一、编写Dao类
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package cn.com.songjy.annotation;import java.util.Date;public class MyDao { public String time(){ return "你好，现在的时间是：" + new Date(); } } |
二、编写属性文件【my.properties,类似spring的配置文件】并将MyDao类配置到其中，如下：
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myDao=cn.com.songjy.annotation.MyDao |
三、编写读取属性配置文件的类
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package cn.com.songjy.annotation;import java.io.FileNotFoundException;import java.io.IOException;import java.io.InputStream;import java.util.Properties;public class PropertiesUtil { private static InputStream in = PropertiesUtil.class.getClassLoader() .getResourceAsStream("my.properties"); public PropertiesUtil() { } private static Properties props = new Properties(); static { try { props.load(in); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } public static String getValue(String key) { return props.getProperty(key); } public static void updateProperties(String key, String value) { props.setProperty(key, value); }} |
四、编写注解类
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package cn.com.songjy.annotation;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;@Retention(RetentionPolicy.RUNTIME)public @interface MyDiAnnotation { //public String name(); String value() default "";//value是Annotation的默认属性} |
五、反射注入工具类编写
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package cn.com.songjy.annotation;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;public class MyAnnotationUtil { MyAnnotationUtil(){ di(this); } public static void di(Object obj){ try { Method[] methods = obj.getClass().getDeclaredMethods(); for (Method method : methods) { if(method.isAnnotationPresent(MyDiAnnotation.class)){//只处理包含MyDiAnnotation的方法 MyDiAnnotation diAnnotation = method.getAnnotation(MyDiAnnotation.class); String class_key = diAnnotation.value(); if(null==class_key || class_key.trim().length()==0){//key值默认为setXXX中的XXX且第一个字母要转换为小写 class_key = method.getName().substring(3); class_key = class_key.substring(0, 1).toLowerCase() + class_key.substring(1); } method.invoke(obj, Class.forName(PropertiesUtil.getValue(class_key)).newInstance()); } } } catch (SecurityException e) { e.printStackTrace(); } catch (IllegalArgumentException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } catch (InstantiationException e) { e.printStackTrace(); } catch (ClassNotFoundException e) { e.printStackTrace(); } } } |
六、编写测试类
测试类一：
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package cn.com.songjy.annotation;public class MyService01 extends MyAnnotationUtil { MyDao myDao; public MyDao getMyDao() { return myDao; } @MyDiAnnotation public void setMyDao(MyDao myDao) { this.myDao = myDao; } public void hello(){ System.out.println(myDao.time()); } public static void main(String[] args) { new MyService01().hello(); }} |
测试类二：
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package cn.com.songjy.annotation;public class MyService02 extends MyAnnotationUtil { MyDao dao; public MyDao getDao() { return dao; } @MyDiAnnotation("myDao") public void setDao(MyDao dao) { this.dao = dao; } public void hello(){ System.out.println(dao.time()); } public static void main(String[] args) { new MyService02().hello(); }} |
输出结果如下：你好，现在的时间是：Sat Jun 29 17:02:03 CST 2013