Spring Cloud Ribbon主要用于客户端的负载均衡。最基本的用法便是使用RestTemplate进行动态的负载均衡。我们只需要加入如下的配置便能完成客户端的负载均衡。
@Configuration public class RestConfiguration { @Bean @LoadBalanced public RestTemplate restTemplate() { return new RestTemplate(); } }
/** * Annotation to mark a RestTemplate bean to be configured to use a LoadBalancerClient * @author Spencer Gibb */ @Target({ ElementType.FIELD, ElementType.PARAMETER, ElementType.METHOD }) @Retention(RetentionPolicy.RUNTIME) @Documented @Inherited @Qualifier public @interface LoadBalanced { }
这里的@LoadBalanced使得RestTemplate可以使用LoadBalancerClient，在LoadBalancerClient在这个路劲下，还存在着LoadBalancerAutoConfiguration这个配置类只要用于对LoadBalancerClient做出配置。我们就以此为入口，开始分析ribbon
LoadBalancer的自动化配置
@Configuration @ConditionalOnClass(RestTemplate.class) @ConditionalOnBean(LoadBalancerClient.class) @EnableConfigurationProperties(LoadBalancerRetryProperties.class) public class LoadBalancerAutoConfiguration { @LoadBalanced @Autowired(required = false) private List<RestTemplate> restTemplates = Collections.emptyList(); @Bean public SmartInitializingSingleton loadBalancedRestTemplateInitializer( final List<RestTemplateCustomizer> customizers) { return new SmartInitializingSingleton() { @Override public void afterSingletonsInstantiated() { for (RestTemplate restTemplate : LoadBalancerAutoConfiguration.this.restTemplates) { for (RestTemplateCustomizer customizer : customizers) { customizer.customize(restTemplate); } } } }; } @Autowired(required = false) private List<LoadBalancerRequestTransformer> transformers = Collections.emptyList(); @Bean @ConditionalOnMissingBean public LoadBalancerRequestFactory loadBalancerRequestFactory( LoadBalancerClient loadBalancerClient) { return new LoadBalancerRequestFactory(loadBalancerClient, transformers); } @Configuration @ConditionalOnMissingClass("org.springframework.retry.support.RetryTemplate"
