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Lombok的功能是什么
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!
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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."":()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." ":()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 #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 // " ":()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." ":()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." ":()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"
到此，相信大家对“Lombok的功能是什么”有了更深的了解，不妨来实际操作一番吧！这里是创新互联网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！
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