Using Default Values for Properties in Spring

I was looking through the Spring Greenhouse application and discovered an existing feature that I was unaware of. We can set a default value when configuring PropertyPlaceholderConfigurer.

1. Set the default value separator in config

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="location" value="classpath:application.properties" />
    <property name="ignoreResourceNotFound" value="true" /> <-- Ignore file not found -->
    <property name="ignoreUnresolvablePlaceholders" value="true" /> <-- Ignore when tokens are not found -->
 
    <!-- Token that separates default values on a placeholder-by-placeholder basis e.g. ${server.name?localhost} -->
    <property name="valueSeparator" value="?" />
            ...
</bean>

2. Set the default values for your properties

<bean id="myServer" class="com.gordondickens.myapp.MyServerConfig">
    <property name="serverName" value="${server.name?localhost}" />
    <property name="serverPort" value="${server.port?25}" />
            ...
</bean>

Notes

• If unspecified, the default separator is a colon “:”
• This option is not available when using the “context” namespace – (submitted Jira ticket: SPR-7794)

From http://gordondickens.com/wordpress/2010/12/06/using-default-values-for-properties-in-spring/