SpringCloud之服务生产者与消费者

﹏ヽ暗。殇╰゛Y 2023-10-06 09:21 51阅读 0赞

### 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-clien`

> 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 #####

![format_png][]

--------------------

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：

![format_png 1][]

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：

![format_png 2][]

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`

![format_png 3][]

根据返回的信息，确认服务调用成功。

总结：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。

如有收获请关注微信公众号！！！

![微信公众号][format_png 4]

[format_png]: https://imgconvert.csdnimg.cn/aHR0cHM6Ly9jZG4uanNkZWxpdnIubmV0L2doL3RyaXVtcGh4eC9teS1pbWFnZXMtaG9zdC9pbWcvMjAyMDA1MjIyMjI4MjUucG5n?x-oss-process=image/format,png
[format_png 1]: https://imgconvert.csdnimg.cn/aHR0cHM6Ly9jZG4uanNkZWxpdnIubmV0L2doL3RyaXVtcGh4eC9teS1pbWFnZXMtaG9zdC9pbWcvMjAyMDA1MjIyMjQ3MjkucG5n?x-oss-process=image/format,png
[format_png 2]: https://imgconvert.csdnimg.cn/aHR0cHM6Ly9jZG4uanNkZWxpdnIubmV0L2doL3RyaXVtcGh4eC9teS1pbWFnZXMtaG9zdC9pbWcvMjAyMDA1MjIyMzEzMDMucG5n?x-oss-process=image/format,png
[format_png 3]: https://imgconvert.csdnimg.cn/aHR0cHM6Ly9jZG4uanNkZWxpdnIubmV0L2doL3RyaXVtcGh4eC9teS1pbWFnZXMtaG9zdC9pbWcvMjAyMDA1MjIyMzE5NTMucG5n?x-oss-process=image/format,png
[format_png 4]: https://imgconvert.csdnimg.cn/aHR0cHM6Ly9jZG4uanNkZWxpdnIubmV0L2doL3RyaXVtcGh4eC9teS1pbWFnZXMtaG9zdC9pbWcvJUU1JTg1JUFDJUU0JUJDJTk3JUU1JThGJUI3MS5qcGVn?x-oss-process=image/format,png