自定义 Java Annotation ,读取注解值

1. 首先是自定义注解： 

package cn.veji.hibernate.po;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Privilege {
    String[] value();

}

2.定义使用注解类： 

package cn.veji.hibernate.po;

package cn.veji.hibernate.po;

public class TestPrivilege {

    @Privilege( { "a" })
    public void a() {
    }

    @Privilege( { "b" })
    public void b() {
    }

    @Privilege( { "c" })
    public void c() {
    }

}

3.读取注解值帮助类： 

package cn.veji.hibernate.po;

package cn.veji.hibernate.test;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;

import cn.veji.hibernate.po.Privilege;
import cn.veji.hibernate.po.TestPrivilege;

public class AnnotationUtil {

    public static AnnotationUtil anno = null;

    public static AnnotationUtil getInstance() {
        if (anno == null) {
            anno = new AnnotationUtil();
        }
        return anno;
    }

    /**
     * 读取注解值
     *
     * @param annotationClasss 处理Annotation类名称
     * @param annotationField 处理Annotation类属性名称
     * @param className 处理Annotation的使用类名称
     * @return
     * @throws Exception
     */
    @SuppressWarnings("all")
    public Map<String, String> loadVlaue(Class annotationClasss,
            String annotationField, String className) throws Exception {

        System.out.println("处理Annotation类名称  === "+annotationClasss.getName());
        System.out.println("处理Annotation类属性名称  === "+annotationField);
        System.out.println("处理Annotation的调用类名称  === "+className);
        Map<String, String> map = new HashMap<String, String>();
        Method[] methods = Class.forName(className).getDeclaredMethods();
        for (Method method : methods) {
            if (method.isAnnotationPresent(annotationClasss)) {
                Annotation p = method.getAnnotation(annotationClasss);
                Method m = p.getClass()
                        .getDeclaredMethod(annotationField, null);
                String[] values = (String[]) m.invoke(p, null);
                for (String key : values) {
                    System.out.println("注解值 === " + key);
                    map.put(key, key);
                }
            }
        }
        System.out.println("map数量  === " + map.size());
        return map;
    }

    public static void main(String[] args) throws Exception {

        AnnotationUtil.getInstance().loadVlaue(Privilege.class, "value",
                TestPrivilege.class.getName());
    }

}

4.执行结果： 

处理Annotation类名称  === cn.veji.hibernate.po.Privilege
处理Annotation类属性名称  === value
处理Annotation的调用类名称  === cn.veji.hibernate.po.TestPrivilege
注解值 === c
注解值 === a
注解值 === b
map数量  === 3