目錄一、項目案例準(zhǔn)備1.Order服務(wù)2.User服務(wù)二、Ribbon原理分析1.RibbonAutoConfiguration2.LoadBalancerAutoConfiguration總結(jié)一、項目案例準(zhǔn)備

首先我們大家案例環(huán)境，通過【RestTemplate】來實現(xiàn)服務(wù)調(diào)用，通過【Ribbon】實現(xiàn)客戶端負載均衡操作。

1.Order服務(wù)

我們的Order服務(wù)作為服務(wù)提供者。創(chuàng)建SpringBoot項目，并添加相關(guān)依賴

<?xml version='1.0' encoding='UTF-8'?><project xmlns='http://maven.apache.org/POM/4.0.0' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd'> <modelVersion>4.0.0</modelVersion> <parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.4.9</version><relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.bobo.springcloud</groupId> <artifactId>spring-cloud-order-server</artifactId> <version>0.0.1-SNAPSHOT</version> <name>spring-cloud-order-server</name> <description>Demo project for Spring Boot</description> <properties><java.version>1.8</java.version> </properties> <dependencies><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</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>Hoxton.SR10</version><type>pom</type><scope>import</scope> </dependency></dependencies> </dependencyManagement> <build><plugins> <plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId> </plugin></plugins> </build></project>

然后在屬性文件中添加相關(guān)的配置

spring.application.name=spring-cloud-order-serviceserver.port=8081

然后創(chuàng)建自定義的Controller 提供對外的服務(wù)

@RestControllerpublic class OrderController { @Value('${server.port}') private int port; @GetMapping('/orders') public String orders(){System.out.println('Order 服務(wù)端口是：'+port);return 'Order Services ..... '; }}

然后我們可以分別啟動兩個Order服務(wù)，端口分別設(shè)置為 8081和8082

2.User服務(wù)

User服務(wù)作為調(diào)用用Order服務(wù)的客戶端。也是我們要重點介紹【Ribbon】的服務(wù)。同樣創(chuàng)建一個SpringBoot項目，添加相關(guān)的依賴

<?xml version='1.0' encoding='UTF-8'?><project xmlns='http://maven.apache.org/POM/4.0.0' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd'> <modelVersion>4.0.0</modelVersion> <parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.3.9.RELEASE</version><relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.bobo.springcloud</groupId> <artifactId>spring-cloud-user-service2</artifactId> <version>0.0.1-SNAPSHOT</version> <name>spring-cloud-user-service2</name> <description>Demo project for Spring Boot</description> <properties><java.version>1.8</java.version><spring-cloud.version>Hoxton.SR10</spring-cloud.version> </properties> <dependencies><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId></dependency><dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-netflix-ribbon</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></dependencies> </dependencyManagement> <build><plugins> <plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId> </plugin></plugins> </build></project>

然后在屬性文件中配置相關(guān)信息

spring.application.name=spring-cloud-user-servicespring-cloud-order-service.ribbon.listOfServers=localhost:8081,localhost:8082

然后創(chuàng)建自定義的Controller來實現(xiàn)服務(wù)的調(diào)用

@RestControllerpublic class UserController { @Autowired public RestTemplate restTemplate; @Autowired LoadBalancerClient loadBalancerClient; @Bean @LoadBalanced public RestTemplate restTemplate(){return new RestTemplate(); } @GetMapping('/users') public String users(){ServiceInstance choose = loadBalancerClient.choose('spring-cloud-order-service');String url = String.format('http://%s:%s',choose.getHost(),choose.getPort()+'/orders');//return restTemplate.getForObject(url,String.class);return restTemplate.getForObject('http://spring-cloud-order-service/orders',String.class); }}

然后啟動User服務(wù)訪問，可以看到【Ribbon】默認通過輪詢的方式來實現(xiàn)了服務(wù)的調(diào)用

二、Ribbon原理分析

應(yīng)用比較簡單，我們主要是來分析下【Ribbon】的核心原理，先來看看自動裝配做了哪些事情。

1.RibbonAutoConfiguration

Ribbon在系統(tǒng)啟動的時候自動裝配完成的設(shè)置，我們先來看看對應(yīng)的spring.factories 中的配置信息吧

emsp; 所以我們要繼續(xù)來看【RibbonAutoConfiguration】配置類，我們貼出【RibbonAutoConfiguration】的關(guān)鍵信息

@Configuration@Conditional({RibbonAutoConfiguration.RibbonClassesConditions.class})@RibbonClients@AutoConfigureAfter( name = {'org.springframework.cloud.netflix.eureka.EurekaClientAutoConfiguration'})// RibbonAutoConfiguration配置類注入容器后會完成 LoadBalancerAutoConfiguration 和 AsyncLoadBalancerAutoConfiguration 的注入@AutoConfigureBefore({LoadBalancerAutoConfiguration.class, AsyncLoadBalancerAutoConfiguration.class})@EnableConfigurationProperties({RibbonEagerLoadProperties.class, ServerIntrospectorProperties.class})public class RibbonAutoConfiguration { /** * 如果IoC容器中不存在 LoadBalancerClient 類型的對象就注入一個 * 具體注入的類型為 RibbonLoadBalancerClient 對象 **/ @Bean @ConditionalOnMissingBean({LoadBalancerClient.class}) public LoadBalancerClient loadBalancerClient() {return new RibbonLoadBalancerClient(this.springClientFactory()); } // 省略其他代碼

通過源碼查看我們知道在SpringBoot項目啟動的時候完成了【LoadBalancerClient】對象的注入，且具體的類型為【RibbonLoadBalancerClient】，同時還會完成【LoadBalancerAutoConfiguration】這個配置類型的加載。在看【LoadBalancerAutoConfiguration】做了什么事情之前，我們先來搞清楚【@LoadBalanced】注解的作用

2.LoadBalancerAutoConfiguration

@Target({ ElementType.FIELD, ElementType.PARAMETER, ElementType.METHOD })@Retention(RetentionPolicy.RUNTIME)@Documented@Inherited@Qualifierpublic @interface LoadBalanced {}

【@LoadBalanced】本質(zhì)上就是一個【@Qualifier】注解。作用就是標(biāo)記，我們通過案例來演示說明。

定義一個簡單的【User】類

public class User { String name; public User(String name) {this.name = name; } public String getName() {return name; } public void setName(String name) {this.name = name; } @Override public String toString() {return 'User{' +'name=’' + name + ’’’ +’}’; }}

然后定義一個Java配置類,有兩個添加了【@LoadBalanced】注解，有一個沒有加。

@Configurationpublic class JavaConfig { @LoadBalanced @Bean('user1') public User user1(){return new User('user1'); } @Bean('user2') public User user2(){return new User('user2'); } @LoadBalanced @Bean('user3') public User user3(){return new User('user3'); }}

然后創(chuàng)建我們的控制器，來測試使用

@RestControllerpublic class UsersController { @LoadBalanced @Autowired List<User> list = Collections.emptyList(); @GetMapping('/querys') public String query(){return list.toString(); }}

項目結(jié)構(gòu)

啟動SpringBoot項目后我們看效果

搞清楚了【@LoadBalanced】的作用后，我們再來看看【LoadBalancerAutoConfiguration】的配置加載做了什么事情

public class LoadBalancerAutoConfiguration { /** * 1. * 獲取IoC容器中所有的被【@LoadBalanced】注解修飾的RestTemplate對象 * 這些對象保存在了一個集合中 **/@LoadBalanced@Autowired(required = false)private List<RestTemplate> restTemplates = Collections.emptyList();@Autowired(required = false)private List<LoadBalancerRequestTransformer> transformers = Collections.emptyList(); /** * 4. * 向容器中注入了 SmartInitializingSingleton 對象，并且實現(xiàn)了 SmartInitializingSingleton 接口中聲明的 * afterSingletonsInstantiated 方法，在該方法中 通過3 中的 RestTemplateCustomizer中定義的 customize 方法 * 實現(xiàn)了 RestTemplate 對象攔截器的植入 **/@Beanpublic SmartInitializingSingleton loadBalancedRestTemplateInitializerDeprecated(final ObjectProvider<List<RestTemplateCustomizer>> restTemplateCustomizers) {return () -> restTemplateCustomizers.ifAvailable(customizers -> {for (RestTemplate restTemplate : LoadBalancerAutoConfiguration.this.restTemplates) {for (RestTemplateCustomizer customizer : customizers) {customizer.customize(restTemplate);}}});}@Bean@ConditionalOnMissingBeanpublic LoadBalancerRequestFactory loadBalancerRequestFactory(LoadBalancerClient loadBalancerClient) {return new LoadBalancerRequestFactory(loadBalancerClient, this.transformers);}@Configuration(proxyBeanMethods = false)@ConditionalOnMissingClass('org.springframework.retry.support.RetryTemplate')static class LoadBalancerInterceptorConfig {/*** 2. * 創(chuàng)建了一個 LoadBalancerInterceptor 并注入到了容器中**/@Beanpublic LoadBalancerInterceptor loadBalancerInterceptor(LoadBalancerClient loadBalancerClient,LoadBalancerRequestFactory requestFactory) {return new LoadBalancerInterceptor(loadBalancerClient, requestFactory);}/*** 3. * 創(chuàng)建了一個 RestTemplateCustomizer 并注入到了容器中* 而且通過內(nèi)部類的方式定義定義了 RestTemplateCustomizer 接口中的 customize 方法的邏輯**/@Bean@ConditionalOnMissingBeanpublic RestTemplateCustomizer restTemplateCustomizer(final LoadBalancerInterceptor loadBalancerInterceptor) {return restTemplate -> {// 獲取 RestTemplate 中原有的 攔截器List<ClientHttpRequestInterceptor> list = new ArrayList<>(restTemplate.getInterceptors());// 在原有的攔截器的基礎(chǔ)上 添加了一個 LoadBalancerInterceptorlist.add(loadBalancerInterceptor);// 然后將添加有新的 攔截器的集合 設(shè)置到了 RestTemplate 對象中restTemplate.setInterceptors(list);};}} // 省略其他代碼}

通過對應(yīng)的備注大家可以搞清楚該配置類的作用是實現(xiàn)了對【RestTemplate】對象(被@LoadBalanced修飾)植入【LoadBalancerInterceptor】攔截器的功能。

總結(jié)

Ribbon系統(tǒng)時的操作

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