SpringCloud之Ribbon组件配置的读取

spring:
  application:
    name: eshop-microservice-gateway-app
server:
  port: 8080
eureka:
  client:
    defautlZone: http://127.0.0.1:8761/eureka,http://127.0.0.1:8762/eureka
#ribbon的全局配置，对所有ribbon客户端都生效
ribbon: 
　MaxAutoRetries: 2
eshop-microservice-user:
  ribbon: 
    ReadTimeout: 4000
zuul:
  ignored-services: '*'
  retryable: true
  stripPrefix: false
  routes:
    userservice:
      serviceId: eshop-microservice-user
      path: /api/v1.0/user/**
      stripPrefix: false
    testservice:
      url: http://www.baidu.com/
      path: /test/**
    demoservice: /aaaa/**

　配置文件中Ribbon的配置如下

eshop-microservice-user:
  ribbon: 
    ReadTimeout: 4000

　在springcloud里是怎么读取的，我们先看ribbon的调用入口：

	public HttpClientRibbonCommand create(final RibbonCommandContext context) {
		FallbackProvider zuulFallbackProvider = getFallbackProvider(
				context.getServiceId());
		final String serviceId = context.getServiceId();
		final RibbonLoadBalancingHttpClient client = this.clientFactory
				.getClient(serviceId, RibbonLoadBalancingHttpClient.class);
		client.setLoadBalancer(this.clientFactory.getLoadBalancer(serviceId));

		return new HttpClientRibbonCommand(serviceId, client, context, zuulProperties,
				zuulFallbackProvider, clientFactory.getClientConfig(serviceId));
	}

　　这是Zuul组件调用Ribbon的入口，由clientFactory创建RibbonLoadBalancingHttpClient，我们进而去看this.clientFactory.getClient方法，通过步步查看可以看出在创建RibbonLoadBalancingHttpClient的时候创建了Spring容器，然后从容器获取的，创建容器的逻辑如下：

protected AnnotationConfigApplicationContext createContext(String name) {
		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
		if (this.configurations.containsKey(name)) {
			for (Class<?> configuration : this.configurations.get(name)
					.getConfiguration()) {
				context.register(configuration);
			}
		}
		for (Map.Entry<String, C> entry : this.configurations.entrySet()) {
			if (entry.getKey().startsWith("default.")) {
				for (Class<?> configuration : entry.getValue().getConfiguration()) {
					context.register(configuration);
				}
			}
		}
		context.register(PropertyPlaceholderAutoConfiguration.class,
				this.defaultConfigType);
		context.getEnvironment().getPropertySources().addFirst(new MapPropertySource(
				this.propertySourceName,
				Collections.<String, Object>singletonMap(this.propertyName, name)));
		if (this.parent != null) {
			// Uses Environment from parent as well as beans
			context.setParent(this.parent);
			// jdk11 issue
			// https://github.com/spring-cloud/spring-cloud-netflix/issues/3101
			context.setClassLoader(this.parent.getClassLoader());
		}
		context.setDisplayName(generateDisplayName(name));
		context.refresh();
		return context;
	}

　　这里面我们主要关心的是红色的代码，里面是在properties集合里添加了一个配置，这个配置我们知道name就是前面的serviceId，这里也就是eshop-microservice-user，但是propertyName具体是啥呢，我们接下来看：

public class SpringClientFactory extends NamedContextFactory<RibbonClientSpecification> {

	static final String NAMESPACE = "ribbon";

	public SpringClientFactory() {
		super(RibbonClientConfiguration.class, NAMESPACE, "ribbon.client.name");
	}
}

　　这是SpringClientFactory的无参构造函数，通过这里我们可以知道propertyName=ribbon.client.name，所以properties集合添加的配置是：ribbon.client.name=eshop-microservice-user，而这到底用在哪里呢？我们可以先看看新创建的这个spring容器到底注入了哪些Configuration，在前面的createContext方法我们看到context.register(PropertyPlaceholderAutoConfiguration.class,this.defaultConfigType);这样一句代码，defaultConfigType就是RibbonClientConfiguration，然后我们看看RibbonClientConfiguration的几个关键地方

@Import({ HttpClientConfiguration.class, OkHttpRibbonConfiguration.class,
		RestClientRibbonConfiguration.class, HttpClientRibbonConfiguration.class })
public class RibbonClientConfiguration {


	@RibbonClientName
	private String name = "client";

	@Bean
	@ConditionalOnMissingBean
	public IClientConfig ribbonClientConfig() {
		DefaultClientConfigImpl config = new DefaultClientConfigImpl();
		config.loadProperties(this.name);
		config.set(CommonClientConfigKey.ConnectTimeout, DEFAULT_CONNECT_TIMEOUT);
		config.set(CommonClientConfigKey.ReadTimeout, DEFAULT_READ_TIMEOUT);
		config.set(CommonClientConfigKey.GZipPayload, DEFAULT_GZIP_PAYLOAD);
		return config;
	}

　　上面的name属性有RibbonClientName注解，如下

@Value("${ribbon.client.name}")
public @interface RibbonClientName {

}

　　这样name的值在容器刷新后被ribbon.client.name替换成eshop-microservice-user，然后注入IClientConfig，ribbonClientConfig里面的逻辑就是初始化ribbon的配置并且加载ribbon的自定义配置。

然后我们看加载配置主要的方法loadProperties：

	public void loadProperties(String restClientName){
        enableDynamicProperties = true;
        setClientName(restClientName);
//这里加载全局的ribbon配置
        loadDefaultValues();
//这里加载对应客户端的配置
        Configuration props = ConfigurationManager.getConfigInstance().subset(restClientName);
        for (Iterator<String> keys = props.getKeys(); keys.hasNext(); ){
            String key = keys.next();
            String prop = key;
            try {
                if (prop.startsWith(getNameSpace())){
                    prop = prop.substring(getNameSpace().length() + 1);
                }
                setPropertyInternal(prop, getStringValue(props, key));
            } catch (Exception ex) {
                throw new RuntimeException(String.format("Property %s is invalid", prop));
            }
        }
    }

在DefaultClientConfigImpl这个实现内部有个地方需要注意：

    protected Object getProperty(String key) {
        if (enableDynamicProperties) {
            String dynamicValue = null;
            DynamicStringProperty dynamicProperty = dynamicProperties.get(key);
            if (dynamicProperty != null) {
                dynamicValue = dynamicProperty.get();
            }
            if (dynamicValue == null) {
                dynamicValue = DynamicProperty.getInstance(getConfigKey(key)).getString();
                if (dynamicValue == null) {
                    dynamicValue = DynamicProperty.getInstance(getDefaultPropName(key)).getString();
                }
            }
            if (dynamicValue != null) {
                return dynamicValue;
            }
        }
        return properties.get(key);
    }

 在DefaultClientConfigImpl的内部有properties和dynamicProperties来存储配置信息，所以读取配置时会先从dynamicProperties中读取，如果没读取到则从properties读，而用户自定义的配置在properties和dynamicProperties中都会存储，所以就有

		config.set(CommonClientConfigKey.ConnectTimeout, DEFAULT_CONNECT_TIMEOUT);
		config.set(CommonClientConfigKey.ReadTimeout, DEFAULT_READ_TIMEOUT);
		config.set(CommonClientConfigKey.GZipPayload, DEFAULT_GZIP_PAYLOAD);

　　这三个重置默认值的代码并不影响用户自定义的配置。