JAVA自定义注解（2） - JAVA

这个例子在实际应用中是比较有用的，用来将配置文件（*.properties)或者系统属性中的指定属性名称的值加载进来。此例是和Spring结合使用的，所以其他配置就略过了。

1、定义注解@Property

package com.kute.test.selfannotation;

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

/**
 * 自定义注解@Property
 * 加载配置文件和相应的属性
 */

@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE, ElementType.METHOD })
public @interface Property {

	//属性名称
	String name() default "";
}

2、解析注解

package com.kute.test.selfannotation;

import java.lang.reflect.Method;
import java.util.Properties;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.config.BeanPostProcessor;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
import org.springframework.util.ReflectionUtils;

public class PropertyParse extends PropertyPlaceholderConfigurer implements
		BeanPostProcessor, InitializingBean {

	private static Logger logger = LoggerFactory.getLogger(PropertyParse.class);
	private Properties pros = null;

	// 在spring容器实例化bean之后添加自己的逻辑
	public Object postProcessAfterInitialization(Object bean, String beanName)
			throws BeansException {
		return bean;
	}

	// 在spring容器实例化bean之前添加自己的逻辑
	public Object postProcessBeforeInitialization(Object bean, String beanName)
			throws BeansException {
		if (bean.getClass().getAnnotation(Property.class) != null) {
			Method[] methods = bean.getClass().getDeclaredMethods();
			for (Method method : methods) {
				Property p = method.getAnnotation(Property.class);
				if (p != null) {
					//获得对应名称的属性的值
					Object para = pros.getProperty(p.name());
					//方法参数类型名称
					String parameterName = (method.getParameterTypes()[0]).getName();
					
					if (parameterName.equals("java.lang.Integer")) {
						para = new Integer(para.toString());
					}else if (parameterName.equals(
							"java.lang.Double")) {
						para = new Long(para.toString());
					}else if (parameterName.equals(
							"java.lang.String")) {
						para = para.toString();
					}
					logger.info("获得了指定名称的属性的值：" + para);
					ReflectionUtils.invokeMethod(method, bean,
							new Object[] { para });
				}
			}
		}
		return bean;
	}

	// 在初始化bean的时候执行该方法
	public void afterPropertiesSet() throws Exception {
		//此方法的作用是将配置的和系统属性加载进来
		pros = mergeProperties();
	}

}

3、应用注解

package com.kute.test.selfannotation;

import java.io.Serializable;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Property
public class Teacher implements Serializable {
	
	private static final long serialVersionUID = 7651360997972750779L;
	private static Logger logger = LoggerFactory.getLogger(Teacher.class);

	@Property(name = "third.kute.blog")
	public void setValue(String value) {
		logger.info("成功设String值：" + value);
	}
	
	@Property(name = "second.kute.age")
	public void setValue(Integer value) {
		logger.info("成功设Integer值：" + value);
	}

	@Property(name = "first.kute.name")
	public void setValue(Double value) {
		logger.info("成功设Double值：" + value

JAVA自定义注解（2）(一)