Lombok-入门篇

电玩女神 2023-01-10 14:31 120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：

/**
     * @author javaerui
     * @Description:
     * @date 2021/1/22
     */
    public class User {
    
        public User() {
        }
    
        public User(String name, long id, Integer age, boolean vip, Boolean svip) {
            this.name = name;
            this.id = id;
            this.age = age;
            this.vip = vip;
            this.svip = svip;
        }
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public long getId() {
            return id;
        }
    
        public void setId(long id) {
            this.id = id;
        }
    
        public Integer getAge() {
            return age;
        }
    
        public void setAge(Integer age) {
            this.age = age;
        }
    
        public boolean isVip() {
            return vip;
        }
    
        public void setVip(boolean vip) {
            this.vip = vip;
        }
    
        public Boolean getSvip() {
            return svip;
        }
    
        public void setSvip(Boolean svip) {
            this.svip = svip;
        }
    
        @Override
        public String toString() {
            return "User{" +
                    "name='" + name + '\'' +
                    ", id=" + id +
                    ", age=" + age +
                    ", vip=" + vip +
                    ", svip=" + svip +
                    '}';
        }
    }

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：

/**
     * @author javaerui
     * @Description:
     * @date 2021/1/22
     */
    @NoArgsConstructor
    @AllArgsConstructor
    @Getter
    @Setter
    @ToString
    public class User {
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

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

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    public class User {
        private String name;
        private long id;
        private Integer age;
        private boolean vip;
        private Boolean svip;
    
        public User() {
        }
    
        public User(String name, long id, Integer age, boolean vip, Boolean svip) {
            this.name = name;
            this.id = id;
            this.age = age;
            this.vip = vip;
            this.svip = svip;
        }
    
        public String getName() {
            return this.name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public long getId() {
            return this.id;
        }
    
        public void setId(long id) {
            this.id = id;
        }
    
        public Integer getAge() {
            return this.age;
        }
    
        public void setAge(Integer age) {
            this.age = age;
        }
    
        public boolean isVip() {
            return this.vip;
        }
    
        public void setVip(boolean vip) {
            this.vip = vip;
        }
    
        public Boolean getSvip() {
            return this.svip;
        }
    
        public void setSvip(Boolean svip) {
            this.svip = svip;
        }
    
        public String toString() {
            return "User{name='" + this.name + '\'' + ", id=" + this.id + ", age=" + this.age + ", vip=" + this.vip + ", svip=" + this.svip + '}';
        }
    }

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：

<dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.18.16</version>
        <scope>provided</scope>
    </dependency>

（3）以User类为例，查看Lombok提供的注解所对应的方法。

public class User {
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

*  **@Getter**

对Bean的属性构建标准getter方法。

源码：

@Getter
    public class User {
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

编译后：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    public class User {
        private String name;
        private long id;
        private Integer age;
        private boolean vip;
        private Boolean svip;
    
        public User() {
        }
    
        public String getName() {
            return this.name;
        }
    
        public long getId() {
            return this.id;
        }
    
        public Integer getAge() {
            return this.age;
        }
    
        public boolean isVip() {
            return this.vip;
        }
    
        public Boolean getSvip() {
            return this.svip;
        }
    }

*  **@Setter**

对属性构建set方法。

源码：

@Setter
    public class User {
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

编译后：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    public class User {
        private String name;
        private long id;
        private Integer age;
        private boolean vip;
        private Boolean svip;
    
        public User() {
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public void setId(long id) {
            this.id = id;
        }
    
        public void setAge(Integer age) {
            this.age = age;
        }
    
        public void setVip(boolean vip) {
            this.vip = vip;
        }
    
        public void setSvip(Boolean svip) {
            this.svip = svip;
        }
    }

*  **@ToString**

重写toString方法。

源码：

@ToString
    public class User {
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

编译后：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    public class User {
        private String name;
        private long id;
        private Integer age;
        private boolean vip;
        private Boolean svip;
    
        public User() {
        }
    
        public String toString() {
            return "User(name=" + this.name + ", id=" + this.id + ", age=" + this.age + ", vip=" + this.vip + ", svip=" + this.svip + ")";
        }
    }

*  **@EqualsAndHashCode**

重写equals与hashcode方法。

源码：

@EqualsAndHashCode
    public class User {
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

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：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    public class User {
        private String name;
        private long id;
        private Integer age;
        private boolean vip;
        private Boolean svip;
    
        public User() {
        }
    
        public boolean equals(Object o) {
            if (o == this) {
                return true;
            } else if (!(o instanceof User)) {
                return false;
            } else {
                User other = (User)o;
                if (!other.canEqual(this)) {
                    return false;
                } else if (this.id != other.id) {
                    return false;
                } else if (this.vip != other.vip) {
                    return false;
                } else {
                    label52: {
                        Object this$age = this.age;
                        Object other$age = other.age;
                        if (this$age == null) {
                            if (other$age == null) {
                                break label52;
                            }
                        } else if (this$age.equals(other$age)) {
                            break label52;
                        }
    
                        return false;
                    }
    
                    Object this$svip = this.svip;
                    Object other$svip = other.svip;
                    if (this$svip == null) {
                        if (other$svip != null) {
                            return false;
                        }
                    } else if (!this$svip.equals(other$svip)) {
                        return false;
                    }
    
                    Object this$name = this.name;
                    Object other$name = other.name;
                    if (this$name == null) {
                        if (other$name != null) {
                            return false;
                        }
                    } else if (!this$name.equals(other$name)) {
                        return false;
                    }
    
                    return true;
                }
            }
        }
    
        protected boolean canEqual(Object other) {
            return other instanceof User;
        }
    
        public int hashCode() {
            int PRIME = true;
            int result = 1;
            long $id = this.id;
            int result = result * 59 + (int)($id >>> 32 ^ $id);
            result = result * 59 + (this.vip ? 79 : 97);
            Object $age = this.age;
            result = result * 59 + ($age == null ? 43 : $age.hashCode());
            Object $svip = this.svip;
            result = result * 59 + ($svip == null ? 43 : $svip.hashCode());
            Object $name = this.name;
            result = result * 59 + ($name == null ? 43 : $name.hashCode());
            return result;
        }
    }

*  **@AllArgsConstructor、@NoArgsConstructor**

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

源码：

@AllArgsConstructor
    @NoArgsConstructor
    public class User {
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

编译后：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    public class User {
        private String name;
        private long id;
        private Integer age;
        private boolean vip;
        private Boolean svip;
    
        public User(String name, long id, Integer age, boolean vip, Boolean svip) {
            this.name = name;
            this.id = id;
            this.age = age;
            this.vip = vip;
            this.svip = svip;
        }
    
        public User() {
        }
    }

*  **@Builder**

对Bean构建Builder构建者模式。

源码：

@Builder
    public class User {
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

编译后：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    public class User {
        private String name;
        private long id;
        private Integer age;
        private boolean vip;
        private Boolean svip;
    
        User(String name, long id, Integer age, boolean vip, Boolean svip) {
            this.name = name;
            this.id = id;
            this.age = age;
            this.vip = vip;
            this.svip = svip;
        }
    
        public static User.UserBuilder builder() {
            return new User.UserBuilder();
        }
    
        public static class UserBuilder {
            private String name;
            private long id;
            private Integer age;
            private boolean vip;
            private Boolean svip;
    
            UserBuilder() {
            }
    
            public User.UserBuilder name(String name) {
                this.name = name;
                return this;
            }
    
            public User.UserBuilder id(long id) {
                this.id = id;
                return this;
            }
    
            public User.UserBuilder age(Integer age) {
                this.age = age;
                return this;
            }
    
            public User.UserBuilder vip(boolean vip) {
                this.vip = vip;
                return this;
            }
    
            public User.UserBuilder svip(Boolean svip) {
                this.svip = svip;
                return this;
            }
    
            public User build() {
                return new User(this.name, this.id, this.age, this.vip, this.svip);
            }
    
            public String toString() {
                return "User.UserBuilder(name=" + this.name + ", id=" + this.id + ", age=" + this.age + ", vip=" + this.vip + ", svip=" + this.svip + ")";
            }
        }
    }

*  **@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：

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

编译后：

public void method() throws IOException {
        FileOutputStream fileOutputStream = new FileOutputStream("E:\\Downloads\\java.txt");
    
        try {
            fileOutputStream.write("Hello World".getBytes());
        } finally {
            if (Collections.singletonList(fileOutputStream).get(0) != null) {
                fileOutputStream.close();
            }
    
        }
    
    }

*  **@NonNull**

非空检查，当设置的值为空时，会抛异常。

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

调用，对name进行赋值为null：

User user = new User();
    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：

@RequiredArgsConstructor
    public class User {
    
        @NonNull
        private String name;
    
        private long id;
    
        private Integer age;
    
        @NonNull
        private boolean vip;
    
        private Boolean svip;
    
    }

编译后，从这里可以看出@NonNull标注的字段会加非空判断：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    import lombok.NonNull;
    
    public class User {
        @NonNull
        private String name;
        private long id;
        private Integer age;
        @NonNull
        private boolean vip;
        private Boolean svip;
    
        public User(@NonNull String name, @NonNull boolean vip) {
            if (name == null) {
                throw new NullPointerException("name is marked non-null but is null");
            } else {
                this.name = name;
                this.vip = vip;
            }
        }
    }

*  **@Data**

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

源码：

@Data
    public class User {
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

编译后：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    import java.util.List;
    import lombok.NonNull;
    
    public class User {
        @NonNull
        private String name;
        private long id;
        private Integer age;
        private boolean vip;
        private Boolean svip;
        private List<String> list;
    
        public User(@NonNull String name) {
            if (name == null) {
                throw new NullPointerException("name is marked non-null but is null");
            } else {
                this.name = name;
            }
        }
    
        @NonNull
        public String getName() {
            return this.name;
        }
    
        public long getId() {
            return this.id;
        }
    
        public Integer getAge() {
            return this.age;
        }
    
        public boolean isVip() {
            return this.vip;
        }
    
        public Boolean getSvip() {
            return this.svip;
        }
    
        public List<String> getList() {
            return this.list;
        }
    
        public void setName(@NonNull String name) {
            if (name == null) {
                throw new NullPointerException("name is marked non-null but is null");
            } else {
                this.name = name;
            }
        }
    
        public void setId(long id) {
            this.id = id;
        }
    
        public void setAge(Integer age) {
            this.age = age;
        }
    
        public void setVip(boolean vip) {
            this.vip = vip;
        }
    
        public void setSvip(Boolean svip) {
            this.svip = svip;
        }
    
        public void setList(List<String> list) {
            this.list = list;
        }
    
        public boolean equals(Object o) {
            if (o == this) {
                return true;
            } else if (!(o instanceof User)) {
                return false;
            } else {
                User other = (User)o;
                if (!other.canEqual(this)) {
                    return false;
                } else if (this.getId() != other.getId()) {
                    return false;
                } else if (this.isVip() != other.isVip()) {
                    return false;
                } else {
                    label64: {
                        Object this$age = this.getAge();
                        Object other$age = other.getAge();
                        if (this$age == null) {
                            if (other$age == null) {
                                break label64;
                            }
                        } else if (this$age.equals(other$age)) {
                            break label64;
                        }
    
                        return false;
                    }
    
                    label57: {
                        Object this$svip = this.getSvip();
                        Object other$svip = other.getSvip();
                        if (this$svip == null) {
                            if (other$svip == null) {
                                break label57;
                            }
                        } else if (this$svip.equals(other$svip)) {
                            break label57;
                        }
    
                        return false;
                    }
    
                    Object this$name = this.getName();
                    Object other$name = other.getName();
                    if (this$name == null) {
                        if (other$name != null) {
                            return false;
                        }
                    } else if (!this$name.equals(other$name)) {
                        return false;
                    }
    
                    Object this$list = this.getList();
                    Object other$list = other.getList();
                    if (this$list == null) {
                        if (other$list != null) {
                            return false;
                        }
                    } else if (!this$list.equals(other$list)) {
                        return false;
                    }
    
                    return true;
                }
            }
        }
    
        protected boolean canEqual(Object other) {
            return other instanceof User;
        }
    
        public int hashCode() {
            int PRIME = true;
            int result = 1;
            long $id = this.getId();
            int result = result * 59 + (int)($id >>> 32 ^ $id);
            result = result * 59 + (this.isVip() ? 79 : 97);
            Object $age = this.getAge();
            result = result * 59 + ($age == null ? 43 : $age.hashCode());
            Object $svip = this.getSvip();
            result = result * 59 + ($svip == null ? 43 : $svip.hashCode());
            Object $name = this.getName();
            result = result * 59 + ($name == null ? 43 : $name.hashCode());
            Object $list = this.getList();
            result = result * 59 + ($list == null ? 43 : $list.hashCode());
            return result;
        }
    
        public String toString() {
            return "User(name=" + this.getName() + ", id=" + this.getId() + ", age=" + this.getAge() + ", vip=" + this.isVip() + ", svip=" + this.getSvip() + ", list=" + this.getList() + ")";
        }
    }

*  **@SneakyThrows**

标记方法抛出的异常。

源码：

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

编译后：

public void method() {
        try {
            FileOutputStream fileOutputStream = new FileOutputStream("E:\\Downloads\\java.txt");
            fileOutputStream.write("Hello World".getBytes());
        } catch (IOException var2) {
            throw var2;
        }
    }

*  **@Synchronized**

对方法体进行同步操作。

源码：

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

编译后：

private final Object $lock = new Object[0];
    
    public void method() throws IOException {
        synchronized(this.$lock) {
            FileOutputStream fileOutputStream = new FileOutputStream("E:\\Downloads\\java.txt");
            fileOutputStream.write("Hello World".getBytes());
        }
    }

*  **@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：

@Value
    public class User {
    
        private String name;
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

编译后：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    public final class User {
        private final String name;
        private final long id;
        private final Integer age;
        private final boolean vip;
        private final Boolean svip;
    
        public User(String name, long id, Integer age, boolean vip, Boolean svip) {
            this.name = name;
            this.id = id;
            this.age = age;
            this.vip = vip;
            this.svip = svip;
        }
    
        public String getName() {
            return this.name;
        }
    
        public long getId() {
            return this.id;
        }
    
        public Integer getAge() {
            return this.age;
        }
    
        public boolean isVip() {
            return this.vip;
        }
    
        public Boolean getSvip() {
            return this.svip;
        }
    
        public boolean equals(Object o) {
            if (o == this) {
                return true;
            } else if (!(o instanceof User)) {
                return false;
            } else {
                User other = (User)o;
                if (this.getId() != other.getId()) {
                    return false;
                } else if (this.isVip() != other.isVip()) {
                    return false;
                } else {
                    label49: {
                        Object this$age = this.getAge();
                        Object other$age = other.getAge();
                        if (this$age == null) {
                            if (other$age == null) {
                                break label49;
                            }
                        } else if (this$age.equals(other$age)) {
                            break label49;
                        }
    
                        return false;
                    }
    
                    Object this$svip = this.getSvip();
                    Object other$svip = other.getSvip();
                    if (this$svip == null) {
                        if (other$svip != null) {
                            return false;
                        }
                    } else if (!this$svip.equals(other$svip)) {
                        return false;
                    }
    
                    Object this$name = this.getName();
                    Object other$name = other.getName();
                    if (this$name == null) {
                        if (other$name != null) {
                            return false;
                        }
                    } else if (!this$name.equals(other$name)) {
                        return false;
                    }
    
                    return true;
                }
            }
        }
    
        public int hashCode() {
            int PRIME = true;
            int result = 1;
            long $id = this.getId();
            int result = result * 59 + (int)($id >>> 32 ^ $id);
            result = result * 59 + (this.isVip() ? 79 : 97);
            Object $age = this.getAge();
            result = result * 59 + ($age == null ? 43 : $age.hashCode());
            Object $svip = this.getSvip();
            result = result * 59 + ($svip == null ? 43 : $svip.hashCode());
            Object $name = this.getName();
            result = result * 59 + ($name == null ? 43 : $name.hashCode());
            return result;
        }
    
        public String toString() {
            return "User(name=" + this.getName() + ", id=" + this.getId() + ", age=" + this.getAge() + ", vip=" + this.isVip() + ", svip=" + this.getSvip() + ")";
        }
    }

*  @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：

@AllArgsConstructor
    @With
    public class User {
    
        private String name;
    
        public User(String name) {
            this.name = name;
        }
    
        private long id;
    
        private Integer age;
    
        private boolean vip;
    
        private Boolean svip;
    
    }

编译后：

//
    // Source code recreated from a .class file by IntelliJ IDEA
    // (powered by Fernflower decompiler)
    //
    
    public class User {
        private String name;
        private long id;
        private Integer age;
        private boolean vip;
        private Boolean svip;
    
        public User(String name) {
            this.name = name;
        }
    
        public User(String name, long id, Integer age, boolean vip, Boolean svip) {
            this.name = name;
            this.id = id;
            this.age = age;
            this.vip = vip;
            this.svip = svip;
        }
    
        public User withName(String name) {
            // 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
            return this.name == name ? this : new User(name, this.id, this.age, this.vip, this.svip);
        }
    
        public User withId(long id) {
            return this.id == id ? this : new User(this.name, id, this.age, this.vip, this.svip);
        }
    
        public User withAge(Integer age) {
            return this.age == age ? this : new User(this.name, this.id, age, this.vip, this.svip);
        }
    
        public User withVip(boolean vip) {
            return this.vip == vip ? this : new User(this.name, this.id, this.age, vip, this.svip);
        }
    
        public User withSvip(Boolean svip) {
            return this.svip == svip ? this : new User(this.name, this.id, this.age, this.vip, svip);
        }
    }

*  **var、val**

声明局部变量。

源码：

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

编译后：

public void method() {
        int x = true;
        double y = 1.1D;
        ArrayList<Object> list = new ArrayList();
        list.add("hello world");
    }

*  **@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：

@CommonsLog
    public class User {
        
    }

编译后：

public class User {
    
        private static final org.apache.commons.logging.Log log = 
                org.apache.commons.logging.LogFactory.getLog(User.class);
    
    }

*  **@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][Lombok-]》

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[20210124180253286.png]: https://img-blog.csdnimg.cn/20210124180253286.png
[Lombok-]: https://blog.csdn.net/weixin_50518271/article/details/113268155