Spring屬性佔位符PropertyPlaceholderConfigurer的使用

一、一個簡單的Demo

1.一、建立conf.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
    <bean id="propertyConfigurer"  class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <!-- 
        使用location屬性定義單個配置文件
        <property name="location">
            <value>classpath:/com/zsw/config/jdbc.properties</value>
        </property>
         -->
  
  <!-- 使用locations屬性定義多個配置文件 -->
  <property name="locations">
     <list>
        <value>classpath:/com/zsw/config/jdbc.properties</value>
     </list>
  </property> 
    </bean>
    <bean id="dataSource"  class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="url">
            <value>${database.url}</value>
        </property>
        <property name="driverClassName">
            <value>${database.driver}</value>
        </property>
        <property name="username">
            <value>${database.user}</value>
        </property>
        <property name="password">
            <value>${database.password}</value>
        </property>
    </bean>
</beans>

1.2.建立jdbc.properties文件

database.driver=com.mysql.jdbc.Driver
database.url=jdbc:mysql://localhost:3306/right?useUnicode=true&autoReconnect=true&characterEncoding=UTF-8
database.user=root
database.password=root
jdbc.pool.c3p0.acquire_increment=2
jdbc.pool.c3p0.max_size=20
jdbc.pool.c3p0.min_size=2
jdbc.pool.c3p0.preferred_test_query='SELECT 1'
jdbc.pool.c3p0.idle_connection_test_period=18000
jdbc.pool.c3p0.max_idle_time=25000

1.3.建立Config.java

package com.zsw.config;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.FileSystemResource;
import org.springframework.jdbc.datasource.DriverManagerDataSource;

public class Config {
     public static void main(String[] args) {
         XmlBeanFactory factory = new XmlBeanFactory(new FileSystemResource("src/com/zsw/config/conf.xml"));
         // 若是要在BeanFactory中使用，bean factory post-processor必須手動運行:
         PropertyPlaceholderConfigurer cfg = new PropertyPlaceholderConfigurer();
         cfg.setLocation(new FileSystemResource("src/com/zsw/config/jdbc.properties"));
         cfg.postProcessBeanFactory(factory);
         DriverManagerDataSource dataSource = (DriverManagerDataSource) factory.getBean("dataSource");
//         System.out.println(dataSource.getDriverClassName());
         
         
         System.out.println(dataSource.getUsername());
         // 注意，ApplicationContext可以自動辨認和應用在其上部署的實現了BeanFactoryPostProcessor的bean。這就意味着，當使用ApplicationContext的時候應用PropertyPlaceholderConfigurer會很是的方便。因爲這個緣由，建議想要使用這個或者其餘bean
         // factory postprocessor的用戶使用ApplicationContext代替BeanFactroy。
         ApplicationContext context = new ClassPathXmlApplicationContext("com/zsw/config/conf.xml");
         DriverManagerDataSource dataSource2 = (DriverManagerDataSource) context.getBean("dataSource");
         System.out.println(dataSource2.getUsername());
     }
 
}

 

2.Spring中PropertyPlaceholderConfigurer多種配置方式

2.1配置單個Properties文件

<bean id="propertyConfigurerForAnalysis" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="location">
        <value>classpath:/spring/include/dbQuery.properties</value>
    </property>
</bean>

其中classpath是引用src目錄下的文件寫法。

2.2 當存在多個Properties文件時，配置就需使用locations了：

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="locations">
       <list>
          <value>classpath:/spring/include/jdbc-parms.properties</value>
          <value>classpath:/spring/include/base-config.properties</value>
        </list>
    </property>
</bean>

 

2.三、接下來咱們要使用多個PropertyPlaceholderConfigurer來分散配置，達到整合多工程下的多個分散的Properties 文件，其配置以下：

<bean id="propertyConfigurerForProject1" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="order" value="1" />
    <property name="ignoreUnresolvablePlaceholders" value="true" />
    <property name="location">
       <value>classpath:/spring/include/dbQuery.properties</value>
    </property>
</bean>

 

<bean id="propertyConfigurerForProject2" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="order" value="2" />
    <property name="ignoreUnresolvablePlaceholders" value="true" />
    <property name="locations">
      <list>
        <value>classpath:/spring/include/jdbc-parms.properties</value>
        <value>classpath:/spring/include/base-config.properties</value>
      </list>
    </property>
</bean>

 

其中order屬性表明其加載順序，而ignoreUnresolvablePlaceholders爲是否忽略不可解析的 Placeholder，如配置了多個PropertyPlaceholderConfigurer，則需設置爲true