Question

I’ve never worked with Spring before, and I’ve run into a configuration object that looks somewhat like this

public class Config {

@Value("${app.module.config1}")
private String config1;

@Value("${app.module.config2}")
private String config2

...

public String getConfig1() {
    return config1;
}

...

Can anyone explain what is happening here? I’m assuming this is some type of code injection, but I can’t find where these values are coming from!

Answer 1

They allow you to direct inject a Value from a properties file (system or declared property) in the variable. Using the util:properties tag you can add something like this in your applicationContext.xml

 <util:properties id="message" location="classpath:com/your/program/resources/message.properties" />

Pointing for a properties file named “message.properties” with some content:

 application.hello.message = Hello World!

And then, in your java source file, inject a direct value from this properties file using the @Value annotation:

 @Value("#{message['application.hello.message']}")
 private String helloWorldMessage;