lombok使用及常用注解

本文轉載自查看原文 2019-09-30 11:39 320 lombok

簡介

大部分項目中都必不可少的包含數據庫實體(Entity)、數據載體(dto,dataObject),而這兩部分都包含着大量的沒有業務邏輯的setter、getter、空參構造，同時我們一般要復寫類的toString(),equals(),hashCode()方法(貧血模型)。這些工作都是重復性的工作，作為程序員，懶是必備素質之一，這些工作肯定已經有大牛封裝好了處理方法,這就是lombok。

idea 安裝插件，支持lombok

lombok是在編譯階段才生成相應的代碼體，所以在項目中直接調用setter，getter,constructor會報錯，這時候可以在IDE安裝相應的插件支持lombok。這里介紹idea插件安裝，eclipse請自行百度。

安裝方法

進入設置頁面(windows:setting,Mac:Preferences)
點擊Plugin
Browse repositories
搜索lombok
點擊Install
安裝完畢后開啟注解權限才能正常使用:
- –>setting
- –>Build,Execution,Deployment
- –>Compiler
- –>Annontation Processors
- –>勾選Enable annotation processing
- –> Apply
重啟Idea

引入方法

gradle

// https://mvnrepository.com/artifact/org.projectlombok/lombok
compile group: 'org.projectlombok', name: 'lombok', version: '1.16.16'

maven

<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.16.16</version>
</dependency>

常用方法

@Setter

生成setter方法,final變量不包含

//原始類
@Setter
public class TestEntity {
 
    private String name;
 
    private Integer age;
 
    private final String type = "type";
}
//反編譯的類
public class TestEntity {
    private String name;
    private Integer age;
    private final String type = "person";
 
    public TestEntity() {
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public void setAge(Integer age) {
        this.age = age;
    }
}

@Getter

生成getter方法,final變量不包含

//原始類
@Getter
public class TestEntity {
 
    private String name;
 
    private Integer age;
 
    private final String type = "person";
}
//反編譯的類
public class TestEntity {
    private String name;
    private Integer age;
    private final String type = "person";
 
    public TestEntity() {
    }
 
    public String getName() {
        return this.name;
    }
 
    public Integer getAge() {
        return this.age;
    }
 
    public String getType() {
        this.getClass();
        return "person";
    }
}

@NoArgsConstructor

生成空參構造

//原始類
@NoArgsConstructor
public class TestEntity {
 
    private String name;
 
    private Integer age;
 
    private final String type = "person";
}
//反編譯的類
public class TestEntity {
    private String name;
    private Integer age;
    private final String type = "person";
 
    public TestEntity() {
    }
}

@AllArgsConstructor

生成全部參數構造

//原始類
@AllArgsConstructor
public class TestEntity {
 
    private String name;
 
    private Integer age;
 
    private final String type = "person";
}
//反編譯的類
public class TestEntity {
    private String name;
    private Integer age;
    private final String type = "person";
 
    @ConstructorProperties({"name", "age"})
    public TestEntity(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
}

@RequiredArgsConstructor

將標記為@NoNull的屬性生成一個構造器

如果運行中標記為@NoNull的屬性為null,會拋出空指針異常。

//原始類
@RequiredArgsConstructor
public class TestEntity {
 
    private String name;
    @NonNull
    private Integer age;
 
    private final String type = "person";
}
//反編譯的類
public class TestEntity {
    private String name;
    @NonNull
    private Integer age;
    private final String type = "person";
 
    @ConstructorProperties({"age"})
    public TestEntity(@NonNull Integer age) {
        if(age == null) {
            throw new NullPointerException("age");
        } else {
            this.age = age;
        }
    }
}

@ToString

生成所有屬性的toString()方法

//原始類
@ToString
public class TestEntity {
 
    private String name;
 
    private Integer age;
 
    private final String type = "person";
}
//反編譯的類
public class TestEntity {
    private String name;
    private Integer age;
    private final String type = "person";
 
    public TestEntity() {
    }
 
    public String toString() {
        StringBuilder var10000 = (new StringBuilder()).append("TestEntity(name=").append(this.name).append(", age=").append(this.age).append(", type=");
        this.getClass();
        return var10000.append("person").append(")").toString();
    }
}

@EqualsAndHashCode

生成equals()方法和hashCode方法

//原始類
@EqualsAndHashCode
public class TestEntity {
 
    private String name;
 
    private Integer age;
 
    private final String type = "person";
}
//反編譯的類
public class TestEntity {
    private String name;
    private Integer age;
    private final String type = "person";
 
    public TestEntity() {
    }
 
    public boolean equals(Object o) {
        if(o == this) {
            return true;
        } else if(!(o instanceof TestEntity)) {
            return false;
        } else {
            TestEntity other = (TestEntity)o;
            if(!other.canEqual(this)) {
                return false;
            } else {
                label47: {
                    String this$name = this.name;
                    String other$name = other.name;
                    if(this$name == null) {
                        if(other$name == null) {
                            break label47;
                        }
                    } else if(this$name.equals(other$name)) {
                        break label47;
                    }
 
                    return false;
                }
 
                Integer this$age = this.age;
                Integer other$age = other.age;
                if(this$age == null) {
                    if(other$age != null) {
                        return false;
                    }
                } else if(!this$age.equals(other$age)) {
                    return false;
                }
 
                this.getClass();
                String this$type = "person";
                other.getClass();
                String other$type = "person";
                if(this$type == null) {
                    if(other$type != null) {
                        return false;
                    }
                } else if(!this$type.equals(other$type)) {
                    return false;
                }
 
                return true;
            }
        }
    }
 
    protected boolean canEqual(Object other) {
        return other instanceof TestEntity;
    }
 
    public int hashCode() {
        boolean PRIME = true;
        byte result = 1;
        String $name = this.name;
        int result1 = result * 59 + ($name == null?43:$name.hashCode());
        Integer $age = this.age;
        result1 = result1 * 59 + ($age == null?43:$age.hashCode());
        this.getClass();
        String $type = "person";
        result1 = result1 * 59 + ($type == null?43:$type.hashCode());
        return result1;
    }
}

@Data(常用)

@Data直接修飾POJO or beans， getter所有的變量，setter所有不為final的變量。如果你不需要默認的生成方式，直接填寫你需要的annotation的就可以了。默認生成的所有的annotation都是public的，如果需要不同權限修飾符可以使用AccessLevel.NONE選項。當然@Data 也可以使用staticConstructor選項生成一個靜態方法。

=@Setter+@Getter+@EqualsAndHashCode+@NoArgsConstructor

//原始類
@Data
public class TestEntity {
    @Setter(AccessLevel.PRIVATE)
    private String name;
 
    private Integer age;
 
    private final String type = "person";
}
//反編譯的類
 
public class TestEntity {
    private String name;
    private Integer age;
    private final String type = "person";
 
    public TestEntity() {
    }
 
    public String getName() {
        return this.name;
    }
 
    public Integer getAge() {
        return this.age;
    }
 
    public String getType() {
        this.getClass();
        return "person";
    }
 
    public void setAge(Integer age) {
        this.age = age;
    }
 
    public boolean equals(Object o) {
        if(o == this) {
            return true;
        } else if(!(o instanceof TestEntity)) {
            return false;
        } else {
            TestEntity other = (TestEntity)o;
            if(!other.canEqual(this)) {
                return false;
            } else {
                label47: {
                    String this$name = this.getName();
                    String other$name = other.getName();
                    if(this$name == null) {
                        if(other$name == null) {
                            break label47;
                        }
                    } else if(this$name.equals(other$name)) {
                        break label47;
                    }
 
                    return false;
                }
 
                Integer this$age = this.getAge();
                Integer other$age = other.getAge();
                if(this$age == null) {
                    if(other$age != null) {
                        return false;
                    }
                } else if(!this$age.equals(other$age)) {
                    return false;
                }
 
                String this$type = this.getType();
                String other$type = other.getType();
                if(this$type == null) {
                    if(other$type != null) {
                        return false;
                    }
                } else if(!this$type.equals(other$type)) {
                    return false;
                }
 
                return true;
            }
        }
    }
 
    protected boolean canEqual(Object other) {
        return other instanceof TestEntity;
    }
 
    public int hashCode() {
        boolean PRIME = true;
        byte result = 1;
        String $name = this.getName();
        int result1 = result * 59 + ($name == null?43:$name.hashCode());
        Integer $age = this.getAge();
        result1 = result1 * 59 + ($age == null?43:$age.hashCode());
        String $type = this.getType();
        result1 = result1 * 59 + ($type == null?43:$type.hashCode());
        return result1;
    }
 
    public String toString() {
        return "TestEntity(name=" + this.getName() + ", age=" + this.getAge() + ", type=" + this.getType() + ")";
    }
 
    private void setName(String name) {
        this.name = name;
    }
}

@Builder

構造Builder模式的結構。通過內部類Builder()進行構建對象。

//原始類
@Builder
public class TestEntity {
 
    private String name;
 
    private Integer age;
 
    private final String type = "person";
}
//反編譯的類
public class TestEntity {
    private String name;
    private Integer age;
    private final String type = "person";
 
    @ConstructorProperties({"name", "age"})
    TestEntity(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
 
    public static TestEntity.TestEntityBuilder builder() {
        return new TestEntity.TestEntityBuilder();
    }
 
    public static class TestEntityBuilder {
        private String name;
        private Integer age;
 
        TestEntityBuilder() {
        }
 
        public TestEntity.TestEntityBuilder name(String name) {
            this.name = name;
            return this;
        }
 
        public TestEntity.TestEntityBuilder age(Integer age) {
            this.age = age;
            return this;
        }
 
        public TestEntity build() {
            return new TestEntity(this.name, this.age);
        }
 
        public String toString() {
            return "TestEntity.TestEntityBuilder(name=" + this.name + ", age=" + this.age + ")";
        }
    }
}
 
//Builder模式使用方法
@Test
public  void test(){
    TestEntity testEntity = TestEntity.builder()
                    .name("java")
                    .age(18)
                    .build();
}

@Value

與@Data相對應的@Value，兩個annotation的主要區別就是如果變量不加@NonFinal ，@Value會給所有的弄成final的。當然如果是final的話，就沒有set方法了。

//原始類
@Value
public class TestEntity {
    @Setter(AccessLevel.PRIVATE)
    private String name;
 
    private Integer age;
 
    private final String type = "person";
}
//反編譯的類
public final class TestEntity {
    private final String name;
    private final Integer age;
    private final String type = "person";
 
    @ConstructorProperties({"name", "age"})
    public TestEntity(String name, Integer age) {
        this.name = name;
        this.age = age;
    }
 
    public String getName() {
        return this.name;
    }
 
    public Integer getAge() {
        return this.age;
    }
 
    public String getType() {
        this.getClass();
        return "person";
    }
 
    public boolean equals(Object o) {
        if(o == this) {
            return true;
        } else if(!(o instanceof TestEntity)) {
            return false;
        } else {
            TestEntity other;
            label44: {
                other = (TestEntity)o;
                String this$name = this.getName();
                String other$name = other.getName();
                if(this$name == null) {
                    if(other$name == null) {
                        break label44;
                    }
                } else if(this$name.equals(other$name)) {
                    break label44;
                }
 
                return false;
            }
 
            Integer this$age = this.getAge();
            Integer other$age = other.getAge();
            if(this$age == null) {
                if(other$age != null) {
                    return false;
                }
            } else if(!this$age.equals(other$age)) {
                return false;
            }
 
            String this$type = this.getType();
            String other$type = other.getType();
            if(this$type == null) {
                if(other$type != null) {
                    return false;
                }
            } else if(!this$type.equals(other$type)) {
                return false;
            }
 
            return true;
        }
    }
 
    public int hashCode() {
        boolean PRIME = true;
        byte result = 1;
        String $name = this.getName();
        int result1 = result * 59 + ($name == null?43:$name.hashCode());
        Integer $age = this.getAge();
        result1 = result1 * 59 + ($age == null?43:$age.hashCode());
        String $type = this.getType();
        result1 = result1 * 59 + ($type == null?43:$type.hashCode());
        return result1;
    }
 
    public String toString() {
        return "TestEntity(name=" + this.getName() + ", age=" + this.getAge() + ", type=" + this.getType() + ")";
    }
}

@Synchronized

同步方法

//原始類
public class TestEntity {
    private String name;
 
    private Integer age;
 
    private final String type = "person";
    @Synchronized
    public void write(){
        //do something
    }
}
//反編譯的類
public class TestEntity {
    private final Object $lock = new Object[0];
    private String name;
    private Integer age;
    private final String type = "person";
 
    public TestEntity() {
    }
 
    public void write() {
        Object var1 = this.$lock;
        synchronized(this.$lock) {
            ;
        }
    }
}

@Cleanup @@SneakyThrows

自動調用close方法關閉資源。

//原始類
public class TestEntity {
    private String name;
 
    private Integer age;
 
    private final String type = "person";
 
    @SneakyThrows
    public  void  outputStream(){
         @Cleanup OutputStream outputStream = new FileOutputStream(new File("/Users/hello"));
    }
}
//反編譯的類
public class TestEntity {
    private String name;
    private Integer age;
    private final String type = "person";
 
    public TestEntity() {
    }
 
    public void outputStream() {
        try {
            FileOutputStream $ex = new FileOutputStream(new File("/Users/hello"));
            if(Collections.singletonList($ex).get(0) != null) {
                $ex.close();
            }
 
        } catch (Throwable var2) {
            throw var2;
        }
    }
}

原文鏈接：https://blog.csdn.net/u013225178/article/details/80721799

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