多服务间的调用
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上文我们把我们项目注册到服务器上了，但是在微服务中，我们会有多个服务，同时也会使用A服务调用B服务的接口。springcloud netflix这里有两种方式ribbon和feign，我们分别介绍。
1.ribbon
ribbon说白了就是使用restTemplate。上文编写了被调用方的代码，下文将编写调用方的代码。
1.修改pom文件
<?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>2.2.5.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.baocl</groupId>
<artifactId>eureka-consumer</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>eureka-consumer</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Hoxton.SR1</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.cloud</groupId>
<artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</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>
2.修改Application
然后修改EurekaConsumerApplication类，需要在新建RestTemplate的bean。
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
@SpringBootApplication
@EnableDiscoveryClient
public class EurekaConsumerApplication {
@Bean
@LoadBalanced // ribbon注解
public RestTemplate restTemplate() {
return new RestTemplate();
}
public static void main(String[] args) {
SpringApplication.run(EurekaConsumerApplication.class, args);
}
}
3.新建调用方接口DcController
新建普通接口，调用上文被调用方的服务。
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
@RestController
@RequestMapping("/eureka1")
public class DcController {
@Autowired
LoadBalancerClient loadBalancerClient;
@Autowired
RestTemplate restTemplate;
@Autowired
DiscoveryClient discoveryClient;
@GetMapping("/consumer")
public ResponseEntity<String> dc() {
//String url = "http://eureka-client/aaa/dc?dk=3001";
String url = "http://EUREKA-CLIENT/aaa/dc?dk=3001";
System.out.println(url);
// ServiceInstance serviceInstance =
// loadBalancerClient.choose("eureka-client");// 获取服务提供者信息
// // String url = "http://localhost:" + serviceInstance.getPort() + "/aaa/dc";
// System.out.println(serviceInstance.getPort() );
// System.out.println(url);
// ResponseEntity r = restTemplate.getForEntity("http://eureka-client/aaa/dc",
// String.class);
// System.out.println("r.getHeaders().getHost():"+r.getHeaders().getHost());
// System.out.println("r.getHeaders().getLocation():"+r.getHeaders().getLocation());
// System.out.println("r.getHeaders().getOrigin():"+r.getHeaders().getOrigin());
return restTemplate.getForEntity(url, String.class); // ribbon应用
}
}
有一个坑 在调用时候需要String url = “http://eureka-client/aaa/dc?dk=3001”，而不是String url =“http://localhost:2002/aaa/dc?dk=3001”，否则会报错java.lang.IllegalStateException: No instances available for localhost.
4.修改application
最后是配置文件application.yml，这里我们使用.yml文件，都是基础配置。
eureka:
client:
registery-fetch-interval-seconds: 5000
serviceUrl:
defaultZone: http://localhost:1001/eureka/
eureka-client:
ribbon:
NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule
server:
port: 3001
spring:
application:
name: eureka-consumer
输入http://localhost:3001/eureka1/consumer就可以调用到上文的client服务了，同时还可以配置负载均衡策略。在NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule 处配置。
2.feign
1.修改pom文件
<?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>2.2.5.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.baocl</groupId>
<artifactId>eureka-consumer-feign</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>eureka-consumer-feign</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>1.8</java.version>
<spring-cloud.version>Hoxton.SR1</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-eureka-client</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
<version>1.4.7.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
<exclusions>
<exclusion>
<groupId>org.junit.vintage</groupId>
<artifactId>junit-vintage-engine</artifactId>
</exclusion>
</exclusions>
</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>
版本问题一定要控制！！！！这里有一个坑 就是版本问题，有时会报错
org.springframework.beans.factory.BeanDefinitionStoreException: Failed to read candidate component class: file [F:\\workspace\\springcloud\\tse9\\eureka-consumer-feign\\target\\classes\\com\\cloud\\DcClient.class]; nested exception is org.springframework.core.annotation.AnnotationConfigurationException: Attribute value in annotation [org.springframework.cloud.netflix.feign.FeignClient] must be declared as an @AliasFor serviceId, not name.
解决办法http://www.pianshen.com/article/2239869942/
2.修改EurekaConsumerFeignApplication
首先在EurekaConsumerFeignApplication使用@EnableFeignClients中开启feign
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class EurekaConsumerFeignApplication {
public static void main(String[] args) {
SpringApplication.run(EurekaConsumerFeignApplication.class, args);
}
}
3.新建接口DcClient
新建一个接口DcClient，配置调用其他服务的名称和接口名称。（被调用方客户端的服务与接口信息）
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
@FeignClient(name = "eureka-client")
public interface DcClient {
@GetMapping("/aaa/dc?dk=3002")
String consumer();
@GetMapping("/aaa/dc?dk=3002")
String consumer2();
}
4.新建调用接口DcController
业务接口的书写，同时注入dcClient调用其他服务。
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.cloud.DcClient;
@RestController
@RequestMapping("/eureka2")
public class DcController {
@Autowired
DcClient dcClient;
@GetMapping("/consumer")
public String dc() {
return dcClient.consumer();
}
}
5.修改application.properties
下文是最基础的配置。
spring.application.name=eureka-consumer-feign
server.port=3002
eureka.client.serviceUrl.defaultZone=http://localhost:1001/eureka/
然后调用http://localhost:3002/eureka2/consumer 可以发现接口掉通了 ，在被调用方也有相应的日志。
3.ribbon和Eureka整合原理
基本流程就是 客户端从eureka中获取到缓存的服务列表，获取到目的服务的信息，然后通过自身的负载均衡策略，去调用对应的服务。
1.负载均衡策略
- BestAvailableRule 选择一个最小的并发请求的server。
- AvailabilityFilteringRule 过滤掉那些因为一直连接失败的被标记为circuit tripped的后端server，并过滤掉那些高并发的的后端server（active connections 超过配置的阈值）。
- WeightedResponseTimeRule 根据响应时间分配一个weight，响应时间越长，weight越小，被选中的可能性越低。
- RetryRule 对选定的负载均衡策略机上重试机制。
- RoundRobinRule roundRobin方式轮询选择server.。
- RandomRule 随机选择一个server。
- ZoneAvoidanceRule 复合判断server所在区域的性能和server的可用性选择server。
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