如何在 spring 引导中从系统属性中获取值

Question

I am using following command to run my spring boot application

java -Dlibrary.system.property=value -jar myapp.jar

Currently, I am able to access it via following command like below

System.getProperty("library.system.property")

However I need to access it via any annotation in Spring something like

@value(${library.system.property})

I tried to use

    @Value("${library.system.property")
    private String property;

    @Bean
    public SampleProvider getSampleProvider () {
        return SampleProvider.from(property);
    }

But the value of the property is null . Do I need to use conditional bean or something?

Answer 1

You can access the system properties using the following expression:

@Value("#{systemProperties['library.system.property']}")
private String property

You can also access the system environment using the following expression:

@Value("#{systemEnvironment['SOME_ENV_VARIABLE']}")
private String property

Lastly, if you are using Spring Boot you can refer to the property name directly as long as you are passing it in the command line. For example, if you launch the JAR like java -jar boot.jar --some.property=value you can read it as:

@Value("${some.property}")
private String property

Answer 2

Thanks all. Issue got resolved by changing the way of passing the argument through command line as below

java -jar myapp.jar --library.system.property=value

Accessing the value by below code snippet

@Value("${library.system.property}")
private String property;

@Bean
public SampleProvider getSampleProvider () {
    return SampleProvider.from(property);
}

Answer 3

Simply use

import org.springframework.boot.system.SystemProperties;
...
String propertyKey = "library.system.property";
String propertyValue = SystemProperties.get(propertyKey);

Answer 4

@Configuration
Public class YourAppConfig {

    @Value("${your.system.property}") String prop
    @Autowired
    Public void LoadProperties() {
        System.setProperty(PROPERTY_NAME, prop) ;
    }

    @Bean
    ...

Answer 5

You can access your data from properties file by using @ Value on your controller. For example: @Value("${library.system.property}") private String property;

Now your value is in property,now you can use it anywhere.