/Object
  #23 = Utf8               name
  #24 = Utf8               Ljava/lang/String;
  #25 = Utf8               age
  #26 = Utf8               I
  #27 = Utf8               good
  #28 = Utf8               Z
  #29 = Utf8               <init>
  #30 = Utf8               ()V
  #31 = Utf8               Code
  #32 = Utf8               LineNumberTable
  #33 = Utf8               LocalVariableTable
  #34 = Utf8               this
  #35 = Utf8               Llombok/UserData;
  #36 = Utf8               getName
  #37 = Utf8               ()Ljava/lang/String;
  #38 = Utf8               getAge
  #39 = Utf8               ()I
  #40 = Utf8               isGood
  #41 = Utf8               ()Z
  #42 = Utf8               setName
  #43 = Utf8               (Ljava/lang/String;)V
  #44 = Utf8               setAge
  #45 = Utf8               (I)V
  #46 = Utf8               setGood
  #47 = Utf8               (Z)V
  #48 = Utf8               equals
  #49 = Utf8               (Ljava/lang/Object;)Z
  #50 = Utf8               o
  #51 = Utf8               Ljava/lang/Object;
  #52 = Utf8               other
  #53 = Utf8               this$name
  #54 = Utf8               other$name
  #55 = Utf8               StackMapTable
  #56 = Class              #70            // lombok/UserData
  #57 = Class              #86            // java/lang/Object
  #58 = Utf8               canEqual
  #59 = Utf8               hashCode
  #60 = Utf8               PRIME
  #61 = Utf8               result
  #62 = Utf8               $name
  #63 = Utf8               toString
  #64 = Utf8               SourceFile
  #65 = Utf8               UserData.java
  #66 = NameAndType        #29:#30        // "<init>":()V
  #67 = NameAndType        #23:#24        // name:Ljava/lang/String;
  #68 = NameAndType        #25:#26        // age:I
  #69 = NameAndType        #27:#28        // good:Z
  #70 = Utf8               lombok/UserData
  #71 = NameAndType        #58:#49        // canEqual:(Ljava/lang/Object;)Z
  #72 = NameAndType        #36:#37        // getName:()Ljava/lang/String;
  #73 = NameAndType        #48:#49        // equals:(Ljava/lang/Object;)Z
  #74 = NameAndType        #38:#39        // getAge:()I
  #75 = NameAndType        #40:#41        // isGood:()Z
  #76 = NameAndType        #59:#39        // hashCode:()I
  #77 = Utf8               java/lang/StringBuilder
  #78 = Utf8               UserData(name=
  #79 = NameAndType        #87:#88        // append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #80 = Utf8               , age=
  #81 = NameAndType        #87:#89        // append:(I)Ljava/lang/StringBuilder;
  #82 = Utf8               , good=
  #83 = NameAndType        #87:#90        // append:(Z)Ljava/lang/StringBuilder;
  #84 = Utf8               )
  #85 = NameAndType        #63:#37        // toString:()Ljava/lang/String;
  #86 = Utf8               java/lang/Object
  #87 = Utf8               append
  #88 = Utf8               (Ljava/lang/String;)Ljava/lang/StringBuilder;
  #89 = Utf8               (I)Ljava/lang/StringBuilder;
  #90 = Utf8               (Z)Ljava/lang/StringBuilder;
{
  public lombok.UserData();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #1                  // Method java/lang/Object."<init>":()V
         4: return
      LineNumberTable: // 源代码行号和字节码的对应关系
        line 3: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       5     0  this   Llombok/UserData;

  public java.lang.String getName();
    descriptor: ()Ljava/lang/String;
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: getfield      #2                  // Field name:Ljava/lang/String;
         4: areturn
      LineNumberTable:
        line 6: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       5     0  this   Llombok/UserData;

  public int getAge();
    descriptor: ()I
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: getfield      #3                  // Field age:I
         4: ireturn
      LineNumberTable:
        line 8: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       5     0  this   Llombok/UserData;

  public boolean isGood();
    descriptor: ()Z
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: getfield      #4                  // Field good:Z
         4: ireturn
      LineNumberTable:
        line 10: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       5     0  this   Llombok/UserData;

  public void setName(java.lang.String);
    descriptor: (Ljava/lang/String;)V
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
         0: aload_0
         1: aload_1
         2: putfield      #2                  // Field name:Ljava/lang/String;
         5: return
      LineNumberTable:
        line 3: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       6     0  this   Llombok/UserData;
            0       6     1  name   Ljava/lang/String;

  public void setAge(int);
    descriptor: (I)V
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
         0: aload_0
         1: iload_1
         2: putfield      #3                  // Field age:I
         5: return
      LineNumberTable:
        line 3: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       6     0  this   Llombok/UserData;
            0       6     1   age   I

  public void setGood(boolean);
    descriptor: (Z)V
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
         0: aload_0
         1: iload_1
         2: putfield      #4                  // Field good:Z
         5: return
      LineNumberTable:
        line 3: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       6     0  this   Llombok/UserData;
            0       6     1  good   Z

  public boolean equals(java.lang.Object);
    descriptor: (Ljava/lang/Object;)Z
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=5, args_size=2
         0: aload_1
         1: aload_0
         2: if_acmpne     7
         5: iconst_1
         6: ireturn
         7: aload_1
         8: instanceof    #5                  // class lombok/UserData
        11: ifne          16
        14: iconst_0
        15: ireturn
        16: aload_1
        17: checkcast     #5                  // class lombok/UserData
        20: astore_2
        21: aload_2
        22: aload_0
        23: invokevirtual #6                  // Method canEqual:(Ljava/lang/Object;)Z
        26: ifne          31
        29: iconst_0
        30: ireturn
        31: aload_0
        32: invokevirtual #7                  // Method getName:()Ljava/lang/String;
        35: astore_3
        36: aload_2
        37: invokevirtual #7                  // Method getName:()Ljava/lang/String;
        40: astore        4
        42: aload_3
        43: ifnonnull     54
        46: aload         4
        48: ifnull        65
        51: goto          63
        54: aload_3
        55: aload         4
        57: invokevirtual #8                  // Method java/lang/Object.equals:(Ljava/lang/Object;)Z
        60: ifne          65
        63: iconst_0
        64: ireturn
        65: aload_0
        66: invokevirtual #9                  // Method getAge:()I
        69: aload_2
        70: invokevirtual #9                  // Method getAge:()I
        73: if_icmpeq     78
        76: iconst_0
        77: ireturn
        78: aload_0
        79: invokevirtual #10                 // Method isGood:()Z
        82: aload_2
        83: invokevirtual #10                 // Method isGood:()Z
        86: if_icmpeq     91
        89: iconst_0
        90: ireturn
        91: iconst_1
        92: ireturn
      LineNumberTable:
        line 3: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0      93     0  this   Llombok/UserData;
            0      93     1     o   Ljava/lang/Object;
           21      72     2 other   Llombok/UserData;
           36      57     3 this$name   Ljava/lang/Object;
           42      51     4 other$name   Ljava/lang/Object;
      StackMapTable: number_of_entries = 8
        frame_type = 7 /* same */
        frame_type = 8 /* same */
        frame_type = 252 /* append */
          offset_delta = 14
          locals = [ class lombok/UserData ]
        frame_type = 253 /* append */
          offset_delta = 22
          locals = [ class java/lang/Object, class java/lang/Object ]
        frame_type = 8 /* same */
        frame_type = 1 /* same */
        frame_type = 12 /* same */
        frame_type = 12 /* same */

  protected boolean canEqual(java.lang.Object);
    descriptor: (Ljava/lang/Object;)Z
    flags: ACC_PROTECTED
    Code:
      stack=1, locals=2, args_size=2
         0: aload_1
         1: instanceof    #5                  // class lombok/UserData
         4: ireturn
      LineNumberTable:
        line 3: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0       5     0  this   Llombok/UserData;
            0       5     1 other   Ljava/lang/Object;

  public int hashCode();
    descriptor: ()I
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=4, args_size=1
         0: bipush        59
         2: istore_1
         3: iconst_1
         4: istore_2
         5: aload_0
         6: invokevirtual #7                  // Method getName:()Ljava/lang/String;
         9: astore_3
        10: iload_2
        11: bipush        59
        13: imul
        14: aload_3
        15: ifnonnull     23
        18: bipush        43
        20: goto          27
        23: aload_3
        24: invokevirtual #11                 // Method java/lang/Object.hashCode:()I
        27: iadd
        28: istore_2
        29: iload_2
        30: bipush        59
        32: imul
        33: aload_0
        34: invokevirtual #9                  // Method getAge:()I
        37: iadd
        38: istore_2
        39: iload_2
        40: bipush        59
        42: imul
        43: aload_0
        44: invokevirtual #10                 // Method isGood:()Z
        47: ifeq          55
        50: bipush        79
        52: goto          57
        55: bipush        97
        57: iadd
        58: istore_2
        59: iload_2
        60: ireturn
      LineNumberTable:
        line 3: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0      61     0  this   Llombok/UserData;
            3      58     1 PRIME   I
            5      56     2 result   I
           10      51     3 $name   Ljava/lang/Object;
      StackMapTable: number_of_entries = 4
        frame_type = 255 /* full_frame */
          offset_delta = 23
          locals = [ class lombok/UserData, int, int, class java/lang/Object ]
          stack = [ int ]
        frame_type = 255 /* full_frame */
          offset_delta = 3
          locals = [ class lombok/UserData, int, int, class java/lang/Object ]
          stack = [ int, int ]
        frame_type = 91 /* same_locals_1_stack_item */
          stack = [ int ]
        frame_type = 255 /* full_frame */
          offset_delta = 1
          locals = [ class lombok/UserData, int, int, class java/lang/Object ]
          stack = [ int, int ]

  public java.lang.String toString();
    descriptor: ()Ljava/lang/String;
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
         0: new           #12                 // class java/lang/StringBuilder
         3: dup
         4: invokespecial #13                 // Method java/lang/StringBuilder."<init>":()V
         7: ldc           #14                 // String UserData(name=
         9: invokevirtual #15                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
        12: aload_0
        13: invokevirtual #7                  // Method getName:()Ljava/lang/String;
        16: invokevirtual #15                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
        19: ldc           #16                 // String , age=
        21: invokevirtual #15                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
        24: aload_0
        25: invokevirtual #9                  // Method getAge:()I
        28: invokevirtual #17                 // Method java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;
        31: ldc           #18                 // String , good=
        33: invokevirtual #15                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
        36: aload_0
        37: invokevirtual #10                 // Method isGood:()Z
        40: invokevirtual #19                 // Method java/lang/StringBuilder.append:(Z)Ljava/lang/StringBuilder;
        43: ldc           #20                 // String )
        45: invokevirtual #15                 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
        48: invokevirtual #21                 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
        51: areturn
      LineNumberTable:
        line 3: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
            0      52     0  this   Llombok/UserData;
}
SourceFile: "UserData.java"

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