1.Spring的框架中,org.springframework.beans.factory.config.PropertyPlaceholderConfigurer类可以将.properties(key/value形式)文件中一些动态设定的值(value),在XML中替换为占位该键($key$)的值,.properties文件可以根据客户需求,自定义一些相关的参数,这样的设计可提供程序的灵活性。
2.在Spring中,使用PropertyPlaceholderConfigurer可以在XML配置文件中加入外部属性文件,当然也可以指定外部文件的编码,如:
<bean id="propertyConfigurerForAnalysis" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="location"> <value>classpath:/spring/include/dbQuery.properties</value> </property> <property name="fileEncoding"> <value>UTF-8</value> </property> </bean>
其中classpath是引用src目录下的文件写法,当存在多个Properties文件时,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> <value>classpath*:config/jdbc.properties</value> </list> </property> </bean>
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="location"> <value>classpath:hb.properties</value> <value>/WEB-INF/config/project/project.properties</value> </property> </bean>
接下来我们要使用多个PropertyPlaceholderConfigurer来分散配置,达到整合多工程下的多个分散的Properties文件,其配置如下
<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属性代表其加载顺序,而ignoreUnresolvablePlaceholders为是否忽略不可解析的Placeholder,如配置了多个PropertyPlaceholderConfigurer,则需设置为true
3.譬如,jdbc.properties的内容为:
jdbc.driverClassName=com.mysql.jdbc.Driver jdbc.url=jdbc:mysql://localhost/mysqldb?useUnicode=true&characterEncoding=UTF-8&zeroDateTimeBehavior=round; jdbc.username=root jdbc.password=123456
备注:一定要在properties文件中&写为&因为在xml文件中不识别&,必须是&
4.那么在spring配置文件中,我们就可以这样写:
<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="locations"> <list> <value>classpath: conf/sqlmap/jdbc.properties </value> </list> </property> </bean> <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close"> <property name="driverClassName" value="${jdbc.driverClassName}" /> <property name="url" value="${jdbc.url}" /> <property name="username" value="${jdbc.username}" /> <property name="password" value="${jdbc.password}" /> </bean>
这样,一个简单的数据源就设置完毕了。可以看出:PropertyPlaceholderConfigurer起的作用就是将占位符指向的数据库配置信息放在bean中定义的工具。