• lombok使用基础教程

     

    前言

    lombok是一个编译级别的插件，它可以在项目编译的时候生成一些代码。在很多工具类的项目中都有这个功能。比如dagger。

    通俗的说，lombok可以通过注解来标示生成getter settter等代码。我们自然可以通过编译器比如IDEA的Generate生成，为啥要用这个？

    在项目开发阶段，一个class的属性是一直变化的，今天可能增加一个字段，明天可能删除一个字段。每次变化都需要修改对应的模板代码。另外，有的class的字段超级多，多到一眼看不完。如果加上模板代码，更难一眼看出来。更有甚者，由于字段太多，想要使用builder来创建。手动创建builder和字段和原来的类夹杂在一起，看起来真的难受。lombok的@Builder即可解决这个问题。

    引入

    引入就是加入lombok的jar包。

    在maven中

    直接加入依赖

    <dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.16.20</version>
</dependency>

    在gradle中

    这里比较麻烦，需要添加一个编译时生成代码的插件。gradle里有几个这样的插件。但为了简化过程，lombok提供了新插件。

    来源：官网， github

    首先，添加一个plugin

    plugins {
    id 'io.franzbecker.gradle-lombok' version '1.11'
}

    然后，就可以了。还可以配置lombok的版本：

    lombok { // optional: values below are the defaults
    version = "1.16.20"
    sha256 = ""
}

    IntelIJ IDEA 插件

    在IDEA里使用需要添加一个插件。在插件里搜索lombok，安装，重启。

    IDEA里需要在设置中启用annotation processors。

    基本用法

    测试代码： https://github.com/Ryan-Miao/someTest/tree/master/src/main/java/com/test/lombok

    Geeter Setter

    最简单的，最常用的，最直观的使用就是getter setter方法。

    package com.test.lombok;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.Setter;

import java.util.Date;

/**
 * Created by Ryan Miao on 1/18/18.
 */
public class GetterSetterExample {
    /**
     * Age of the person. Water is wet.
     *
     * @param age New value for this person's age. Sky is blue.
     * @return The current value of this person's age. Circles are round.
     */
    @Getter
    @Setter
    private int age = 10;

    @Getter
    @Setter
    private boolean active;

    @Getter
    @Setter
    private Boolean none;

    @Getter
    @Setter
    private Date date;

    /**
     * Name of the person.
     * -- SETTER --
     * Changes the name of this person.
     *
     * @param name The new value.
     */
    @Setter(AccessLevel.PROTECTED) private String name;

    @Override public String toString() {
        return String.format("%s (age: %d)", name, age);
    }

    public static void main(String[] args) {
        GetterSetterExample example = new GetterSetterExample();
        example.setActive(true);
        example.setAge(123);
        example.setDate(new Date());
        example.setName("abc");
        example.setNone(false);

        Date date = example.getDate();
        Boolean none = example.getNone();
        boolean active = example.isActive();
        
    }
}

    简单使用没有问题，深入一点可以看到有些特殊设定。比如javadoc.

    1. Getter声明创建getter方法；
    2. Setter声明创建setter方法；
    3. @Setter(AccessLevel.PROTECTED)可以添加参数，指定权限为私有；
    4. Attention！关于boolean的set前缀都是set，但getter不同，小写的boolean，即基本类型，前缀是is; Boolean，即包装类型，前缀是get；

    编译后的结果如下：

     1 //
 2 // Source code recreated from a .class file by IntelliJ IDEA
 3 // (powered by Fernflower decompiler)
 4 //
 5 
 6 package com.test.lombok;
 7 
 8 import java.util.Date;
 9 
10 public class GetterSetterExample {
11     private int age = 10;
12     private boolean active;
13     private Boolean none;
14     private Date date;
15     private String name;
16 
17     public GetterSetterExample() {
18     }
19 
20     public String toString() {
21         return String.format("%s (age: %d)", this.name, this.age);
22     }
23 
24     public static void main(String[] args) {
25         GetterSetterExample example = new GetterSetterExample();
26         example.setActive(true);
27         example.setAge(123);
28         example.setDate(new Date());
29         example.setName("abc");
30         example.setNone(false);
31         Date date = example.getDate();
32         Boolean none = example.getNone();
33         boolean active = example.isActive();
34     }
35 
36     public int getAge() {
37         return this.age;
38     }
39 
40     public void setAge(int age) {
41         this.age = age;
42     }
43 
44     public boolean isActive() {
45         return this.active;
46     }
47 
48     public void setActive(boolean active) {
49         this.active = active;
50     }
51 
52     public Boolean getNone() {
53         return this.none;
54     }
55 
56     public void setNone(Boolean none) {
57         this.none = none;
58     }
59 
60     public Date getDate() {
61         return this.date;
62     }
63 
64     public void setDate(Date date) {
65         this.date = date;
66     }
67 
68     protected void setName(String name) {
69         this.name = name;
70     }
71 }

    ToString

    虽然ToString在生产环境貌似没什么卵用。但是，很多情况下，我们还是需要这个的。因为记log。不想每次看log的时候是一串@地址，那就好好把toString()加上。

    package com.test.lombok;

import lombok.Setter;
import lombok.ToString;


/**
 * Created by Ryan Miao on 1/18/18.
 */
@Setter
@ToString(exclude="id")
public class ToStringExample {
    private static final int STATIC_VAR = 10;
    private String name;
    private Shape shape = new Square(5, 10);
    private String[] tags;
    private int id;


    @ToString(callSuper=true, includeFieldNames=true)
    public static class Square extends Shape {
        private final int width, height;

        public Square(int width, int height) {
            this.width = width;
            this.height = height;
        }
    }

    @ToString
    public static class Shape {
        private int color;

    }

    public static void main(String[] args) {
        final ToStringExample example = new ToStringExample();
        example.setId(1);
        example.setName("abc");
        example.setTags(new String[]{"a","b","c"});

        final Shape shape = new Square(1,2);
        example.setShape(shape);

        System.out.println(example.toString());
    }
}

    1.@ToString最简单使用即可

    打印结果如下：

    ToStringExample(name=abc, shape=ToStringExample.Square(super=ToStringExample.Shape(color=0), width=1, height=2), tags=[a, b, c])

    编译后的代码如下：

     1 //
 2 // Source code recreated from a .class file by IntelliJ IDEA
 3 // (powered by Fernflower decompiler)
 4 //
 5 
 6 package com.test.lombok;
 7 
 8 import java.util.Arrays;
 9 
10 public class ToStringExample {
11     private static final int STATIC_VAR = 10;
12     private String name;
13     private ToStringExample.Shape shape = new ToStringExample.Square(5, 10);
14     private String[] tags;
15     private int id;
16 
17     public ToStringExample() {
18     }
19 
20     public static void main(String[] args) {
21         ToStringExample example = new ToStringExample();
22         example.setId(1);
23         example.setName("abc");
24         example.setTags(new String[]{"a", "b", "c"});
25         ToStringExample.Shape shape = new ToStringExample.Square(1, 2);
26         example.setShape(shape);
27         System.out.println(example.toString());
28     }
29 
30     public void setName(String name) {
31         this.name = name;
32     }
33 
34     public void setShape(ToStringExample.Shape shape) {
35         this.shape = shape;
36     }
37 
38     public void setTags(String[] tags) {
39         this.tags = tags;
40     }
41 
42     public void setId(int id) {
43         this.id = id;
44     }
45 
46     public String toString() {
47         return "ToStringExample(name=" + this.name + ", shape=" + this.shape + ", tags=" + Arrays.deepToString(this.tags) + ")";
48     }
49 
50     public static class Shape {
51         private int color;
52 
53         public Shape() {
54         }
55 
56         public String toString() {
57             return "ToStringExample.Shape(color=" + this.color + ")";
58         }
59     }
60 
61     public static class Square extends ToStringExample.Shape {
62         private final int width;
63         private final int height;
64 
65         public Square(int width, int height) {
66             this.width = width;
67             this.height = height;
68         }
69 
70         public String toString() {
71             return "ToStringExample.Square(super=" + super.toString() + ", width=" + this.width + ", height=" + this.height + ")";
72         }
73     }
74 }

    @EqualsAndHashCode

    equals()和hashCode()在Java中有着举足轻重的基地作用，虽然通常很少关注。但是，这个必须不可省。不知道有几个可以手写出来的。

     1 package com.test.lombok;
 2 
 3 import lombok.EqualsAndHashCode;
 4 
 5 /**
 6  * Created by Ryan Miao on 1/18/18.
 7  */
 8 @EqualsAndHashCode(exclude={"id", "shape"})
 9 public class EqualsAndHashCodeExample {
10     private transient int transientVar = 10;
11     private String name;
12     private double score;
13     private ToStringExample.Shape shape = new Square(5, 10);
14     private String[] tags;
15     private int id;
16 
17     public String getName() {
18         return this.name;
19     }
20 
21     @EqualsAndHashCode(callSuper=true)
22     public static class Square extends ToStringExample.Shape {
23         private final int width, height;
24 
25         public Square(int width, int height) {
26             this.width = width;
27             this.height = height;
28         }
29     }
30 
31     public static void main(String[] args) {
32         EqualsAndHashCodeExample example = new EqualsAndHashCodeExample();
33         EqualsAndHashCodeExample example1 = new EqualsAndHashCodeExample();
34         boolean equals = example.equals(example1);
35         boolean b = example.canEqual(example);
36         int i = example.hashCode();
37     }
38 }

    编译后的结果为：

      1 //
  2 // Source code recreated from a .class file by IntelliJ IDEA
  3 // (powered by Fernflower decompiler)
  4 //
  5 
  6 package com.test.lombok;
  7 
  8 import com.test.lombok.ToStringExample.Shape;
  9 import java.util.Arrays;
 10 
 11 public class EqualsAndHashCodeExample {
 12     private transient int transientVar = 10;
 13     private String name;
 14     private double score;
 15     private Shape shape = new EqualsAndHashCodeExample.Square(5, 10);
 16     private String[] tags;
 17     private int id;
 18 
 19     public EqualsAndHashCodeExample() {
 20     }
 21 
 22     public String getName() {
 23         return this.name;
 24     }
 25 
 26     public static void main(String[] args) {
 27         EqualsAndHashCodeExample example = new EqualsAndHashCodeExample();
 28         EqualsAndHashCodeExample example1 = new EqualsAndHashCodeExample();
 29         example.equals(example1);
 30         boolean b = example.canEqual(example);
 31         int i = example.hashCode();
 32     }
 33 
 34     public boolean equals(Object o) {
 35         if (o == this) {
 36             return true;
 37         } else if (!(o instanceof EqualsAndHashCodeExample)) {
 38             return false;
 39         } else {
 40             EqualsAndHashCodeExample other = (EqualsAndHashCodeExample)o;
 41             if (!other.canEqual(this)) {
 42                 return false;
 43             } else {
 44                 label31: {
 45                     Object this$name = this.getName();
 46                     Object other$name = other.getName();
 47                     if (this$name == null) {
 48                         if (other$name == null) {
 49                             break label31;
 50                         }
 51                     } else if (this$name.equals(other$name)) {
 52                         break label31;
 53                     }
 54 
 55                     return false;
 56                 }
 57 
 58                 if (Double.compare(this.score, other.score) != 0) {
 59                     return false;
 60                 } else {
 61                     return Arrays.deepEquals(this.tags, other.tags);
 62                 }
 63             }
 64         }
 65     }
 66 
 67     protected boolean canEqual(Object other) {
 68         return other instanceof EqualsAndHashCodeExample;
 69     }
 70 
 71     public int hashCode() {
 72         int PRIME = true;
 73         int result = 1;
 74         Object $name = this.getName();
 75         int result = result * 59 + ($name == null ? 43 : $name.hashCode());
 76         long $score = Double.doubleToLongBits(this.score);
 77         result = result * 59 + (int)($score >>> 32 ^ $score);
 78         result = result * 59 + Arrays.deepHashCode(this.tags);
 79         return result;
 80     }
 81 
 82     public static class Square extends Shape {
 83         private final int width;
 84         private final int height;
 85 
 86         public Square(int width, int height) {
 87             this.width = width;
 88             this.height = height;
 89         }
 90 
 91         public boolean equals(Object o) {
 92             if (o == this) {
 93                 return true;
 94             } else if (!(o instanceof EqualsAndHashCodeExample.Square)) {
 95                 return false;
 96             } else {
 97                 EqualsAndHashCodeExample.Square other = (EqualsAndHashCodeExample.Square)o;
 98                 if (!other.canEqual(this)) {
 99                     return false;
100                 } else if (!super.equals(o)) {
101                     return false;
102                 } else if (this.width != other.width) {
103                     return false;
104                 } else {
105                     return this.height == other.height;
106                 }
107             }
108         }
109 
110         protected boolean canEqual(Object other) {
111             return other instanceof EqualsAndHashCodeExample.Square;
112         }
113 
114         public int hashCode() {
115             int PRIME = true;
116             int result = super.hashCode();
117             result = result * 59 + this.width;
118             result = result * 59 + this.height;
119             return result;
120         }
121     }
122 }

    构造函数@NoArgsConstructor, @RequiredArgsConstructor, @AllArgsConstructor

    Java中class的一切起源于构造器。大家最喜欢的还是构造函数创建对象。这里有一点比较坑的是无参构造函数。当你自己添加一个带有参数的构造函数后，无参构造函数则别隐藏。通常也没啥问题，但当你使用jackson反序列化对象的时候就被恶心到了。jackson通过无参构造函数创建对象。因此，当你考虑这个class会用来序列化为json的时候，即必须手动添加一个无参数构造函数。

    @NoArgsConstructor

    当你想要创建一个valueobject，DDD中的值对象，要求实现Immutable，那么无参数构造器就不合适了。@NoArgsConstructor会生成一个空的构造器。如果你设置了final field，那么编译会报错。如果你强制执行创建无参数构造器。即，@NoArgsConstructor(force = true)，那么final的field会初始化为0/false/null。通常适合与@Data集成。

    @NoArgsConstructor
public static class NoArgsExample {
    @NonNull private String field;
}
    • NonNull被忽略了

    最终生成代码如下：

    public static class NoArgsExample {
    @NonNull
    private String field;

    public NoArgsExample() {
    }
}

    对于final的字段，我认为我不会用空构造器来做这件事。所以，感觉这个参数force=true不要也罢，鸡肋。

    @RequiredArgsConstructor

    一个class可以有很多属性，但你可能只关心其中的几个字段，那么可以使用@RequiredArgsConstructor。@NonNull将标注这个字段不应为null，初始化的时候会检查是否为空，否则抛出NullPointException。在上面的无参构造函数中被忽略了。那么，对于关注的字段标注@NonNull, @RequiredArgsConstructor则会生成带有这些字段的构造器。

    @RequiredArgsConstructor
public class RequiredArgsExample {
    @NonNull private String field;
    private Date date;
    private Integer integer;
    private int i;
    private boolean b;
    private Boolean aBoolean;
}

    最终生成结果：

     1 public class RequiredArgsExample {
 2     @NonNull
 3     private String field;
 4     private Date date;
 5     private Integer integer;
 6     private int i;
 7     private boolean b;
 8     private Boolean aBoolean;
 9 
10     public RequiredArgsExample(@NonNull String field) {
11         if (field == null) {
12             throw new NullPointerException("field");
13         } else {
14             this.field = field;
15         }
16     }
17 }

    只有@NonNull会生成构造器。其他默认，Java的class初始化默认为null.false,0.

    lombok提供了另一种初始化做法，静态初始化。即私有构造器，使用静态方法创建对象。这种做法看起来简单，但通常用的不多。因为静态初始化的东西很难mock，对测试不够友好。

    @RequiredArgsConstructor(staticName = "of")
public static class RequiredArgsStaticExample {
    @NonNull private String field;
    private Date date;
    private Integer integer;
    private int i;
    private boolean b;
    private Boolean aBoolean;
}

    最终生成代码如下：

    public class ConstructorExample<T> {
    private int x;
    private int y;
    @NonNull
    private T description;
    private ConstructorExample(@NonNull T description) {
        if (description == null) {
            throw new NullPointerException("description");
        } else {
            this.description = description;
        }
    }
    public static <T> ConstructorExample<T> of(@NonNull T description) {
        return new ConstructorExample(description);
    }
}

    @AllArgsConstructor

    想要初始化所有字段。

    @AllArgsConstructor(access = AccessLevel.PROTECTED)
public class ConstructorExample<T> {
    private int x, y;
    @NonNull
    private T description;
}

    最终生成代码如下：

    public class ConstructorExample<T> {
    private int x;
    private int y;
    @NonNull
    private T description;
    protected ConstructorExample(int x, int y, @NonNull T description) {
        if (description == null) {
            throw new NullPointerException("description");
        } else {
            this.x = x;
            this.y = y;
            this.description = description;
        }
    }
}

    必用项@Data

    @Data是一个集合体。包含Getter,Setter,RequiredArgsConstructor,ToString,EqualsAndHashCode

    不可变对象valueobject @Value

    这个看起来很美好，就是可以帮忙生成一个不可变对象。对于所有的字段都将生成final的。但我感觉有点失控。注解的优势应该是所见即所得，可以通过字面量来传递消息。而@Value字段给字段加final会让人困惑，因为这更改了我们的定义。当我想声明一个Immutable对象的时候，我会显示的给字段加一个限定final。

    同@Data， @Value是一个集合体。包含Getter,AllArgsConstructor,ToString,EqualsAndHashCode。

    /**
 * Created by Ryan Miao on 1/18/18.
 */
@Value
public class Room {
    @NonNull
    private String id;
    private String name;
    private boolean active;
    private Date createTime;

}

    编译后

      1 public final class Room {
  2     @NonNull
  3     private final String id;
  4     private final String name;
  5     private final boolean active;
  6     private final Date createTime;
  7 
  8     public Room(@NonNull String id, String name, boolean active, Date createTime) {
  9         if (id == null) {
 10             throw new NullPointerException("id");
 11         } else {
 12             this.id = id;
 13             this.name = name;
 14             this.active = active;
 15             this.createTime = createTime;
 16         }
 17     }
 18 
 19     @NonNull
 20     public String getId() {
 21         return this.id;
 22     }
 23 
 24     public String getName() {
 25         return this.name;
 26     }
 27 
 28     public boolean isActive() {
 29         return this.active;
 30     }
 31 
 32     public Date getCreateTime() {
 33         return this.createTime;
 34     }
 35 
 36     public boolean equals(Object o) {
 37         if (o == this) {
 38             return true;
 39         } else if (!(o instanceof Room)) {
 40             return false;
 41         } else {
 42             Room other = (Room)o;
 43             Object this$id = this.getId();
 44             Object other$id = other.getId();
 45             if (this$id == null) {
 46                 if (other$id != null) {
 47                     return false;
 48                 }
 49             } else if (!this$id.equals(other$id)) {
 50                 return false;
 51             }
 52 
 53             label41: {
 54                 Object this$name = this.getName();
 55                 Object other$name = other.getName();
 56                 if (this$name == null) {
 57                     if (other$name == null) {
 58                         break label41;
 59                     }
 60                 } else if (this$name.equals(other$name)) {
 61                     break label41;
 62                 }
 63 
 64                 return false;
 65             }
 66 
 67             if (this.isActive() != other.isActive()) {
 68                 return false;
 69             } else {
 70                 Object this$createTime = this.getCreateTime();
 71                 Object other$createTime = other.getCreateTime();
 72                 if (this$createTime == null) {
 73                     if (other$createTime != null) {
 74                         return false;
 75                     }
 76                 } else if (!this$createTime.equals(other$createTime)) {
 77                     return false;
 78                 }
 79 
 80                 return true;
 81             }
 82         }
 83     }
 84 
 85     public int hashCode() {
 86         int PRIME = true;
 87         int result = 1;
 88         Object $id = this.getId();
 89         int result = result * 59 + ($id == null ? 43 : $id.hashCode());
 90         Object $name = this.getName();
 91         result = result * 59 + ($name == null ? 43 : $name.hashCode());
 92         result = result * 59 + (this.isActive() ? 79 : 97);
 93         Object $createTime = this.getCreateTime();
 94         result = result * 59 + ($createTime == null ? 43 : $createTime.hashCode());
 95         return result;
 96     }
 97 
 98     public String toString() {
 99         return "Room(id=" + this.getId() + ", name=" + this.getName() + ", active=" + this.isActive() + ", createTime=" + this.getCreateTime() + ")";
100     }
101 }
     

    最喜欢的项 @Builder

    对于喜欢builder模式的人来说，声明式简化对象创建流程让一切看得美好。但是，手动复制字段，手动创建方法很让人不喜。@Builder解决了刚需。

    /**
 * Created by Ryan Miao on 1/18/18.
 */
@Data
@Builder(toBuilder = true)
public class Room {
    @NonNull
    private String id;
    private String name;
    private boolean active;
    private Date createTime;
    @Singular
    private Set<String> occupations;

    public static void main(String[] args) {
        Room room = Room.builder().active(true)
                .name("name")
                .id("id")
                .createTime(new Date())
                .occupation("1")
                .occupation("2")
                .build();

        Assert.assertEquals(2, room.getOccupations().size());

    }
}

    这才是我们想要的建造者。对应生成的代码为：

      1 //
  2 // Source code recreated from a .class file by IntelliJ IDEA
  3 // (powered by Fernflower decompiler)
  4 //
  5 
  6 package com.test.lombok;
  7 
  8 import java.util.ArrayList;
  9 import java.util.Collection;
 10 import java.util.Collections;
 11 import java.util.Date;
 12 import java.util.LinkedHashSet;
 13 import java.util.Set;
 14 import lombok.NonNull;
 15 import org.junit.Assert;
 16 
 17 public class Room {
 18     @NonNull
 19     private String id;
 20     private String name;
 21     private boolean active;
 22     private Date createTime;
 23     private Set<String> occupations;
 24 
 25     public static void main(String[] args) {
 26         Room room = builder().active(true).name("name").id("id").createTime(new Date()).occupation("1").occupation("2").build();
 27         Assert.assertEquals(2L, (long)room.getOccupations().size());
 28     }
 29 
 30     Room(@NonNull String id, String name, boolean active, Date createTime, Set<String> occupations) {
 31         if (id == null) {
 32             throw new NullPointerException("id");
 33         } else {
 34             this.id = id;
 35             this.name = name;
 36             this.active = active;
 37             this.createTime = createTime;
 38             this.occupations = occupations;
 39         }
 40     }
 41 
 42     public static Room.RoomBuilder builder() {
 43         return new Room.RoomBuilder();
 44     }
 45 
 46     public Room.RoomBuilder toBuilder() {
 47         return (new Room.RoomBuilder()).id(this.id).name(this.name).active(this.active).createTime(this.createTime).occupations(this.occupations);
 48     }
 49 
 50     @NonNull
 51     public String getId() {
 52         return this.id;
 53     }
 54 
 55     public String getName() {
 56         return this.name;
 57     }
 58 
 59     public boolean isActive() {
 60         return this.active;
 61     }
 62 
 63     public Date getCreateTime() {
 64         return this.createTime;
 65     }
 66 
 67     public Set<String> getOccupations() {
 68         return this.occupations;
 69     }
 70 
 71     public void setId(@NonNull String id) {
 72         if (id == null) {
 73             throw new NullPointerException("id");
 74         } else {
 75             this.id = id;
 76         }
 77     }
 78 
 79     public void setName(String name) {
 80         this.name = name;
 81     }
 82 
 83     public void setActive(boolean active) {
 84         this.active = active;
 85     }
 86 
 87     public void setCreateTime(Date createTime) {
 88         this.createTime = createTime;
 89     }
 90 
 91     public void setOccupations(Set<String> occupations) {
 92         this.occupations = occupations;
 93     }
 94 
 95     public boolean equals(Object o) {
 96         if (o == this) {
 97             return true;
 98         } else if (!(o instanceof Room)) {
 99             return false;
100         } else {
101             Room other = (Room)o;
102             if (!other.canEqual(this)) {
103                 return false;
104             } else {
105                 label63: {
106                     Object this$id = this.getId();
107                     Object other$id = other.getId();
108                     if (this$id == null) {
109                         if (other$id == null) {
110                             break label63;
111                         }
112                     } else if (this$id.equals(other$id)) {
113                         break label63;
114                     }
115 
116                     return false;
117                 }
118 
119                 Object this$name = this.getName();
120                 Object other$name = other.getName();
121                 if (this$name == null) {
122                     if (other$name != null) {
123                         return false;
124                     }
125                 } else if (!this$name.equals(other$name)) {
126                     return false;
127                 }
128 
129                 if (this.isActive() != other.isActive()) {
130                     return false;
131                 } else {
132                     Object this$createTime = this.getCreateTime();
133                     Object other$createTime = other.getCreateTime();
134                     if (this$createTime == null) {
135                         if (other$createTime != null) {
136                             return false;
137                         }
138                     } else if (!this$createTime.equals(other$createTime)) {
139                         return false;
140                     }
141 
142                     Object this$occupations = this.getOccupations();
143                     Object other$occupations = other.getOccupations();
144                     if (this$occupations == null) {
145                         if (other$occupations != null) {
146                             return false;
147                         }
148                     } else if (!this$occupations.equals(other$occupations)) {
149                         return false;
150                     }
151 
152                     return true;
153                 }
154             }
155         }
156     }
157 
158     protectedbooleancanEqual(Object other) {
159         return other instanceof Room;
160     }
161 
162     publicinthashCode() {
163         int PRIME = true;
164         int result = 1;
165         Object $id = this.getId();
166         int result = result * 59 + ($id == null ? 43 : $id.hashCode());
167         Object $name = this.getName();
168         result = result * 59 + ($name == null ? 43 : $name.hashCode());
169         result = result * 59 + (this.isActive() ? 79 : 97);
170         Object $createTime = this.getCreateTime();
171         result = result * 59 + ($createTime == null ? 43 : $createTime.hashCode());
172         Object $occupations = this.getOccupations();
173         result = result * 59 + ($occupations == null ? 43 : $occupations.hashCode());
174         return result;
175     }
176 
177     public String toString() {
178         return "Room(id=" + this.getId() + ", name=" + this.getName() + ", active=" + this.isActive() + ", createTime=" + this.getCreateTime() + ", occupations=" + this.getOccupations() + ")";
179     }
180 
181     public static classRoomBuilder {
182         private String id;
183         private String name;
184         private boolean active;
185         private Date createTime;
186         private ArrayList<String> occupations;
187 
188         RoomBuilder() {
189         }
190 
191         public Room.RoomBuilderid(String id) {
192             this.id = id;
193             return this;
194         }
195 
196         public Room.RoomBuildername(String name) {
197             this.name = name;
198             return this;
199         }
200 
201         public Room.RoomBuilderactive(boolean active) {
202             this.active = active;
203             return this;
204         }
205 
206         public Room.RoomBuildercreateTime(Date createTime) {
207             this.createTime = createTime;
208             return this;
209         }
210 
211         public Room.RoomBuilderoccupation(String occupation) {
212             if (this.occupations == null) {
213                 this.occupations = new ArrayList();
214             }
215 
216             this.occupations.add(occupation);
217             return this;
218         }
219 
220         public Room.RoomBuilderoccupations(Collection<? extends String> occupations) {
221             if (this.occupations == null) {
222                 this.occupations = new ArrayList();
223             }
224 
225             this.occupations.addAll(occupations);
226             return this;
227         }
228 
229         public Room.RoomBuilderclearOccupations() {
230             if (this.occupations != null) {
231                 this.occupations.clear();
232             }
233 
234             return this;
235         }
236 
237         public Room build() {
238             Set occupations;
239             switch(this.occupations == null ? 0 : this.occupations.size()) {
240             case 0:
241                 occupations = Collections.emptySet();
242                 break;
243             case 1:
244                 occupations = Collections.singleton(this.occupations.get(0));
245                 break;
246             default:
247                 Set<String> occupations = new LinkedHashSet(this.occupations.size() < 1073741824 ? 1 + this.occupations.size() + (this.occupations.size() - 3) / 3 : 2147483647);
248                 occupations.addAll(this.occupations);
249                 occupations = Collections.unmodifiableSet(occupations);
250             }
251 
252             return new Room(this.id, this.name, this.active, this.createTime, occupations);
253         }
254 
255         public String toString() {
256             return "Room.RoomBuilder(id=" + this.id + ", name=" + this.name + ", active=" + this.active + ", createTime=" + this.createTime + ", occupations=" + this.occupations + ")";
257         }
258     }
259 }

    总结

    lombok还提供了其他几个注解，以及还有好多内置的参数没有讲解。但是，根据2-8原理，我们根本不需要。上面这几个足够了。更多的注解只会增加理解阅读难度。

    参考

    https://projectlombok.org/features/all

    http://kriszhang.com/lombok/
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  • 原文地址：https://www.cnblogs.com/guodong-wang/p/8333888.html
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