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Java注解Annotation的使用
RuntimeAnnotation注解
package annotation;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;@Retention(RetentionPolicy.RUNTIME)@Target(ElementType.FIELD)public @interface RuntimeAnnotation {}
ClassAnnotation注解
package annotation;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;@Retention(RetentionPolicy.CLASS)@Target(ElementType.FIELD)public @interface ClassAnnotation {}
枚举类AnType中使用注解
package annotation;import java.lang.annotation.Annotation;import java.lang.reflect.Field;public enum AnType { @RuntimeAnnotation @ClassAnnotation TYPE_TEST_1, @ClassAnnotation TYPE_TEST_2; /** * 注解使用:可以在运行时通过反射判断某字段是否有某注解进而进行一些操作 */ public boolean isRuntimeAnnotation(){ Field field = new Field(); try { /** * 通过反射获取该对象在枚举中的字段 */ field = this.getClass().getField(this.name()); } catch (Exception e) { } return isFieldAnnotated(field, RuntimeAnnotation.class); } /** * 该field的注解中是否匹配输入的注解 */ private boolean isFieldAnnotated(Field field, Class annotationClass) { if (field == null) { return false; } /** * annotations中有RuntimeAnnotation,但是没有ClassAnnotation * 因为RuntimeAnnotation被注解为Runtime,可以被反射出来 */ Annotation[] annotations = field.getAnnotations(); if(annotations == null || annotations.length == 0){ return false; } for (Annotation annotation : annotations) { if (annotation.annotationType().equals(annotationClass)) { return true; } } return false; }}
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