SpringCloud

转载原文： https://segmentfault.com/a/1190000015804295

服务注册中心

1.新建项目名为eureka-server的Spring Boot项目， 并添加eureka server依赖，pom.xml如下：

<?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>

    <groupId>com.beigege.cloud</groupId>
    <artifactId>eureka-server</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>eureka-server</name>
    <description>spring cloud学习</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <spring-cloud.version>Finchley.RELEASE</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </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. EurekaServerApplication 类启用Eureka Server

@SpringBootApplication
@EnableEurekaServer
public class EurekaServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(EurekaServerApplication.class, args);
    }
}

3. application.properties配置Eureka Server

server.port: 8761 #服务端口
spring.application.name: eurka-server #服务应用名称

eureka.instance.hostname: localhost
eureka.client.registerWithEureka: false  #是否将自己注册到Eureka Server，默认为true
eureka.client.fetchRegistry: false       #是否从Eureka Server获取注册信息，默认为true
eureka.client.service-url.defaultZone: http://${eureka.instance.hostname}:${server.port}/eureka/ #服务注册的URL

   registerWithEureka: false 和 fetchRegistry: false 来表明项目是一个 Eureka Server。

4.运行 EurekaServerApplication 类，启动项目，访问项目 http://localhost:8761， 即可查看当前注册中心的运行状态

服务提供者

1.新建项目名为eureka-client的Spring Boot项目，并添加euraka discovery和web依赖。

2. application.yml 设置euraka注册中心

server.port: 8762
spring.application.name: service-hi #服务之间的调用都是根据这个name   
eureka.client.service-url.defaultZone: http://localhost:8761/eureka/

3. 新建EurekaClientApplication类，提供 hi 服务

@SpringBootApplication
@EnableEurekaClient
@RestController
public class EurekaClientApplication {

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

    @Value("${server.port}")
    String port;

    @RequestMapping("/hi")
    public String home(@RequestParam(value = "name", defaultValue = "Lucy") String name) {
        return "hi " + name + ", I am from port:" + port;
    }
}

4.启动 Eureka Server 和 Eureka Client 项目，访问http://localhost:8761 ，即eureka server 的网址：

Ribbon客户端

ribbon 在客户端实现了负载均衡。

1. 现在已经启动 一个Eureka Server [8761] 和 一个Eureka Client [8762]，修改 Eureka Client 端口，再启动一个 Eureka Client 实例 [8763]，相当于一个小的服务提供者集群，现在再访问eureka注册中心管理界面http://localhost:8761，可以看到已经注册两个service-hi实例。

2.新建一个 spring boot 工程，名称为 service-ribbon，创建过程和 eureka-client 一样，组件多选一个 Cloud Routing 下的 Ribbon，创建完成之后的 pom 文件依赖：

        <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-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

3. application.properties 配置eureka注册中心地址

server.port: 8764  
spring.application.name: service-ribbon    
eureka.client.service-url.defaultZone: http://localhost:8761/eureka/

4. 新建ServiceRibbonApplication类，向 Spring 注入一个 restTemplate bean，并添加 @LoadBalanced 注解，表明这个 restTemplate 开启负载均衡功能：

@SpringBootApplication
@EnableEurekaClient
@RestController
public class ServiceRibbonApplication { 
　　public static void main(String[] args) { 
　　　　SpringApplication.run(ServiceRibbonApplication.class, args); 
　　}
  
    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }

    @Autowired
    HelloService helloService;

    @RequestMapping(value = "/hello")
    public String hello(@RequestParam String name){
        return helloService.hello(name);
    }
}

5. 新建 HelloService类，来调用之前的 service-hi 服务的 /hi 接口，这里用服务名 SERVICE-HI 代替具体的 URL：

@Service
public class HelloService {

    @Autowired
    RestTemplate restTemplate;

    public String hello(String name) {
        return restTemplate.getForObject("http://SERVICE-HI/hi?name="+name,String.class);
    }
}

6. 启动 service-ribbon 工程，多次访问该工程的 /hello 接口，即 localhost:8764/hello?name=test：

  hi test , I am from port:8762
  hi test , I am from port:8763

Feign

整合了 Ribbon，具有负载均衡的能力，整合了Hystrix，具有熔断的能力.

1.创建一个 spring boot工程，创建过程和 eureka-client 一样，多添加一个组件 Cloud Routing 下的 Feign，项目名叫 service-feign，创建完后的 pom 文件依赖：

        <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-openfeign</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

2. application.properties 配置文件：

server.port: 8765
spring.application.name: service-feign
eureka.client.serviceUrl.defaultZone: http://localhost:8761/eureka/

3. 新建ServiceFeignApplication类

@SpringBootApplication
@EnableEurekaClient
@EnableFeignClients
public class SericeFeignApplication {

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

4.写一个 SchedualService接口，通过@ FeignClient（“服务名”），来指定调用哪个服务，@GetMapping("接口名")，来向接口发送 Get 请求：

@FeignClient(value = "service-hi")
public interface SchedualService {

    @GetMapping("/hello")
    String sayHello(@RequestParam(value = "name") String name);    
}

@RestController
public class HiController {
    
    @Autowired
    SchedualService schedualService;

    @GetMapping(value = "/hello")
    public String sayHi(@RequestParam String name) {
        return schedualService.sayHello( name );
    }
}

5.启动 service-feign，访问localhost:8765/hello?name=test 测试，下面交替显示，说明实现了负载均衡：

  hi test ,i am from port:8762 
  hi test ,i am from port:8763

断路器 - Hystrix

ribbon + Hystrix

1.在 pom 文件中加入 Hystrix 依赖：

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

2.在程序的启动类 ServiceRibbonApplication 加 @EnableHystrix 注解开启Hystrix：

@SpringBootApplication
@EnableEurekaClient
@EnableHystrix
public class ServiceRibbonApplication {
    public static void main(String[] args) {
        SpringApplication.run( ServiceRibbonApplication.class, args );
    }

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

3.添加熔断方法，改造 HelloService 类，在 hello方法上面添加 @HystrixCommand 注解，fallbackMethod 是熔断方法，当服务不可用时会执行 hiError 方法：

@Service
public class HelloService {

    @Autowired
    RestTemplate restTemplate;

    @HystrixCommand(fallbackMethod = "hiError")
    public String hello(String name) {
        return restTemplate.getForObject("http://SERVICE-HI/hi?name="+name,String.class);
    }

    public String hiError(String name) {
        return "hi,"+name+",sorry for the error!";
    }
}

4. 重启 service-ribbon，访问 localhost:8764/hi?name=test

   hi test ,i am from port:8763

5. 关闭两个 eureka-client 实例，在访问 localhost:8764/hi?name=test，浏览器显示：

   hi,test,sorry for the error!

   当服务不可用时，断路器会迅速执行熔断方法。

feign + Hystrix

1.Feign 自带断路器，在低版本的Spring Cloud之后，它没有默认打开。需要在配置文件中配置打开：

feign.hystrix.enabled: true

2.在请求接口指定熔断实现类，fallback 指定熔断实现类：

@FeignClient(value ="service-hi",fallback = SchedualServiceHiHystric.class)
public interface SchedualServiceHi {
    
    @GetMapping("/hello")
    String sayHello(@RequestParam(value = "name") String name);

}