枚举与注解的应用

灰太狼 2022-09-09 13:00 145阅读 0赞

### 枚举与注解的应用 ###

*  枚举的遍历
 *  获取枚类上的注解
 *  获取枚举值的注解

# 枚举的遍历 #

@TestEnumClassAnno(target = SystemVersionEnum.class)
    public enum SystemVersionEnum { 
        @TestEnumAnno(target = String.class, des = "初始发布")
        V1_0("v1.0", "127.0.0.1", "第一版"),
        @TestEnumAnno(target = Map.class, des = "迭代版本")
        V2_0("v2.0", "www.baidu.com", "第而版"),
        V3_0("v3.0", "www.百川.com", "第三版"),
        ;
        String sysVersion;
        String sysAddr;
        String sysName;
    
        SystemVersionEnum(String sysVersion, String sysAddr, String sysName) { 
            this.sysVersion = sysVersion;
            this.sysAddr = sysAddr;
            this.sysName = sysName;
        }
    
        public SystemVersionEnum getByVersion(String version) { 
            SystemVersionEnum sve = null;
            for(SystemVersionEnum en : SystemVersionEnum.values()) { 
                if(en.sysVersion.equals(version)) { 
                    sve = en;
                    break;
                }
            }
            return sve;
        }
    }

# 获取枚类上的注解 #

//Test.java
    import com.test.annotation.TestEnumAnno;
    import com.test.annotation.TestEnumClassAnno;
    import com.test.menu.SystemVersionEnum;
    import com.test.menu.TestEnum;
    
    import java.lang.annotation.Annotation;
    public class Test { 
    
       public static void main(String[] args) throws NoSuchFieldException { 
    
            getEnumClassAnnotations();
        }
    
        public static  void getEnumClassAnnotations(){ 
            Annotation [] as = SystemVersionEnum.class.getAnnotations();
            for(Annotation a : as) { 
                if(a.annotationType() == TestEnumClassAnno.class) { 
                    //处理业务
                    System.out.println("...处理业务");
                }
                System.out.println(a.annotationType());
            }
        }
     }

![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAY2Pnmb7lt50_size_20_color_FFFFFF_t_70_g_se_x_16]

# 获取枚举值的注解 #

public static void getEnumFieldAnnotaionts() throws NoSuchFieldException { 
            //获取指定枚举变量的注解
            SystemVersionEnum sve = SystemVersionEnum.V1_0;
            TestEnumAnno annotation = sve.getClass().getField(sve.name()).getAnnotation(TestEnumAnno.class);
            System.out.println(annotation.target()+":"+annotation.des());
            System.out.println("---------");
            for(SystemVersionEnum te : SystemVersionEnum.values()) { 
                //知道类注解名称是
                Annotation [] annotations = te.getClass().getField(te.name()).getAnnotations();
                for(Annotation a : annotations) { 
                    if(a.annotationType() == TestEnumAnno.class) { 
                        TestEnumAnno tea = (TestEnumAnno) a;
                        System.out.println(tea.target()+":"+tea.des());
                    }
                }
            }
    
        }

![在这里插入图片描述][watermark_type_ZHJvaWRzYW5zZmFsbGJhY2s_shadow_50_text_Q1NETiBAY2Pnmb7lt50_size_20_color_FFFFFF_t_70_g_se_x_16 1]

实例用到的注解

//TestEnumAnno .java
    import java.lang.annotation.*;
    @Target({ ElementType.FIELD})
    @Retention(RetentionPolicy.RUNTIME)
    @Inherited
    public @interface TestEnumAnno { 
        Class target();
        String des();
    }
    
    //TestEnumClassAnno.java
    import java.lang.annotation.*;
    @Target({ ElementType.TYPE})
    @Retention(RetentionPolicy.RUNTIME)
    @Documented
    @Inherited
    public @interface TestEnumClassAnno { 
        Class target();
    }

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