@RequestParam @RequestBody @PathVariable 等参数绑定注解详解(转)

    xiaoxiao2021-03-25  187

    @RequestMapping RequestMapping是一个用来处理请求地址映射的注解,可用于类或方法上。用于类上,表示类中的所有响应请求的方法都是以该地址作为父路径。 RequestMapping注解有六个属性,下面我们把她分成三类进行说明。 1、 value, method; value: 指定请求的实际地址,指定的地址可以是URI Template 模式(后面将会说明); method: 指定请求的method类型, GET、POST、PUT、DELETE等; 2、 consumes,produces; consumes: 指定处理请求的提交内容类型(Content-Type),例如application/json, text/html; produces: 指定返回的内容类型,仅当request请求头中的(Accept)类型中包含该指定类型才返回; 3、 params,headers; params: 指定request中必须包含某些参数值是,才让该方法处理。 headers: 指定request中必须包含某些指定的header值,才能让该方法处理请求。 示例: 1、value / method 示例 默认RequestMapping("....str...")即为value的值; 复制代码 @Controller @RequestMapping("/appointments") public class AppointmentsController { private AppointmentBook appointmentBook; @Autowired public AppointmentsController(AppointmentBook appointmentBook) { this.appointmentBook = appointmentBook; } @RequestMapping(method = RequestMethod.GET) public Map<String, Appointment> get() { return appointmentBook.getAppointmentsForToday(); } @RequestMapping(value="/{day}", method = RequestMethod.GET) public Map<String, Appointment> getForDay(@PathVariable @DateTimeFormat(iso=ISO.DATE) Date day, Model model) { return appointmentBook.getAppointmentsForDay(day); } @RequestMapping(value="/new", method = RequestMethod.GET) public AppointmentForm getNewForm() { return new AppointmentForm(); } @RequestMapping(method = RequestMethod.POST) public String add(@Valid AppointmentForm appointment, BindingResult result) { if (result.hasErrors()) { return "appointments/new"; } appointmentBook.addAppointment(appointment); return "redirect:/appointments"; } } 复制代码 value的uri值为以下三类: A) 可以指定为普通的具体值; B) 可以指定为含有某变量的一类值(URI Template Patterns with Path Variables); C) 可以指定为含正则表达式的一类值( URI Template Patterns with Regular Expressions); example B) @RequestMapping(value="/owners/{ownerId}", method=RequestMethod.GET) public String findOwner(@PathVariable String ownerId, Model model) { Owner owner = ownerService.findOwner(ownerId); model.addAttribute("owner", owner); return "displayOwner"; } example C) @RequestMapping("/spring-web/{symbolicName:[a-z-]+}-{version:\d\.\d\.\d}.{extension:\.[a-z]}") public void handle(@PathVariable String version, @PathVariable String extension) { // ... } } 2 consumes、produces 示例 cousumes的样例: @Controller @RequestMapping(value = "/pets", method = RequestMethod.POST, consumes="application/json") public void addPet(@RequestBody Pet pet, Model model) { // implementation omitted } 方法仅处理request Content-Type为“application/json”类型的请求。 produces的样例: @Controller @RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET, produces="application/json") @ResponseBody public Pet getPet(@PathVariable String petId, Model model) { // implementation omitted } 方法仅处理request请求中Accept头中包含了"application/json"的请求,同时暗示了返回的内容类型为application/json; 3 params、headers 示例 params的样例: 复制代码 @Controller @RequestMapping("/owners/{ownerId}") public class RelativePathUriTemplateController { @RequestMapping(value = "/pets/{petId}", method = RequestMethod.GET, params="myParam=myValue") public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) { // implementation omitted } } 复制代码 仅处理请求中包含了名为“myParam”,值为“myValue”的请求; headers的样例: 复制代码 @Controller @RequestMapping("/owners/{ownerId}") public class RelativePathUriTemplateController { @RequestMapping(value = "/pets", method = RequestMethod.GET, headers="Referer=http://www.ifeng.com/") public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) { // implementation omitted } } 复制代码 仅处理request的header中包含了指定“Refer”请求头和对应值为“http://www.ifeng.com/”的请求; 接上一篇文章讲述处理@RequestMapping的方法参数绑定之后,详细介绍下@RequestBody@ResponseBody的具体用法和使用时机;同时对曾经看的一篇文章中讲述的某些部分进行澄清 (文章地址:http://www.byywee.com/page/M0/S702/702424.html)。 简介: @RequestBody 作用: i) 该注解用于读取Request请求的body部分数据,使用系统默认配置的HttpMessageConverter进行解析,然后把相应的数据绑定到要返回的对象上; ii) 再把HttpMessageConverter返回的对象数据绑定到 controller中方法的参数上。 使用时机: A) GET、POST方式提时, 根据request header Content-Type的值来判断: application/x-www-form-urlencoded, 可选(即非必须,因为这种情况的数据@RequestParam, @ModelAttribute也可以处理,当然@RequestBody也能处理); multipart/form-data, 不能处理(即使用@RequestBody不能处理这种格式的数据); 其他格式, 必须(其他格式包括application/json, application/xml等。这些格式的数据,必须使用@RequestBody来处理); B) PUT方式提交时, 根据request header Content-Type的值来判断: application/x-www-form-urlencoded, 必须; multipart/form-data, 不能处理; 其他格式, 必须; 说明:request的body部分的数据编码格式由header部分的Content-Type指定; @ResponseBody 作用: 该注解用于将Controller的方法返回的对象,通过适当的HttpMessageConverter转换为指定格式后,写入到Response对象的body数据区。 使用时机: 返回的数据不是html标签的页面,而是其他某种格式的数据时(如json、xml等)使用; HttpMessageConverter 复制代码 <span style="font-family:Microsoft YaHei;">/** * Strategy interface that specifies a converter that can convert from and to HTTP requests and responses. * * @author Arjen Poutsma * @author Juergen Hoeller * @since 3.0 */ public interface HttpMessageConverter<T> { /** * Indicates whether the given class can be read by this converter. * @param clazz the class to test for readability * @param mediaType the media type to read, can be {@code null} if not specified. * Typically the value of a {@code Content-Type} header. * @return {@code true} if readable; {@code false} otherwise */ boolean canRead(Class<?> clazz, MediaType mediaType); /** * Indicates whether the given class can be written by this converter. * @param clazz the class to test for writability * @param mediaType the media type to write, can be {@code null} if not specified. * Typically the value of an {@code Accept} header. * @return {@code true} if writable; {@code false} otherwise */ boolean canWrite(Class<?> clazz, MediaType mediaType); /** * Return the list of {@link MediaType} objects supported by this converter. * @return the list of supported media types */ List<MediaType> getSupportedMediaTypes(); /** * Read an object of the given type form the given input message, and returns it. * @param clazz the type of object to return. This type must have previously been passed to the * {@link #canRead canRead} method of this interface, which must have returned {@code true}. * @param inputMessage the HTTP input message to read from * @return the converted object * @throws IOException in case of I/O errors * @throws HttpMessageNotReadableException in case of conversion errors */ T read(Class<? extends T> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException; /** * Write an given object to the given output message. * @param t the object to write to the output message. The type of this object must have previously been * passed to the {@link #canWrite canWrite} method of this interface, which must have returned {@code true}. * @param contentType the content type to use when writing. May be {@code null} to indicate that the * default content type of the converter must be used. If not {@code null}, this media type must have * previously been passed to the {@link #canWrite canWrite} method of this interface, which must have * returned {@code true}. * @param outputMessage the message to write to * @throws IOException in case of I/O errors * @throws HttpMessageNotWritableException in case of conversion errors */ void write(T t, MediaType contentType, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException; } </span> 复制代码 该接口定义了四个方法,分别是读取数据时的 canRead(), read() 和 写入数据时的canWrite(), write()方法。 在使用 <mvc:annotation-driven />标签配置时,默认配置了RequestMappingHandlerAdapter(注意是RequestMappingHandlerAdapter不是AnnotationMethodHandlerAdapter,详情查看Spring 3.1 document “16.14 Configuring Spring MVC”章节),并为他配置了一下默认的HttpMessageConverter: 复制代码 ByteArrayHttpMessageConverter converts byte arrays. StringHttpMessageConverter converts strings. ResourceHttpMessageConverter converts to/from org.springframework.core.io.Resource for all media types. SourceHttpMessageConverter converts to/from a javax.xml.transform.Source. FormHttpMessageConverter converts form data to/from a MultiValueMap<String, String>. Jaxb2RootElementHttpMessageConverter converts Java objects to/from XML — added if JAXB2 is present on the classpath. MappingJacksonHttpMessageConverter converts to/from JSON — added if Jackson is present on the classpath. AtomFeedHttpMessageConverter converts Atom feeds — added if Rome is present on the classpath. RssChannelHttpMessageConverter converts RSS feeds — added if Rome is present on the classpath. 复制代码 ByteArrayHttpMessageConverter: 负责读取二进制格式的数据和写出二进制格式的数据; StringHttpMessageConverter: 负责读取字符串格式的数据和写出二进制格式的数据; ResourceHttpMessageConverter:负责读取资源文件和写出资源文件数据; FormHttpMessageConverter: 负责读取form提交的数据(能读取的数据格式为 application/x-www-form-urlencoded,不能读取multipart/form-data格式数据);负责写入application/x-www-from-urlencoded和multipart/form-data格式的数据; MappingJacksonHttpMessageConverter: 负责读取和写入json格式的数据; SouceHttpMessageConverter: 负责读取和写入 xml 中javax.xml.transform.Source定义的数据; Jaxb2RootElementHttpMessageConverter: 负责读取和写入xml 标签格式的数据; AtomFeedHttpMessageConverter: 负责读取和写入Atom格式的数据; RssChannelHttpMessageConverter: 负责读取和写入RSS格式的数据; 当使用@RequestBody@ResponseBody注解时,RequestMappingHandlerAdapter就使用它们来进行读取或者写入相应格式的数据。 HttpMessageConverter匹配过程: @RequestBody注解时: 根据Request对象header部分的Content-Type类型,逐一匹配合适的HttpMessageConverter来读取数据; spring 3.1源代码如下: 复制代码 private Object readWithMessageConverters(MethodParameter methodParam, HttpInputMessage inputMessage, Class paramType) throws Exception { MediaType contentType = inputMessage.getHeaders().getContentType(); if (contentType == null) { StringBuilder builder = new StringBuilder(ClassUtils.getShortName(methodParam.getParameterType())); String paramName = methodParam.getParameterName(); if (paramName != null) { builder.append(' '); builder.append(paramName); } throw new HttpMediaTypeNotSupportedException( "Cannot extract parameter (" + builder.toString() + "): no Content-Type found"); } List<MediaType> allSupportedMediaTypes = new ArrayList<MediaType>(); if (this.messageConverters != null) { for (HttpMessageConverter<?> messageConverter : this.messageConverters) { allSupportedMediaTypes.addAll(messageConverter.getSupportedMediaTypes()); if (messageConverter.canRead(paramType, contentType)) { if (logger.isDebugEnabled()) { logger.debug("Reading [" + paramType.getName() + "] as \"" + contentType +"\" using [" + messageConverter + "]"); } return messageConverter.read(paramType, inputMessage); } } } throw new HttpMediaTypeNotSupportedException(contentType, allSupportedMediaTypes); } 复制代码 @ResponseBody注解时: 根据Request对象header部分的Accept属性(逗号分隔),逐一按accept中的类型,去遍历找到能处理的HttpMessageConverter; 源代码如下: 复制代码 private void writeWithMessageConverters(Object returnValue, HttpInputMessage inputMessage, HttpOutputMessage outputMessage) throws IOException, HttpMediaTypeNotAcceptableException { List<MediaType> acceptedMediaTypes = inputMessage.getHeaders().getAccept(); if (acceptedMediaTypes.isEmpty()) { acceptedMediaTypes = Collections.singletonList(MediaType.ALL); } MediaType.sortByQualityValue(acceptedMediaTypes); Class<?> returnValueType = returnValue.getClass(); List<MediaType> allSupportedMediaTypes = new ArrayList<MediaType>(); if (getMessageConverters() != null) { for (MediaType acceptedMediaType : acceptedMediaTypes) { for (HttpMessageConverter messageConverter : getMessageConverters()) { if (messageConverter.canWrite(returnValueType, acceptedMediaType)) { messageConverter.write(returnValue, acceptedMediaType, outputMessage); if (logger.isDebugEnabled()) { MediaType contentType = outputMessage.getHeaders().getContentType(); if (contentType == null) { contentType = acceptedMediaType; } logger.debug("Written [" + returnValue + "] as \"" + contentType + "\" using [" + messageConverter + "]"); } this.responseArgumentUsed = true; return; } } } for (HttpMessageConverter messageConverter : messageConverters) { allSupportedMediaTypes.addAll(messageConverter.getSupportedMediaTypes()); } } throw new HttpMediaTypeNotAcceptableException(allSupportedMediaTypes); } 复制代码 补充: MappingJacksonHttpMessageConverter 调用了 objectMapper.writeValue(OutputStream stream, Object)方法,使用@ResponseBody注解返回的对象就传入Object参数内。若返回的对象为已经格式化好的json串时,不使用@RequestBody注解,而应该这样处理: 1、response.setContentType("application/json; charset=UTF-8"); 2、response.getWriter().print(jsonStr); 直接输出到body区,然后的视图为void。 @RequestParam @RequestBody @PathVariable 等参数绑定注解详解(转) 引言: 接上一篇文章,对@RequestMapping进行地址映射讲解之后,该篇主要讲解request 数据到handler method 参数数据的绑定所用到的注解和什么情形下使用; 简介: handler method 参数绑定常用的注解,我们根据他们处理的Request的不同内容部分分为四类:(主要讲解常用类型) A、处理requet uri 部分(这里指uri template中variable,不含queryString部分)的注解: @PathVariable; B、处理request header部分的注解: @RequestHeader, @CookieValue; C、处理request body部分的注解:@RequestParam, @RequestBody; D、处理attribute类型是注解: @SessionAttributes, @ModelAttribute; 1@PathVariable 当使用@RequestMapping URI template 样式映射时, 即 someUrl/{paramId}, 这时的paramId可通过 @Pathvariable注解绑定它传过来的值到方法的参数上。 示例代码: 复制代码 @Controller @RequestMapping("/owners/{ownerId}") public class RelativePathUriTemplateController { @RequestMapping("/pets/{petId}") public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) { // implementation omitted } } 复制代码 上面代码把URI template 中变量 ownerId的值和petId的值,绑定到方法的参数上。若方法参数名称和需要绑定的uri template中变量名称不一致,需要在@PathVariable("name")指定uri template中的名称。 2@RequestHeader@CookieValue @RequestHeader 注解,可以把Request请求header部分的值绑定到方法的参数上。 示例代码: 这是一个Request 的header部分: Host localhost:8080 Accept text/html,application/xhtml+xml,application/xml;q=0.9 Accept-Language fr,en-gb;q=0.7,en;q=0.3 Accept-Encoding gzip,deflate Accept-Charset ISO-8859-1,utf-8;q=0.7,*;q=0.7 Keep-Alive 300 复制代码 @RequestMapping("/displayHeaderInfo.do") public void displayHeaderInfo(@RequestHeader("Accept-Encoding") String encoding, @RequestHeader("Keep-Alive") long keepAlive) { //... } 复制代码 上面的代码,把request header部分的 Accept-Encoding的值,绑定到参数encoding上了, Keep-Alive header的值绑定到参数keepAlive上。 @CookieValue 可以把Request header中关于cookie的值绑定到方法的参数上。 例如有如下Cookie值: JSESSIONID=415A4AC178C59DACE0B2C9CA727CDD84 参数绑定的代码: @RequestMapping("/displayHeaderInfo.do") public void displayHeaderInfo(@CookieValue("JSESSIONID") String cookie) { //... } 即把JSESSIONID的值绑定到参数cookie上。 3@RequestParam, @RequestBody @RequestParam A) 常用来处理简单类型的绑定,通过Request.getParameter() 获取的String可直接转换为简单类型的情况( String--> 简单类型的转换操作由ConversionService配置的转换器来完成);因为使用request.getParameter()方式获取参数,所以可以处理get 方式中queryString的值,也可以处理post方式中 body data的值; B)用来处理Content-Type: 为 application/x-www-form-urlencoded编码的内容,提交方式GET、POST; C) 该注解有两个属性: value、required; value用来指定要传入值的id名称,required用来指示参数是否必须绑定; 示例代码: 复制代码 @Controller @RequestMapping("/pets") @SessionAttributes("pet") public class EditPetForm { // ... @RequestMapping(method = RequestMethod.GET) public String setupForm(@RequestParam("petId") int petId, ModelMap model) { Pet pet = this.clinic.loadPet(petId); model.addAttribute("pet", pet); return "petForm"; } // ... 复制代码 @RequestBody 该注解常用来处理Content-Type: 不是application/x-www-form-urlencoded编码的内容,例如application/json, application/xml等; 它是通过使用HandlerAdapter 配置的HttpMessageConverters来解析post data body,然后绑定到相应的bean上的。 因为配置有FormHttpMessageConverter,所以也可以用来处理 application/x-www-form-urlencoded的内容,处理完的结果放在一个MultiValueMap<String, String>里,这种情况在某些特殊需求下使用,详情查看FormHttpMessageConverter api; 示例代码: @RequestMapping(value = "/something", method = RequestMethod.PUT) public void handle(@RequestBody String body, Writer writer) throws IOException { writer.write(body); } 4@SessionAttributes, @ModelAttribute @SessionAttributes: 该注解用来绑定HttpSession中的attribute对象的值,便于在方法中的参数里使用。 该注解有value、types两个属性,可以通过名字和类型指定要使用的attribute 对象; 示例代码: @Controller @RequestMapping("/editPet.do") @SessionAttributes("pet") public class EditPetForm { // ... } @ModelAttribute 该注解有两个用法,一个是用于方法上,一个是用于参数上; 用于方法上时: 通常用来在处理@RequestMapping之前,为请求绑定需要从后台查询的model; 用于参数上时: 用来通过名称对应,把相应名称的值绑定到注解的参数bean上;要绑定的值来源于: A) @SessionAttributes 启用的attribute 对象上; B) @ModelAttribute 用于方法上时指定的model对象; C) 上述两种情况都没有时,new一个需要绑定的bean对象,然后把request中按名称对应的方式把值绑定到bean中。 用到方法上@ModelAttribute的示例代码: 复制代码 // Add one attribute // The return value of the method is added to the model under the name "account" // You can customize the name via @ModelAttribute("myAccount") @ModelAttribute public Account addAccount(@RequestParam String number) { return accountManager.findAccount(number); } 复制代码 这种方式实际的效果就是在调用@RequestMapping的方法之前,为request对象的model里put(“account”, Account); 用在参数上的@ModelAttribute示例代码: @RequestMapping(value="/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST) public String processSubmit(@ModelAttribute Pet pet) { } 首先查询 @SessionAttributes有无绑定的Pet对象,若没有则查询@ModelAttribute方法层面上是否绑定了Pet对象,若没有则将URI template中的值按对应的名称绑定到Pet对象的各属性上。 补充讲解: 问题: 在不给定注解的情况下,参数是怎样绑定的? 通过分析AnnotationMethodHandlerAdapter和RequestMappingHandlerAdapter的源代码发现,方法的参数在不给定参数的情况下: 若要绑定的对象时简单类型: 调用@RequestParam来处理的。 若要绑定的对象时复杂类型: 调用@ModelAttribute来处理的。 这里的简单类型指java的原始类型(boolean, int 等)、原始类型对象(Boolean, Int等)、String、Date等ConversionService里可以直接String转换成目标对象的类型; 下面贴出AnnotationMethodHandlerAdapter中绑定参数的部分源代码: 复制代码 private Object[] resolveHandlerArguments(Method handlerMethod, Object handler, NativeWebRequest webRequest, ExtendedModelMap implicitModel) throws Exception { Class[] paramTypes = handlerMethod.getParameterTypes(); Object[] args = new Object[paramTypes.length]; for (int i = 0; i < args.length; i++) { MethodParameter methodParam = new MethodParameter(handlerMethod, i); methodParam.initParameterNameDiscovery(this.parameterNameDiscoverer); GenericTypeResolver.resolveParameterType(methodParam, handler.getClass()); String paramName = null; String headerName = null; boolean requestBodyFound = false; String cookieName = null; String pathVarName = null; String attrName = null; boolean required = false; String defaultValue = null; boolean validate = false; Object[] validationHints = null; int annotationsFound = 0; Annotation[] paramAnns = methodParam.getParameterAnnotations(); for (Annotation paramAnn : paramAnns) { if (RequestParam.class.isInstance(paramAnn)) { RequestParam requestParam = (RequestParam) paramAnn; paramName = requestParam.value(); required = requestParam.required(); defaultValue = parseDefaultValueAttribute(requestParam.defaultValue()); annotationsFound++; } else if (RequestHeader.class.isInstance(paramAnn)) { RequestHeader requestHeader = (RequestHeader) paramAnn; headerName = requestHeader.value(); required = requestHeader.required(); defaultValue = parseDefaultValueAttribute(requestHeader.defaultValue()); annotationsFound++; } else if (RequestBody.class.isInstance(paramAnn)) { requestBodyFound = true; annotationsFound++; } else if (CookieValue.class.isInstance(paramAnn)) { CookieValue cookieValue = (CookieValue) paramAnn; cookieName = cookieValue.value(); required = cookieValue.required(); defaultValue = parseDefaultValueAttribute(cookieValue.defaultValue()); annotationsFound++; } else if (PathVariable.class.isInstance(paramAnn)) { PathVariable pathVar = (PathVariable) paramAnn; pathVarName = pathVar.value(); annotationsFound++; } else if (ModelAttribute.class.isInstance(paramAnn)) { ModelAttribute attr = (ModelAttribute) paramAnn; attrName = attr.value(); annotationsFound++; } else if (Value.class.isInstance(paramAnn)) { defaultValue = ((Value) paramAnn).value(); } else if (paramAnn.annotationType().getSimpleName().startsWith("Valid")) { validate = true; Object value = AnnotationUtils.getValue(paramAnn); validationHints = (value instanceof Object[] ? (Object[]) value : new Object[] {value}); } } if (annotationsFound > 1) { throw new IllegalStateException("Handler parameter annotations are exclusive choices - " + "do not specify more than one such annotation on the same parameter: " + handlerMethod); } if (annotationsFound == 0) {// 若没有发现注解 Object argValue = resolveCommonArgument(methodParam, webRequest); //判断WebRquest是否可赋值给参数 if (argValue != WebArgumentResolver.UNRESOLVED) { args[i] = argValue; } else if (defaultValue != null) { args[i] = resolveDefaultValue(defaultValue); } else { Class<?> paramType = methodParam.getParameterType(); if (Model.class.isAssignableFrom(paramType) || Map.class.isAssignableFrom(paramType)) { if (!paramType.isAssignableFrom(implicitModel.getClass())) { throw new IllegalStateException("Argument [" + paramType.getSimpleName() + "] is of type " + "Model or Map but is not assignable from the actual model. You may need to switch " + "newer MVC infrastructure classes to use this argument."); } args[i] = implicitModel; } else if (SessionStatus.class.isAssignableFrom(paramType)) { args[i] = this.sessionStatus; } else if (HttpEntity.class.isAssignableFrom(paramType)) { args[i] = resolveHttpEntityRequest(methodParam, webRequest); } else if (Errors.class.isAssignableFrom(paramType)) { throw new IllegalStateException("Errors/BindingResult argument declared " + "without preceding model attribute. Check your handler method signature!"); } else if (BeanUtils.isSimpleProperty(paramType)) {// 判断是否参数类型是否是简单类型,若是在使用@RequestParam方式来处理,否则使用@ModelAttribute方式处理 paramName = ""; } else { attrName = ""; } } } if (paramName != null) { args[i] = resolveRequestParam(paramName, required, defaultValue, methodParam, webRequest, handler); } else if (headerName != null) { args[i] = resolveRequestHeader(headerName, required, defaultValue, methodParam, webRequest, handler); } else if (requestBodyFound) { args[i] = resolveRequestBody(methodParam, webRequest, handler); } else if (cookieName != null) { args[i] = resolveCookieValue(cookieName, required, defaultValue, methodParam, webRequest, handler); } else if (pathVarName != null) { args[i] = resolvePathVariable(pathVarName, methodParam, webRequest, handler); } else if (attrName != null) { WebDataBinder binder = resolveModelAttribute(attrName, methodParam, implicitModel, webRequest, handler); boolean assignBindingResult = (args.length > i + 1 && Errors.class.isAssignableFrom(paramTypes[i + 1])); if (binder.getTarget() != null) { doBind(binder, webRequest, validate, validationHints, !assignBindingResult); } args[i] = binder.getTarget(); if (assignBindingResult) { args[i + 1] = binder.getBindingResult(); i++; } implicitModel.putAll(binder.getBindingResult().getModel()); } } return args; } 复制代码 RequestMappingHandlerAdapter中使用的参数绑定,代码稍微有些不同,有兴趣的同仁可以分析下,最后处理的结果都是一样的。 示例: 复制代码 @RequestMapping ({"/", "/home"}) public String showHomePage(String key){ logger.debug("key="+key); return "home"; } 复制代码 这种情况下,就调用默认的@RequestParam来处理。 复制代码 @RequestMapping (method = RequestMethod.POST) public String doRegister(User user){ if(logger.isDebugEnabled()){ logger.debug("process url[/user], method[post] in "+getClass()); logger.debug(user); } return "user"; } 复制代码 这种情况下,就调用@ModelAttribute来处理。 pringMVC层跟JSon结合,几乎不需要做什么配置,代码实现也相当简洁。再也不用为了组装协议而劳烦辛苦了! 一、Spring注解@ResponseBody@RequestBody和HttpMessageConverter Spring 3.X系列增加了新注解@ResponseBody@RequestBody @RequestBody 将HTTP请求正文转换为适合的HttpMessageConverter对象。 @ResponseBody 将内容或对象作为 HTTP 响应正文返回,并调用适合HttpMessageConverter的Adapter转换对象,写入输出流。 HttpMessageConverter接口,需要开启<mvc:annotation-driven />。 AnnotationMethodHandlerAdapter将会初始化7个转换器,可以通过调用AnnotationMethodHandlerAdapter的getMessageConverts()方法来获取转换器的一个集合 List<HttpMessageConverter> 引用 ByteArrayHttpMessageConverter StringHttpMessageConverter ResourceHttpMessageConverter SourceHttpMessageConverter XmlAwareFormHttpMessageConverter Jaxb2RootElementHttpMessageConverter MappingJacksonHttpMessageConverter 可以理解为,只要有对应协议的解析器,你就可以通过几行配置,几个注解完成协议——对象的转换工作! PS:Spring默认的json协议解析由Jackson完成。 二、servlet.xml配置 Spring的配置文件,简洁到了极致,对于当前这个需求只需要三行核心配置: <context:component-scan base-package="org.zlex.json.controller" /> <context:annotation-config /> <mvc:annotation-driven /> 三、pom.xml配置 闲言少叙,先说依赖配置,这里以Json+Spring为参考: pom.xml <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>3.1.2.RELEASE</version> <type>jar</type> <scope>compile</scope> </dependency> <dependency> <groupId>org.codehaus.jackson</groupId> <artifactId>jackson-mapper-asl</artifactId> <version>1.9.8</version> <type>jar</type> <scope>compile</scope> </dependency> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>1.2.17</version> <scope>compile</scope> </dependency> 主要需要spring-webmvc、jackson-mapper-asl两个包,其余依赖包Maven会帮你完成。至于log4j,我还是需要看日志嘛。 包依赖图: 至于版本,看项目需要吧! 四、代码实现 域对象: public class Person implements Serializable { private int id; private String name; private boolean status; public Person() { // do nothing } } 这里需要一个空构造,由Spring转换对象时,进行初始化。 @ResponseBody@RequestBody@PathVariable 控制器: @Controller public class PersonController { /** * 查询个人信息 * * @param id * @return */ @RequestMapping(value = "/person/profile/{id}/{name}/{status}", method = RequestMethod.GET) public @ResponseBody Person porfile(@PathVariable int id, @PathVariable String name, @PathVariable boolean status) { return new Person(id, name, status); } /** * 登录 * * @param person * @return */ @RequestMapping(value = "/person/login", method = RequestMethod.POST) public @ResponseBody Person login(@RequestBody Person person) { return person; } } 备注:@RequestMapping(value = "/person/profile/{id}/{name}/{status}", method = RequestMethod.GET)中的{id}/{name}/{status}与@PathVariable int id, @PathVariable String name,@PathVariable boolean status一一对应,按名匹配。 这是restful式风格。 如果映射名称有所不一,可以参考如下方式: @RequestMapping(value = "/person/profile/{id}", method = RequestMethod.GET) public @ResponseBody Person porfile(@PathVariable("id") int uid) { return new Person(uid, name, status); } GET模式下,这里使用了@PathVariable绑定输入参数,非常适合Restful风格。因为隐藏了参数与路径的关系,可以提升网站的安全性,静态化页面,降低恶意攻击风险。 POST模式下,使用@RequestBody绑定请求对象,Spring会帮你进行协议转换,将Json、Xml协议转换成你需要的对象。 @ResponseBody可以标注任何对象,由Srping完成对象——协议的转换。 做个页面测试下: JS $(document).ready(function() { $("#profile").click(function() { profile(); }); $("#login").click(function() { login(); }); }); function profile() { var url = 'http://localhost:8080/spring-json/json/person/profile/'; var query = $('#id').val() + '/' + $('#name').val() + '/' + $('#status').val(); url += query; alert(url); $.get(url, function(data) { alert("id: " + data.id + "\nname: " + data.name + "\nstatus: " + data.status); }); } function login() { var mydata = '{"name":"' + $('#name').val() + '","id":"' + $('#id').val() + '","status":"' + $('#status').val() + '"}'; alert(mydata); $.ajax({ type : 'POST', contentType : 'application/json', url : 'http://localhost:8080/spring-json/json/person/login', processData : false, dataType : 'json', data : mydata, success : function(data) { alert("id: " + data.id + "\nname: " + data.name + "\nstatus: " + data.status); }, error : function() { alert('Err...'); } }); Table <table> <tr> <td>id</td> <td><input id="id" value="100" /></td> </tr> <tr> <td>name</td> <td><input id="name" value="snowolf" /></td> </tr> <tr> <td>status</td> <td><input id="status" value="true" /></td> </tr> <tr> <td><input type="button" id="profile" value="Profile——GET" /></td> <td><input type="button" id="login" value="Login——POST" /></td> </tr> </table> 四、简单测试 Get方式测试: Post方式测试: 五、常见错误 POST操作时,我用$.post()方式,屡次失败,一直报各种异常: 引用 org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/x-www-form-urlencoded;charset=UTF-8' not supported org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/x-www-form-urlencoded;charset=UTF-8' not supported org.springframework.web.HttpMediaTypeNotSupportedException: Content type 'application/x-www-form-urlencoded;charset=UTF-8' not supported 直接用$.post()直接请求会有点小问题,尽管我标识为json协议,但实际上提交的ContentType还是application/x-www-form-urlencoded。需要使用$.ajaxSetup()标示下ContentType。 function login() { var mydata = '{"name":"' + $('#name').val() + '","id":"' + $('#id').val() + '","status":"' + $('#status').val() + '"}'; alert(mydata); $.ajaxSetup({ contentType : 'application/json' }); $.post('http://localhost:8080/spring-json/json/person/login', mydata, function(data) { alert("id: " + data.id + "\nname: " + data.name + "\nstatus: " + data.status); }, 'json'); }; 效果是一样! 详见附件!
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