Eureka配置及三种远程跨域调用方式（简单易懂,手把手教学）

本文链接：https://blog.youkuaiyun.com/weixin_42433978/article/details/126534089

一、Eureka创建服务中心在页面展示

1.前置工作,先创建spring initializr父工程myek,父pom文件修改并添加相关依赖

<properties>
    <java.version>1.8</java.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <spring-boot.version>2.3.2.RELEASE</spring-boot.version>
    <spring-cloud.version>Hoxton.SR9</spring-cloud.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter</artifactId>
    </dependency>
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
        <exclusions>
            <exclusion>
                <groupId>org.junit.vintage</groupId>
                <artifactId>junit-vintage-engine</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
</dependencies>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-dependencies</artifactId>
            <version>${spring-boot.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>${spring-cloud.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

2.正式创建Maven子模块 myek-regserver

（1) 先在pom文件中增加依赖

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
    </dependencies>

(2)启动类上加开启Eureka服务注解

@SpringBootApplication
@EnableEurekaServer   //开启服务
public class RegServerApplication {
    public static void main(String[] args) {
        SpringApplication.run(RegServerApplication.class,args);

    }
}

(3)resources下新建 application.yml


spring:
  application:   # 应用名字，eureka 会根据它作为服务id
    name: regserver
server:
  port: 9100
eureka:
  client:
    service-url:   #  eureka server 的地址， 咱们单实例模式就写自己好了
      defaultZone: http://localhost:9100/eureka/
    register-with-eureka: false     # 不向eureka server 注册自己
    fetch-registry: false          # 不向eureka server 获取服务列表

(4)打开页面,即可看到eureka服务中心

浏览器打开输入 localhost:9100

二、创建子模块Eureka myek-myprovider---->服务提供者

1.创建服务提供者

(1)新建子module，maven 下一步,修改名字myek-myprovider---->服务提供者
pom文件加依赖

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

(2)resources下新建 application.yml

spring:
  application:
    name: myprovider
server:
  port: 9101
eureka:
  client:
    service-url:
      defaultZone: http://localhost:9100/eureka   #注册地址，到哪注册

3.启动类上加@EnableDiscoveryClient注解


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

4.controller包下新建类InitCtrl

@RestController
@RequestMapping("/myprov")
public class InitCtrl {
    @RequestMapping(value = "/hello",method = RequestMethod.GET)
    public String sayHello(){
        return "hello,world";
    }
}
----启动，浏览器输入http://localhost:9101/myprov/hello
eureka服务中心会出现MYPROVIDER

如图：

三、创建子模块Eureka myek-myconsumer---->服务调用者 (调用服务两种方式)

1.方式1：第一种httpclient 帮助理解相当于ajax-

继续新建子module，maven 下一步,修改名字myek-myconsumer---->服务调用者
（1）pom下加依赖--->
        <dependencies>
    <!--     <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>  -->先注释掉，此种方式有它就必须注册

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.2</version>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.47</version>
        </dependency>
</dependencies>

(2)resources下新建 application.yml
spring:
  application:
    name: myconsumer
server:
  port: 9102
  
  
(3)新建类com.kgc.myek.myconsumer.ConsumerApplication
      @SpringBootApplication
public class ConsumerApplication {
    public static void main(String[] args) {
        SpringApplication.run(ConsumerApplication.class,args);
    }
}

(4)新建类com.kgc.myek.myconsumer.controller.ConsumerCtrl

@RestController
@RequestMapping("/mycons")
public class ConsumerCtrl {

@RequestMapping(value = "/find",method = RequestMethod.GET)
public String say(){
    //ajax调用provideer 程序接口
    CloseableHttpClient client = HttpClientBuilder.create().build();
    //生成一个远程调用的地址
    HttpGet addr = new HttpGet("http://localhost:9101/myprov/hello");
    String infos = null;
    try {
        //向远程服务器发送消息,并获得response响应
        CloseableHttpResponse response = client.execute(addr);
        //从响应中获取远程的数据
        infos = EntityUtils.toString(response.getEntity());
    } catch (IOException e) {
        e.printStackTrace();
    } 
    //返回给用户
    return  infos+",myh";
}
}

----浏览器输入地址localhost:9102/mycons/find

2. 方式2：第二种RestTemplate

第二种：RestTemplate  ---->须熟练掌握 

（1）先写个配置类com.kgc.myek.myconsumer.config.RemoteConfiguration

@Configuration
public class RemoteConfiguration {
    @Bean
    public RestTemplate getTemplate(){
        return new RestTemplate();
    }
}


（2）修改ConsumerCtrl代码
@RestController
@RequestMapping("/mycons2")
public class ConsumerCtrl1 {

    @Autowired
    private RestTemplate template;

@GetMapping(value = "/find2")
public String sayh(){
    return template.getForObject("http://localhost:9101/myprov/hello",String.class)+",xxx";
}

}

 ---------浏览器输入地址：http://localhost:9102/mycons2/find2------     

此方法有弊端，端口号，地址等在程序中写死了，如果地址等发生变化，就会报错，除非改掉相应地方，微服中地址太多，修改方案不可行,所以必须用openfeign

正确方式3：调用远程连接，使用Openfeign远程调用

（1）添加spring-cloud-starter-openfeign依赖

修改myconsumer的pom文件,dependencies变为：
 <dependencies>
        <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>

    </dependencies>

(2) 修改yml文件

yml文件修改为
spring:
  application:
    name: myconsumer
server:
  port: 9102
eureka:
  client:
    service-url:
      defaultZone: http://localhost:9100/eureka/

(3)启动类加注解

ConsumerApplication类加@EnableFeignClients 注解：
@SpringBootApplication
@EnableFeignClients   
public class ConsumerApplication {
    public static void main(String[] args) {
        SpringApplication.run(ConsumerApplication.class,args);
    }
}

(4) 新建接口com.kgc.myek.myconsumer.remoteservice.HelloService

新建接口com.kgc.myek.myconsumer.remoteservice.HelloService
注意：consumer在调用provider时，按名字在注册中心查的是 工程名/模块名/接口名

@Component   //MYPROVIDER为工程名
@FeignClient(value = "MYPROVIDER",path = "/myprov")  //path为模块名
public interface HelloService {
//"/hello"  为接口名
    @RequestMapping(value = "/hello",method = RequestMethod.GET)
    public String sayHello();

}

注意：此处用的openfeign,意味着比如某个消费者想要调用某个服务提供者的方法，我们可以设置个接口，在注解中设置，要调用的服务的服务名，和具体的controller跳转地址，方法名和对应的url不变。

(5)在controller中注入刚创建的接口，并调用其方法

ConsumerCtrl 改为
@RestController
@RequestMapping("/mycons")
public class ConsumerCtrl {
    @Resource
    private HelloService helloService;

    @RequestMapping("/myms")
    public String says(){
        return helloService.sayHello()+",yyds";
    }
  
}

---------浏览器输入地址：localhost:9102/mycons/myms------