Java反射及依赖注入简单模拟

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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1	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