🤓目前为止我们看下都介绍了哪些东西，梳理一下。
一下子干掉了好多啊！后边还有呢！😀
👉上面提到过@LoadBalancerClient和@LoadBalancerClients
/**
* Declarative configuration for a load balancer client. Add this annotation to any
* <code>@Configuration</code> and then inject a {@link LoadBalancerClientFactory} to
* access the client that is created.
*
* @author Dave Syer
*/
@Configuration(proxyBeanMethods = false)
@Import(LoadBalancerClientConfigurationRegistrar.class)
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface LoadBalancerClient {
/**
* Synonym for name (the name of the client).
*
* @see #name()
* @return the name of the load balancer client
*/
//name 和 value 都是微服务名称
@AliasFor("name")
String value() default "";
/**
* The name of the load balancer client, uniquely identifying a set of client
* resources, including a load balancer.
* @return the name of the load balancer client
*/
@AliasFor("value")
String name() default "";
/**
* A custom <code>@Configuration</code> for the load balancer client. Can contain
* override <code>@Bean</code> definition for the pieces that make up the client.
*
* @see LoadBalancerClientConfiguration for the defaults
* @return configuration classes for the load balancer client.
*/
//这个微服务的配置
Class<?>[] configuration() default {};
}
从官方注释我们可以看出，该注解为负载均衡客户端声明了一个配置，添加该注解的配置将会被注入到LoadBalancerClientFactory中。我们关注下@Import(LoadBalancerClientConfigurationRegistrar.class)这个。LoadBalancerClientConfigurationRegistrar将会被加入到容器。
/**
* 完成对@LoadBalanceClient或者@LoadBalanceClients注解标注类的解析
* @author Dave Syer
*/
public class LoadBalancerClientConfigurationRegistrar implements ImportBeanDefinitionRegistrar {
//解析@LoadBalanceClient或者@LoadBalanceClients的参数
private static String getClientName(Map<String, Object> client) {
if (client == null) {
return null;
}
String value = (String) client.get("value");
if (!StringUtils.hasText(value)) {
value = (String) client.get("name");
}
if (StringUtils.hasText(value)) {
return value;
}
throw new IllegalStateException("Either 'name' or 'value' must be provided in @LoadBalancerClient");
}
//利用BeanDefinitionBuilder创建LoadBalancerClientSpecification类型的Bean，这些Bean
//将自动注入到LoadBalancerAutoConfiguration类的configurations中，最终会注入到LoadBalancerClientFactory中
private static void registerClientConfiguration(BeanDefinitionRegistry registry, Object name,
Object configuration) {
BeanDefinitionBuilder builder = BeanDefinitionBuilder
.genericBeanDefinition(LoadBalancerClientSpecification.class);
builder.addConstructorArgValue(name);
builder.addConstructorArgValue(configuration);
registry.registerBeanDefinition(name + ".LoadBalancerClientSpecification", builder.getBeanDefinition());
}
@Override
//注册Bean
public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
Map<String, Object> attrs = metadata.getAnnotationAttributes(LoadBalancerClients.class.getName(), true);
if (attrs != null && attrs.containsKey("value")) {
AnnotationAttributes[] clients = (AnnotationAttributes[]) attrs.get("value");
for (AnnotationAttributes client : clients) {
registerClientConfiguration(registry, getClientName(client), client.get("configuration"));
}
}
if (attrs != null && attrs.containsKey("defaultConfiguration")) {
String name;
if (metadata.hasEnclosingClass()) {
name = "default." + metadata.getEnclosingClassName();
}
else {
name = "default." + metadata.getClassName();
}
registerClientConfiguration(registry, name, attrs.get("defaultConfiguration"));
}
Map<String, Object> client = metadata.getAnnotationAttributes(LoadBalancerClient.class.getName(), true);
//以下是将我们自定义的配置类加入到容器中
String name = getClientName(client);
if (name != null) {
registerClientConfiguration(registry, name, client.get("configuration"));
}
}
}
我们从registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) 开始看起
它先解析了注解的配置属性，并使用registerClientConfiguration(registry, getClientName(client), client.get("configuration"));来注册配置，主要时利用BeanDefinitionBuilder创建LoadBalancerClientSpecification类型的Bean，这些Bean将自动注入到LoadBalancerAutoConfiguration类的configurations中，最终会注入到LoadBalancerClientFactory中。这里就成功反映了我们在上面切换负载均衡算法时的配置。其他的部分正如我所注释那样，主要是默认配置和自定义配置的注册。
至于@LoadBalanceClients基本差不多，不在赘述了。
这下就完成了大半了
