在spring cloud體系中，有多種手段實現注冊中心，本例中采用zookeeper作為注冊中心的角色。服務提供者向zookeeper注冊，服務消費者從zookeeper中發現服務提供者的相關信息，從而遠程調用服務提供方。

服務提供者

引入相關依賴

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.4.2.RELEASE</version>
</parent>

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-config</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
    </dependency>
    
    <!-- 熱部署工具 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
    </dependency>
</dependencies>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>Camden.SR2</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

spring cloud與zookeeper的集成主要依賴spring-cloud-starter-zookeeper-discovery模塊

定義DTO對象

public class UserDTO {
    
    private Long id;
    private String name;
    private Date birthday;
    
    /*
        省略getter,setter方法
    */
}

定義服務提供接口

@RestController
public class ComputeController {

    @Autowired
    private DiscoveryClient client;
    
    @RequestMapping(value = "/show", method = {RequestMethod.POST})
    @ResponseBody
    public UserDTO show(@RequestParam(value="id") Long id) {
        ServiceInstance instance = client.getLocalServiceInstance();
        UserDTO dto = new UserDTO();
        dto.setId(id);
        dto.setName("scott");
        dto.setBirthday(new Date());
        return dto;
    }

}

在show方法中返回了dto對象。

配置文件

application.properties

server.port=8080
spring.application.name=server

bootstrap.properties

spring.cloud.zookeeper.connectString=192.168.179.200:2181
spring.cloud.zookeeper.discovery.instanceHost=127.0.0.1
spring.cloud.zookeeper.discovery.instancePort=${server.port} 

啟動項目

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

啟動項目后可以在zookeeper中看到新增了/service節點，該節點有一個子節點server

服務消費者

引入與依賴項，這里用feign作為rest調用工具

<dependencies>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-config</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-zookeeper-discovery</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-feign</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-hystrix</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
    </dependency>
    
    <!-- 熱部署工具 -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-devtools</artifactId>
    </dependency>
</dependencies>

定義遠程調用代理對象

@Component
@FeignClient(value="server",fallback=FeignConsumerClientHystrix.class)
public interface FeignConsumerClient {
    
    @RequestMapping(method = RequestMethod.POST, value = "/show")
    public String getUser(@RequestParam(value = "id") Long id);
    
}

以POST方式發起遠程調用，調用地址根據@FeignClient中value值決定。

通過@FeignClient創建消費端代理對象。value指定服務名,該值與服務提供者的spring.application.name參數值相等，fallback指定異常處理類，異常處理類需實現本接口。

異常處理

@Component
public class FeignConsumerClientHystrix implements FeignConsumerClient{

    @Override
    public String getUser(@RequestParam("id") Long id) {
        return "error";
    }
}

所實現方法即為異常處理代碼

注入代理對象，發起遠程調用

@RestController
public class ClientController {
    
    @Autowired
    private FeignConsumerClient feignConsumerClient;

    @RequestMapping(value = "/get", method = RequestMethod.GET)
    @ResponseBody
    public String add(@RequestParam(value = "id") Long id) {
        return feignConsumerClient.getUser(id);
    }
}

配置文件

application.properties

server.port=8081
spring.application.name=client

#斷路器，斷路器跳閘后等待多長時間重試
hystrix.command.default.circuitBreaker.sleepWindowInMilliseconds=1000
#斷路器，請求發出后多長時間超時
hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=5000
#ribbon連接到服務端的超時時間
ribbon.ConnectTimeout=5000
#ribbon連接到服務端后，多長時間沒有獲取到響應的超時時間
ribbon.ReadTimeout=5000

bootstrap.properties

spring.cloud.zookeeper.connectString=192.168.179.200:2181
#不向zookeeper注冊
spring.cloud.zookeeper.discovery.register=false

服務消費者啟動項目

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
@EnableHystrix
@EnableHystrixDashboard
@EnableCircuitBreaker
public class AppStart {
    public static void main(String[] args) {
        SpringApplication.run(AppStart.class, args);
    }
}

啟動項目后瀏覽器訪問http://127.0.0.1:8081/get?id=xxx，正常情況即可看到由userDTO對象轉換得到的json字符串。

后續補充spring cloud中的異常處理方法，故障轉移，負載均衡等。