Using Default Values for Properties in Spring

Defaults for Property Values? I didn’t know that?

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)

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