Spring @Value 注解

Question

I'm Spring newbie and I'm wondering what are prerequisites/conditions of using @Value annotation in Spring?

What I have for now is a Token class which has hardcoded secret key as a field. What I'm trying to do is to move this secret key to config file to eliminate hardcoding but for some reason the following is not working.

public class Token {
//...some code

    @Value("${my.secretKey}")
    private String key;

//...some code
}

Maybe there is any standard technique to solving this type of tasks.
Thanks for help!

ps I have .properties file which contains my.secretKey=123 entry.

Answer 1

Injecting dependencies and values only works on objects that are managed by Spring - when you manually create an object using new , for example by doing new Token() , then Spring cannot process the object to inject dependencies and values.

The Token object must be a Spring bean for this to work.

Answer 2

To use @Value annotation your Spring version must be 3.0+

You must register a static PropertySourcesPlaceholderConfigurer bean in either XML or annotation, so that Spring @Value know how to interpret ${}

For more information

https://www.mkyong.com/spring3/spring-value-default-value/

Answer 3

One mistake can also be in proper location of .properties file. Your .properties file location is very important. Your xyz.properties file must be place in your project's src folder, like : src/xyz.properties After that,
Load your properties file in the XML config file : File: applicationContext.xml Add the following lines:

<context:property-placeholder location="classpath:xyz.properties"/>

This code should appear just after the <context:component-scan .../> line in your xml config file. And now
Inject the properties values into your Token class, It should work now.
Happy Coding.