Spring注解工具类
1、AnnotationUtils
AnnotationUtils是Spring提供的重要的注解工具类，主要方法有以下几个：
public staticA getAnnotation(Annotation annotation,Class annotationType)
publicstatic A getAnnotation(AnnotatedElement annotatedElement, Class annotationType)
publicstatic A getAnnotation(Method method, Class annotationType)
public staticAnnotation[] getAnnotations(AnnotatedElement annotatedElement)
public staticAnnotation[] getAnnotations(Method method)
publicstatic Set getRepeatableAnnotations(AnnotatedElementannotatedElement,Class annotationType)
publicstatic Set getRepeatableAnnotations(AnnotatedElementannotatedElement,Class annotationType,@Nullable ClasscontainerAnnotationType)
publicstatic Set getDeclaredRepeatableAnnotations(AnnotatedElementannotatedElement,Class annotationType)
publicstatic A findAnnotation(AnnotatedElement annotatedElement,Class annotationType)
publicstatic A findAnnotation(Method method,@Nullable Class annotationType)
publicstatic A findAnnotation(Class clazz, Class annotationType)
public staticClass findAnnotationDeclaringClass(Class annotationType,@Nullable Class clazz)
public staticClass findAnnotationDeclaringClassForTypes(List> annotationTypes,@Nullable Class clazz)
public staticboolean isAnnotationInherited(Class annotationType, Class clazz)
public staticboolean isAnnotationMetaPresent(ClassannotationType,@Nullable Class metaAnnotationType)
public staticObject getDefaultValue(Annotation annotation)
public staticObject getDefaultValue(@Nullable Annotation annotation,@Nullable StringattributeName)
其中，getAnnotation方法，返回的是一个经过spring动态代理后的Annotation，通过getAnnotation方法不仅可以返回当前传入的注解，还可以获取注解的元注解
例如：
//自定义注解类MyAnnotation
@Target({ElementType.TYPE})
@Service
@Retention(RetentionPolicy.RUNTIME)
@Inherited
public @interfaceMyAnnotation {}
//自定义注解类MyMethodAnnotation
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
public @interface MyMethodAnnotation {}
@MyAnnotation
public class AnnotationModel {
@MyMethodAnnotation
public void call(String name){
System.out.println("call:"+name);
}
}
public void testAnnotationUtils() throws NoSuchMethodException {
MyAnnotation myAnn = AnnotationModel.class.getAnnotation(MyAnnotation.class);
//获取类上的注解
Annotation ann = AnnotationUtils.getAnnotation(myAnn,MyAnnotation.class);
System.out.println(ann); //@com.xc.annotate.MyAnnotation()
/***获取元注解Service*/
Service service1 = AnnotationUtils.getAnnotation(MyAnnotation.class,Service.class);
System.out.println(service1); //@org.springframework.stereotype.Service(value=)
/***获取元注解Retention*/
Retention retention = AnnotationUtils.getAnnotation(myAnn,Retention.class);
System.out.println(retention); //@java.lang.annotation.Retention(value=RUNTIME)
//获取方法上的注解
Method method = AnnotationModel.class.getDeclaredMethod("call", String.class);
Annotation annotation = AnnotationUtils.getAnnotation(method, MyMethodAnnotation.class);
System.out.println(annotation); //@com.xc.annotate.MyMethodAnnotation()
//获取方法上的所有注解
Annotation[] annotations = AnnotationUtils.getAnnotations(method);
for(Annotation a:annotations){
System.out.println(a);
//@com.xc.annotate.MyMethodAnnotation()@org.springframework.web.bind.annotation.RequestMapping(name=, value=[], path=[], method=[], params=[], headers=[], produces=[], consumes=[])
}
}
AnnotatedElementUtils注释元素工具类，主要用于查找注释，元注释
public classAnnotateUtils {
/**
*判断一个类是否含有指定的注解
*@param clsType
*@param annotationClass
*@return
*/
publicstatic boolean hasAnnotation(Class clsType, Class annotationClass){
returnAnnotatedElementUtils.hasAnnotation(clsType,annotationClass);
}
}