[java] Is there a way to specify a default property value in Spring XML?

We are using a PropertyPlaceholderConfigurer to use java properties in our Spring configuration (details here)

eg:

<foo name="port">
  <value>${my.server.port}</value>
</foo>

We would like to add an additional property, but have a distributed system where existing instances could all use a default value. Is there a way to avoid updating all of our properties files, by indicating a default value in the Spring config for when there isn't an overriding property value defined?

The default value can be followed with a : after the property key, e.g.

<property name="port" value="${my.server.port:8080}" />

Or in java code:

@Value("${my.server.port:8080}")
private String myServerPort;

See:

• valueSeparator (from AbstractPropertyResolver)

• and VALUE_SEPARATOR (from SystemPropertyUtils)

BTW, the Elvis Operator is only available within Spring Expression Language (SpEL),
e.g.: https://stackoverflow.com/a/37706167/537554

http://thiamteck.blogspot.com/2008/04/spring-propertyplaceholderconfigurer.html points out that "local properties" defined on the bean itself will be considered defaults to be overridden by values read from files:

<bean id="propertyConfigurer"class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">  
  <property name="location"><value>my_config.properties</value></property>  
  <property name="properties">  
    <props>  
      <prop key="entry.1">123</prop>  
    </props>  
  </property>  
</bean> 

Spring 3 supports ${my.server.port:defaultValue} syntax.

Also i find another solution which work for me. In our legacy spring project we use this method for give our users possibilities to use this own configurations:

<bean id="appUserProperties" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
    <property name="ignoreResourceNotFound" value="false"/>
    <property name="locations">
        <list>
            <value>file:./conf/user.properties</value>
        </list>
    </property>
</bean>

And in our code to access this properties need write something like that:

@Value("#{appUserProperties.userProperty}")
private String userProperty

And if a situation arises when you need to add a new property but right now you don't want to add it in production user config it very fast become a hell when you need to patch all your test contexts or your application will be fail on startup.

To handle this problem you can use the next syntax to add a default value:

@Value("#{appUserProperties.get('userProperty')?:'default value'}")
private String userProperty

It was a real discovery for me.

<foo name="port">
   <value>${my.server.port:8088}</value>
</foo>

should work for you to have 8088 as default port

See also: http://blog.callistaenterprise.se/2011/11/17/configure-your-spring-web-application/

There is a little known feature, which makes this even better. You can use a configurable default value instead of a hard-coded one, here is an example:

config.properties:

timeout.default=30
timeout.myBean=60

context.xml:

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="location">
        <value>config.properties</value>
    </property>
</bean>

<bean id="myBean" class="Test">
    <property name="timeout" value="${timeout.myBean:${timeout.default}}" />
</bean>

To use the default while still being able to easily override later, do this in config.properties:

timeout.myBean = ${timeout.default}