聊聊spring cloud netflix ribbon的eager load

@Configuration
@Conditional(RibbonAutoConfiguration.RibbonClassesConditions.class)
@RibbonClients
@AutoConfigureAfter(name = "org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration")
@AutoConfigureBefore({ LoadBalancerAutoConfiguration.class,
AsyncLoadBalancerAutoConfiguration.class })
@EnableConfigurationProperties({ RibbonEagerLoadProperties.class,
ServerIntrospectorProperties.class })
public class RibbonAutoConfiguration {

@Autowired(required = false)
private List<RibbonClientSpecification> configurations = new ArrayList<>();

@Autowired
private RibbonEagerLoadProperties ribbonEagerLoadProperties;

@Bean
public HasFeatures ribbonFeature() {
return HasFeatures.namedFeature("Ribbon", Ribbon.class);
}

@Bean
public SpringClientFactory springClientFactory() {
SpringClientFactory factory = new SpringClientFactory();
factory.setConfigurations(this.configurations);
return factory;
}

@Bean
@ConditionalOnMissingBean(LoadBalancerClient.class)
public LoadBalancerClient loadBalancerClient() {
return new RibbonLoadBalancerClient(springClientFactory());
}

@Bean
@ConditionalOnClass(name = "org.springframework.retry.support.RetryTemplate")
@ConditionalOnMissingBean
public LoadBalancedRetryFactory loadBalancedRetryPolicyFactory(
final SpringClientFactory clientFactory) {
return new RibbonLoadBalancedRetryFactory(clientFactory);
}

@Bean
@ConditionalOnMissingBean
public PropertiesFactory propertiesFactory() {
return new PropertiesFactory();
}

@Bean
@ConditionalOnProperty("ribbon.eager-load.enabled")
public RibbonApplicationContextInitializer ribbonApplicationContextInitializer() {
return new RibbonApplicationContextInitializer(springClientFactory(),
ribbonEagerLoadProperties.getClients());
}

@Configuration
@ConditionalOnClass(HttpRequest.class)
@ConditionalOnRibbonRestClient
protected static class RibbonClientHttpRequestFactoryConfiguration {

@Autowired
private SpringClientFactory springClientFactory;

@Bean
public RestTemplateCustomizer restTemplateCustomizer(
final RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory) {
return restTemplate -> restTemplate
.setRequestFactory(ribbonClientHttpRequestFactory);
}

@Bean
public RibbonClientHttpRequestFactory ribbonClientHttpRequestFactory() {
return new RibbonClientHttpRequestFactory(this.springClientFactory);
}

}

// TODO: support for autoconfiguring restemplate to use apache http client or okhttp

@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Conditional(OnRibbonRestClientCondition.class)
@interface ConditionalOnRibbonRestClient {

}

private static class OnRibbonRestClientCondition extends AnyNestedCondition {

OnRibbonRestClientCondition() {
super(ConfigurationPhase.REGISTER_BEAN);
}

@Deprecated // remove in Edgware"
@ConditionalOnProperty("ribbon.http.client.enabled")
static class ZuulProperty {

}

@ConditionalOnProperty("ribbon.restclient.enabled")
static class RibbonProperty {

}

}

/**
 * {@link AllNestedConditions} that checks that either multiple classes are present.
 */
static class RibbonClassesConditions extends AllNestedConditions {

RibbonClassesConditions() {
super(ConfigurationPhase.PARSE_CONFIGURATION);
}

@ConditionalOnClass(IClient.class)
static class IClientPresent {

}

@ConditionalOnClass(RestTemplate.class)
static class RestTemplatePresent {

}

@ConditionalOnClass(AsyncRestTemplate.class)
static class AsyncRestTemplatePresent {

}

@ConditionalOnClass(Ribbon.class)
static class RibbonPresent {

}

}

}

public class RibbonApplicationContextInitializer
implements ApplicationListener<ApplicationReadyEvent> {

private final SpringClientFactory springClientFactory;

// List of Ribbon client names
private final List<String> clientNames;

public RibbonApplicationContextInitializer(SpringClientFactory springClientFactory,
List<String> clientNames) {
this.springClientFactory = springClientFactory;
this.clientNames = clientNames;
}

protected void initialize() {
if (clientNames != null) {
for (String clientName : clientNames) {
this.springClientFactory.getContext(clientName);
}
}
}

@Override
public void onApplicationEvent(ApplicationReadyEvent event) {
initialize();
}

}

public class SpringClientFactory extends NamedContextFactory<RibbonClientSpecification> {
//......

protected AnnotationConfigApplicationContext getContext(String name) {
return super.getContext(name);
}

//......
}

public abstract class NamedContextFactory<C extends NamedContextFactory.Specification>
implements DisposableBean, ApplicationContextAware {

//......

protected AnnotationConfigApplicationContext getContext(String name) {
if (!this.contexts.containsKey(name)) {
synchronized (this.contexts) {
if (!this.contexts.containsKey(name)) {
this.contexts.put(name, createContext(name));
}
}
}
return this.contexts.get(name);
}

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;
}

//......
}