SpringCloud 系列文章 - HelloWorld开发者社区

SpringCloud

生产者与消费者

上一篇文章我们介绍了Euarka的搭建，本篇文章，我们搭建俩个服务，生产者服务与消费者服务。

我们就以电商系统为例：服务生产者，订单查询服务order-server，服务消费者order-client

说明：order-server 服务提供查询订单信息的功能
order-client作为消费者服务，查询订单信息。

生产者服务搭建

SpringCloud 系列文章

选择我们需要的依赖,具体依赖如下：

<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>

spring-cloud-starter-netflix-eureka-client 表示该服务是一个eureka的客户端，
订单服务会注册到eureka服务端上

依赖添加完成后，我们需要在SpringBoot项目的入口类上加上@EnableDiscoveryClient注解，
表示开启服务注册到eureka服务上：

@SpringBootApplication
@EnableDiscoveryClient
public class OrderServiceApplication {

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

}

接下来，需要我们对订单服务进行必要的配置：

server:
  port: 8081

spring:
  application:
    name: order-service

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka

说明：server.prot:订单服务的端口
spring.application.name:订单服务的名称，
这个名称会注册到eureka服务上
eureka.client.service-url.defaultZone:eureka服务的地址。

经过简单的配置以后，我们启动服务，访问eureka服务,http://localhost:8761，如下图：

SpringCloud 系列文章

我们将订单服务以及注册到eureka服务上了。此事，我们提供一个订单查询的接口，模拟订单查询功能。

@RestController
@RequestMapping("query")
public class OrderQueryController {
    @Autowired
    OrderQueryService queryService;

    @RequestMapping("info")
    public String queryOrder(){
        return queryService.queryOrder();
    }
}


@Service
public class OrderQueryService {

    public String queryOrder(){
        return "订单信息查询成功";
    }
}

消费者服务搭建

只需要像搭建服务提供者一样搭建服务消费者就可以，搭建完成以后，我们使用RestTemplate来调用订单服务进行订单信息查询，具体配置及代码如下：

server:
  port: 8082

spring:
  application:
    name: order-client

eureka:
  client:
    service-url:
      defaultZone: http://localhost:8761/eureka


//提供一个RestTemplate实例
@SpringBootApplication
@EnableDiscoveryClient
public class OrderClientApplication {

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

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

//编写测试接口
@RestController
public class ClientController {
    @Autowired
    ClientService clientService;

    @RequestMapping(value = "/info",method = RequestMethod.GET)
    public String queryOrderInfo(){
        return "restTemplate访问服务提供者返回的信息:"+clientService.queryOrderInfo();
    }
}

//模拟具体查询业务逻辑
@Service
public class ClientService {

    @Autowired
    RestTemplate restTemplate;

    public String queryOrderInfo(){
        System.out.println("通过restTemplate访问服务提供者");
        return restTemplate.getForEntity("http://ORDER-SERVER/query/info",               String.class).getBody();
    }

}

RestTemplate 介绍：
是spring框架提供的可用于在应用中调用rest服务，它简化了与http服务的通信方式，统一了RESTful的标准，封装了http链接，我们只需要传入url及返回值类型即可。相较于之前常用的HttpClient，RestTemplate是一种更优雅的调用RESTful服务的方式。

源码分析

部分源码如下，可以看出，它包含了Get、Post、Put等请求，比如Get请求包含俩种方法getForObject、getForEntity,他们有什么区别呢？

从接口的签名上，可以看出一个是直接返回预期的对象，一个则是将对象包装到 ResponseEntity 封装类中
如果只关心返回结果，那么直接用 getForObject 即可
如果除了返回的实体内容之外，还需要获取返回的header等信息，则可以使用 getForEntity

@Override @Nullable public T getForObject(String url, Class responseType, Object... uriVariables) throws RestClientException { RequestCallback requestCallback = acceptHeaderRequestCallback(responseType); HttpMessageConverterExtractor responseExtractor = new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger); return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables); } @Override @Nullable public T getForObject(String url, Class responseType, Map<String, ?> uriVariables) throws RestClientException { RequestCallback requestCallback = acceptHeaderRequestCallback(responseType); HttpMessageConverterExtractor responseExtractor = new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger); return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables); } @Override @Nullable public T getForObject(URI url, Class responseType) throws RestClientException { RequestCallback requestCallback = acceptHeaderRequestCallback(responseType); HttpMessageConverterExtractor responseExtractor = new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger); return execute(url, HttpMethod.GET, requestCallback, responseExtractor); } @Override public ResponseEntity getForEntity(String url, Class responseType, Object... uriVariables) throws RestClientException { RequestCallback requestCallback = acceptHeaderRequestCallback(responseType); ResponseExtractor<ResponseEntity> responseExtractor = responseEntityExtractor(responseType); return nonNull(execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables)); } @Override public ResponseEntity getForEntity(String url, Class responseType, Map<String, ?> uriVariables) throws RestClientException { RequestCallback requestCallback = acceptHeaderRequestCallback(responseType); ResponseExtractor<ResponseEntity> responseExtractor = responseEntityExtractor(responseType); return nonNull(execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables)); } @Override public ResponseEntity getForEntity(URI url, Class responseType) throws RestClientException { RequestCallback requestCallback = acceptHeaderRequestCallback(responseType); ResponseExtractor<ResponseEntity> responseExtractor = responseEntityExtractor(responseType); return nonNull(execute(url, HttpMethod.GET, requestCallback, responseExtractor)); } // HEAD @Override public HttpHeaders headForHeaders(String url, Object... uriVariables) throws RestClientException { return nonNull(execute(url, HttpMethod.HEAD, null, headersExtractor(), uriVariables)); } @Override public HttpHeaders headForHeaders(String url, Map<String, ?> uriVariables) throws RestClientException { return nonNull(execute(url, HttpMethod.HEAD, null, headersExtractor(), uriVariables)); } @Override public HttpHeaders headForHeaders(URI url) throws RestClientException { return nonNull(execute(url, HttpMethod.HEAD, null, headersExtractor())); } // POST @Override @Nullable public URI postForLocation(String url, @Nullable Object request, Object... uriVariables) throws RestClientException { RequestCallback requestCallback = httpEntityCallback(request); HttpHeaders headers = execute(url, HttpMethod.POST, requestCallback, headersExtractor(), uriVariables); return (headers != null ? headers.getLocation() : null); } @Override @Nullable public URI postForLocation(String url, @Nullable Object request, Map<String, ?> uriVariables) throws RestClientException { RequestCallback requestCallback = httpEntityCallback(request); HttpHeaders headers = execute(url, HttpMethod.POST, requestCallback, headersExtractor(), uriVariables); return (headers != null ? headers.getLocation() : null); } @Override @Nullable public URI postForLocation(URI url, @Nullable Object request) throws RestClientException { RequestCallback requestCallback = httpEntityCallback(request); HttpHeaders headers = execute(url, HttpMethod.POST, requestCallback, headersExtractor()); return (headers != null ? headers.getLocation() : null); } @Override @Nullable public T postForObject(String url, @Nullable Object request, Class responseType, Object... uriVariables) throws RestClientException { RequestCallback requestCallback = httpEntityCallback(request, responseType); HttpMessageConverterExtractor responseExtractor = new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger); return execute(url, HttpMethod.POST, requestCallback, responseExtractor, uriVariables); } @Override @Nullable public T postForObject(String url, @Nullable Object request, Class responseType, Map<String, ?> uriVariables) throws RestClientException { RequestCallback requestCallback = httpEntityCallback(request, responseType); HttpMessageConverterExtractor responseExtractor = new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger); return execute(url, HttpMethod.POST, requestCallback, responseExtractor, uriVariables); } @Override @Nullable public T postForObject(URI url, @Nullable Object request, Class responseType) throws RestClientException { RequestCallback requestCallback = httpEntityCallback(request, responseType); HttpMessageConverterExtractor responseExtractor = new HttpMessageConverterExtractor<>(responseType, getMessageConverters()); return execute(url, HttpMethod.POST, requestCallback, responseExtractor); } @Override public ResponseEntity postForEntity(String url, @Nullable Object request, Class responseType, Object... uriVariables) throws RestClientException { RequestCallback requestCallback = httpEntityCallback(request, responseType); ResponseExtractor<ResponseEntity> responseExtractor = responseEntityExtractor(responseType); return nonNull(execute(url, HttpMethod.POST, requestCallback, responseExtractor, uriVariables)); } @Override public ResponseEntity postForEntity(String url, @Nullable Object request, Class responseType, Map<String, ?> uriVariables) throws RestClientException { RequestCallback requestCallback = httpEntityCallback(request, responseType); ResponseExtractor<ResponseEntity> responseExtractor = responseEntityExtractor(responseType); return nonNull(execute(url, HttpMethod.POST, requestCallback, responseExtractor, uriVariables)); } @Override public ResponseEntity postForEntity(URI url, @Nullable Object request, Class responseType) throws RestClientException { RequestCallback requestCallback = httpEntityCallback(request, responseType); ResponseExtractor<ResponseEntity> responseExtractor = responseEntityExtractor(responseType); return nonNull(execute(url, HttpMethod.POST, requestCallback, responseExtractor)); }