本文章主要介绍HandlerMethodArgumentResolver在SpringMVC中的使用,介绍几个HandlerMethodArgumentResolver具体的使用情况,然后说明HandlerMethodArgumentResolver的注册来源以及如何自定义注册。 首先具体看下请求映射到的handler的对应的映射函数的参数形式有哪些: HandlerMethodArgumentResolver接口只有两个方法:
Java代码
boolean supportsParameter(MethodParameter parameter); Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception;
HandlerMethodArgumentResolver接口的抽象类:AbstractMessageConverterMethodArgumentResolver仅仅引入了HttpMessageConverter,即转换的工作有这些HttpMessageConverter来完成具体的转换和判断由子类来实现。 如下:
Java代码
public abstract class AbstractMessageConverterMethodArgumentResolver implements HandlerMethodArgumentResolver { protected final Log logger = LogFactory.getLog(getClass()); protected final List<HttpMessageConverter<?>> messageConverters; protected final List<MediaType> allSupportedMediaTypes; }
AbstractMessageConverterMethodArgumentResolver 的抽象子类AbstractMessageConverterMethodProcessor仅仅是加入了对响应数据进行转换的支持。 也就是AbstractMessageConverterMethodProcessor的子类不仅可以用来转换请求数据,也可以用来转换响应数据。 AbstractMessageConverterMethodProcessor的子类HttpEntityMethodProcessor,支持请求和响应的转换,代码如下:
Java代码
@Override public boolean supportsParameter(MethodParameter parameter) { return HttpEntity.class.equals(parameter.getParameterType()); } @Override public boolean supportsReturnType(MethodParameter returnType) { return HttpEntity.class.isAssignableFrom(returnType.getParameterType()); }
使用场景如下:
Java代码
@RequestMapping(value="/test/http",method=RequestMethod.POST) @ResponseBody public Map<String,Object> testHttp(HttpEntity<String> httpEntity) } @RequestMapping(value="/test/httpEntity",method=RequestMethod.GET) public HttpEntity<String> testHttpEntity(){ }
AbstractMessageConverterMethodProcessor的子类RequestResponseBodyMethodProcessor:支持@RequestBody和@ResponseBody,代码如下:
Java代码
@Override public boolean supportsParameter(MethodParameter parameter) { return parameter.hasParameterAnnotation(RequestBody.class); } @Override public boolean supportsReturnType(MethodParameter returnType) { return ((AnnotationUtils.findAnnotation(returnType.getContainingClass(), ResponseBody.class) != null) || (returnType.getMethodAnnotation(ResponseBody.class) != null)); }
使用场景如下:
Java代码
@RequestMapping(value="/test/requestBody",method=RequestMethod.POST) @ResponseBody public Map<String,Object> testrequestBody(@RequestBody Map<String,Object> map1){ Map<String,Object> map=new HashMap<String,Object>(); map.put("name","lg"); map.put("age",23); map.put("date",new Date()); return map; }
HttpEntityMethodProcessor具体的解析参数的过程:
Java代码
@Override public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws IOException, HttpMediaTypeNotSupportedException { HttpInputMessage inputMessage = createInputMessage(webRequest); Type paramType = getHttpEntityType(parameter); Object body = readWithMessageConverters(webRequest, parameter, paramType); return new HttpEntity<Object>(body, inputMessage.getHeaders()); }
就是通过HttpMessageConverter来进一步的判断是否支持HttpEntity<T>中我们想要的T类型以及是否支持相应的content-type,如public Map<String,Object> testHttp(HttpEntity<String> httpEntity) ,则会选择StringHttpMessageConverter来进行转换。具体的选择过程如下:
Java代码
protected <T> Object readWithMessageConverters(HttpInputMessage inputMessage, MethodParameter methodParam, Type targetType) throws IOException, HttpMediaTypeNotSupportedException { MediaType contentType; try { contentType = inputMessage.getHeaders().getContentType(); } catch (InvalidMediaTypeException ex) { throw new HttpMediaTypeNotSupportedException(ex.getMessage()); } if (contentType == null) { contentType = MediaType.APPLICATION_OCTET_STREAM; } Class<?> contextClass = methodParam.getContainingClass(); for (HttpMessageConverter<?> converter : this.messageConverters) { if (converter instanceof GenericHttpMessageConverter) { GenericHttpMessageConverter<?> genericConverter = (GenericHttpMessageConverter<?>) converter; if (genericConverter.canRead(targetType, contextClass, contentType)) { if (logger.isDebugEnabled()) { logger.debug("Reading [" + targetType + "] as \"" + contentType + "\" using [" + converter + "]"); } return genericConverter.read(targetType, contextClass, inputMessage); } } Class<T> targetClass = (Class<T>) ResolvableType.forMethodParameter(methodParam, targetType).resolve(Object.class); if (converter.canRead(targetClass, contentType)) { if (logger.isDebugEnabled()) { logger.debug("Reading [" + targetClass.getName() + "] as \"" + contentType + "\" using [" + converter + "]"); } return ((HttpMessageConverter<T>) converter).read(targetClass, inputMessage); } } throw new HttpMediaTypeNotSupportedException(contentType, this.allSupportedMediaTypes); }
同理RequestResponseBodyMethodProcessor也会使用相应的HttpMessageConverter来进行转换。如public Map<String,Object> testrequestBody(@RequestBody Map<String,Object> map1)则会选择MappingJackson2HttpMessageConverter或者MappingJacksonHttpMessageConverter来完成转换。 再看看另一类的HandlerMethodArgumentResolver: RequestParamMethodArgumentResolver支持的类型有,一种是含@RequestParam注解的参数,另一种就是简单类型,如Integer、String、Date、URI, URL,Locale等: 源代码如下:
Java代码
public boolean supportsParameter(MethodParameter parameter) { Class<?> paramType = parameter.getParameterType(); if (parameter.hasParameterAnnotation(RequestParam.class)) { if (Map.class.isAssignableFrom(paramType)) { String paramName = parameter.getParameterAnnotation(RequestParam.class).value(); return StringUtils.hasText(paramName); } else { return true; } } else { if (parameter.hasParameterAnnotation(RequestPart.class)) { return false; } else if (MultipartFile.class.equals(paramType) || "javax.servlet.http.Part".equals(paramType.getName())) { return true; } else if (this.useDefaultResolution) { return BeanUtils.isSimpleProperty(paramType); } else { return false; } } }
BeanUtils.isSimpleProperty(paramType)判断是否是简单类型的具体内容如下:
Java代码
public static boolean isSimpleProperty(Class<?> clazz) { Assert.notNull(clazz, "Class must not be null"); return isSimpleValueType(clazz) || (clazz.isArray() && isSimpleValueType(clazz.getComponentType())); } public static boolean isSimpleValueType(Class<?> clazz) { return ClassUtils.isPrimitiveOrWrapper(clazz) || clazz.isEnum() || CharSequence.class.isAssignableFrom(clazz) || Number.class.isAssignableFrom(clazz) || Date.class.isAssignableFrom(clazz) || clazz.equals(URI.class) || clazz.equals(URL.class) || clazz.equals(Locale.class) || clazz.equals(Class.class); }
即当请求为 http://localhost:8080/test?name=abc时,处理函数若为test(String name),则对name的解析就是采用RequestParamMethodArgumentResolver来解析的。 RequestHeaderMethodArgumentResolver:主要用来处理含有@RequestHeader注解的参数,但同时该参数又不是Map类型。如下:
Java代码
@Override public boolean supportsParameter(MethodParameter parameter) { return parameter.hasParameterAnnotation(RequestHeader.class) && !Map.class.isAssignableFrom(parameter.getParameterType()); } @Override protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest request) throws Exception { String[] headerValues = request.getHeaderValues(name); if (headerValues != null) { return (headerValues.length == 1 ? headerValues[0] : headerValues); } else { return null; } }
源代码已经说明的很明白了。 使用场景:
Java代码
@RequestMapping(value="/test/requestHeader",method=RequestMethod.GET) @ResponseBody public Map<String,Object> testrequestHeader(@RequestHeader String Accept){
若想获取所有的header信息:则使用另一个RequestHeaderMapMethodArgumentResolver,它则用来获取所有的header信息:
Java代码
public class RequestHeaderMapMethodArgumentResolver implements HandlerMethodArgumentResolver { @Override public boolean supportsParameter(MethodParameter parameter) { return parameter.hasParameterAnnotation(RequestHeader.class) && Map.class.isAssignableFrom(parameter.getParameterType()); } @Override public Object resolveArgument( MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception { Class<?> paramType = parameter.getParameterType(); if (MultiValueMap.class.isAssignableFrom(paramType)) { MultiValueMap<String, String> result; if (HttpHeaders.class.isAssignableFrom(paramType)) { result = new HttpHeaders(); } else { result = new LinkedMultiValueMap<String, String>(); } for (Iterator<String> iterator = webRequest.getHeaderNames(); iterator.hasNext();) { String headerName = iterator.next(); for (String headerValue : webRequest.getHeaderValues(headerName)) { result.add(headerName, headerValue); } } return result; } else { Map<String, String> result = new LinkedHashMap<String, String>(); for (Iterator<String> iterator = webRequest.getHeaderNames(); iterator.hasNext();) { String headerName = iterator.next(); String headerValue = webRequest.getHeader(headerName); result.put(headerName, headerValue); } return result; } } }
从上面的解析过程可以看出,参数类型可以是普通的Map类型,也可以是MultiValueMap或者进一步的HttpHeaders,他们与普通Map类型的区别是他们对value值后者们是以List形式存放,前者是以String形式存放。 使用场景:
Java代码
@RequestMapping(value="/test/requestHeader",method=RequestMethod.GET) @ResponseBody public Map<String,Object> testrequestHeader(@RequestHeader Map<String,Object> map1){ public Map<String,Object> testrequestHeader(@RequestHeader MultiValueMap<String,Object> map1){
PathVariableMethodArgumentResolver:主要针对含有@PathVariable的参数,代码如下:
Java代码
@Override public boolean supportsParameter(MethodParameter parameter) { if (!parameter.hasParameterAnnotation(PathVariable.class)) { return false; } if (Map.class.isAssignableFrom(parameter.getParameterType())) { String paramName = parameter.getParameterAnnotation(PathVariable.class).value(); return StringUtils.hasText(paramName); } return true; } @Override @SuppressWarnings("unchecked") protected Object resolveName(String name, MethodParameter parameter, NativeWebRequest request) throws Exception { Map<String, String> uriTemplateVars = (Map<String, String>) request.getAttribute( HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, RequestAttributes.SCOPE_REQUEST); return (uriTemplateVars != null) ? uriTemplateVars.get(name) : null; }
对于支持的类型也说明的很详细。首先必须含有@PathVariable注解,其次如果是Map类型,必须要指定@PathVariable的值,即这个 ArgumentResolver只能获取一个uri变量。要想获取多个则要使用PathVariableMapMethodArgumentResolver:
Java代码
@Override public boolean supportsParameter(MethodParameter parameter) { PathVariable annot = parameter.getParameterAnnotation(PathVariable.class); return ((annot != null) && (Map.class.isAssignableFrom(parameter.getParameterType())) && (!StringUtils.hasText(annot.value()))); } public Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception { @SuppressWarnings("unchecked") Map<String, String> uriTemplateVars = (Map<String, String>) webRequest.getAttribute( HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, RequestAttributes.SCOPE_REQUEST); if (!CollectionUtils.isEmpty(uriTemplateVars)) { return new LinkedHashMap<String, String>(uriTemplateVars); } else { return Collections.emptyMap(); } }
它要求必须含有@PathVariable注解,并且必须是Map类型,并且@PathVariable注解的value没有值。同时我们可以从PathVariableMapMethodArgumentResolver和PathVariableMethodArgumentResolver上面看出,他们的取值都是从request的属性上进行获取的webRequest.getAttribute( HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, RequestAttributes.SCOPE_REQUEST);也就是说,在解析完@RequestMapping匹配工作后,便将这些参数设置进request的属性上,属性名为HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE。其他的HandlerMethodArgumentResolver可以自行研究,这里不再说明。 至此,我们就要说明下HandlerMethodArgumentResolver的注册来源: 它的来源分为两部分,一部分spring默认的HandlerMethodArgumentResolver,另一部分就是我们自定义的HandlerMethodArgumentResolver。 还是先看mvc:annotation-driven中配置自定义的HandlerMethodArgumentResolver:
Java代码
<mvc:annotation-driven > <mvc:argument-resolvers> <bean class="xxx"></bean> </mvc:argument-resolvers> </mvc:annotation-driven>
在mvc:argument-resolvers标签下配置相应的自定义的HandlerMethodArgumentResolver。 然后在mvc:annotation-driven的注解驱动类AnnotationDrivenBeanDefinitionParser中会有这样的代码:
Java代码
ManagedList<?> argumentResolvers = getArgumentResolvers(element, parserContext); if (argumentResolvers != null) { handlerAdapterDef.getPropertyValues().add("customArgumentResolvers", argumentResolvers); }
其中getArgumentResolvers就是获取我们自定义的HandlerMethodArgumentResolver
Java代码
private ManagedList<?> getArgumentResolvers(Element element, ParserContext parserContext) { Element resolversElement = DomUtils.getChildElementByTagName(element, "argument-resolvers"); if (resolversElement != null) { ManagedList<BeanDefinitionHolder> argumentResolvers = extractBeanSubElements(resolversElement, parserContext); return wrapWebArgumentResolverBeanDefs(argumentResolvers, parserContext); } return null; }
从上面的代码可以看出,获取我们自定义的HandlerMethodArgumentResolver然后把它设置进RequestMappingHandlerAdapter的customArgumentResolvers参数中,RequestMappingHandlerAdapter有两个与HandlerMethodArgumentResolver有关的参数:
Java代码
private List<HandlerMethodArgumentResolver> customArgumentResolvers; private HandlerMethodArgumentResolverComposite argumentResolvers;
HandlerMethodArgumentResolverComposite 也仅仅是内部存放一个List<HandlerMethodArgumentResolver>集合,同时本身又继承HandlerMethodArgumentResolver,所以它的实现都是靠内部的List<HandlerMethodArgumentResolver>集合来实现的。
Java代码
private final List<HandlerMethodArgumentResolver> argumentResolvers = new LinkedList<HandlerMethodArgumentResolver>(); private final Map<MethodParameter, HandlerMethodArgumentResolver> argumentResolverCache = new ConcurrentHashMap<MethodParameter, HandlerMethodArgumentResolver>(256); public List<HandlerMethodArgumentResolver> getResolvers() { return Collections.unmodifiableList(this.argumentResolvers); } @Override public boolean supportsParameter(MethodParameter parameter) { return getArgumentResolver(parameter) != null; } @Override public Object resolveArgument( MethodParameter parameter, ModelAndViewContainer mavContainer, NativeWebRequest webRequest, WebDataBinderFactory binderFactory) throws Exception { HandlerMethodArgumentResolver resolver = getArgumentResolver(parameter); Assert.notNull(resolver, "Unknown parameter type [" + parameter.getParameterType().getName() + "]"); return resolver.resolveArgument(parameter, mavContainer, webRequest, binderFactory); } private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) { HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter); if (result == null) { for (HandlerMethodArgumentResolver methodArgumentResolver : this.argumentResolvers) { if (logger.isTraceEnabled()) { logger.trace("Testing if argument resolver [" + methodArgumentResolver + "] supports [" + parameter.getGenericParameterType() + "]"); } if (methodArgumentResolver.supportsParameter(parameter)) { result = methodArgumentResolver; this.argumentResolverCache.put(parameter, result); break; } } } return result; }
在RequestMappingHandlerAdapter完成参数设置后,会调用afterPropertiesSet方法
Java代码
@Override public void afterPropertiesSet() { if (this.argumentResolvers == null) { List<HandlerMethodArgumentResolver> resolvers = getDefaultArgumentResolvers(); this.argumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers); } if (this.initBinderArgumentResolvers == null) { List<HandlerMethodArgumentResolver> resolvers = getDefaultInitBinderArgumentResolvers(); this.initBinderArgumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers); } if (this.returnValueHandlers == null) { List<HandlerMethodReturnValueHandler> handlers = getDefaultReturnValueHandlers(); this.returnValueHandlers = new HandlerMethodReturnValueHandlerComposite().addHandlers(handlers); } initControllerAdviceCache(); }
getDefaultArgumentResolvers方法完成了所有的HandlerMethodArgumentResolver的汇总,如下:
Java代码
private List<HandlerMethodArgumentResolver> getDefaultArgumentResolvers() { List<HandlerMethodArgumentResolver> resolvers = new ArrayList<HandlerMethodArgumentResolver>(); resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), false)); resolvers.add(new RequestParamMapMethodArgumentResolver()); resolvers.add(new PathVariableMethodArgumentResolver()); resolvers.add(new PathVariableMapMethodArgumentResolver()); resolvers.add(new MatrixVariableMethodArgumentResolver()); resolvers.add(new MatrixVariableMapMethodArgumentResolver()); resolvers.add(new ServletModelAttributeMethodProcessor(false)); resolvers.add(new RequestResponseBodyMethodProcessor(getMessageConverters())); resolvers.add(new RequestPartMethodArgumentResolver(getMessageConverters())); resolvers.add(new RequestHeaderMethodArgumentResolver(getBeanFactory())); resolvers.add(new RequestHeaderMapMethodArgumentResolver()); resolvers.add(new ServletCookieValueMethodArgumentResolver(getBeanFactory())); resolvers.add(new ExpressionValueMethodArgumentResolver(getBeanFactory())); resolvers.add(new ServletRequestMethodArgumentResolver()); resolvers.add(new ServletResponseMethodArgumentResolver()); resolvers.add(new HttpEntityMethodProcessor(getMessageConverters())); resolvers.add(new RedirectAttributesMethodArgumentResolver()); resolvers.add(new ModelMethodProcessor()); resolvers.add(new MapMethodProcessor()); resolvers.add(new ErrorsMethodArgumentResolver()); resolvers.add(new SessionStatusMethodArgumentResolver()); resolvers.add(new UriComponentsBuilderMethodArgumentResolver()); if (getCustomArgumentResolvers() != null) { resolvers.addAll(getCustomArgumentResolvers()); } resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), true)); resolvers.add(new ServletModelAttributeMethodProcessor(true)); return resolvers; }
不仅汇总了spring默认的,同时加进来我们自定义的HandlerMethodArgumentResolver。至此,HandlerMethodArgumentResolver的来龙去脉都说清楚了。然后就是我们自定义HandlerMethodArgumentResolver,下一篇文章再说。
转载自:http://blog.csdn.net/z69183787/article/details/52817089