Lombok插件的简介

时间  2021-08-12
标签 html java api 数组 markdown 框架 ide oop this 栏目 Java 繁體版
原文   原文链接

官网: projectlombok.org/html

官方文档: projectlombok.org/api/lombok/…java

参考资料:api

www.jianshu.com/p/2543c71a8…数组

blog.csdn.net/zhaoyanjun6…markdown

1 Lombok引入

==未使用lombok的Java的Bean:==框架

public class DepartMent {

    private String name;

    public DepartMent() {
    }

    public DepartMent(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

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

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        DepartMent that = (DepartMent) o;
        return Objects.equals(name, that.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name);
    }

    @Override
    public String toString() {
        return "DepartMent{" +
                "name='" + name + '\'' +
                '}';
    }
}
复制代码

==使用lombok的Java的Bean:==ide

@Data
@NoArgsConstructor
@AllArgsConstructor
@ToString
@EqualsAndHashCode
public class DepartMent {
    private String name;
}  
复制代码

总结:oop

lombok的出现,是为了简化Java的Bean对象,将大量重复,没有技术意义的代码省略,不只能使代码整洁美观,还能人们将注意力放到更重要的业务代码中.ui

使用前准备:this

1 在IDEA中plugins中安装Lombok插件,重启IDEA.

image-20210406213944545

2 添加lombok坐标

<dependency>
                    <groupId>org.projectlombok</groupId>
                    <artifactId>lombok</artifactId>
                    <version>1.18.16</version>
                </dependency>
复制代码

2 Lombok常见注解使用

1 @Data

@Data注解,自动生成对象属性的getter方法，setter方法，equals方法，hashCode方法，toString方法,无参构造方法.

厉害的童鞋提醒滴

@Data
public class DepartMent {
    private String name;
}  
复制代码

等同于:

public class DepartMent {
    private String name;
    
 	public DepartMent() {}
    
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        DepartMent that = (DepartMent) o;
        return Objects.equals(name, that.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name);
    }
}
复制代码

2 @AllArgsConstructor

@AllArgsConstructor注解, 对象的全参数构造

@NoArgsConstructor
public class DepartMent {
    private String name;
}  
复制代码

等同于:

public class DepartMent {
    private String name;

    public DepartMent(String name) {
        this.name = name;
    }

}
复制代码

3 @NoArgsConstructor

@NoArgsConstructor注解,对象的无参构造

@NoArgsConstructor
public class DepartMent {
    private String name;
}  
复制代码

等同于:

public class DepartMent {
    private String name;

    public DepartMent() {}

}
复制代码

4 @ToString

@ToString注解,对象的toString方法

@ToString
public class DepartMent {
    private String name;
}  
复制代码

等同于:

public class DepartMent {
    private String name;
    
    @Override
    public String toString() {
        return "DepartMent{" +
                "name='" + name + '\'' +
                '}';
    }
}  
复制代码

5 @EqualsAndHashCode

@EqualsAndHashCode注解,对象的equals和hashcode方法.

@EqualsAndHashCode
public class DepartMent {
    private String name;
}  
复制代码

等同于:

public class DepartMent {
    private String name;
    
    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        DepartMent that = (DepartMent) o;
        return Objects.equals(name, that.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name);
    }
} 
复制代码

6 @Getter/@Setter

@Getter/@Setter注解,对象的get/set方法

@Getter
@Setter  
public class DepartMent {
    private String name;
} 
复制代码

等同于:

public class DepartMent {
    private String name;
    
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}
复制代码

7 @Slf4j

@Slf4j注解,日志打印,至关于public static final Logger log = LoggerFactory.getLogger(类名.class);

@Slf4j 
public class DepartMent {
    private String name;
    
  public static void main(String[] args) {
        log.info("日志: {}" + "Hello World!");
    }
} 
复制代码

等同于:

public class DepartMent {
    private String name;
    
    public static final Logger log = LoggerFactory.getLogger(DepartMent.class);
    
    public static void main(String[] args) {
        log.info("日志: {}" + "Hello World!");
    }
} 
复制代码

8 @NonNull

@NonNull注解, 对象的成员变量和参数，标识不能为空，不然抛出空指针异常.

public class DepartMent {
    @NonNull
    private String name;
    
    public String getName() {
        return name;
    }

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

9 @Value

@Value注解, 把对象为final类,把成员变量默认定义private final,且不生成set方法.

@Value
public class DepartMent {
    private String name;
} 
复制代码

等同于:

public final class DepartMent {
    private final String name;
} 
复制代码

10 @Builder

@Builder注解, 给类添加构造者模式

@Builder
public class DepartMent {
    private String name;
} 
复制代码

等同于:

public class DepartMent {
  
   private String name;
    
   DepartMent(String name) {
        this.name = name;
    }
   public static DepartMent.DepartMentBuilder builder() {
        return new DepartMent.DepartMentBuilder();
    }
    
     public static class DepartMentBuilder {
   	 	private String name;
         DepartMentBuilder(){};
         
         public DepartMent.DepartMentBuilder name(String name) {
            this.name = name;
            return this;
        }
         
         public DepartMent build() {
            return new DepartMent(this.name);
        }
         public String toString() {
            return "DepartMent.DepartMentBuilder( name=" + this.name +")";
        }
   }

} 
复制代码

11 @Synchronized

@Synchronized注解,加一个同步锁

public class DepartMent {
   
    private String name;
    
    //普通方法，至关于对象锁
    @Synchronized
    void before() {
       //代码逻辑
    }
    
    //静态方法，至关于类锁
    @Synchronized
    static void after() {
       //代码逻辑
    }   

} 
复制代码

等同于:

public class DepartMent {
    private final Object $lock = new Object[0];
    private static final Object $LOCK = new Object[0];
    private String name;
    

    void before() {
        Object var1 = this.$lock;
        synchronized(this.$lock) {
             //代码逻辑
        }
    }
    
    static void after() {
	    Object var0 = $LOCK;
        synchronized($LOCK) {
             //代码逻辑
        }
     
    }   

} 
复制代码

12 @SneakyThrows

@SneakyThrows注解, 等同于try/catch 捕获异常.

public class DepartMent {
    private String name;
    
    @SneakyThrows
    public void init(){
        int a = 1 / 0;
    }
} 
复制代码

等同于:

public class DepartMent {
    private String name;
    
    public void init(){
        try{
        int a = 1 / 0;
        }catch(Exception e){
            //处理
        }
    }
} 
复制代码

13 @Cleanup

@Cleanup注解,自动关闭资源,例如IO流对象.

public class DepartMent {
    private String name;
    
    public void init(){
       @Cleanup InputStream in = new InputStream(); 
    }
}
复制代码

等同于:

public class DepartMent {
    private String name;
    
    public void init(){
        try{          
       		InputStream in = new InputStream();  
        }finally{
            in.close();
    }
}
复制代码

14 @Accessors

@Accessors注解,存取器,控制getter和setter方法的形式.注解有三个属性. fluent fluent默认为false,若是为true,则getter和setter方法的方法名都是属性名(以下name),且setter方法返回当前对象.(以下DepartMent )

@Data
@Accessors(fluent = true)
public class DepartMent {
    private String name;
    
     public String name() {
        return name;
    }

    public DepartMent name(String name) {
       //Xxx
    }   
}
复制代码

chain chain默认为false,若是为true,setter方法返回当前对象.(以下DepartMent )

@Data
@Accessors(chain = true)
public class DepartMent {
    private String name;
    
     public String getName() {
        return name;
    }

    public DepartMent setName(String name) {
       //Xxx
    }   
}
复制代码

prefix prefix默认为空的字符数组.可自定义前缀.(以下f),getter和setter方法会忽视属性名前的前缀.(剩下按照驼峰命名规则)

@Data
@Accessors(prefix = "f")
public class DepartMent {
    private String fname;
    
     public String name() {
        return name;
    }

    public void name(String name) {
       //Xxx
    }   
}
复制代码

3 Lombok原理

jdk1.6,javac支持JSR 269 Pluggable Annotation Processing API规范,程序实现该规范,在javac运行时,就能够调用.

Lombok就是实现了该规范的程序.在javac过程当中的工做流程:

  • 1 javac对源代码分析,生成一棵抽象语法树(AST)

  • 2 javac编译过程调用Lombok程序

  • 3 插件对获得的AST处理,找到注解地点,修改语法树,添加注解定义响应的树节点

  • 4 javac将修改后的语法树(AST)生成字节码文件

4 关于Lombok总结

关于Lombok的使用,众说纷纭,有人支持,有份反对. 新的技术出现,一定解决了一些生活中的问题,也必然带来新的问题.

Lombok的使用,给代码带来了简洁美观, 节省大量基础代码.同时也带来了不少问题,如一人使用,全人必须使用;项目升级,新的框架可否使用该插件?

我相信Lombok插件将来发展会愈来愈好.

tips:

IDEA2020.3版本,已经将Lombok做为内置插件.SpringBoot的2.1.x版本在Starter中内置了Lombok依赖.

相关文章
相关标签/搜索
每日一句
    每一个你不满意的现在，都有一个你没有努力的曾经。
本站公众号
   欢迎关注本站公众号,获取更多信息
联系我们 最近搜索 最新文章 沪ICP备13005482号-10 MyBatis教程 SQL 教程 MySQL教程 Java 教程 Thymeleaf 教程 Hibernate教程 Spring教程 Redis教程