Spring cloud负载均衡@LoadBalanced & LoadBalancerClient

@Bean
@LoadBalanced
public RestTemplate restTemplate(){
    return new RestTemplate();
}

@Service
public class OrderService {
    @Autowired
    private RestTemplate restTemplate;
    public String getOrder(){
        //通过userService获取user信息
        String url="http://userservice/user/getUser";
        System.out.println("url"+url);
        User user=restTemplate.getForObject(url,User.class);
        System.out.println(user);
        return user.getName();
    }
}

private LoadBalancerClient loadBalancer;
    public ClientHttpResponse intercept(final HttpRequest request, final byte[] body,
            final ClientHttpRequestExecution execution) throws IOException {
        final URI originalUri = request.getURI();
        String serviceName = originalUri.getHost();
        Assert.state(serviceName != null, "Request URI does not contain a valid hostname: " + originalUri);
        return this.loadBalancer.execute(serviceName, this.requestFactory.createRequest(request, body, execution));
    }

@Override
    public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
        String hint = getHint(serviceId);
        LoadBalancerRequestAdapter<T, TimedRequestContext> lbRequest = new LoadBalancerRequestAdapter<>(request,
                buildRequestContext(request, hint));
        Set<LoadBalancerLifecycle> supportedLifecycleProcessors = getSupportedLifecycleProcessors(serviceId);
        supportedLifecycleProcessors.forEach(lifecycle -> lifecycle.onStart(lbRequest));
        ServiceInstance serviceInstance = choose(serviceId, lbRequest);
        if (serviceInstance == null) {
            supportedLifecycleProcessors.forEach(lifecycle -> lifecycle.onComplete(
                    new CompletionContext<>(CompletionContext.Status.DISCARD, lbRequest, new EmptyResponse())));
            throw new IllegalStateException("No instances available for " + serviceId);
        }
        return execute(serviceId, serviceInstance, lbRequest);
    }

@Override
    public <T> ServiceInstance choose(String serviceId, Request<T> request) {
        ReactiveLoadBalancer<ServiceInstance> loadBalancer = loadBalancerClientFactory.getInstance(serviceId);
        if (loadBalancer == null) {
            return null;
        }
        Response<ServiceInstance> loadBalancerResponse = Mono.from(loadBalancer.choose(request)).block();
        if (loadBalancerResponse == null) {
            return null;
        }
        return loadBalancerResponse.getServer();
    }

@ConditionalOnMissingBean
    @Bean
    public LoadBalancerClientFactory loadBalancerClientFactory(LoadBalancerClientsProperties properties) {
        LoadBalancerClientFactory clientFactory = new LoadBalancerClientFactory(properties);
        clientFactory.setConfigurations(this.configurations.getIfAvailable(Collections::emptyList));
        return clientFactory;
    }

public LoadBalancerClientFactory(LoadBalancerClientsProperties properties) {
        super(LoadBalancerClientConfiguration.class, NAMESPACE, PROPERTY_NAME);
        this.properties = properties;
    }

public NamedContextFactory(Class<?> defaultConfigType, String propertySourceName, String propertyName) {
        this.defaultConfigType = defaultConfigType;
        this.propertySourceName = propertySourceName;
        this.propertyName = propertyName;
    }

@Override
    public void setApplicationContext(ApplicationContext parent) throws BeansException {
        this.parent = parent;
    }

@Override
    public ReactiveLoadBalancer<ServiceInstance> getInstance(String serviceId) {
        return getInstance(serviceId, ReactorServiceInstanceLoadBalancer.class);
    }
    public <T> T getInstance(String name, Class<T> type) {
        AnnotationConfigApplicationContext context = getContext(name);
        try {
            return context.getBean(type);
        }
        catch (NoSuchBeanDefinitionException e) {
            // ignore
        }
        return null;
    }

private Map<String, AnnotationConfigApplicationContext> contexts = new ConcurrentHashMap<>();
    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;
        if (this.parent != null) {
            // jdk11 issue
            // https://github.com/spring-cloud/spring-cloud-netflix/issues/3101
            // https://github.com/spring-cloud/spring-cloud-openfeign/issues/475
            DefaultListableBeanFactory beanFactory = new DefaultListableBeanFactory();
            if (parent instanceof ConfigurableApplicationContext) {
                beanFactory.setBeanClassLoader(
                        ((ConfigurableApplicationContext) parent).getBeanFactory().getBeanClassLoader());
            }
            else {
                beanFactory.setBeanClassLoader(parent.getClassLoader());
            }
            context = new AnnotationConfigApplicationContext(beanFactory);
            context.setClassLoader(this.parent.getClassLoader());
        }
        else {
            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);
                }
            }
        }
        //注意这里会注册this.defaultConfigType到容器中
        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);
        }
        context.setDisplayName(generateDisplayName(name));
        context.refresh();
        return context;
    }

@Override
    public ReactiveLoadBalancer<ServiceInstance> getInstance(String serviceId) {
        return getInstance(serviceId, ReactorServiceInstanceLoadBalancer.class);
    }

@Bean
    @ConditionalOnMissingBean
    public ReactorLoadBalancer<ServiceInstance> reactorServiceInstanceLoadBalancer(Environment environment,
            LoadBalancerClientFactory loadBalancerClientFactory) {
        String name = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
        return new RoundRobinLoadBalancer(
                loadBalancerClientFactory.getLazyProvider(name, ServiceInstanceListSupplier.class), name);
    }