how to read System environment variable in Spring applicationContext

You are close :o)Spring 3.0 adds Spring Expression Language. You can use

<util:properties id="dbProperties"     location="classpath:config_#{systemProperties['env']}/db.properties" />

Combined with java ... -Denv=QA should solve your problem.

Note also a comment by @yiling:

In order to access system environment variable, that is OS level variables as amoe commented, we can simply use "systemEnvironment" instead of "systemProperties" in that EL. Like #{systemEnvironment['ENV_VARIABLE_NAME']}

Nowadays you can put

@Autowiredprivate Environment environment;

in your @Component, @Bean, etc., and then access the properties through the Environment class:

environment.getProperty("myProp");

For a single property in a @Bean

@Value("${my.another.property:123}") // value after ':' is the defaultInteger property;

Another way are the handy @ConfigurationProperties beans:

@ConfigurationProperties(prefix="my.properties.prefix")public class MyProperties {  // value from my.properties.prefix.myProperty will be bound to this variable  String myProperty;  // and this will even throw a startup exception if the property is not found  @javax.validation.constraints.NotNull  String myRequiredProperty;  //getters}@Componentpublic class MyOtherBean {  @Autowired  MyProperties myProperties;}

Note: Just remember to restart eclipse after setting a new environment variable

Check this article. It gives you several ways to do this, via the PropertyPlaceholderConfigurer which supports external properties (via the systemPropertiesMode property).