远程调用常用有RestTemplate和Feign，底层均使用Ribbon实现负载均衡。简单样例，演示远程集群调用。
一、RestTemplate + Ribbon
访问方式：http://localhost:7903/condition/test，然后会执行以下访问：http://microservice-b/condition/self，如果microservice-b有多个节点，会按照负载均衡策略轮流访问。注意为顺利执行样例，microservice-b要实现/condition/self的mapping。
该例子无需额外添加spring-cloud-starter-netflix-ribbon依赖。
pom.xml
<?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>2.6.1</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.abcd</groupId><artifactId>SpringCloudServiceConsumer</artifactId><version>0.0.1-SNAPSHOT</version><name>SpringCloudServiceConsumer</name><description>SpringCloudServiceConsumer</description><properties><java.version>1.8</java.version><spring-cloud.version>2021.0.0</spring-cloud.version></properties><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-eureka-client</artifactId></dependency><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>--><!-- <version>1.4.5.RELEASE</version>--><!-- </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>
application.yml
server:port: 7903spring:application:name: microservice-aeureka:client:service-url:defaultZone: http://localhost:8761/eureka/ServiceA的java代码如下
Application代码@EnableDiscoveryClient
@SpringBootApplication
public class ServiceAApplication {public static void main(String[] args) {SpringApplication.run(ServiceAApplication.class, args);}@Bean@LoadBalancedpublic RestTemplate restTemplate(){return new RestTemplate();}
}
Controller代码：@RestController
@RequestMapping("condition")
public class ServiceAController {@Autowiredprivate RestTemplate restTemplate;@GetMapping("self")public String self(){return "microService A:7903";}@GetMapping("test")public String test(){System.out.println("test in service A");String test = restTemplate.getForEntity("http://microservice-b/condition/self",String.class).getBody();return "This is ribbon call from microService A to " + test;}}
二、Feign + Ribbon
引入spring-cloud-starter-openfeign，feign整合了ribbon。
访问方式：http://localhost:7900/condition/feignTest，然后会访问到microservice-a的 /condition/self接口。
pom.xml
<?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>2.6.1</version><relativePath/> <!-- lookup parent from repository --></parent><groupId>com.example</groupId><artifactId>EurekaClientSample</artifactId><version>0.0.1-SNAPSHOT</version><name>EurekaClientSample</name><description>EurekaClientSample</description><properties><java.version>1.8</java.version><spring-cloud.version>2021.0.0</spring-cloud.version></properties><dependencies><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-eureka-client</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-openfeign</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>
application.yml
server:port: 7900spring:application:name: microservice-beureka:client:service-url:defaultZone: http://localhost:8761/eureka/.java
Application代码@EnableFeignClients
@EnableEurekaClient
@SpringBootApplication
public class ServiceBApplication {public static void main(String[] args) {SpringApplication.run(ServiceBApplication.class, args);}}
Controller代码@RestController
@RequestMapping("condition")
public class ServiceBController {@GetMapping("self")public String self(){return "microService B: 7900";}@Autowiredprivate RemoteClient remoteClient;//http://localhost:7900/condition/feignTest@GetMapping("feignTest")public String feignTest(){String test = remoteClient.self();return "This is feign call from microService B to " + test;}
}FeignClient代码@FeignClient("microservice-a")
public interface RemoteClient {@GetMapping("condition/self")public String self();
}
