首页 > 代码库 > 【转】@RequestParam @RequestBody @PathVariable 等参数绑定注解详解

【转】@RequestParam @RequestBody @PathVariable 等参数绑定注解详解

 

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

目录(?)[+]

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:

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  1. @Controller 
  2. @RequestMapping("/owners/{ownerId}") 
  3. public class RelativePathUriTemplateController { 
  4.  
  5.   @RequestMapping("/pets/{petId}") 
  6.   public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {     
  7.     // implementation omitted 
  8.   } 
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  1. @Controller  
  2. @RequestMapping("/owners/{ownerId}")  
  3. public class RelativePathUriTemplateController {  
  4.   
  5.   @RequestMapping("/pets/{petId}")  
  6.   public void findPet(@PathVariable String ownerId, @PathVariable String petId, Model model) {      
  7.     // implementation omitted  
  8.   }  
  9. }  
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:

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  1. Host                    localhost:8080 
  2. Accept                  text/html,application/xhtml+xml,application/xml;q=0.9 
  3. Accept-Language         fr,en-gb;q=0.7,en;q=0.3 
  4. Accept-Encoding         gzip,deflate 
  5. Accept-Charset          ISO-8859-1,utf-8;q=0.7,*;q=0.7 
  6. Keep-Alive              300 
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  1. Host                    localhost:8080  
  2. Accept                  text/html,application/xhtml+xml,application/xml;q=0.9  
  3. Accept-Language         fr,en-gb;q=0.7,en;q=0.3  
  4. Accept-Encoding         gzip,deflate  
  5. Accept-Charset          ISO-8859-1,utf-8;q=0.7,*;q=0.7  
  6. Keep-Alive              300  

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  1. @RequestMapping("/displayHeaderInfo.do") 
  2. public void displayHeaderInfo(@RequestHeader("Accept-Encoding") String encoding, 
  3.                               @RequestHeader("Keep-Alive") long keepAlive)  { 
  4.  
  5.   //... 
  6.  
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  1. @RequestMapping("/displayHeaderInfo.do")  
  2. public void displayHeaderInfo(@RequestHeader("Accept-Encoding") String encoding,  
  3.                               @RequestHeader("Keep-Alive") long keepAlive)  {  
  4.   
  5.   //...  
  6.   
  7. }  
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:

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  1. JSESSIONID=415A4AC178C59DACE0B2C9CA727CDD84 
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  1. JSESSIONID=415A4AC178C59DACE0B2C9CA727CDD84  
参数绑定的代码:
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  1. @RequestMapping("/displayHeaderInfo.do") 
  2. public void displayHeaderInfo(@CookieValue("JSESSIONID") String cookie)  { 
  3.  
  4.   //... 
  5.  
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  1. @RequestMapping("/displayHeaderInfo.do")  
  2. public void displayHeaderInfo(@CookieValue("JSESSIONID") String cookie)  {  
  3.   
  4.   //...  
  5.   
  6. }  
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:

[java] view plaincopyprint?
  1. @Controller 
  2. @RequestMapping("/pets") 
  3. @SessionAttributes("pet") 
  4. public class EditPetForm { 
  5.  
  6.     // ... 
  7.  
  8.     @RequestMapping(method = RequestMethod.GET) 
  9.     public String setupForm(@RequestParam("petId") int petId, ModelMap model) { 
  10.         Pet pet = this.clinic.loadPet(petId); 
  11.         model.addAttribute("pet", pet); 
  12.         return "petForm"; 
  13.     } 
  14.  
  15.     // ... 
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  1. @Controller  
  2. @RequestMapping("/pets")  
  3. @SessionAttributes("pet")  
  4. public class EditPetForm {  
  5.   
  6.     // ...  
  7.   
  8.     @RequestMapping(method = RequestMethod.GET)  
  9.     public String setupForm(@RequestParam("petId") int petId, ModelMap model) {  
  10.         Pet pet = this.clinic.loadPet(petId);  
  11.         model.addAttribute("pet", pet);  
  12.         return "petForm";  
  13.     }  
  14.   
  15.     // ...  


@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:

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  1. @RequestMapping(value =http://www.mamicode.com/ "/something", method = RequestMethod.PUT) 
  2. public void handle(@RequestBody String body, Writer writer) throws IOException { 
  3.   writer.write(body); 
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  1. @RequestMapping(value = "/something", method = RequestMethod.PUT)  
  2. public void handle(@RequestBody String body, Writer writer) throws IOException {  
  3.   writer.write(body);  
  4. }  

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:

[java] view plaincopyprint?
  1. @Controller 
  2. @RequestMapping("/editPet.do") 
  3. @SessionAttributes("pet") 
  4. public class EditPetForm { 
  5.     // ... 
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  1. @Controller  
  2. @RequestMapping("/editPet.do")  
  3. @SessionAttributes("pet")  
  4. public class EditPetForm {  
  5.     // ...  
  6. }  


@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:

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  1. // Add one attribute 
  2. // The return value of the method is added to the model under the name "account" 
  3. // You can customize the name via @ModelAttribute("myAccount") 
  4.  
  5. @ModelAttribute 
  6. public Account addAccount(@RequestParam String number) { 
  7.     return accountManager.findAccount(number); 
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  1. // Add one attribute  
  2. // The return value of the method is added to the model under the name "account"  
  3. // You can customize the name via @ModelAttribute("myAccount")  
  4.   
  5. @ModelAttribute  
  6. public Account addAccount(@RequestParam String number) {  
  7.     return accountManager.findAccount(number);  
  8. }  

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:

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  1. @RequestMapping(value=http://www.mamicode.com/"/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST) 
  2. public String processSubmit(@ModelAttribute Pet pet) { 
  3.     
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  1. @RequestMapping(value=http://www.mamicode.com/"/owners/{ownerId}/pets/{petId}/edit", method = RequestMethod.POST)  
  2. public String processSubmit(@ModelAttribute Pet pet) {  
  3.      
  4. }  
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:

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  1. private Object[] resolveHandlerArguments(Method handlerMethod, Object handler, 
  2.             NativeWebRequest webRequest, ExtendedModelMap implicitModel) throws Exception { 
  3.  
  4.         Class[] paramTypes = handlerMethod.getParameterTypes(); 
  5.         Object[] args = new Object[paramTypes.length]; 
  6.  
  7.         for (int i = 0; i < args.length; i++) { 
  8.             MethodParameter methodParam = new MethodParameter(handlerMethod, i); 
  9.             methodParam.initParameterNameDiscovery(this.parameterNameDiscoverer); 
  10.             GenericTypeResolver.resolveParameterType(methodParam, handler.getClass()); 
  11.             String paramName = null; 
  12.             String headerName = null; 
  13.             boolean requestBodyFound = false; 
  14.             String cookieName = null; 
  15.             String pathVarName = null; 
  16.             String attrName = null; 
  17.             boolean required = false; 
  18.             String defaultValue =http://www.mamicode.com/ null; 
  19.             boolean validate = false; 
  20.             Object[] validationHints = null; 
  21.             int annotationsFound = 0; 
  22.             Annotation[] paramAnns = methodParam.getParameterAnnotations(); 
  23.  
  24.             for (Annotation paramAnn : paramAnns) { 
  25.                 if (RequestParam.class.isInstance(paramAnn)) { 
  26.                     RequestParam requestParam = (RequestParam) paramAnn; 
  27.                     paramName = requestParam.value(); 
  28.                     required = requestParam.required(); 
  29.                     defaultValue = http://www.mamicode.com/parseDefaultValueAttribute(requestParam.defaultValue());
  30.                     annotationsFound++; 
  31.                 } 
  32.                 else if (RequestHeader.class.isInstance(paramAnn)) { 
  33.                     RequestHeader requestHeader = (RequestHeader) paramAnn; 
  34.                     headerName = requestHeader.value(); 
  35.                     required = requestHeader.required(); 
  36.                     defaultValue = http://www.mamicode.com/parseDefaultValueAttribute(requestHeader.defaultValue());
  37.                     annotationsFound++; 
  38.                 } 
  39.                 else if (RequestBody.class.isInstance(paramAnn)) { 
  40.                     requestBodyFound = true; 
  41.                     annotationsFound++; 
  42.                 } 
  43.                 else if (CookieValue.class.isInstance(paramAnn)) { 
  44.                     CookieValue cookieValue = http://www.mamicode.com/(CookieValue) paramAnn;
  45.                     cookieName = cookieValue.value(); 
  46.                     required = cookieValue.required(); 
  47.                     defaultValue = http://www.mamicode.com/parseDefaultValueAttribute(cookieValue.defaultValue());
  48.                     annotationsFound++; 
  49.                 } 
  50.                 else if (PathVariable.class.isInstance(paramAnn)) { 
  51.                     PathVariable pathVar = (PathVariable) paramAnn; 
  52.                     pathVarName = pathVar.value(); 
  53.                     annotationsFound++; 
  54.                 } 
  55.                 else if (ModelAttribute.class.isInstance(paramAnn)) { 
  56.                     ModelAttribute attr = (ModelAttribute) paramAnn; 
  57.                     attrName = attr.value(); 
  58.                     annotationsFound++; 
  59.                 } 
  60.                 else if (Value.class.isInstance(paramAnn)) { 
  61.                     defaultValue = http://www.mamicode.com/((Value) paramAnn).value();
  62.                 } 
  63.                 else if (paramAnn.annotationType().getSimpleName().startsWith("Valid")) { 
  64.                     validate = true; 
  65.                     Object value = http://www.mamicode.com/AnnotationUtils.getValue(paramAnn);
  66.                     validationHints = (value instanceof Object[] ? (Object[]) value : new Object[] {value}); 
  67.                 } 
  68.             } 
  69.  
  70.             if (annotationsFound > 1) { 
  71.                 throw new IllegalStateException("Handler parameter annotations are exclusive choices - " + 
  72.                         "do not specify more than one such annotation on the same parameter: " + handlerMethod); 
  73.             } 
  74.  
  75.             if (annotationsFound == 0) {// 若没有发现注解 
  76.                 Object argValue = http://www.mamicode.com/resolveCommonArgument(methodParam, webRequest);  //判断WebRquest是否可赋值给参数 
  77.                 if (argValue != WebArgumentResolver.UNRESOLVED) { 
  78.                     args[i] = argValue; 
  79.                 } 
  80.                 else if (defaultValue != null) { 
  81.                     args[i] = resolveDefaultValue(defaultValue); 
  82.                 } 
  83.                 else { 
  84.                     Class<?> paramType = methodParam.getParameterType(); 
  85.                     if (Model.class.isAssignableFrom(paramType) || Map.class.isAssignableFrom(paramType)) { 
  86.                         if (!paramType.isAssignableFrom(implicitModel.getClass())) { 
  87.                             throw new IllegalStateException("Argument [" + paramType.getSimpleName() + "] is of type " + 
  88.                                     "Model or Map but is not assignable from the actual model. You may need to switch " + 
  89.                                     "newer MVC infrastructure classes to use this argument."); 
  90.                         } 
  91.                         args[i] = implicitModel; 
  92.                     } 
  93.                     else if (SessionStatus.class.isAssignableFrom(paramType)) { 
  94.                         args[i] = this.sessionStatus; 
  95.                     } 
  96.                     else if (HttpEntity.class.isAssignableFrom(paramType)) { 
  97.                         args[i] = resolveHttpEntityRequest(methodParam, webRequest); 
  98.                     } 
  99.                     else if (Errors.class.isAssignableFrom(paramType)) { 
  100.                         throw new IllegalStateException("Errors/BindingResult argument declared " + 
  101.                                 "without preceding model attribute. Check your handler method signature!"); 
  102.                     } 
  103.                     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 
  104.                         paramName = ""; 
  105.                     } 
  106.                     else { 
  107.                         attrName = ""; 
  108.                     } 
  109.                 } 
  110.             } 
  111.  
  112.             if (paramName != null) { 
  113.                 args[i] = resolveRequestParam(paramName, required, defaultValue, methodParam, webRequest, handler); 
  114.             } 
  115.             else if (headerName != null) { 
  116.                 args[i] = resolveRequestHeader(headerName, required, defaultValue, methodParam, webRequest, handler); 
  117.             } 
  118.             else if (requestBodyFound) { 
  119.                 args[i] = resolveRequestBody(methodParam, webRequest, handler); 
  120.             } 
  121.             else if (cookieName != null) { 
  122.                 args[i] = resolveCookieValue(cookieName, required, defaultValue, methodParam, webRequest, handler); 
  123.             } 
  124.             else if (pathVarName != null) { 
  125.                 args[i] = resolvePathVariable(pathVarName, methodParam, webRequest, handler); 
  126.             } 
  127.             else if (attrName != null) { 
  128.                 WebDataBinder binder = 
  129.                         resolveModelAttribute(attrName, methodParam, implicitModel, webRequest, handler); 
  130.                 boolean assignBindingResult = (args.length > i + 1 && Errors.class.isAssignableFrom(paramTypes[i + 1])); 
  131.                 if (binder.getTarget() != null) { 
  132.                     doBind(binder, webRequest, validate, validationHints, !assignBindingResult); 
  133.                 } 
  134.                 args[i] = binder.getTarget(); 
  135.                 if (assignBindingResult) { 
  136.                     args[i + 1] = binder.getBindingResult(); 
  137.                     i++; 
  138.                 } 
  139.                 implicitModel.putAll(binder.getBindingResult().getModel()); 
  140.             } 
  141.         } 
  142.  
  143.         return args; 
  144.     } 
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  1. private Object[] resolveHandlerArguments(Method handlerMethod, Object handler,  
  2.             NativeWebRequest webRequest, ExtendedModelMap implicitModel) throws Exception {  
  3.   
  4.         Class[] paramTypes = handlerMethod.getParameterTypes();  
  5.         Object[] args = new Object[paramTypes.length];  
  6.   
  7.         for (int i = 0; i < args.length; i++) {  
  8.             MethodParameter methodParam = new MethodParameter(handlerMethod, i);  
  9.             methodParam.initParameterNameDiscovery(this.parameterNameDiscoverer);  
  10.             GenericTypeResolver.resolveParameterType(methodParam, handler.getClass());  
  11.             String paramName = null;  
  12.             String headerName = null;  
  13.             boolean requestBodyFound = false;  
  14.             String cookieName = null;  
  15.             String pathVarName = null;  
  16.             String attrName = null;  
  17.             boolean required = false;  
  18.             String defaultValue = null;  
  19.             boolean validate = false;  
  20.             Object[] validationHints = null;  
  21.             int annotationsFound = 0;  
  22.             Annotation[] paramAnns = methodParam.getParameterAnnotations();  
  23.   
  24.             for (Annotation paramAnn : paramAnns) {  
  25.                 if (RequestParam.class.isInstance(paramAnn)) {  
  26.                     RequestParam requestParam = (RequestParam) paramAnn;  
  27.                     paramName = requestParam.value();  
  28.                     required = requestParam.required();  
  29.                     defaultValue = parseDefaultValueAttribute(requestParam.defaultValue());  
  30.                     annotationsFound++;  
  31.                 }  
  32.                 else if (RequestHeader.class.isInstance(paramAnn)) {  
  33.                     RequestHeader requestHeader = (RequestHeader) paramAnn;  
  34.                     headerName = requestHeader.value();  
  35.                     required = requestHeader.required();  
  36.                     defaultValue = parseDefaultValueAttribute(requestHeader.defaultValue());  
  37.                     annotationsFound++;  
  38.                 }  
  39.                 else if (RequestBody.class.isInstance(paramAnn)) {  
  40.                     requestBodyFound = true;  
  41.                     annotationsFound++;  
  42.                 }  
  43.                 else if (CookieValue.class.isInstance(paramAnn)) {  
  44.                     CookieValue cookieValue = (CookieValue) paramAnn;  
  45.                     cookieName = cookieValue.value();  
  46.                     required = cookieValue.required();  
  47.                     defaultValue = parseDefaultValueAttribute(cookieValue.defaultValue());  
  48.                     annotationsFound++;  
  49.                 }  
  50.                 else if (PathVariable.class.isInstance(paramAnn)) {  
  51.                     PathVariable pathVar = (PathVariable) paramAnn;  
  52.                     pathVarName = pathVar.value();  
  53.                     annotationsFound++;  
  54.                 }  
  55.                 else if (ModelAttribute.class.isInstance(paramAnn)) {  
  56.                     ModelAttribute attr = (ModelAttribute) paramAnn;  
  57.                     attrName = attr.value();  
  58.                     annotationsFound++;  
  59.                 }  
  60.                 else if (Value.class.isInstance(paramAnn)) {  
  61.                     defaultValue = ((Value) paramAnn).value();  
  62.                 }  
  63.                 else if (paramAnn.annotationType().getSimpleName().startsWith("Valid")) {  
  64.                     validate = true;  
  65.                     Object value = AnnotationUtils.getValue(paramAnn);  
  66.                     validationHints = (value instanceof Object[] ? (Object[]) value : new Object[] {value});  
  67.                 }  
  68.             }  
  69.   
  70.             if (annotationsFound > 1) {  
  71.                 throw new IllegalStateException("Handler parameter annotations are exclusive choices - " +  
  72.                         "do not specify more than one such annotation on the same parameter: " + handlerMethod);  
  73.             }  
  74.   
  75.             if (annotationsFound == 0) {// 若没有发现注解  
  76.                 Object argValue = resolveCommonArgument(methodParam, webRequest);    //判断WebRquest是否可赋值给参数  
  77.                 if (argValue != WebArgumentResolver.UNRESOLVED) {  
  78.                     args[i] = argValue;  
  79.                 }  
  80.                 else if (defaultValue != null) {  
  81.                     args[i] = resolveDefaultValue(defaultValue);  
  82.                 }  
  83.                 else {  
  84.                     Class<?> paramType = methodParam.getParameterType();  
  85.                     if (Model.class.isAssignableFrom(paramType) || Map.class.isAssignableFrom(paramType)) {  
  86.                         if (!paramType.isAssignableFrom(implicitModel.getClass())) {  
  87.                             throw new IllegalStateException("Argument [" + paramType.getSimpleName() + "] is of type " +  
  88.                                     "Model or Map but is not assignable from the actual model. You may need to switch " +  
  89.                                     "newer MVC infrastructure classes to use this argument.");  
  90.                         }  
  91.                         args[i] = implicitModel;  
  92.                     }  
  93.                     else if (SessionStatus.class.isAssignableFrom(paramType)) {  
  94.                         args[i] = this.sessionStatus;  
  95.                     }  
  96.                     else if (HttpEntity.class.isAssignableFrom(paramType)) {  
  97.                         args[i] = resolveHttpEntityRequest(methodParam, webRequest);  
  98.                     }  
  99.                     else if (Errors.class.isAssignableFrom(paramType)) {  
  100.                         throw new IllegalStateException("Errors/BindingResult argument declared " +  
  101.                                 "without preceding model attribute. Check your handler method signature!");  
  102.                     }  
  103.                     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  
  104.                         paramName = "";  
  105.                     }  
  106.                     else {  
  107.                         attrName = "";  
  108.                     }  
  109.                 }  
  110.             }  
  111.   
  112.             if (paramName != null) {  
  113.                 args[i] = resolveRequestParam(paramName, required, defaultValue, methodParam, webRequest, handler);  
  114.             }  
  115.             else if (headerName != null) {  
  116.                 args[i] = resolveRequestHeader(headerName, required, defaultValue, methodParam, webRequest, handler);  
  117.             }  
  118.             else if (requestBodyFound) {  
  119.                 args[i] = resolveRequestBody(methodParam, webRequest, handler);  
  120.             }  
  121.             else if (cookieName != null) {  
  122.                 args[i] = resolveCookieValue(cookieName, required, defaultValue, methodParam, webRequest, handler);  
  123.             }  
  124.             else if (pathVarName != null) {  
  125.                 args[i] = resolvePathVariable(pathVarName, methodParam, webRequest, handler);  
  126.             }  
  127.             else if (attrName != null) {  
  128.                 WebDataBinder binder =  
  129.                         resolveModelAttribute(attrName, methodParam, implicitModel, webRequest, handler);  
  130.                 boolean assignBindingResult = (args.length > i + 1 && Errors.class.isAssignableFrom(paramTypes[i + 1]));  
  131.                 if (binder.getTarget() != null) {  
  132.                     doBind(binder, webRequest, validate, validationHints, !assignBindingResult);  
  133.                 }  
  134.                 args[i] = binder.getTarget();  
  135.                 if (assignBindingResult) {  
  136.                     args[i + 1] = binder.getBindingResult();  
  137.                     i++;  
  138.                 }  
  139.                 implicitModel.putAll(binder.getBindingResult().getModel());  
  140.             }  
  141.         }  
  142.   
  143.         return args;  
  144.     }  

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:

[java] view plaincopyprint?
  1. @RequestMapping ({"/", "/home"}) 
  2.     public String showHomePage(String key){ 
  3.          
  4.         logger.debug("key="+key); 
  5.          
  6.         return "home"; 
  7.     } 
[java] view plain copy print?技术分享技术分享
  1. @RequestMapping ({"/", "/home"})  
  2.     public String showHomePage(String key){  
  3.           
  4.         logger.debug("key="+key);  
  5.           
  6.         return "home";  
  7.     }  
这种情况下,就调用默认的@RequestParam来处理。

 

[java] view plaincopyprint?
  1. @RequestMapping (method = RequestMethod.POST) 
  2. public String doRegister(User user){ 
  3.     if(logger.isDebugEnabled()){ 
  4.         logger.debug("process url[/user], method[post] in "+getClass()); 
  5.         logger.debug(user); 
  6.     } 
  7.  
  8.     return "user"; 
[java] view plain copy print?技术分享技术分享
  1. @RequestMapping (method = RequestMethod.POST)  
  2. public String doRegister(User user){  
  3.     if(logger.isDebugEnabled()){  
  4.         logger.debug("process url[/user], method[post] in "+getClass());  
  5.         logger.debug(user);  
  6.     }  
  7.   
  8.     return "user";  
  9. }  

这种情况下,就调用@ModelAttribute来处理。

【转】@RequestParam @RequestBody @PathVariable 等参数绑定注解详解