java注解的获取方式

注解

注解就是一种元信息，一般对应着注解处理器的。
获取注解的方式，对应着获取反射的三种方式，然后再获取其注解。

注解接口

package CusAnnontation;

import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Documented;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import java.lang.annotation.Repeatable;

@Documented
@Retention(RUNTIME)
@Target(TYPE)
@Inherited
@Repeatable(CustomDescriptions.class)  //这个必须有value的方法实现。
public @interface CustomDescription {
	String description() default "";
}

package CusAnnontation;

import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import java.lang.annotation.Documented;
import java.lang.annotation.Inherited;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

@Documented
@Retention(RUNTIME)
@Target(TYPE)
@Inherited
public @interface CustomDescriptions {
	CustomDescription[] value();
}

对象类

package CusAnnontation;

@CustomDescription(description="基类")
@CustomDescription(description="人")
public class Person {
	
	private String Name;
	
	public String getName() {
		return Name;
	}
	
	public void setName(String name) {
		Name = name;
	}
}

package CusAnnontation;

@CustomDescription(description="学生")
@CustomDescription(description="人")
public class Student extends Person {
	private String StudentId;

	public String getStudentId() {
		return StudentId;
	}

	public void setStudentId(String studentId) {
		StudentId = studentId;
	}
}

自定义注解实现

package CusAnnontation;

public class AnnontationTest {

	public static void main(String[] args) throws ClassNotFoundException {
		// TODO Auto-generated method stub
		Person person =new Person();
		//通过对象获取
		//CustomDescriptions customDescriptions  = person.getClass().getAnnotation(CustomDescriptions.class);
		//通过对象类.class
		//CustomDescriptions customDescriptions = Person.class.getAnnotation(CustomDescriptions.class);
		// 通过class.forname(包路径)获取，正好对应到反射的三种形式。
		CustomDescriptions customDescriptions = Class.forName("CusAnnontation.Person").getAnnotation(CustomDescriptions.class);
		if(customDescriptions==null){
			System.out.println("null");
		}else{
			for(CustomDescription h: customDescriptions.value()){
				System.out.println("description:" + h.description().toString());
			}
		}

	}

}