在非spring boot程序中， 使用spring cloud config client

spring cloud config可以集中管理配置文件，不同的（spring-boot)应用程序，通过简单的配置就可以像使用; 但是普通的spring web application要使用config client却要费一番周折；

参考： https://github.com/spring-cloud/spring-cloud-config/issues/299

重点：

Well the "normal" way is to use Spring Cloud Config as part of a Spring Boot app. You really should consider doing that at some point.

If you want to try and cobble it together yourself you need a ConfigServicePropertySourceLocatorand you need to apply it to the Environment before the application context is started. How you do that will depend a lot on how you are creating the ApplicationContext (SpringApplication from Spring Boot would be much easier than whatever you are doing probably).

我们是一个spring web application，下面的方法也只是对web app有效；

1. maven 加入spring cloud config client:

 <!-- https://mvnrepository.com/artifact/org.springframework.cloud/spring-cloud-config-client -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-config-client</artifactId>
            <version>1.2.0.RELEASE</version>
        </dependency>

2. 配置web.xml， 让spring context loader 使用定制过的context;

    <context-param>
        <param-name>contextClass</param-name>
        <param-value>com.me.MyConfigurableWebApplicationContext</param-value>
    </context-param>

3. 实现 MyConfigurableWebApplicationContext, 主要的作用是使用自定义的environment;

public class MyConfigurableWebApplicationContext extends XmlWebApplicationContext {


    @Override
    protected ConfigurableEnvironment createEnvironment() {
        return new CloudEnvironment();
    }
}

4. 实现CloundEnvironment

public class CloudEnvironment extends StandardServletEnvironment {

    @Override
    protected void customizePropertySources(MutablePropertySources propertySources) {
        super.customizePropertySources(propertySources);
        try {
            propertySources.addLast(initConfigServicePropertySourceLocator(this));
        } catch (Exception ex) {
            logger.warn("failed to initialize cloud config environment", ex);
        }
    }

    private PropertySource<?> initConfigServicePropertySourceLocator(Environment environment) {
        ConfigClientProperties configClientProperties = new ConfigClientProperties(environment);
        configClientProperties.setUri("http://localhost:8888");
        configClientProperties.setName("myapp");
        configClientProperties.setLabel("master");
        ConfigServicePropertySourceLocator configServicePropertySourceLocator =
            new ConfigServicePropertySourceLocator(configClientProperties);
        return configServicePropertySourceLocator.locate(environment);
    }

}

5. 测试, 在server端配置cloud.config=true, 如果有效，那么这里应该能够得到true；

    @Value("${cloud.config: false}")
    public void setCloudConfig(boolean cloudConfig) {
        this.cloudConfig = cloudConfig;
    }