## 14.5 Property Placeholder Configuration

Grails supports the notion of property placeholder configuration through an extended version of Spring's PropertyPlaceholderConfigurer, which is typically useful when used in combination with externalized configuration.

Settings defined in either ConfigSlurper scripts of Java properties files can be used as placeholder values for Spring configuration in `grails-app/conf/spring/resources.xml`. For example given the following entries in `grails-app/conf/Config.groovy` (or an externalized config):

    database.driver="com.mysql.jdbc.Driver"
    database.dbname="mysql:mydb"

You can then specify placeholders in `resources.xml` as follows using the familiar ${..} syntax:

    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
       <property name="driverClassName"><value>${database.driver}</value></property>
       <property name="url"><value>jdbc:${database.dbname}</value></property>
     </bean>