They modify the POM at build time, and are meant to be used in complementary sets to give equivalent-but-different parameters for a set of target environments (providing, for example, the path of the appserver root in the development, testing, and production environments). \

Profiles specified in the POM can modify the following POM elements:

• <repositories>
• <pluginRepositories>
• <dependencies>
• <plugins>
• <properties> (这是compile time的maven properties，不是system properties)
• <modules>
• <reporting>
• <dependencyManagement>
• <distributionManagement>
• a subset of the <build> element, which consists of:
  • <defaultGoal>
  • <resources>
  • <testResources>
  • <finalName>

可以用mvn help:active-profiles来查看被active的profiles。

在spring configuration file里用的${sut.env}是system properties，如果想让maven properties来代替它，需要将这个spring xml file包含进<build><resources>里面。否则的话，就需要在profile里加上<build><plugin><configuration><systemPropertyVariables>。