第一章 Spring Cloud简介

Spring Cloud是Spring提供的微服务框架，由下面几个部分组成。

• 注册中心
• 配置中心
• 服务链路追踪
• 负载均衡
• 服务容错
• 服务网关
• 服务发布与回滚
• 服务动态伸缩、容器化

下面我们来搭建一个简单的Spring Cloud项目。

第二章 Eureka

Eureka是一个用于服务注册和发现的组件，也就是上面说的注册中心的部分。

Eureka基本机构主要包括以下3个角色。

• Eureka Server：服务注册中心，提供服务注册和发现功能。
• Provider Service：服务提供者。
• Consumer Service：服务消费者。

首先推荐使用Spring Initializr创建注册中心，Spring Boot的版本我们用2.4.9

 EurekaApplication中添加注解作为Eureka服务器

@SpringBootApplication
@EnableEurekaServer  //启动Eureka服务器
public class EurekaApplication {

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

}

application.yml配置相关信息

server:
  port: 9004
spring:
  application:
    name: eureka-server
eureka:
  client:
    service-url:
      # eureka 服务地址，如果是集群的话；需要指定其它集群eureka地址
      defaultZone: http://127.0.0.1:9004/eureka
    # 不注册自己
    register-with-eureka: false
    # 不拉取服务
    fetch-registry: false

接下来创建同样两个订单和支付项目，注册到Eureka中，订单调用支付服务

• 支付服务

pom添加依赖

<!--eureka-client-->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

PaymentApplication添加注解

@SpringBootApplication
@EnableDiscoveryClient  //Eureka Client，用这个以后换成nacos也不用变了
public class PaymentApplication {

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

}

application.yml配置相关信息

server:
  port: 9001
spring:
  application:
    name: cloud-payment-service
eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:9004/eureka
    register-with-eureka: true
    fetch-registry: true

PaymentController

@RestController
@RequestMapping("/payment")
public class PaymentController {

    @GetMapping("/{id}")
    public ResponseEntity<Payment> payment(@PathVariable("id") Integer id) {
        Payment payment = new Payment(id,"支付成功");
        return ResponseEntity.ok(payment);
    }
}

• 订单服务

pom添加依赖

<!--eureka-client-->
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
</dependency>

OrderApplication添加注解

@SpringBootApplication
@EnableDiscoveryClient
public class OrderApplication {

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

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

}

application.yml配置相关信息

server:
  port: 9002
spring:
  application:
    name: cloud-order-service
eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:9004/eureka

OrderController

@RestController
@RequestMapping("/order")
public class OrderController {

    @Autowired
    private RestTemplate restTemplate;

    @Autowired
    private DiscoveryClient discoveryClient;

    @GetMapping("/payment/{id}")
    public ResponseEntity<Payment> getPaymentById(@PathVariable("id") Integer id) {
//        String url = "http://localhost:9001/payment/" + id;
        //1.通过discoveryClient输入服务名获得注册列表
        List<ServiceInstance> serviceInstances = discoveryClient.getInstances("CLOUD-PAYMENT-SERVICE");
        //2.获得第一条
        ServiceInstance serviceInstance = serviceInstances.get(0);
        String url = "http://" + serviceInstance.getHost() + ":" + serviceInstance.getPort() + "/payment/" + id;
        Payment payment = restTemplate.getForObject(url, Payment.class);
        return ResponseEntity.ok(payment);
    }
}

第三章 Spring Cloud OpenFeign

Feign是一个声明式的HTTP客户端组件，它旨在是编写Http客户端变得更加容易。OpenFeign添加了对于Spring MVC注解的支持，同时集成了Spring Cloud LoadBalancer和Spring Cloud CircuitBreaker，在使用Feign时，提供负载均衡和熔断降级的功能。

在订单工程工程的pom.xml中添加如下依赖

<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

OrderApplication中开启OpenFeign

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients  //开启OpenFeign
public class OrderApplication {

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

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

}

创建接口

@FeignClient(value = "cloud-payment-service")  //调用的服务
public interface PaymentClient {

    @GetMapping("/payment/{id}")
    public Payment payment(@PathVariable("id") Integer id);
}

OrderController

@Autowired
private PaymentClient paymentClient;

@GetMapping("/feign/payment/{id}")
public ResponseEntity<Payment> getPaymentByFeign(@PathVariable("id") Integer id) {
    Payment payment = paymentClient.payment(id);
    return ResponseEntity.ok(payment);
}

第四章 微服务网关Spring Cloud Gateway

SpringCloud Gateway 作为 Spring Cloud 生态系统中的网关，目标是替代 Zuul，SpringCloud Gateway是基于WebFlux框架实现的，而WebFlux框架底层则使用了高性能的Reactor模式通信框架Netty。

同样创建网关工程

 GatewayApplication中开启网关功能

@SpringBootApplication
@EnableDiscoveryClient
public class GatewayApplication {

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

}

application.yml中完成配置

server:
  port: 9005
spring:
  application:
    name: api-gateway
  #配置路由
  cloud:
    gateway:
      routes:
        - id: service1
          uri: lb://cloud-payment-service  #使用LoadBalancer负载均衡路由
          predicates:
              - Path=/payment/{sagment}  #或者/payment/**
eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:9004/eureka