【SpringCloud教程】2.SpringCloud 负载均衡Loadbalancer和OpenFeign

在SpringCloud第一代中是通过Ribbon负载平衡，第二代在Ribbon封装在基础上LoadBalancer。本文采用的注册中心是SpringCloud Alibaba Nacos，如果采用SpringCloud Eureka依赖可以直接改变。LoadBalancer和OpenFeign都属于SpringCloud第二代产品。

在SpringBoot项目通信可以通过以下方式实现:

代码完全相同，但端口不同，代码如下： user-api-9001

@RestController public class UserService { 
              @GetMapping("getUser")     public String getUser(){ 
                 return "terry-9001";     } } 

user-api-9002

@RestController public class UserService { 
              @GetMapping("getUser")     public String getUser(){ 
                 return "terry-9002";     } } 

pom.xml依赖

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">     <modelVersion>4.0.0</modelVersion>      <artifactId>user-consumer</artifactId>      <properties>         <maven.compiler.source>8</maven.compiler.source>         <maven.compiler.target>8</maven.compiler.target> </properties> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.3.2.RELEASE</version> </parent> <dependencies> <!-- SpringBoot web组件 --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <!-- nacos 注册中心 --> <dependency> <groupId>com.alibaba.cloud</groupId> <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId> <version>2.2.6.RELEASE</version> </dependency> </dependencies> </project> 

服务消费者依赖：

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <artifactId>user-consumer</artifactId>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.2.RELEASE</version>
    </parent>
    <dependencies>
        <!-- SpringBoot web组件 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- nacos 注册中心 -->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
            <version>2.2.6.RELEASE</version>
        </dependency>
    </dependencies>
</project>

起一个配置类，配置RestTemplate和@LoadBanlanced

import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
public class RestTemplateConfig { 
        

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

Controller配置

    
@RestController
public class UserService { 
        

    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("/restTemplateGetUser")
    public String restTemplateGetUser(){ 
        
        return restTemplate.getForObject("http://user-api/getUser", String.class);
    }
}

打开浏览器输入地址：http://localhost:8080/restTemplateGetUser 多次刷新可以看到是交替运行的。

@RestController
public class UserService { 
        

    @Autowired
    private RestTemplate restTemplate;

    @Autowired
    private LoadBalancerClient loadBalancerClient;
    
    /** * 使用 LoadBalancerClient实现负载均衡 * @return */
    @GetMapping("/loadBalancerClientGetUser")
    public String loadBalancerClientGetUser(){ 
        
        ServiceInstance choose = loadBalancerClient.choose("user-api");
        System.out.println(choose.getUri().toString());
        return restTemplate.getForObject(choose.getUri().toString() + "/getUser", String.class);
    }
}

消费者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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <artifactId>user-consumer</artifactId>

    <properties>
        <maven.compiler.source>8</maven.compiler.source>
        <maven.compiler.target>8</maven.compiler.target>
    </properties>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.2.RELEASE</version>
    </parent>
    <dependencies>
        <!-- SpringBoot web组件 -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- nacos 注册中心 -->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
            <version>2.2.6.RELEASE</version>
        </dependency>
        <!-- openfeign 客户端 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
            <version>2.2.6.RELEASE</version>
        </dependency>
    </dependencies>
</project>

启动类配置

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableFeignClients
public class App { 
        

    public static void main(String[] args) { 
        
        SpringApplication.run(App.class, args);
    }
}

openFeign配置类

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Component;
import org.springframework.web.bind.annotation.GetMapping;

@Component
// 指定服务名称
@FeignClient("user-api")
public interface UserFeign { 
        

    /** * 对应 user-api 的getUser * @return */
    @GetMapping("getUser")
    public String getUser();
}

Controller

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class UserService { 
        

    @Autowired
    private UserFeign userFeign;

    /** * 使用 openFeign实现负载均衡 * @return */
    @GetMapping("/openFeignGetUser")
    public String openFeignGetUser(){ 
        
        return userFeign.getUser();
    }
}

打开浏览器输入地址：http://localhost:8080/restTemplateGetUser 多次刷新可以看到是交替运行的。