Java开发神器Lombok的安装与使用

我会带着你远行 2022-01-22 11:41 298阅读 0赞

项目中经常使用bean，entity等类，绝大部分数据类类中都需要get、set、toString、equals和hashCode方法，虽然eclipse和idea开发环境下都有自动生成的快捷方式，但自动生成这些代码后，如果bean中的属性一旦有修改、删除或增加时，需要重新生成或删除get/set等方法，给代码维护增加负担。而使用了lombok则不一样，使用了lombok的注解(@Setter,@Getter,@ToString,@@RequiredArgsConstructor,@EqualsAndHashCode或@Data)之后，就不需要编写或生成get/set等方法，很大程度上减少了代码量，而且减少了代码维护的负担。故强烈建议项目中使用lombok，去掉bean中get、set、toString、equals和hashCode等方法的代码。

### 一、IDEA安装Lombok ###

安装过程如下图  
![在这里插入图片描述][2019060609442894.png]  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2FfaGVsbG93b3Jk_size_16_color_FFFFFF_t_70]  
安装完成后，重启IDEA即可。

### 二、在pom中添加依赖 ###

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

### 三、Lombok常用注解 ###

1、**@Getter/@Setter**注解为属性自动生成get/set方法。

@Setter
    @Getter
    public class User {
    
        private Long id;
    
        private String name;
    
        private String password;
    
        private String salt;
    
        private Integer status;
    
        private String address;
    
        private String phone;
    
        private Date lasttime;
    
    }

2、**@ToString**注解，生成一个toString方法，默认的toString格式为：ClassName(fieldName= fieleValue ,fieldName1=fieleValue)。

@ToString
    public class User {
    
        private Long id;
    
        private String name;
    
        private String password;
    
        private String salt;
    
        private Integer status;
    
        private String address;
    
        private String phone;
    
        private Date lasttime;
    
    }

@ToString和下面的代码含义一样

@Override
        public String toString() {
            return "User{" +
                    "id=" + id +
                    ", name='" + name + '\'' +
                    ", password='" + password + '\'' +
                    ", salt='" + salt + '\'' +
                    ", status=" + status +
                    ", address='" + address + '\'' +
                    ", phone='" + phone + '\'' +
                    ", lasttime=" + lasttime +
                    '}';
        }

3、**Val**将变量申明为final类型。

val defaultCount = new ArrayList<>();
    
    // 下面的代码和上面的含义一样
    final List<Integer> defaultCount = new ArrayList<>();

4、**@NonNull**注解能够为方法或构造函数的参数提供非空检查。

public void notNullExample(@NonNull String string) {
        //方法内的代码
    }
    
    //=>上面代码相当于如下：
    
    public void notNullExample(String string) {
        if (string != null) {
            //方法内的代码相当于如下：
        } else {
            throw new NullPointerException("null");
        }
    }

5、**@Cleanup**注解能够自动释放资源。

public   void jedisExample(String[] args) {
        try {
            @Cleanup Jedis jedis =   redisService.getJedis();
        } catch (Exception ex) {
            logger.error(“Jedis异常:”,ex)
        }
    
        //=>上面代码相当于如下：
        Jedis jedis= null;
        try {
            jedis = redisService.getJedis();
        } catch (Exception e) {
            logger.error(“Jedis异常:”,ex)
        } finally {
            if (jedis != null) {
                try {
                    jedis.close();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
    }

6、**@EqualsAndHashCode**注解，自动生成equals和hashCode方法。

@EqualsAndHashCode(exclude = {"id"}, callSuper =true)
    public class LombokDemo extends Demo{
        private int id;
        private String name;
        private String gender;
    }
    
    //上面代码相当于如下：
    
    public class LombokDemo extends Demo{
    
        private int id;
        private String name;
        private String gender;
        
        @Override
        public boolean equals(final Object o) {
            if (o == this) return true;
            if (o == null) return false;
            if (o.getClass() != this.getClass()) return false;
            if (!super.equals(o)) return false;
            final LombokDemo other = (LombokDemo)o;
            if (this.name == null ? other.name != null : !this.name.equals(other.name)) return false;
            if (this.gender == null ? other.gender != null : !this.gender.equals(other.gender)) return false;
            return true;
        }
    
        @Override
        public int hashCode() {
            final int PRIME = 31;
            int result = 1;
            result = result * PRIME + super.hashCode();
            result = result * PRIME + (this.name == null ? 0 : this.name.hashCode());
            result = result * PRIME + (this.gender == null ? 0 : this.gender.hashCode());
            return result;
        }
    
    }

7、**@NoArgsConstructor, @RequiredArgsConstructor, @AllArgsConstructor**,这几个注解分别自动生成了无参构造器、指定参数的构造器和包含所有参数的构造器。

@RequiredArgsConstructor(staticName = "of") 
    @AllArgsConstructor(access = AccessLevel.PROTECTED) 
    public class ConstructorExample<T> { 
    
      private int x, y; 
      @NonNull private T description; 
      
      @NoArgsConstructor 
      public static class NoArgsExample { 
        @NonNull private String field; 
      } 
    
    }
    
    //上面代码相当于如下：
    @RequiredArgsConstructor(staticName = "of") 
    @AllArgsConstructor(access = AccessLevel.PROTECTED) 
    public class ConstructorExample<T> { 
    
      private int x, y; 
      @NonNull private T description; 
    
      @NoArgsConstructor 
      public static class NoArgsExample { 
        @NonNull private String field; 
      } 
    
    }
    
    public class ConstructorExample<T> { 
      private int x, y; 
      @NonNull private T description; 
    
      private ConstructorExample(T description) { 
        if (description == null) throw new NullPointerException("description"); 
        this.description = description; 
      } 
    
      public static <T> ConstructorExample<T> of(T description) { 
        return new ConstructorExample<T>(description); 
      } 
    
      @java.beans.ConstructorProperties({"x", "y", "description"}) 
      protected ConstructorExample(int x, int y, T description) { 
        if (description == null) throw new NullPointerException("description"); 
        this.x = x; 
        this.y = y; 
        this.description = description; 
      } 
      
      public static class NoArgsExample { 
        @NonNull private String field;
        
        public NoArgsExample() { 
        } 
      } 
    }

8、**@Data**注解作用比较全，其包含注解的集合@ToString，@EqualsAndHashCode，所有字段的@Getter和所有非final字段的@Setter, @RequiredArgsConstructor。其示例代码可以参考上面几个注解的组合。

9、**@Builder**注解提供了一种比较推崇的构建值对象的方式。

@Builder 
    public class BuilderExample { 
    
      private String name; 
      private int age; 
    
      @Singular private Set<String> occupations; 
    
    }
    
    //上面代码相当于如下：
    
    public class BuilderExample { 
    
      private String name; 
      private int age; 
      private Set<String> occupations; 
    
      BuilderExample(String name, int age, Set<String> occupations) { 
        this.name = name; 
        this.age = age; 
        this.occupations = occupations; 
      } 
    
      public static BuilderExampleBuilder builder() { 
        return new BuilderExampleBuilder(); 
      } 
    
      public static class BuilderExampleBuilder { 
    
        private String name; 
        private int age; 
        private java.util.ArrayList<String> occupations;    
    
        BuilderExampleBuilder() { 
        } 
    
        public BuilderExampleBuilder name(String name) { 
          this.name = name; 
          return this; 
        } 
    
        public BuilderExampleBuilder age(int age) { 
          this.age = age; 
          return this; 
        } 
    
        public BuilderExampleBuilder occupation(String occupation) { 
          if (this.occupations == null) { 
            this.occupations = new java.util.ArrayList<String>(); 
          } 
          this.occupations.add(occupation); 
          return this; 
        } 
    
        public BuilderExampleBuilder occupations(Collection<? extends String> occupations) { 
          if (this.occupations == null) { 
            this.occupations = new java.util.ArrayList<String>(); 
          } 
          this.occupations.addAll(occupations); 
          return this; 
        } 
    
        public BuilderExampleBuilder clearOccupations() { 
          if (this.occupations != null) { 
            this.occupations.clear(); 
          }
          return this; 
        } 
    
        public BuilderExample build() {  
          Set<String> occupations = new HashSet<>(); 
          return new BuilderExample(name, age, occupations); 
        } 
    
        @verride 
        public String toString() { 
          return "BuilderExample.BuilderExampleBuilder(name = " + this.name + ", age = " + this.age + ", occupations = " + this.occupations + ")"; 
        } 
      } 
    }

10、**@Synchronized**注解类似Java中的Synchronized 关键字，但是可以隐藏同步锁。

public class SynchronizedExample { 
    
     private final Object readLock = new   Object(); 
    
     @Synchronized 
     public static void hello() { 
         System.out.println("world");   
     } 
    
     @Synchronized("readLock") 
     public void foo() { 
       System.out.println("bar"); 
     } 
    
    //上面代码相当于如下：
    
     public class SynchronizedExample { 
    
      private static final Object $LOCK = new   Object[0]; 
      private final Object readLock = new   Object(); 
    
      public static void hello() { 
        synchronized($LOCK) { 
          System.out.println("world"); 
        } 
      }   
    
      public void foo() { 
        synchronized(readLock) { 
            System.out.println("bar");   
        } 
      } 
    
    }

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