Spring Cloud微服务体系的组成（一）

Eureka只能绑定域名,在本地测试需要修改DNS配置文件hosts
编辑 c:/windows/system32/drivers/etc/hosts
# localhost name resolution is handled within DNS itself.
#   127.0.0.1       localhost
#   ::1             localhost
127.0.0.1 server1
127.0.0.1 server2
127.0.0.1 server3
高可用配置:
application-p8761.yml
启动项 Program arguments:--spring.profiles.active=8761
server:
  port: 8761
eureka:
  instance:
    appname: provider-service
    hostname: server1 #必须是域名
  client:
    service-url:
      defaultZone:
        http://server2:8762/eureka/,http://server3:8763/eureka/ #向其他注册中心节点注册
application-p8762.yml
启动项 Program arguments:--spring.profiles.active=8762
server:
  port: 8762
eureka:
  instance:
    appname: provider-service
    hostname: server2
  client:
    service-url:
      defaultZone:
        http://server1:8761/eureka/,http://server3:8763/eureka/ #向其他注册中心节点注册
application-p8763.yml
启动项 Program arguments:--spring.profiles.active=8763
server:
  port: 8763
eureka:
  instance:
    appname: provider-service
    hostname: server3
  client:
    service-url:
      defaultZone:
        http://server1:8761/eureka/,http://server2:8762/eureka/ #向其他注册中心节点注册
入口类增加@EnableEurekaServer
@SpringBootApplication
@EnableEurekaServer
public class HaEurekaServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(HaEurekaServerApplication.class, args);
    }
}
客户端指向所有Eureka注册中心节点
server:
  port: 80
spring:
  application:
    name: order-service
eureka:
  client:
    service-url:
      defaultZone:
        http://server1:8761/eureka/,http://server1:8762/eureka/,http://server1:8763/eureka/

图书服务
Spring Initializr
Web->Eureka Discovery Client
application.yml
spring:
  application:
    name: book-service
eureka:
  client:
    service-url:
      defaultZone:
        http://localhost:8761/eureka/
BookController
    @GetMapping("/bsn")
    public Book findBySN(String sn, HttpServletRequest request){
        /*try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }*/
        Book book = null;
        if(sn.equals("1111")){
            book = new Book("1111", "测试图书1", String.valueOf(request.getLocalPort()));
        }else if(sn.equals("2222")){
            book = new Book("2222", "测试图书2", String.valueOf(request.getLocalPort()));
        }else if(sn.equals("3333")){
            book = new Book("3333", "测试图书3", String.valueOf(request.getLocalPort()));
        }
        return book;
    }
启动两个服务,复制两个启动项,修改启动端口
Program arguments: --server.port=8000
Program arguments: --server.port=8001
![image.png](https://upload-images.jianshu.io/upload_images/15616626-85a94565554a22ff.png?imageMogr2/auto-orient/strip%7CimageView2/2/w/1240)

RestTemplate介绍
RestTemplate是Spring Cloud访问Restful API的请求对象
RestTemplate与HttpClient、OKHttp职能类似
@LoadBalanced注解
@LoadBalanced是Ribbon提供的客户端负载均衡注解
通常RestTemplate与@LoadBalanced联合使用
创建订单服务
Spring Initializr 
web->Spring Web
Spring Cloud Discovery -> Eureka Discover Client
Spring Cloud Routing -> Ribbon
确保pom.xml引入ribbon
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
        </dependency>
 appliaction.yml
spring:
  application:
    name: member-service
eureka:
  client:
    service-url:
      defaultZone:
        http://localhost:8761/eureka
入口类注入RestTemplate
@SpringBootApplication
@EnableEurekaClient
public class MemberServiceApplication {
    @Bean //注入
    @LoadBalanced //Ribbon负载均衡,默认轮询
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }
}
业务开发,服务间通信
@Controller
public class MemberController {
    @Resource
    private RestTemplate restTemplate;
    @GetMapping("/borrow")
    @ResponseBody
    public String borrow(String sn){
        /*
            RestTemplate负载均衡格式要求：
            http://微服务id/webapi地址
        */
        Book book = restTemplate.getForObject("http://book-service/bsn?sn=" + sn, Book.class);#传入参数为返回值的实体类
        return book.getName() + ":" + book.getDesc() + "图书借阅成功";
    }
}
业务实体Book与JSON属性对应即可
public class Book {
    private String sn;
    private String name;
    private String desc;
    public String getSn() {
        return sn;
    }
    public void setSn(String sn) {
        this.sn = sn;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getDesc() {
        return desc;
    }
    public void setDesc(String desc) {
        this.desc = desc;
    }
}

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
    <groupId>com.alibaba.cloud</groupId>
    <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
</dependency>

package com.example.productservice;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ProductServiceApplication {
    public static void main(String[] args) {
        SpringApplication.run(ProductServiceApplication.class, args);
    }
}