如何从 Spring 中的 application.properties 重新加载 @Value 属性? [英] How to reload a @Value property from application.properties in Spring?

问题描述

我有一个 spring-boot 应用程序.在运行文件夹下，还有一个额外的配置文件:

I have a spring-boot application. Under the run folder, there is an additional config file:

dir/config/application.properties

当应用程序启动时，它使用文件中的值并将它们注入:

When the applications starts, it uses the values from the file and injects them into:

@Value("${my.property}")
private String prop;

问题:如何触发那些 @Value 属性的重新加载?我希望能够在运行时更改 application.properties 配置，并更新 @Value 字段(可能通过调用 /reload 应用程序内的 servlet).

Question: how can I trigger a reload of those @Value properties? I want to be able to change the application.properties configuration during runtime, and have the @Value fields updated (maybe trigger that update by calling a /reload servlet inside the app).

但是怎么做?

推荐答案

使用下面的 bean 每 1 秒重新加载 config.properties.

Use the below bean to reload config.properties every 1 second.

@Component
public class PropertyLoader {

    @Autowired
    private StandardEnvironment environment;

    @Scheduled(fixedRate=1000)
    public void reload() throws IOException {
        MutablePropertySources propertySources = environment.getPropertySources();
        PropertySource<?> resourcePropertySource = propertySources.get("class path resource [config.properties]");
        Properties properties = new Properties();
        InputStream inputStream = getClass().getResourceAsStream("/config.properties");
        properties.load(inputStream);
        inputStream.close();
        propertySources.replace("class path resource [config.properties]", new PropertiesPropertySource("class path resource [config.properties]", properties));
    }
}

您的主要配置将类似于:

Your main config will look something like :

@EnableScheduling
@PropertySource("classpath:/config.properties")
public class HelloWorldConfig {
}

而不是使用@Value，每次您想要使用最新的属性时

The instead of using @Value, each time you wanted the latest property you would use

environment.get("my.property");

注意

虽然示例中的 config.properties 取自类路径，但它仍然可以是已添加到类路径中的外部文件.

Although the config.properties in the example is taken from the classpath, it can still be an external file which has been added to the classpath.

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