Spring Cloud 实战二：创建和调用服务

创建一个服务，首先得明白这个服务既是服务的提供者service又是服务的消费者client。

一、创建服务：service-user

1、项目创建：同注册中心创建过程，只是在包依赖时不同。

创建完成之后：

2、pom.xml依赖：

<?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.hx.demo</groupId>
    <artifactId>service-user</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>service-user</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.13.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>Edgware.SR3</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
        <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-eureka</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>

3、启动类注解配置：

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication
@EnableEurekaClient
public class ServiceUserApplication {

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

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4、application.yml配置：

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:9000/eureka/
server:
  port: 9001
spring:
  application:
    name: service-user

defaultZone：声明注册中心地址

name：服务名称

5、启动应用：

如图，应用已成功注入：

服务名为：SERVICE-USER

6、添加服务调用接口：

@RestController
@RequestMapping("/user/")
public class UserController {

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

    @RequestMapping("sayHello")
    public String getUser(@RequestBody String say){
        return say + " say hello! port=" + port;
    }
}

7、使用Postman调用:

结果如图，调用结果。

二、创建服务：service-user-1 再次创建服务，创建内容和以上一样。仅修改端口号。

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:9000/eureka/
server:
  port: 9002
spring:
  application:
    name: service-user

三、基于rest+ribbon创建服务：作为服务的调用者，创建步骤同上。

1、添加启动配置：RestTemplate 表明开启负载均衡

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@SpringBootApplication
@EnableEurekaClient
public class ServiceUserApplication {

    public static void main(String[] args) {
        SpringApplication.run(ServiceUserApplication.class, args);
    }
    /**
     *  向程序的ioc注入一个bean: restTemplate;并通过@LoadBalanced注解表明这个restRemplate开启负载均衡的功能。
     * @return
     */
    @Bean
    @LoadBalanced
    RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

2、创建一个接口，调用服务SERVICE-USER

@RestController
@RequestMapping("/user/")
public class UserController {

    @Autowired
    private RestTemplate restTemplate;
    @RequestMapping("sayHello")
    public String getUser(@RequestBody String say){
        ResponseEntity<String> result = restTemplate.postForEntity("http://SERVICE-USER/user/sayHello", say, String.class);
        System.out.println(result);
        return result.getBody();
    }
}

3、启动后：

可以发现，SERVICE-USER服务有两个端口，分别是9001和9002

4、通过端口9003调用

5、调用结果：很显然实现了实现了负载均衡。访问了9001和9002两端口，

四、基于Feign创建服务：作为客户端，调用服务提供者

1、pom.xml依赖：主要添加spring-cloud-starter-eureka 和spring-cloud-starter-feign两个依赖包

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.hx.demo</groupId>
    <artifactId>client-1</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>service-user</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.13.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>Edgware.SR3</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
        </dependency>
        <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-eureka</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</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、application.yml配置：

eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:9000/eureka/
server:
  port: 9004
spring:
  application:
    name: client-1

3、启动类配置

3.1、注解@EnableDiscoveryClient

spring cloud中discovery service有许多种实现（eureka、consul、zookeeper等等），@EnableDiscoveryClient基于spring-cloud-commons, @EnableEurekaClient基于spring-cloud-netflix。

可以这样理解：如果选用的注册中心是eureka，那么就推荐@EnableEurekaClient，如果是其他的注册中心，那么推荐使用@EnableDiscoveryClient。

3.2、@EnableFeignClients：声明开启Feign的功能

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ServiceUserApplication {

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

}

4、写一个服务调用接口@FeignClient 声明这是一个服务调用接口

@FeignClient括号内为调用服务名

细心点会发现这里调用名用的是小写，与RestTemplate 调用接口用大小有差异。其实这里大小写都可以。

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

@FeignClient("service-user")
public interface UserService {

    @RequestMapping(value = "/user/sayHello",method = RequestMethod.POST)
    String say(String say);
}

5、controller写一个对外接口，供外部调用

@RestController
@RequestMapping("/user/")
public class UserController {

    @Autowired
    private UserService userService;
    @RequestMapping("sayHello")
    public String getUser(@RequestBody String say){
        String result = userService.say(say);
        System.out.println(result);
        return result;
    }
}

6、启动项目，请求调用

7、调用结果分析：

可见Feign默认实现了负载均衡，查看源码不难发现：Feign默认集成了Ribbon，并和Eureka结合，默认实现了负载均衡的效果。

最后：github地址：https://github.com/houxi1234/demo.git