java - Spring @Value annotation returns null

Question

I'm trying to take advantage of @Value annotation and auto-populate my string-variable from the properties file, but with no luck. Values are not being set and are null .

Here is my configuration:

SendMessageController.java

@RestController
public class SendMessageController {

    @Value("${client.keystore.type}")
    private static String keystoreType;

    @RequestMapping(value = "/sendMessage", method = RequestMethod.POST)
    public ResponseEntity<SendMessageResponse> sendMessage(@Validated @RequestBody SendMessageRequest messageRequest) {
    .......
    }

application.properties

client.keystore.type=JKS

rest-servlet.xml

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
http://www.springframework.org/schema/context
http://www.springframework.org/schema/context/spring-context-4.0.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">


    <context:component-scan base-package="org.example.controllers" />

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

    <bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean"/>
    <mvc:annotation-driven />

</beans>

When I run my application and try to access keystoreType variable it is always null . What am I doing wrong?

Answer 1

Spring can not inject @Value to a static field directly.

you can either add inject the value through an annotated setter like this:

private static String keystoreType;

@Value("${client.keystore.type}")
public void setKeystoreType(String keystoreType) {
    SendMessageController.keystoreType = keystoreType;
} 

Or Change :

    @Value("${client.keystore.type}")
    private static String keystoreType;

to :

@Value("${client.keystore.type}")
private String keystoreType;

Answer 2

对于在所有上述建议之后仍然面临问题的人，请确保在按照本答案中所述构造 bean 之前您没有访问该变量。