SpringMvc接口中转设计（策略+模板方法）

一、前言

　　最近带着两个兄弟做支付宝小程序后端相关的开发，小程序首页涉及到很多查询的服务。小程序后端服务在我司属于互联网域，相关的查询服务已经在核心域存在了，查询这块所要做的工作就是做接口中转。参考了微信小程序的代码，发现他们要么新写一个接口调用，要么新写一个接口包裹多个接口调用。这种方式不容易扩展。由于开发周期比较理想，所以决定设计一个接口中转器。

二、接口中转器整体设计

三、接口中转器核心Bean

@Bean
public SimpleUrlHandlerMapping directUrlHandlerMapping(@Autowired RequestMappingHandlerAdapter handlerAdapter, ObjectProvider<List<IDirectUrlProcessor>> directUrlProcessorsProvider) {List<IDirectUrlProcessor> directUrlProcessors = directUrlProcessorsProvider.getIfAvailable();Assert.notEmpty(directUrlProcessors, "接口直达解析器（IDirectUrlProcessor）列表不能为空！！！");SimpleUrlHandlerMapping mapping = new SimpleUrlHandlerMapping();Map<String, Controller> urlMappings = Maps.newHashMap();urlMappings.put("/alipay-applet/direct/**", new AbstractController() {@Overrideprotected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response) throws Exception {for (IDirectUrlProcessor directUrlProcessor : directUrlProcessors) {if (directUrlProcessor.support(request)) {String accept = request.getHeader("Accept");request.setAttribute(PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE, Sets.newHashSet(MediaType.APPLICATION_JSON_UTF8));if (StringUtils.isNotBlank(accept) && !accept.contains(MediaType.ALL_VALUE)) {request.setAttribute(PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE, Sets.newHashSet(Arrays.stream(accept.split(",")).map(value -> MediaType.parseMediaType(value.trim())).toArray(size -> new MediaType[size])));}HandlerMethod handlerMethod = new HandlerMethod(directUrlProcessor, ReflectionUtils.findMethod(IDirectUrlProcessor.class, "handle", HttpServletRequest.class));return handlerAdapter.handle(request, response, handlerMethod);}}throw new RuntimeException("未找到具体的接口直达处理器...");}});mapping.setUrlMap(urlMappings);mapping.setOrder(Ordered.HIGHEST_PRECEDENCE + 1);return mapping;
}

　　关于核心Bean的示意如下。

使用SimpleUrlHandlerMapping 来过滤请求路径中包含"/alipay-applet/direct/**"的请求，认为这样的请求需要做接口中转。
针对中转的请求使用一个Controller进行处理，即AbstractController的一个实例，并重写其handleRequestInternal。
对于不同的中转请求找到对应的中转处理器，然后创建相应的HandlerMethod ，再借助SpringMvc的RequestMappingHandlerAdapter调用具体中转处理器接口以及返回值的处理。

　　为什么要使用RequestMappingHandlerAdapter？因为中转处理器的返回值类型统一为ReponseEntity<String>，想借助RequestMappingHandlerAdapter中的HandlerMethodReturnValueHandler来处理返回结果。

request.setAttribute(PRODUCIBLE_MEDIA_TYPES_ATTRIBUTE, Sets.newHashSet(MediaType.APPLICATION_JSON_UTF8));

　　为什么会有这段代码？这是HandlerMethodReturnValueHandler调用的MessageConverter需要的，代码如下。

　　我手动设置的原因是因为RequestMappingHandlerAdapter是和RequestMappingHandlerMapping配合使用的，RequestMappingHandlerMapping会在request的attribute中设置RequestMappingInfo.producesCondition.getProducibleMediaTypes()这个值。具体参考代码如下。

org.springframework.web.servlet.mvc.method.RequestMappingInfoHandlerMapping#handleMatch
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping#createRequestMappingInfo

四、请求转发RestTempate配置

@Bean
public RestTemplate directRestTemplate() throws Exception {try {RestTemplate restTemplate = new RestTemplate(clientHttpRequestFactory());restTemplate.setErrorHandler(new DefaultResponseErrorHandler() {@Overridepublic void handleError(ClientHttpResponse response) throws IOException {throw new RestClientResponseException(response.getStatusCode().value() + " " + response.getStatusText(),response.getStatusCode().value(), response.getStatusText(), response.getHeaders(), getResponseBody(response), getCharset(response));}protected byte[] getResponseBody(ClientHttpResponse response) {try {InputStream responseBody = response.getBody();if (responseBody != null) {return FileCopyUtils.copyToByteArray(responseBody);}} catch (IOException ex) {// ignore
                }return new byte[0];}protected Charset getCharset(ClientHttpResponse response) {HttpHeaders headers = response.getHeaders();MediaType contentType = headers.getContentType();return contentType != null ? contentType.getCharset() : null;}});// 修改StringHttpMessageConverter内容转换器restTemplate.getMessageConverters().set(1, new StringHttpMessageConverter(StandardCharsets.UTF_8));return restTemplate;} catch (Exception e) {throw new Exception("网络异常或请求错误.", e);}
}/*** 接受未信任的请求** @return* @throws KeyStoreException* @throws NoSuchAlgorithmException* @throws KeyManagementException*/
@Bean
public ClientHttpRequestFactory clientHttpRequestFactory()throws KeyStoreException, NoSuchAlgorithmException, KeyManagementException {HttpClientBuilder httpClientBuilder = HttpClientBuilder.create();SSLContext sslContext = new SSLContextBuilder().loadTrustMaterial(null, (arg0, arg1) -> true).build();httpClientBuilder.setSSLContext(sslContext).setMaxConnTotal(MAX_CONNECTION_TOTAL).setMaxConnPerRoute(ROUTE_MAX_COUNT).evictIdleConnections(CONNECTION_IDLE_TIME_OUT, TimeUnit.MILLISECONDS);httpClientBuilder.setRetryHandler(new DefaultHttpRequestRetryHandler(RETRY_COUNT, true));httpClientBuilder.setKeepAliveStrategy(new DefaultConnectionKeepAliveStrategy());CloseableHttpClient client = httpClientBuilder.build();HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory(client);clientHttpRequestFactory.setConnectTimeout(CONNECTION_TIME_OUT);clientHttpRequestFactory.setReadTimeout(READ_TIME_OUT);clientHttpRequestFactory.setConnectionRequestTimeout(CONNECTION_REQUEST_TIME_OUT);clientHttpRequestFactory.setBufferRequestBody(false);return clientHttpRequestFactory;
}

　　关于RestTemplte配置的示意如下。

设置RestTemplte统一异常处理器，统一返回RestClientResponseException。
设置RestTemplte HttpRequestFactory连接池工厂（HttpClientBuilder的build方法会创建PoolingHttpClientConnectionManager）。
设置RestTemplte StringHttpMessageConverter的编码格式为UTF-8。
设置最大连接数、路由并发数、重试次数、连接超时、数据超时、连接等待、连接空闲超时等参数。

五、接口中转处理器设计

　　考虑到针对不同类型的接口直达请求会对应不同的接口中转处理器，设计原则一定要明确（open-close）。平时也阅读spingmvc源码，很喜欢其中消息转换器和参数解析器的设计模式（策略+模板方法）。仔细想想，接口中转处理器的设计也可以借鉴一下。

　　接口中转处理器接口类

public interface IDirectUrlProcessor {/*** 接口直达策略方法* 处理接口直达请求* */ResponseEntity<String> handle(HttpServletRequest request) throws Exception;/*** 处理器是否支持当前直达请求* */boolean support(HttpServletRequest request);
}

　　接口定义了子类需要根据不同的策略实现的两个方法。

　　接口中转处理器抽象类

public abstract class AbstractIDirectUrlProcessor implements IDirectUrlProcessor {private static Logger LOGGER = LoggerFactory.getLogger(AbstractIDirectUrlProcessor.class);@Autowiredprivate RestTemplate directRestTemplate;/*** 接口直达模板方法* */protected ResponseEntity<String> handleRestfulCore(HttpServletRequest request, URI uri, String userId) throws Exception {HttpMethod method = HttpMethod.resolve(request.getMethod());Object body;if (method == HttpMethod.GET) {body = null;} else {body = new BufferedReader(new InputStreamReader(request.getInputStream())).lines().collect(Collectors.joining());// post/formif (StringUtils.isBlank((String) body)) {MultiValueMap<String, String> params = new LinkedMultiValueMap<>();if (!CollectionUtils.isEmpty(request.getParameterMap())) {request.getParameterMap().forEach((paramName, paramValues) -> Arrays.stream(paramValues).forEach(paramValue -> params.add(paramName, paramValue)));body = params;}}}HttpHeaders headers = new HttpHeaders();CollectionUtils.toIterator(request.getHeaderNames()).forEachRemaining(headerName -> CollectionUtils.toIterator(request.getHeaders(headerName)).forEachRemaining(headerValue -> headers.add(headerName, headerValue)));RequestEntity directRequest = new RequestEntity(body, headers, method, uri);try {LOGGER.info(String.format("接口直达UserId = %s, RequestEntity = %s", userId, directRequest));ResponseEntity<String> directResponse = directRestTemplate.exchange(directRequest, String.class);LOGGER.info(String.format("接口直达UserId = %s, URL = %s, ResponseEntity = %s", userId, directRequest.getUrl(), directResponse));return ResponseEntity.ok(directResponse.getBody());} catch (RestClientResponseException e) {LOGGER.error("restapi 内部异常", e);return ResponseEntity.status(e.getRawStatusCode()).body(e.getResponseBodyAsString());} catch (Exception e) {LOGGER.error("restapi 内部异常，未知错误...", e);return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR).body("restapi 内部异常，未知错误...");}}
}

　　抽象类中带有接口直达模板方法，子类可以直接调用，完成请求的转发。

　　接口中转处理器具体实现类

/*** 自助服务直达查询*/
@Component
public class SelfServiceIDirectUrlProcessor extends AbstractIDirectUrlProcessor {private static final String CONDITION_PATH = "/alipay-applet/direct";@Reference(group = "wmhcomplexmsgcenter")private IAlipayAppletUserInfoSV alipayAppletUserInfoSV;private void buildQueryAndPath(UriComponentsBuilder uriComponentsBuilder, AlipayAppletUser userInfo) {uriComponentsBuilder.path("/" + userInfo.getTelephone()).queryParam("channel", "10008").queryParam("uid", userInfo.getUserId()).queryParam("provinceid", userInfo.getProvinceCode());}public ResponseEntity<String> handle(HttpServletRequest request) throws Exception {String userId = JwtUtils.resolveUserId();AlipayAppletUser userInfo = alipayAppletUserInfoSV.queryUserInfo(userId);UriComponentsBuilder uriComponentsBuilder = UriComponentsBuilder.fromHttpUrl(AppletConstants.ISERVICE_BASEURL+ request.getServletPath().replace(CONDITION_PATH, StringUtils.EMPTY));if (StringUtils.isNotBlank(request.getQueryString())) {uriComponentsBuilder.query(request.getQueryString());}this.buildQueryAndPath(uriComponentsBuilder, userInfo);String url = uriComponentsBuilder.build().toUriString();URI uri = URI.create(url);return handleRestfulCore(request, uri, userId);}@Overridepublic boolean support(HttpServletRequest request) {return request.getServletPath().contains(CONDITION_PATH);}
}

　　接口中转处理器具体实现类需要根据请求的URL判断是否支持处理当前请求，如果中转请求中带有敏感信息（如手机号）需要特殊处理（UriComponentsBuilder 是一个不错的选择呦）。

六、总结

　　接口中转器扩展方便，只要按照如上方式根据不同类型的request实现具体的接口中转处理器就可以了。另外就是接口文档了，有了接口中转处理器，只需要改一下真实服务的接口文档就可以。比如真实服务的请求地址是http://172.17.20.92:28000/XXX/business/points/手机号信息，只需要改成http://172.17.20.92:28000/YYY/alipay-applet/direct/business/points。【手机号信息是敏感信息，需要后端从会话信息中获取】。还有，不要问我为啥要花时间设计这个东西，第一领导同意了，第二开发周期理想，第三我喜欢！！！

转载于:https://www.cnblogs.com/hujunzheng/p/10250403.html