lombok

Lombok

作用：幫使用者提高編碼效率，減少重複與冗餘的代碼

原理：ASM 動態修改class文件

---

配置

maven

依賴

     <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>1.16.8</version>
    </dependency>

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編譯

     <build>
      <plugins>
          <plugin>
              <groupId>org.projectlombok</groupId>
              <artifactId>lombok-maven-plugin</artifactId>
              <version>1.16.6.1</version>
          </plugin>
      </plugins>
    </build>

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idea

• 安裝插件
  

---

常用註解：

java bean相關

@Setter

• 功能

  生成setter方法

• 源碼

    @Setter
        public class LombokDemo {

            private Integer id;
            private String name;
        }

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• 編譯後

  package xyz.mrwood.study.lombok;

  public class LombokDemo {
      private Integer id;
      private String name;

      public LombokDemo() {
      }

      public void setId(Integer id) {
          this.id = id;
      }

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

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@Getter

• 功能

  生成getter方法

• 源碼

@Getter
public class LombokDemo {

  private Integer id;
  private String name;
}

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• 編譯後

package xyz.mrwood.study.lombok;

public class LombokDemo {
    private Integer id;
    private String name;

    public LombokDemo() {
    }

    public Integer getId() {
        return this.id;
    }

    public String getName() {
        return this.name;
    }
}

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​

@ToString

• 功能

  生成toString方法

• 源碼

  @ToString
  public class LombokDemo {
  
    private Integer id;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  public class LombokDemo {
    private Integer id;
    private String name;
  
    public LombokDemo() {
    }
  
    public String toString() {
        return "LombokDemo(id=" + this.id + ", name=" + this.name + ")";
    }
  }

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  ​

@Getter(lazy = true)

• 功能

  懶加載屬性

• 注意:

  這個與上面@Getter不同，那個是修飾在類上的，也可以修飾在屬性上。如果有lazy=true只能修飾在屬性，並且還要是private final修飾，限制很大

• 編碼

  public class LombokDemo {
  
    @Getter(lazy = true) private final List<Integer> ids = Arrays.asList(1, 2, 3, 4);
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import java.util.Arrays;
  import java.util.List;
  import java.util.concurrent.atomic.AtomicReference;
  
  public class LombokDemo {
    private final AtomicReference<Object> ids = new AtomicReference();
    private String name;
  
    public LombokDemo() {
    }
  
    public List<Integer> getIds() {
        Object value = this.ids.get();
        if(value == null) {
            AtomicReference var2 = this.ids;
            synchronized(this.ids) {
                value = this.ids.get();
                if(value == null) {
                    List actualValue = Arrays.asList(new Integer[]{Integer.valueOf(1), Integer.valueOf(2), Integer.valueOf(3), Integer.valueOf(4)});
                    value = actualValue == null?this.ids:actualValue;
                    this.ids.set(value);
                }
            }
        }
  
        return (List)((List)(value == this.ids?null:value));
    }
  }
  

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  ​

@EqualsAndHashCode

• 功能

  生成equals方法與hashCode方法

• 源碼

@EqualsAndHashCode
public class LombokDemo {

    private Integer id;
    private String name;
}

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• 編譯後

package xyz.mrwood.study.lombok;

public class LombokDemo {
    private Integer id;
    private String name;

    public LombokDemo() {
    }

    public boolean equals(Object o) {
        if(o == this) {
            return true;
        } else if(!(o instanceof LombokDemo)) {
            return false;
        } else {
            LombokDemo other = (LombokDemo)o;
            if(!other.canEqual(this)) {
                return false;
            } else {
                Integer this$id = this.id;
                Integer other$id = other.id;
                if(this$id == null) {
                    if(other$id != null) {
                        return false;
                    }
                } else if(!this$id.equals(other$id)) {
                    return false;
                }

                String this$name = this.name;
                String other$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 LombokDemo;
    }

    public int hashCode() {
        boolean PRIME = true;
        byte result = 1;
        Integer $id = this.id;
        int result1 = result * 59 + ($id == <span class="hljs-keyword">null</span>?<span class="hljs-number">43</span>:$id.hashCode());
        String $name = this.name;
        result1 = result1 * 59 + ($name == <span class="hljs-keyword">null</span>?<span class="hljs-number">43</span>:$name.hashCode());
        return result1;
    }
}

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​

@NoAragsConstructor

• 功能

  添加一個無參構造函數

• 注意

  這個註解在沒有其它有參構造函數的情況下使用意義不大，因爲在這種情況下java默認會添加一個無參構造函數

• 源碼

  @NoArgsConstructor
  public class LombokDemo {
  
    private Integer id;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  public class LombokDemo {
    private Integer id;
    private String name;
  
    public LombokDemo() {
    }
  }

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  ​

@AllArgsConstructor

• 功能

  添加一個所有參數的構造函數

• 源碼

  @AllArgsConstructor
  public class LombokDemo {
  
    private Integer id;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import java.beans.ConstructorProperties;
  
  public class LombokDemo {
    private Integer id;
    private String name;
  
    @ConstructorProperties({"id", "name"})
    public LombokDemo(Integer id, String name) {
        this.id = id;
        this.name = name;
    }
  }

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  ​

@RequiredArgsConstructor

• 功能

  生成一個包含必填參數的構造函數

• 注意

  要與@NonNull 搭配使用，該註解修飾的屬性就是必填參數

• 源碼

  @RequiredArgsConstructor
  public class LombokDemo {
  
    @NonNull private Integer id;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import java.beans.ConstructorProperties;
  import lombok.NonNull;
  
  public class LombokDemo {
    @NonNull
    private Integer id;
    private String name;
  
    @ConstructorProperties({"id"})
    public LombokDemo(@NonNull Integer id) {
        if(id == null) {
            throw new NullPointerException("id");
        } else {
            this.id = id;
        }
    }
  }

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  ​

@Date

• 功能

  這是一個綜合註解了，等於同時使用

  @Getter, @Setter, @ToString, @EqualsAndHashCode,@RequiredArgsConstructor

• 源碼

  @Data
  public class LombokDemo {
  
    @NonNull private Integer id;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  public class LombokDemo {
    private Integer id;
    private String name;
  
    public LombokDemo() {
    }
  
    public Integer getId() {
        return this.id;
    }
  
    public String getName() {
        return this.name;
    }
  
    public void setId(Integer id) {
        this.id = id;
    }
  
    public void setName(String name) {
        this.name = name;
    }
  
    public boolean equals(Object o) {
        if(o == this) {
            return true;
        } else if(!(o instanceof LombokDemo)) {
            return false;
        } else {
            LombokDemo other = (LombokDemo)o;
            if(!other.canEqual(this)) {
                return false;
            } else {
                Integer this$id = this.getId();
                Integer other$id = other.getId();
                if(this$id == null) {
                    if(other$id != null) {
                        return false;
                    }
                } else if(!this$id.equals(other$id)) {
                    return false;
                }
  
                String this$name = this.getName();
                String other$name = other.getName();
                if(this$name == null) {
                    if(other$name != null) {
                        return false;
                    }
                } else if(!this$name.equals(other$name)) {
                    return false;
                }
  
                return true;
            }
        }
    }
  
    protected boolean canEqual(Object other) {
        return other instanceof LombokDemo;
    }
  
    public int hashCode() {
        boolean PRIME = true;
        byte result = 1;
        Integer $id = this.getId();
        int result1 = result * 59 + ($id == <span class="hljs-keyword">null</span>?<span class="hljs-number">43</span>:$id.hashCode());
        String $name = this.getName();
        result1 = result1 * 59 + ($name == <span class="hljs-keyword">null</span>?<span class="hljs-number">43</span>:$name.hashCode());
        return result1;
    }
  
    public String toString() {
        return "LombokDemo(id=" + this.getId() + ", name=" + this.getName() + ")";
    }
  }
  

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  ​

@Value

• 功能

  不可變類的@Date, 他會默認給屬性加上final

• 源碼

  @Value
  public class LombokDemo {
  
    private Integer id;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import java.beans.ConstructorProperties;
  
  public final class LombokDemo {
    private final Integer id;
    private final String name;
  
    @ConstructorProperties({"id", "name"})
    public LombokDemo(Integer id, String name) {
        this.id = id;
        this.name = name;
    }
  
    public Integer getId() {
        return this.id;
    }
  
    public String getName() {
        return this.name;
    }
  
    public boolean equals(Object o) {
        if(o == this) {
            return true;
        } else if(!(o instanceof LombokDemo)) {
            return false;
        } else {
            LombokDemo other = (LombokDemo)o;
            Integer this$id = this.getId();
            Integer other$id = other.getId();
            if(this$id == null) {
                if(other$id != null) {
                    return false;
                }
            } else if(!this$id.equals(other$id)) {
                return false;
            }
  
            String this$name = this.getName();
            String other$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() {
        boolean PRIME = true;
        byte result = 1;
        Integer $id = this.getId();
        int result1 = result * 59 + ($id == <span class="hljs-keyword">null</span>?<span class="hljs-number">43</span>:$id.hashCode());
        String $name = this.getName();
        result1 = result1 * 59 + ($name == <span class="hljs-keyword">null</span>?<span class="hljs-number">43</span>:$name.hashCode());
        return result1;
    }
  
    public String toString() {
        return "LombokDemo(id=" + this.getId() + ", name=" + this.getName() + ")";
    }
  }
  

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  ​

@Accessors

• 功能

  這個註解要搭配@Getter與@Setter使用，用來修改默認的setter與getter方法的形式

• 注意

  @Accessors有三個參數可以使用

  1. chain 鏈式的形式
  2. fluent 流式的形式
  3. prefix 生成指定前綴的屬性的getter與setter方法，並且生成的getter與setter方法時會去除前綴

• 源碼 chain = true

  @Accessors(chain = true)
  @Setter
  @Getter
  public class LombokDemo {
  
    private Integer id;
    private String name;
  }

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• 編譯後 chain = true

  package xyz.mrwood.study.lombok;
  
  public class LombokDemo {
    private Integer id;
    private String name;
  
    public LombokDemo() {
    }
  
    public LombokDemo setId(Integer id) {
        this.id = id;
        return this;
    }
  
    public LombokDemo setName(String name) {
        this.name = name;
        return this;
    }
  
    public Integer getId() {
        return this.id;
    }
  
    public String getName() {
        return this.name;
    }
  }
  

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• 源碼 fluent = true

  @Accessors(fluent = true)
  @Setter
  @Getter
  public class LombokDemo {
  
    private Integer id;
    private String name;
  }

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• 編譯後 fluent = true

  package xyz.mrwood.study.lombok;
  
  public class LombokDemo {
    private Integer id;
    private String name;
  
    public LombokDemo() {
    }
  
    public LombokDemo id(Integer id) {
        this.id = id;
        return this;
    }
  
    public LombokDemo name(String name) {
        this.name = name;
        return this;
    }
  
    public Integer id() {
        return this.id;
    }
  
    public String name() {
        return this.name;
    }
  }

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• 源碼 prefix = "xxx"

  @Accessors(prefix = "xxx")
  @Setter
  @Getter
  public class LombokDemo {
  
    private Integer xxxId;
    private String name;
  }

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• 編譯後 prefix = "xxx"

  package xyz.mrwood.study.lombok;
  
  public class LombokDemo {
    private Integer xxxId;
    private String name;
  
    public LombokDemo() {
    }
  
    public void setId(Integer xxxId) {
        this.xxxId = xxxId;
    }
  
    public Integer getId() {
        return this.xxxId;
    }
  }

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  ​

---

其它註解：

日誌相關

@Log4j

• 源碼

  @Log4j
  public class LombokDemo {
  
    private Integer xxxId;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import org.apache.log4j.Logger;
  
  public class LombokDemo {
    private static final Logger log = Logger.getLogger(LombokDemo.class);
    private Integer xxxId;
    private String name;
  
    public LombokDemo() {
    }
  }

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@CommonsLog

• 源碼

  @CommonsLog
  public class LombokDemo {
  
    private Integer xxxId;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  public class LombokDemo {
    private static final Log log = LogFactory.getLog(LombokDemo.class);
    private Integer xxxId;
    private String name;
  
    public LombokDemo() {
    }
  }

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@Log

• 源碼

  @Log
  public class LombokDemo {
  
    private Integer xxxId;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import java.util.logging.Logger;
  
  public class LombokDemo {
    private static final Logger log = Logger.getLogger(LombokDemo.class.getName());
    private Integer xxxId;
    private String name;
  
    public LombokDemo() {
    }
  }

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@Log4j2

• 源碼

  @Log4j2
  public class LombokDemo {
  
    private Integer xxxId;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import org.apache.logging.log4j.LogManager;
  import org.apache.logging.log4j.Logger;
  
  public class LombokDemo {
    private static final Logger log = LogManager.getLogger(LombokDemo.class);
    private Integer xxxId;
    private String name;
  
    public LombokDemo() {
    }
  }

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@Slf4j

• 源碼

  @Slf4j
  public class LombokDemo {
  
    private Integer xxxId;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class LombokDemo {
    private static final Logger log = LoggerFactory.getLogger(LombokDemo.class);
    private Integer xxxId;
    private String name;
  
    public LombokDemo() {
    }
  }

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設計模式相關

@Builder

• 功能

  通過建造者模塊來生成bean

• 源碼

  @Builder
  public class LombokDemo {
  
    private Integer id;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  public class LombokDemo {
    private Integer id;
    private String name;
  
    LombokDemo(Integer id, String name) {
        this.id = id;
        this.name = name;
    }
  
    public static LombokDemo.LombokDemoBuilder builder() {
        return new LombokDemo.LombokDemoBuilder();
    }
  
    public static class LombokDemoBuilder {
        private Integer id;
        private String name;
  
        LombokDemoBuilder() {
        }
  
        public LombokDemo.LombokDemoBuilder id(Integer id) {
            this.id = id;
            return this;
        }
  
        public LombokDemo.LombokDemoBuilder name(String name) {
            this.name = name;
            return this;
        }
  
        public LombokDemo build() {
            return new LombokDemo(this.id, this.name);
        }
  
        public String toString() {
            return "LombokDemo.LombokDemoBuilder(id=" + this.id + ", name=" + this.name + ")";
        }
    }
  }

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  ​

@Delegate

• 功能

  @Delegate註釋的屬性，會把這個屬性對象的公有非靜態方法合到當前類

• 注意

  公共 非靜態方法

• 源碼

  public class LombokDemo {
  
    @Delegate
    private Integer id;
    private String name;
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  public class LombokDemo {
    private Integer id;
    private String name;
  
    public LombokDemo() {
    }
  
    public byte byteValue() {
        return this.id.byteValue();
    }
  
    public short shortValue() {
        return this.id.shortValue();
    }
  
    public int intValue() {
        return this.id.intValue();
    }
  
    public long longValue() {
        return this.id.longValue();
    }
  
    public float floatValue() {
        return this.id.floatValue();
    }
  
    public double doubleValue() {
        return this.id.doubleValue();
    }
  
    public int compareTo(Integer arg0) {
        return this.id.compareTo(arg0);
    }
  }

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工具相關

@Cleanup

• 功能

  關閉流

• 注意

  關閉流的方式有點怪異，而且沒有在finally裏面關閉，如果出現異常的就不會關閉了

• 源碼

  public class LombokDemo {
  
    public void test() throws IOException {
  
        @Cleanup InputStream inputStream = new FileInputStream("xxx.txt");
  
    }
  
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.util.Collections;
  
  public class LombokDemo {
    public LombokDemo() {
    }
  
    public void test() throws IOException {
        FileInputStream inputStream = new FileInputStream("xxx.txt");
        if(Collections.singletonList(inputStream).get(0) != null) {
            inputStream.close();
        }
  
    }
  }

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  ​

@Synchronized

• 功能

  給方法加一個同步塊

• 源碼

  public class LombokDemo {
  
    @Synchronized
    public void test() throws IOException {
  
        System.out.println("test");
  
    }
  
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import java.io.IOException;
  
  public class LombokDemo {
    private final Object $lock = new Object[0];
  
    public LombokDemo() {
    }
  
    public void test() throws IOException {
        Object var1 = this.$lock;
        synchronized(this.$lock) {
            System.out.println("test");
        }
    }
  }
  

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  ​

@SneakyThrows

• 功能

  忽略異常

• 源碼

  public class LombokDemo {
  
    @SneakyThrows
    public void test() {
  
        String s = new String("test".getBytes(), "utf-8");
  
    }
  
  }

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• 編譯後

  package xyz.mrwood.study.lombok;
  
  import java.io.IOException;
  
  public class LombokDemo {
    private final Object $lock = new Object[0];
  
    public LombokDemo() {
    }
  
    public void test() throws IOException {
        Object var1 = this.$lock;
        synchronized(this.$lock) {
            System.out.println("test");
        }
    }
  }

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@NonNull

• 功能

設置不能爲空的參數

源碼

public class LombokDemo {

  public void test(@NonNull String val) {

  }
}

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編譯後

package xyz.mrwood.study.lombok;

import lombok.NonNull;

public class LombokDemo {
    public LombokDemo() {
    }

    public void test(@NonNull String val) {
        if(val == null) {
            throw new NullPointerException("val");
        }
    }
}

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@UtilityClass

功能

把普通類轉爲工具類

源碼

  @UtilityClass
  public class LombokDemo {

      private Integer id = 1;
      private String name = "kiwi";

      public void util(){

          System.out.println("xxx");
      }
  }

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編譯後

package xyz.mrwood.study.lombok;

public final class LombokDemo {
  private static Integer id = Integer.valueOf(1);
  private static String name = "kiwi";

  public static void util() {
      System.out.println("xxx");
  }

  private LombokDemo() {
      throw new UnsupportedOperationException("This is a utility class and cannot be instantiated");
  }
}

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​