SpringMVC用PropertyPlaceholderConfigurer读取配置文件

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在使用SpringMVC做Web开发的时候，为了便于统一管理配置项，常常会看到用占位符的配置方式。这样，可以将分散在spring配置文件中的配置项的值集中到一个(多个)属性文件中，方便管理。

PropertyPlaceholderConfigurer是个bean工厂后置处理器的实现，也就是 BeanFactoryPostProcessor接口的一个实现。PropertyPlaceholderConfigurer可以将上下文（配置文 件）中的属性值放在另一个单独的标准java Properties文件中去。在XML文件中用${key}替换指定的properties文件中的值。这样的话，只需要对properties文件进 行修改，而不用对xml配置文件进行修改。

首先在spring.xml配置

<bean id="loadPropertyPlaceholderConfigurer"class="com.gx.cms.api.filter.LoadPropertyPlaceholderConfigurer"lazy-init="false"><property name="order" value="1" /><property name="ignoreUnresolvablePlaceholders" value="true" /><property name="locations"><list><!-- <value>file:config/url.properties</value> -->                   <value>classpath:/config/url.properties</value></list></property></bean>

重写PropertyPlaceholderConfigurer

package com.gx.cms.api.filter;import java.util.HashMap;import java.util.Map;import java.util.Properties;import org.codehaus.jackson.map.ObjectMapper;import org.springframework.beans.BeansException;import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;public class LoadPropertyPlaceholderConfigurer extends PropertyPlaceholderConfigurer {private static Map<String, Object> ctxPropertiesMap;      @Override protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props)throws BeansException {         super.processProperties(beanFactoryToProcess, props);         ctxPropertiesMap = new HashMap<String, Object>();         for (Object key : props.keySet()) {            String keyStr = key.toString();            String value = props.getProperty(keyStr);             ctxPropertiesMap.put(keyStr, value);         }//        try {//System.out.println("1111-"+new ObjectMapper().writeValueAsString(props));//System.out.println("1111-"+new ObjectMapper().writeValueAsString(ctxPropertiesMap));//} catch (Exception e) {//e.printStackTrace();//}    }      public static <T> T getContextProperty(String name) {        return (T)ctxPropertiesMap.get(name);     }         @SuppressWarnings("all")public void reload(){    try{    Properties result = mergeProperties();//    logger.error("reload properties!"+result);    HashMap nc =new HashMap<String, Object>();    nc.putAll(result);    ctxPropertiesMap=nc;//    try {//    System.out.println("22-"+new ObjectMapper().writeValueAsString(nc));//    System.out.println("222-"+new ObjectMapper().writeValueAsString(ctxPropertiesMap));//    } catch (Exception e) {//    e.printStackTrace();//    }    }catch(Exception ex){    logger.error("reload properties error!",ex);    }    }    }

定时刷新配置文件

package com.gx.cms.api.filter;import javax.annotation.Resource;import org.springframework.scheduling.annotation.Scheduled;import org.springframework.stereotype.Component;@Componentpublic class PropertyReloader {@Resourceprivate LoadPropertyPlaceholderConfigurer loadPropertyPlaceholderConfigurer;@Scheduled(initialDelay = 5 * 60 * 1000,fixedDelay = 5 * 60 * 1000)    public void reload(){loadPropertyPlaceholderConfigurer.reload();}}

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