Is there any syntax like : #{systemProperties['

问题:

Does using #{systemProperties['environment']} in the applicationcontext.xml file of Spring return the value associated with environment?

Or is there any way to ge the system variable value in the spring applicationcontext.xml file.

回答1:

When I remember right, then there is a difference between:

You can access the system properties in different ways:

• #{systemProperties['databaseName']}
• #{systemProperties.databaseName}
• ${databaseName} //$ instead of # !!

With #{systemProperties['databaseName']} you have access to system-system-properties.

With #{systemProperties.databaseName} you have access to the system properties readed for example from the command line (-DdatabaseName="testDB").

With ${databaseName} you have access the the properties from the properties files loaded and provided for example by the PropertyPlaceholderConfigurer and to the system prooperties too

@Value("#{systemProperties['java.version']}")
private String javaVersionMap;

//Dont know how
//@Value("#{systemProperties.javav.version}")
//private String javaVersionDirect;

@Value("${java.version}")
private String javaVersionProp;

---

//-DcmdParam=helloWorld
@Value("#{systemProperties['cmdParam']}")
private String cmdParamMap;

@Value("#{systemProperties.cmdParam}")
private String cmdParamDirect;

@Value("${cmdParam}")
private String cmdParamProp

You can use all of them in a @Value annotation or the config.xml files (<property name="databaseName" value="#{systemProperties.databaseName}"/>)

回答2:

One way to do this kind of thing is to use a PropertyPlaceholderConfigurer which can be configured to use the system properties.

I also noticed that the Spring 3.1 M1 blog entry talks about new stuff for accessing configuration information from "the environment". Of course, that is only a milestone ... not a production-ready release.