On all the pages of my webapp I want to see when the WAR was built (i.e. a build timestamp). Here is how I did it:

Add this to the pom.xml of your webapp module:

<build>
  <resources>
    <resource>
      <directory>src/main/resources</directory>
      <filtering>true</filtering>
    </resource>
  </resources>
</build> 

<properties>
  <mavenBuildTimestamp>${maven.build.timestamp}</mavenBuildTimestamp>
</properties>

Create a file src/main/resources/build.properties in  in your webapp module with the following content:

# Build Time Information
build.timestamp=${mavenBuildTimestamp}

The Maven build will replace the Maven property and the resulting file WEB-INF/classes/build.properties will look like this:

# Build Time Information
build.timestamp=20101016-0303

Now we just need a Spring PropertiesFactoryBean definition to make properties available at runtime:

<bean id="appProperties" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
  <property name="locations">
    <list>
      <value>classpath:build.properties</value>
    </list>
  </property>
</bean>

I used a simple Spring bean to make the timestamp easily available in Spring Web Flow / Spring Faces EL expressions:

@Component
public class ViewUtil {

  private Properties appProperties;

  /**
   * @param appProperties Global Application properties
   */
  @Resource
  public void setAppProperties(Properties appProperties) {
    this.appProperties = appProperties;
  }

  /**
   * @return The Build Timestamp as generated by Maven
   */
  public String getBuildTimestamp() {
    return appProperties.getProperty("build.timestamp", "UNKNOWN");
  }
}

The EL expression code in the JSF page is then something like this:

Build timestamp: #{viewUtil.buildTimestamp} 

And this is what the result looks like on the page:

If you want to be able to refer to properties directly by name in your Spring configuration you can define a Spring PropertyPlaceholderConfigurer:

<bean id="propertyConfigurer"
      class="org.springframework.web.context.support.ServletContextPropertyPlaceholderConfigurer">
  <property name="properties" ref="appProperties" />
</bean>