1.简介

微服务架构中使用 OpenFeign 进行服务调用， OpenFeign 提供了一种简洁的方式来定义和处理服 务间的调用。 OpenFeign 作为一个声明式的、模块化的 HTTP 客户端，通过 「接口」 的定义和 「注解」 的使用，简化了微服务之间的通信调用。

 2.案例openfeign

创建alibaba-user-provider-8080

启动类添加注解 @EnableDiscoveryClient

 编写配置文件application.yml

server:
    port: 8080
spring:
    application:
        name: alibaba-user-provider-8080 #服务名
    cloud:
        nacos:
            discovery:
                server-addr: 127.0.0.1:3333 #注册服务
    datasource:
        url: jdbc:mysql://127.0.0.1:3307/hz_security?useUnicode=true&characterEncoding=utf-8
    driver-class-name: com.mysql.jdbc.Driver
    password: root
    username: root
mybatis-plus:
    type-aliases-package: com.hz.pojo
    configuration:
        log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
        map-underscore-to-camel-case: true

 编写dao接口（使用mybatisplus）

 编写serviceAP

 创建alibaba-user-consumer-8090

 编写配置文件

server:
    port: 8090
spring:
    application:
        name: alibaba-user-consumer-8090 #服务名
    cloud:
        nacos:
            discovery:
                server-addr: 127.0.0.1:3333
    datasource:
    url: jdbc:mysql://127.0.0.1:3307/hz_security?useUnicode=true&characterEncoding=utf-8
    driver-class-name: com.mysql.jdbc.Driver
    password: root
    username: root
mybatis-plus:
    type-aliases-package: com.hz.pojo
    configuration:
        log-impl: org.apache.ibatis.logging.stdout.StdOutImpl
        map-underscore-to-camel-case: true

 创建controller进行测试

 公共jar包

<?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>2.1.17.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.hz</groupId>
    <artifactId>cloud-alibaba-demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>cloud-alibaba-demo</name>



    <packaging>pom</packaging>


    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud-alibaba-version>2.1.3.RELEASE</spring-cloud-alibabaversion>
    </properties>

         <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
            <version>2.2.9.RELEASE</version>
        </dependency>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
        <!--引入nacos-->
        <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacosdiscovery</artifactId>
            <version>${spring-cloud-alibaba-version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
            <version>${spring-cloud-alibaba-version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-loadbalancer</artifactId>
        </dependency>
        <!--json-->
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-core</artifactId>
            <version>2.9.9</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-annotations</artifactId>
            <version>2.9.9</version>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.9.9</version>
        </dependency>
        <!--开启Spring Cloud 应用程序启动时加载bootstrap配置文件-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-bootstrap</artifactId>
            <version>3.1.4</version>
        </dependency>

 添加前缀

使用@FeignClient下path属性

hystrix 熔断降级：

使用 fallback 进行服务降级

在配置文件中开启服务降级：

feign:

        hystrix:

                enabled: true

 不能用的的话换下面的

 

feign:        #开启熔断处理
  circuitbreaker:
    enabled: true

 编写serviceimpl

@Component
public class SysUserServiceImpl implements SysUserService {
@Override
    public ResultJSON findUserById(Integer id) {
        return ResultJSON.error("系统异常。。。。");
    }
}

@FeignClient(name = "alibaba-user-provider",path = "user",fallback =SysUserServiceImpl.class)

3.ribbon负载均衡Ribbon（负载均衡）注意：2021版本已经不支持 ribbon

服务名必须一致

 也可在consumer中配置策略

demo-provider: #provider服务名称
ribbon:
NFLoadBalancerRuleClassName:
com.netflix.loadbalancer.WeightedResponseTimeRule
默认为轮询策略
com.netflix.loadbalancer.RandomRule 随机分配策略
com.netflix.loadbalancer.WeightedResponseTimeRule 根据响应时间长短分配权重

4. loadbalancer负载均衡

 在consumer中引入jar文件

<!--客户端负载均衡loadbalancer-->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>

 在config包中添加配置类RandomLoadBalancerConfig，实现随机策略

ppublic class RandomLoadBalancerConfig {
    @Bean
    ReactorLoadBalancer<ServiceInstance> randomLoadBalancer(
            Environment environment, LoadBalancerClientFactory
            loadBalancerClientFactory) {
        String name =
                environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
        return new RandomLoadBalancer(loadBalancerClientFactory
                .getLazyProvider(name, ServiceInstanceListSupplier.class),
                name);
    }
}

@FeignClient(name = "bill-provider",path = "bill")
@LoadBalancerClient(name = "bill-provider",configuration =RandomLoadBalancerConfig.class)
public interface BillServive {

    @GetMapping("/find")
    public ResultAJAX findBillById(@RequestParam("id") Integer id);
}