/*** Annotation for support Multi-version Restful API** @author Tony Mu(tonymu@qq.com)* @since 2017-07-07*/
@Target({ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Mapping
public @interface ApiVersion {/*** api version code*/double value() default 1.0;}

/*** Custom RequestMappingHandlerMapping for support multi-version of spring mvc restful api with same url.* Version code provide by {@code ApiVersionCodeDiscoverer}.* <p>** How to use ?** Spring mvc config case:** <pre class="code">* @Configuration* public class WebConfig extends WebMvcConfigurationSupport {*      @Override protected RequestMappingHandlerMapping createRequestMappingHandlerMapping() {*          MultiVersionRequestMappingHandlerMapping requestMappingHandlerMapping = new MultiVersionRequestMappingHandlerMapping();*          requestMappingHandlerMapping.registerApiVersionCodeDiscoverer(new DefaultApiVersionCodeDiscoverer());*          return requestMappingHandlerMapping;*      }* }</pre>** Controller/action case:** <pre class="code">* @RestController* @RequestMapping(value = "/api/product")* public class ProductController {**      @RequestMapping(value = "detail", method = GET)*      public something detailDefault(int id) {*          return something;*      }**      @RequestMapping(value = "detail", method = GET)*      @ApiVersion(value = 1.1)*      public something detailV11(int id) {*          return something;*      }**      @RequestMapping(value = "detail", method = GET)*      @ApiVersion(value = 1.2)*      public something detailV12(int id) {*          return something;*      }* }</pre>** Client case:** <pre class="code">* $.ajax({*      type: "GET",*      url: "http://www.xxx.com/api/product/detail?id=100",*      headers: {*          value: 1.1*      },*      success: function(data){*          do something*      }* });</pre>** @since 2017-07-07*/
public class MultiVersionRequestMappingHandlerMapping extends RequestMappingHandlerMapping {private static final Logger logger = LoggerFactory.getLogger(MultiVersionRequestMappingHandlerMapping.class);private final static Map<String, HandlerMethod> HANDLER_METHOD_MAP = new HashMap<>();/*** key pattern,such as：/api/product/detail[GET]@1.1*/private final static String HANDLER_METHOD_KEY_PATTERN = "%s[%s]@%s";private List<ApiVersionCodeDiscoverer> apiVersionCodeDiscoverers = new ArrayList<>();@Overrideprotected void registerHandlerMethod(Object handler, Method method, RequestMappingInfo mapping) {ApiVersion apiVersionAnnotation = method.getAnnotation(ApiVersion.class);if (apiVersionAnnotation != null) {registerMultiVersionApiHandlerMethod(handler, method, mapping, apiVersionAnnotation);return;}super.registerHandlerMethod(handler, method, mapping);}@Overrideprotected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {HandlerMethod restApiHandlerMethod = lookupMultiVersionApiHandlerMethod(lookupPath, request);if (restApiHandlerMethod != null)return restApiHandlerMethod;return super.lookupHandlerMethod(lookupPath, request);}public void registerApiVersionCodeDiscoverer(ApiVersionCodeDiscoverer apiVersionCodeDiscoverer){if(!apiVersionCodeDiscoverers.contains(apiVersionCodeDiscoverer)){apiVersionCodeDiscoverers.add(apiVersionCodeDiscoverer);}}private void registerMultiVersionApiHandlerMethod(Object handler, Method method, RequestMappingInfo mapping, ApiVersion apiVersionAnnotation) {PatternsRequestCondition patternsCondition = mapping.getPatternsCondition();RequestMethodsRequestCondition methodsCondition = mapping.getMethodsCondition();if (patternsCondition == null|| methodsCondition == null|| patternsCondition.getPatterns().size() == 0|| methodsCondition.getMethods().size() == 0) {return;}Iterator<String> patternIterator = patternsCondition.getPatterns().iterator();Iterator<RequestMethod> methodIterator = methodsCondition.getMethods().iterator();while (patternIterator.hasNext() && methodIterator.hasNext()) {String patternItem = patternIterator.next();RequestMethod methodItem = methodIterator.next();String key = String.format(HANDLER_METHOD_KEY_PATTERN, patternItem, methodItem.name(), apiVersionAnnotation.value());HandlerMethod handlerMethod = super.createHandlerMethod(handler, method);if (!HANDLER_METHOD_MAP.containsKey(key)) {HANDLER_METHOD_MAP.put(key, handlerMethod);if (logger.isDebugEnabled()) {logger.debug("register ApiVersion HandlerMethod of %s %s", key, handlerMethod);}}}}private HandlerMethod lookupMultiVersionApiHandlerMethod(String lookupPath, HttpServletRequest request) {String version = tryResolveApiVersion(request);if (StringUtils.hasText(version)) {String key = String.format(HANDLER_METHOD_KEY_PATTERN, lookupPath, request.getMethod(), version);HandlerMethod handlerMethod = HANDLER_METHOD_MAP.get(key);if (handlerMethod != null) {if (logger.isDebugEnabled()) {logger.debug("lookup ApiVersion HandlerMethod of %s %s", key, handlerMethod);}return handlerMethod;}logger.debug("lookup ApiVersion HandlerMethod of %s failed", key);}return null;}private String tryResolveApiVersion(HttpServletRequest request) {for (int i = 0; i < apiVersionCodeDiscoverers.size(); i++) {ApiVersionCodeDiscoverer apiVersionCodeDiscoverer = apiVersionCodeDiscoverers.get(i);String versionCode = apiVersionCodeDiscoverer.getVersionCode(request);if(StringUtils.hasText(versionCode))return versionCode;}return null;}
}

/*** Interface to discover api version code in http request.** @author Tony Mu(tonymu@qq.com)* @since 2017-07-11*/
public interface ApiVersionCodeDiscoverer {/*** Return an api version code that can indicate the version of current api.** @param request current HTTP request* @return an api version code that can indicate the version of current api or {@code null}.*/String getVersionCode(HttpServletRequest request);}

/*** Default implementation of the {@link ApiVersionCodeDiscoverer} interface, get api version code* named "version" in headers or named "@version" in parameters.** @author Tony Mu(tonymu@qq.com)* @since 2017-07-11*/
public class DefaultApiVersionCodeDiscoverer implements ApiVersionCodeDiscoverer {/*** Get api version code named "version" in headers or named "@version" in parameters.** @param request current HTTP request* @return api version code named "version" in headers or named "@version" in parameters.*/@Overridepublic String getVersionCode(HttpServletRequest request) {String version = request.getHeader("version");if (!StringUtils.hasText(version)) {String versionFromUrl = request.getParameter("@version");//for debugif (StringUtils.hasText(versionFromUrl)) {version = versionFromUrl;}}return version;}
}