有条件的spring bean创建 [英] Conditional spring bean creation

问题描述

我有一个关于 Spring 注释配置的问题.我有一颗豆子:

I have a question about Spring annotation configurations. I have a bean:

@Bean 
public ObservationWebSocketClient observationWebSocketClient(){
    log.info("creating web socket connection...");
    return new ObservationWebSocketClient();
}

我有一个属性文件:

@Autowired
Environment env;

在属性文件中我想要一个特殊的布尔属性

In the property file I want to have a special boolean property

createWebsocket=true/false

表示是否应创建 bean ObservationWebSocketClient.如果属性值为false，我根本不想建立网络套接字连接.

which signs whether a bean ObservationWebSocketClient should be created. If property value is false I don't want to establish web socket connection at all.

是否有任何技术可能性来实现这一点?

Is there any technical possibility to realize this?

推荐答案

虽然我没有使用过这个功能，但似乎你可以用 spring 4 的 @Conditional 注释.

Though I've not used this functionality, it appears that you can do this with spring 4's @Conditional annotation.

首先创建一个Condition类，其中ConditionContext可以访问Environment:

First, create a Condition class, in which the ConditionContext has access to the Environment:

public class MyCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, 
                           AnnotatedTypeMetadata metadata) {
        Environment env = context.getEnvironment();
        return null != env 
               && "true".equals(env.getProperty("createWebSocket"));
    }
}

然后注释你的bean:

Then annotate your bean:

@Bean
@Conditional(MyCondition.class)
public ObservationWebSocketClient observationWebSocketClient(){
    log.info("creating web socket connection...");
    return new ObservationWebSocketClient();
}

edit spring-boot 注释 @ConditionalOnProperty 已经通用实现了这一点；用于评估它的 Condition 的源代码 可在 github 上找到，供感兴趣的人使用.如果您发现自己经常需要这种功能，建议使用类似的实现，而不是制作大量自定义 Condition 实现.

edit The spring-boot annotation @ConditionalOnProperty has implemented this generically; the source code for the Condition used to evaluate it is available on github here for those interested. If you find yourself often needing this funcitonality, using a similar implementation would be advisable rather than making lots of custom Condition implementations.

这篇关于有条件的spring bean创建的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！