Sharing Properties in Spring and Ant

Sharing properties among different modules of application is a big topic of discussion. Its very important for changing the properties per environment while production deployment and also effectively  testing the application pointing to or injecting  a mock implemention . One of many advantages of spring frame work is this testing flexibility.We can even test the production using the mock objects. In order to get these full benefit we need to use PropertyPlaceholderConfigurer class from spring frame work.

1. Define sample.properties

jdbc.driver=org.hsqldb.jdbcDriver

2. Set up PropertyPlaceholderConfigurer

  <bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
<property name="locations" value="classpath:bin/sample.properties" />

</bean>

3.Use them as follows

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

This class resolves placeholders in bean property values of context definitions. It pulls values from a properties file into bean definitions.The default placeholder syntax follows the Ant / Log4J / JSP EL style:  ${...}. If you want to check against multiple properties files, specify multiple resources via the "locations" setting. You can also define multiple PropertyPlaceholderConfigurers, each with its own placeholder syntax. Default property values can be defined via "properties", to make overriding definitions in properties files optional. A configurer will also check against system properties (e.g. "user.dir") if it cannot resolve a placeholder with any of the specified properties. This can be customized via "systemPropertiesMode". Property values can be converted after reading them in, through overriding the PropertyResourceConfigurer.convertPropertyValue(java.lang.String) method. For example, encrypted values can be detected and decrypted accordingly before processing them.

Another benefit is the same file can be used in ant build file also :

<property file="sample.properties"/>
...
<target name="browse">
<java classname="org.hsqldb.util.DatabaseManager" fork="yes" failonerror="true">
<classpath refid="classpath"/>
<arg value="-url"/>
<arg value="${jdbc.url}"/>
</java>
</target>
<property name="driverClassName"><value>${jdbc.driver}</value></property><br />
...<br />
<br />
...<br />
</bean><br />
<br />
<br />