SpringCloud生产消费者
生产者与消费者
上一篇文章介绍了Euarka的搭建，SpringCloud服务注册中心
本篇文章，我们搭建俩个服务，生产者服务与消费者服务。
本文就以电商系统为例：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
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：
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> T getForObject(String url, Class<T> responseType, Object... uriVariables) throws RestClientException {
RequestCallback requestCallback = acceptHeaderRequestCallback(responseType);
HttpMessageConverterExtractor<T> responseExtractor =
new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger);
return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
}
@Override
@Nullable
public <T> T getForObject(String url, Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException {
RequestCallback requestCallback = acceptHeaderRequestCallback(responseType);
HttpMessageConverterExtractor<T> responseExtractor =
new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger);
return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
}
@Override
@Nullable
public <T> T getForObject(URI url, Class<T> responseType) throws RestClientException {
RequestCallback requestCallback = acceptHeaderRequestCallback(responseType);
HttpMessageConverterExtractor<T> responseExtractor =
new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger);
return execute(url, HttpMethod.GET, requestCallback, responseExtractor);
}
@Override
public <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Object... uriVariables)
throws RestClientException {
RequestCallback requestCallback = acceptHeaderRequestCallback(responseType);
ResponseExtractor<ResponseEntity<T>> responseExtractor = responseEntityExtractor(responseType);
return nonNull(execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables));
}
@Override
public <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Map<String, ?> uriVariables)
throws RestClientException {
RequestCallback requestCallback = acceptHeaderRequestCallback(responseType);
ResponseExtractor<ResponseEntity<T>> responseExtractor = responseEntityExtractor(responseType);
return nonNull(execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables));
}
@Override
public <T> ResponseEntity<T> getForEntity(URI url, Class<T> responseType) throws RestClientException {
RequestCallback requestCallback = acceptHeaderRequestCallback(responseType);
ResponseExtractor<ResponseEntity<T>> 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> T postForObject(String url, @Nullable Object request, Class<T> responseType,
Object... uriVariables) throws RestClientException {
RequestCallback requestCallback = httpEntityCallback(request, responseType);
HttpMessageConverterExtractor<T> responseExtractor =
new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger);
return execute(url, HttpMethod.POST, requestCallback, responseExtractor, uriVariables);
}
@Override
@Nullable
public <T> T postForObject(String url, @Nullable Object request, Class<T> responseType,
Map<String, ?> uriVariables) throws RestClientException {
RequestCallback requestCallback = httpEntityCallback(request, responseType);
HttpMessageConverterExtractor<T> responseExtractor =
new HttpMessageConverterExtractor<>(responseType, getMessageConverters(), logger);
return execute(url, HttpMethod.POST, requestCallback, responseExtractor, uriVariables);
}
@Override
@Nullable
public <T> T postForObject(URI url, @Nullable Object request, Class<T> responseType)
throws RestClientException {
RequestCallback requestCallback = httpEntityCallback(request, responseType);
HttpMessageConverterExtractor<T> responseExtractor =
new HttpMessageConverterExtractor<>(responseType, getMessageConverters());
return execute(url, HttpMethod.POST, requestCallback, responseExtractor);
}
@Override
public <T> ResponseEntity<T> postForEntity(String url, @Nullable Object request,
Class<T> responseType, Object... uriVariables) throws RestClientException {
RequestCallback requestCallback = httpEntityCallback(request, responseType);
ResponseExtractor<ResponseEntity<T>> responseExtractor = responseEntityExtractor(responseType);
return nonNull(execute(url, HttpMethod.POST, requestCallback, responseExtractor, uriVariables));
}
@Override
public <T> ResponseEntity<T> postForEntity(String url, @Nullable Object request,
Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException {
RequestCallback requestCallback = httpEntityCallback(request, responseType);
ResponseExtractor<ResponseEntity<T>> responseExtractor = responseEntityExtractor(responseType);
return nonNull(execute(url, HttpMethod.POST, requestCallback, responseExtractor, uriVariables));
}
@Override
public <T> ResponseEntity<T> postForEntity(URI url, @Nullable Object request, Class<T> responseType)
throws RestClientException {
RequestCallback requestCallback = httpEntityCallback(request, responseType);
ResponseExtractor<ResponseEntity<T>> responseExtractor = responseEntityExtractor(responseType);
return nonNull(execute(url, HttpMethod.POST, requestCallback, responseExtractor));
}
接下来，我们启动，服务消费者，
此时访问我们的eureka服务，
已经有俩个服务注册上来了，如下：
最后我们来验证一下，服务消费者是否能调用到服务提供者，
在浏览器输出http://localhost:8082/info
根据返回的信息，确认服务调用成功。
小结
以上就是我们基于eureka的服务注册发现机制，实现的服务之间的相互调用。
当然，这里边还有很多的细节需要讨论，后续的文章，继续和大家讨论。
