一、编写示例
1.服务端
pom.xml
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Finchley.SR2</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-alibaba-dependencies</artifactId>
<version>0.2.1.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>2.提供者代码，就是一个普通的HTTP REST接口。
@SpringBootApplication
@EnableDiscoveryClient
@RestController
@Slf4j
public class ProviderApplication {
public static void main(String[] args) {
SpringApplication.run(ProviderApplication.class, args);
}
@GetMapping("provider")
public String provider(){
log.info("..................................");
return "hello,provider";
}
}
3.消费端
POM
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Finchley.SR2</spring-cloud.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
<exclusions>
<exclusion>
<groupId>org.springframework.retry</groupId>
<artifactId>spring-retry</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- <dependency>-->
<!-- <groupId>org.springframework.retry</groupId>-->
<!-- <artifactId>spring-retry</artifactId>-->
<!-- </dependency>-->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
</dependency>
<!--<dependency>-->
<!--<groupId>org.springframework.retry</groupId>-->
<!--<artifactId>spring-retry</artifactId>-->
<!--</dependency>-->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<dependencyManagement>
<dependencies>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-dependencies</artifactId>
<version>${spring-cloud.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-alibaba-dependencies</artifactId>
<version>0.2.1.RELEASE</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>这里注意，如果不想要RetryTemplate，就去掉Retry的依赖，否则默认会引入的。
消费端代码
@SpringBootApplication
@Slf4j
@EnableDiscoveryClient
@RestController
public class ConsumeApplication {
@Autowired
RestTemplate restTemplate;
@Bean
@LoadBalanced
public RestTemplate getRestTemplate(){
HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory();
clientHttpRequestFactory.setConnectTimeout(5 * 1000);
clientHttpRequestFactory.setReadTimeout(5 * 1000);
return new RestTemplate(clientHttpRequestFactory);
}
public static void main(String[] args) {
SpringApplication.run(ConsumeApplication.class, args);
}
@GetMapping("test")
public String getContent(){
log.info("发起请求");
return restTemplate.getForObject("http://provider/provider",String.class);
}
}
二、初始化自动配置代码分析
1.org.springframework.cloud.netflix.ribbon.RibbonAutoConfiguration，这个为RIBBON私有的
LoadBalancerClient,LoadBalancer,IRule对象的初始化。
@Configuration
@ConditionalOnClass({ IClient.class, RestTemplate.class, AsyncRestTemplate.class, Ribbon.class})
@RibbonClients
@AutoConfigureAfter(name = "org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration")
@AutoConfigureBefore({LoadBalancerAutoConfiguration.class, AsyncLoadBalancerAutoConfiguration.class})
@EnableConfigurationProperties({RibbonEagerLoadProperties.class, ServerIntrospectorProperties.class})
public class RibbonAutoConfiguration {
@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);
}2.org.springframework.cloud.client.loadbalancer.LoadBalancerAutoConfiguration为springcloud-common的对象自动初始化。
@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 loadBalancedRestTemplateInitializerDeprecated(
final ObjectProvider<List<RestTemplateCustomizer>> restTemplateCustomizers) {
return () -> restTemplateCustomizers.ifAvailable(customizers -> {
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")
static class LoadBalancerInterceptorConfig {
@Bean
public LoadBalancerInterceptor ribbonInterceptor(
LoadBalancerClient loadBalancerClient,
LoadBalancerRequestFactory requestFactory) {
return new LoadBalancerInterceptor(loadBalancerClient, requestFactory);
}
@Bean
@ConditionalOnMissingBean
public RestTemplateCustomizer restTemplateCustomizer(
final LoadBalancerInterceptor loadBalancerInterceptor) {
return restTemplate -> {
List<ClientHttpRequestInterceptor> list = new ArrayList<>(
restTemplate.getInterceptors());
list.add(loadBalancerInterceptor);
restTemplate.setInterceptors(list);
};
}
}这里的 restTemplate只会取加了@LoadBalance注解的，因为@LoadBalance加上了@Qualifer，这个注解会有筛选过滤作用。
去除了RetryTemplate就会走默认，否则走重试balance.
1.首先创建LoadBalancerRequestFactory工厂对象。
2.创建LoadBalancerInterceptor对象
3.对RestTemplate列表对象，设置拦截器属性。
三、调用分析
1.RestTemplate.getObject方法开始。这个方法会调用doExecute
public class RestTemplate extends InterceptingHttpAccessor implements RestOperations {
@Nullable
protected <T> T doExecute(URI url, @Nullable HttpMethod method, @Nullable RequestCallback requestCallback,
@Nullable ResponseExtractor<T> responseExtractor) throws RestClientException {
Assert.notNull(url, "URI is required");
Assert.notNull(method, "HttpMethod is required");
ClientHttpResponse response = null;
try {
ClientHttpRequest request = createRequest(url, method);
if (requestCallback != null) {
requestCallback.doWithRequest(request);
}
response = request.execute();
handleResponse(url, method, response);
return (responseExtractor != null ? responseExtractor.extractData(response) : null);
}
catch (IOException ex) {
String resource = url.toString();
String query = url.getRawQuery();
resource = (query != null ? resource.substring(0, resource.indexOf('?')) : resource);
throw new ResourceAccessException("I/O error on " + method.name() +
" request for \"" + resource + "\": " + ex.getMessage(), ex);
}
finally {
if (response != null) {
response.close();
}
}
}
2.createRequest方法，RestTemplate是继承于InterceptingHttpAccessor和HttpAccessor
HttpAccessor
protected ClientHttpRequest createRequest(URI url, HttpMethod method) throws IOException {
ClientHttpRequest request = getRequestFactory().createRequest(url, method);
if (logger.isDebugEnabled()) {
logger.debug("Created " + method.name() + " request for \"" + url + "\"");
}
return request;
}3.getRequestFactory方法又是来源于InterceptingHttpAccessor，这里会对原有httpRequestFactory工厂包装。
public ClientHttpRequestFactory getRequestFactory() {
List<ClientHttpRequestInterceptor> interceptors = getInterceptors();
if (!CollectionUtils.isEmpty(interceptors)) {
ClientHttpRequestFactory factory = this.interceptingRequestFactory;
if (factory == null) {
factory = new InterceptingClientHttpRequestFactory(super.getRequestFactory(), interceptors);
this.interceptingRequestFactory = factory;
}
return factory;
}
else {
return super.getRequestFactory();
}
}public class InterceptingClientHttpRequestFactory extends AbstractClientHttpRequestFactoryWrapper {
private final List<ClientHttpRequestInterceptor> interceptors;
/**
* Create a new instance of the {@code InterceptingClientHttpRequestFactory} with the given parameters.
* @param requestFactory the request factory to wrap
* @param interceptors the interceptors that are to be applied (can be {@code null})
*/
public InterceptingClientHttpRequestFactory(ClientHttpRequestFactory requestFactory,
@Nullable List<ClientHttpRequestInterceptor> interceptors) {
super(requestFactory);
this.interceptors = (interceptors != null ? interceptors : Collections.emptyList());
}
@Override
protected ClientHttpRequest createRequest(URI uri, HttpMethod httpMethod, ClientHttpRequestFactory requestFactory) {
return new InterceptingClientHttpRequest(requestFactory, this.interceptors, uri, httpMethod);
}
}
所以最后的ClientHttpRequest为InterceptingClientHttpRequest
3.接着我们回到第一步，response = request.execute();因为已经创建好request，现在开始执行。
class InterceptingClientHttpRequest extends AbstractBufferingClientHttpRequest {
private final ClientHttpRequestFactory requestFactory;
private final List<ClientHttpRequestInterceptor> interceptors;
private HttpMethod method;
private URI uri;
protected InterceptingClientHttpRequest(ClientHttpRequestFactory requestFactory,
List<ClientHttpRequestInterceptor> interceptors, URI uri, HttpMethod method) {
this.requestFactory = requestFactory;
this.interceptors = interceptors;
this.method = method;
this.uri = uri;
}
@Override
public HttpMethod getMethod() {
return this.method;
}
@Override
public String getMethodValue() {
return this.method.name();
}
@Override
public URI getURI() {
return this.uri;
}
@Override
protected final ClientHttpResponse executeInternal(HttpHeaders headers, byte[] bufferedOutput) throws IOException {
InterceptingRequestExecution requestExecution = new InterceptingRequestExecution();
return requestExecution.execute(this, bufferedOutput);
}
private class InterceptingRequestExecution implements ClientHttpRequestExecution {
private final Iterator<ClientHttpRequestInterceptor> iterator;
public InterceptingRequestExecution() {
this.iterator = interceptors.iterator();
}
@Override
public ClientHttpResponse execute(HttpRequest request, byte[] body) throws IOException {
if (this.iterator.hasNext()) {
ClientHttpRequestInterceptor nextInterceptor = this.iterator.next();
return nextInterceptor.intercept(request, body, this);
}
else {
HttpMethod method = request.getMethod();
Assert.state(method != null, "No standard HTTP method");
ClientHttpRequest delegate = requestFactory.createRequest(request.getURI(), method);
request.getHeaders().forEach((key, value) -> delegate.getHeaders().addAll(key, value));
if (body.length > 0) {
if (delegate instanceof StreamingHttpOutputMessage) {
StreamingHttpOutputMessage streamingOutputMessage = (StreamingHttpOutputMessage) delegate;
streamingOutputMessage.setBody(outputStream -> StreamUtils.copy(body, outputStream));
}
else {
StreamUtils.copy(body, delegate.getBody());
}
}
return delegate.execute();
}
}
}
}
InterceptingClientHttpRequest的execute会执行executeInternel方法，最后调用
InterceptingRequestExecution.execute
InterceptingRequestExecution.execute这个方法先会调用各种拦截器进行处理，处理完后，再会由拦截器重新调用这个对象的execute方法，做成责任链模式。最后调用缺省的HTTP代理请求工厂生成代理对象真正发起HTTP请求。
目前的拦截器就是从注册中心获取实例地址，替换URL.
4.接着进行LoadBalancerInterceptor.interropt方法。
public class LoadBalancerInterceptor implements ClientHttpRequestInterceptor {
private LoadBalancerClient loadBalancer;
private LoadBalancerRequestFactory requestFactory;
public LoadBalancerInterceptor(LoadBalancerClient loadBalancer, LoadBalancerRequestFactory requestFactory) {
this.loadBalancer = loadBalancer;
this.requestFactory = requestFactory;
}
public LoadBalancerInterceptor(LoadBalancerClient loadBalancer) {
// for backwards compatibility
this(loadBalancer, new LoadBalancerRequestFactory(loadBalancer));
}
@Override
public ClientHttpResponse intercept(final HttpRequest request, final byte[] body,
final ClientHttpRequestExecution execution) throws IOException {
final URI originalUri = request.getURI();
String serviceName = originalUri.getHost();
return this.loadBalancer.execute(serviceName, requestFactory.createRequest(request, body, execution));
}
}5.这里的loadBalancer就是RibbonLoadBalancerClient，所以调用这个进行URL替换。
public class RibbonLoadBalancerClient implements LoadBalancerClient {
private SpringClientFactory clientFactory;
public RibbonLoadBalancerClient(SpringClientFactory clientFactory) {
this.clientFactory = clientFactory;
}
@Override
public URI reconstructURI(ServiceInstance instance, URI original) {
Assert.notNull(instance, "instance can not be null");
String serviceId = instance.getServiceId();
RibbonLoadBalancerContext context = this.clientFactory
.getLoadBalancerContext(serviceId);
URI uri;
Server server;
if (instance instanceof RibbonServer) {
RibbonServer ribbonServer = (RibbonServer) instance;
server = ribbonServer.getServer();
uri = updateToSecureConnectionIfNeeded(original, ribbonServer);
} else {
server = new Server(instance.getScheme(), instance.getHost(), instance.getPort());
IClientConfig clientConfig = clientFactory.getClientConfig(serviceId);
ServerIntrospector serverIntrospector = serverIntrospector(serviceId);
uri = updateToSecureConnectionIfNeeded(original, clientConfig,
serverIntrospector, server);
}
return context.reconstructURIWithServer(server, uri);
}
@Override
public ServiceInstance choose(String serviceId) {
Server server = getServer(serviceId);
if (server == null) {
return null;
}
return new RibbonServer(serviceId, server, isSecure(server, serviceId),
serverIntrospector(serviceId).getMetadata(server));
}
@Override
public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
Server server = getServer(loadBalancer);
if (server == null) {
throw new IllegalStateException("No instances available for " + serviceId);
}
RibbonServer ribbonServer = new RibbonServer(serviceId, server, isSecure(server,
serviceId), serverIntrospector(serviceId).getMetadata(server));
return execute(serviceId, ribbonServer, request);
}6.接着调用RibbonLoadBalancerClient.getLoadBalancer获取负载均衡器。
7.SpringClientFactory.getLoadBalancer
return getInstance(name, ILoadBalancer.class);这个会去容器工厂自动创建获取ILoadBalancer类。
8.ribbonLoadBalancingHttpClient为实现类。
package org.springframework.cloud.netflix.ribbon.apache;
/**
* @author Spencer Gibb
*/
@Configuration
@ConditionalOnClass(name = "org.apache.http.client.HttpClient")
@ConditionalOnProperty(name = "ribbon.httpclient.enabled", matchIfMissing = true)
public class HttpClientRibbonConfiguration {
@Bean
@ConditionalOnMissingBean(AbstractLoadBalancerAwareClient.class)
@ConditionalOnMissingClass(value = "org.springframework.retry.support.RetryTemplate")
public RibbonLoadBalancingHttpClient ribbonLoadBalancingHttpClient(
IClientConfig config, ServerIntrospector serverIntrospector,
ILoadBalancer loadBalancer, RetryHandler retryHandler, CloseableHttpClient httpClient) {
RibbonLoadBalancingHttpClient client = new RibbonLoadBalancingHttpClient(httpClient, config, serverIntrospector);
client.setLoadBalancer(loadBalancer);
client.setRetryHandler(retryHandler);
Monitors.registerObject("Client_" + this.name, client);
return client;
}9.这个依赖于ribbonLoadBalancer，实际为这个类ZoneAwareLoadBalancer
package org.springframework.cloud.netflix.ribbon;
/**
* @author Dave Syer
* @author Tim Ysewyn
*/
@SuppressWarnings("deprecation")
@Configuration
@EnableConfigurationProperties
//Order is important here, last should be the default, first should be optional
// see https://github.com/spring-cloud/spring-cloud-netflix/issues/2086#issuecomment-316281653
@Import({HttpClientConfiguration.class, OkHttpRibbonConfiguration.class, RestClientRibbonConfiguration.class, HttpClientRibbonConfiguration.class})
public class RibbonClientConfiguration {
@Bean
@ConditionalOnMissingBean
public ILoadBalancer ribbonLoadBalancer(IClientConfig config,
ServerList<Server> serverList, ServerListFilter<Server> serverListFilter,
IRule rule, IPing ping, ServerListUpdater serverListUpdater) {
if (this.propertiesFactory.isSet(ILoadBalancer.class, name)) {
return this.propertiesFactory.get(ILoadBalancer.class, config, name);
}
return new ZoneAwareLoadBalancer<>(config, rule, ping, serverList,
serverListFilter, serverListUpdater);
}10.上面那个类又依赖于IRULE，所以最后创建 ribbonRule，实现类为
ZoneAvoidanceRule
11.创建完RULE后，创建loadBalance
12.创建ribbonLoadBalancer
13.我们再回到第5步， @Override
public <T> T execute(String serviceId, LoadBalancerRequest<T> request) throws IOException {
ILoadBalancer loadBalancer = getLoadBalancer(serviceId);
Server server = getServer(loadBalancer);，开始获取server
14.选择好server后开始执行。
15.回到LoadBalancerRequestFactory.apply
16.又回到InterceptingRequestExecution.execute
17.接下来开始替换URL
18。RibbonLoadBalancerClient.reconstructURI
19.
LoadBalancerContext.reconstructURIWithServer
20.url替换完毕，调用默认的HTTP代理对象发起请求，返回
21 请求结束，处理消息体转换，返回数据。
21.请求完毕。