代码分析3 HandlerMethodArgumentResolver

1.@Requestbody

1.1谁是他的boss,看出来怎么生成的

  1. public class HandlerMethodArgumentResolverComposite implements HandlerMethodArgumentResolver {
  3.     private final List<HandlerMethodArgumentResolver> argumentResolvers = new ArrayList<>();
  5.     private final Map<MethodParameter, HandlerMethodArgumentResolver> argumentResolverCache =
  6.             new ConcurrentHashMap<>(256);

1.2.接口核心方法

  • boolean supportsParameter(MethodParameter parameter);

  • Object resolveArgument(MethodParameter parameter, ModelAndViewContainer mavContainer,

    1. NativeWebRequest webRequest,WebDataBinderFactory binderFactory**) throws **Exception;<br />做了两件事情,解析参数,

    1.3.举例

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解析参数
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继续跟就是
AbstractJackson2HttpMessageConverter#

  1. if (isUnicode) {
  2.     return objectMapper.readValue(inputMessage.getBody(), javaType);
  3. }

告一段落

2.无任何注解的对象

DispatcherServlet.doDispatch()

  • 获得Handler

  • 获得HandlerAdapter RequestMappingHandlerAdapter

    • ServletInvocableHandlerMethod.invokeAndHandle(webRequest, mavContainer)

    • ServletInvocableHandlerMethod的字段resolvers->很多参数解析器

      1. 代码入口在这ServletInvocableHandlerMethod
      2. if (!this.resolvers.supportsParameter(parameter)) {
      3. throw new IllegalStateException());
      4. }
      5. try {
      6. args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);
      7. }

      其实是ServletModelAttributeMethodProcessor
      image.png
      image.png ```java public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,

      1.    NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {

      ……. // Bean property binding and validation; // skipped in case of binding failure on construction. WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name); if (binder.getTarget() != null) { if (!mavContainer.isBindingDisabled(name)) {

      1.    bindRequestParameters(binder, webRequest);//核心代码在这

      } validateIfApplicable(binder, parameter); if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {

      1.    throw new BindException(binder.getBindingResult());

      } } // Value type adaptation, also covering java.util.Optional if (!parameter.getParameterType().isInstance(attribute)) { attribute = binder.convertIfNecessary(binder.getTarget(), parameter.getParameterType(), parameter); } bindingResult = binder.getBindingResult();

  1.     return attribute;
  2. }
  1. ServletRequestDataBinder.bind
  2. ```java
  3. protected void applyPropertyValues(MutablePropertyValues mpvs) {
  4.         try {
  5.             // Bind request parameters onto target object. 核心代码
  6.             getPropertyAccessor().setPropertyValues(mpvs, isIgnoreUnknownFields(), isIgnoreInvalidFields());
  7.         }
  8.         catch (PropertyBatchUpdateException ex) {
  9.             // Use bind error processor to create FieldErrors.
  10.             for (PropertyAccessException pae : ex.getPropertyAccessExceptions()) {
  11.                 getBindingErrorProcessor().processPropertyAccessException(pae, getInternalBindingResult());
  12.             }
  13.         }
  14.     }

转到这个对象了
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  1. @Override
  2.     public void setPropertyValues(PropertyValues pvs, boolean ignoreUnknown, boolean ignoreInvalid)
  3.             throws BeansException {
  5.         List<PropertyAccessException> propertyAccessExceptions = null;
  6.         List<PropertyValue> propertyValues = (pvs instanceof MutablePropertyValues ?
  7.                 ((MutablePropertyValues) pvs).getPropertyValueList() : Arrays.asList(pvs.getPropertyValues()));
  9.         if (ignoreUnknown) {
  10.             this.suppressNotWritablePropertyException = true;
  11.         }
  12.         try {
  13.             for (PropertyValue pv : propertyValues) {
  14.                 // setPropertyValue may throw any BeansException, which won't be caught
  15.                 // here, if there is a critical failure such as no matching field.
  16.                 // We can attempt to deal only with less serious exceptions.
  17.                 try {
  18.                     //核心代码
  19.                     setPropertyValue(pv);
  20.                 }
  21.                 catch (NotWritablePropertyException ex) {
  22.                     if (!ignoreUnknown) {
  23.                         throw ex;
  24.                     }
  25.                     // Otherwise, just ignore it and continue...
  26.                 }
  27.                 catch (NullValueInNestedPathException ex) {
  28.                     if (!ignoreInvalid) {
  29.                         throw ex;
  30.                     }
  31.                     // Otherwise, just ignore it and continue...
  32.                 }
  33.                 catch (PropertyAccessException ex) {
  34.                     if (propertyAccessExceptions == null) {
  35.                         propertyAccessExceptions = new ArrayList<>();
  36.                     }
  37.                     propertyAccessExceptions.add(ex);
  38.                 }
  39.             }
  40.         }
  41.         finally {
  42.             if (ignoreUnknown) {
  43.                 this.suppressNotWritablePropertyException = false;
  44.             }
  45.         }
  47.         // If we encountered individual exceptions, throw the composite exception.
  48.         if (propertyAccessExceptions != null) {
  49.             PropertyAccessException[] paeArray = propertyAccessExceptions.toArray(new PropertyAccessException[0]);
  50.             throw new PropertyBatchUpdateException(paeArray);
  51.         }
  52.     }

同类的方法

  1. private void processLocalProperty(PropertyTokenHolder tokens, PropertyValue pv) {
  2.         PropertyHandler ph = getLocalPropertyHandler(tokens.actualName);
  3.         if (ph == null || !ph.isWritable()) {
  4.             if (pv.isOptional()) {
  5.                 if (logger.isDebugEnabled()) {
  6.                     logger.debug("Ignoring optional value for property '" + tokens.actualName +
  7.                             "' - property not found on bean class [" + getRootClass().getName() + "]");
  8.                 }
  9.                 return;
  10.             }
  11.             if (this.suppressNotWritablePropertyException) {
  12.                 // Optimization for common ignoreUnknown=true scenario since the
  13.                 // exception would be caught and swallowed higher up anyway...
  14.                 return;
  15.             }
  16.             throw createNotWritablePropertyException(tokens.canonicalName);
  17.         }
  19.         Object oldValue = null;
  20.         try {
  21.             Object originalValue = pv.getValue();
  22.             Object valueToApply = originalValue;
  23.             if (!Boolean.FALSE.equals(pv.conversionNecessary)) {
  24.                 if (pv.isConverted()) {
  25.                     valueToApply = pv.getConvertedValue();
  26.                 }
  27.                 else {
  28.                     if (isExtractOldValueForEditor() && ph.isReadable()) {
  29.                         try {
  30.                             oldValue = ph.getValue();
  31.                         }
  32.                         catch (Exception ex) {
  33.                             if (ex instanceof PrivilegedActionException) {
  34.                                 ex = ((PrivilegedActionException) ex).getException();
  35.                             }
  36.                             if (logger.isDebugEnabled()) {
  37.                                 logger.debug("Could not read previous value of property '" +
  38.                                         this.nestedPath + tokens.canonicalName + "'", ex);
  39.                             }
  40.                         }
  41.                     }
  42.                     //转换核心代码
  43.                     valueToApply = convertForProperty(
  44.                             tokens.canonicalName, oldValue, originalValue, ph.toTypeDescriptor());
  45.                 }
  46.                 pv.getOriginalPropertyValue().conversionNecessary = (valueToApply != originalValue);
  47.             }
  48.             ph.setValue(valueToApply);
  49.         }
  50.         catch (TypeMismatchException ex) {
  51.             throw ex;
  52.         }
  53.         catch (InvocationTargetException ex) {
  54.             PropertyChangeEvent propertyChangeEvent = new PropertyChangeEvent(
  55.                     getRootInstance(), this.nestedPath + tokens.canonicalName, oldValue, pv.getValue());
  56.             if (ex.getTargetException() instanceof ClassCastException) {
  57.                 throw new TypeMismatchException(propertyChangeEvent, ph.getPropertyType(), ex.getTargetException());
  58.             }
  59.             else {
  60.                 Throwable cause = ex.getTargetException();
  61.                 if (cause instanceof UndeclaredThrowableException) {
  62.                     // May happen e.g. with Groovy-generated methods
  63.                     cause = cause.getCause();
  64.                 }
  65.                 throw new MethodInvocationException(propertyChangeEvent, cause);
  66.             }
  67.         }
  68.         catch (Exception ex) {
  69.             PropertyChangeEvent pce = new PropertyChangeEvent(
  70.                     getRootInstance(), this.nestedPath + tokens.canonicalName, oldValue, pv.getValue());
  71.             throw new MethodInvocationException(pce, ex);
  72.         }
  73.     }

代码:
this.typeConverterDelegate.convertIfNecessary(propertyName, oldValue, newValue, requiredType, td);

org.springframework.beans.TypeConverterDelegate#convertIfNecessary(java.lang.String, java.lang.Object, java.lang.Object, java.lang.Class, org.springframework.core.convert.TypeDescriptor)

(T) conversionService.convert(newValue, sourceTypeDesc, typeDescriptor);

GenericConversionService#convert(java.lang.Object, org.springframework.core.convert.TypeDescriptor, org.springframework.core.convert.TypeDescriptor)

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底层是converter在帮我们做 对象的属性转换问题

挺复杂的,需要跟着代码去看,贴出来没啥意义
3.自定义converter
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Cannot convert value of type ‘java.lang.String’ to required type ‘com.atguigu.demo.bean.Pet’ for property ‘pet’: no matching editors or conversion strategy found]
如果我们要扩展converter的话,可以参考配置类
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默认会把对象的属性,一层一层的去解析很聪明,底层暂时没去看,有需要时候去看

3.解析HttpSession,Request这种原生的

ServletRequestMethodArgumentResolver
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4.解析Model

ModelMethodProcessor
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默认已经有2个属性了
参数是:
model=mavContainer.getModel()
来自ServletInvocableHandlerMethod
来自RequestMappingHandlerAdapter#invokeHandlerMethod的invocableMethod.invokeAndHandle(webRequest, mavContainer);

  1. ModelAndViewContainer mavContainer = new ModelAndViewContainer();
  2. mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
  3. modelFactory.initModel(webRequest, mavContainer, invocableMethod);
  4. mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);

不是这里.再找找看 找到了
ServletInvocableHandlerMethod#resolveArgument

  1. @Override
  2.     @Nullable
  3.     public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,
  4.             NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {
  6.         BindingResult bindingResult = null;
  7.         attribute = createAttribute(...);
  8.         出异常了就catch保存到bindingResult
  9.         没出异常就
  10.         WebDataBinder binder = binderFactory.createBinder(工厂模式new ExtendedServletRequestDataBinder 然后初始化);
  11.         //核心逻辑绑定参数
  12.         bindRequestParameters(binder);
  13.         bindingResult = binder.getBindingResult();
  14.         //真正赋值
  15.         Map<String, Object> bindingResultModel = bindingResult.getModel();//这里也有逻辑
  16.         mavContainer.removeAttributes(bindingResultModel);
  17.         mavContainer.addAllAttributes(bindingResultModel);
  19.     }

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看看核心代码
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  1. ExtendedServletRequestDataBinder
  2. public void bind(ServletRequest request) {
  3.         MutablePropertyValues mpvs = new ServletRequestParameterPropertyValues(request);
  4.         MultipartRequest multipartRequest = WebUtils.getNativeRequest(request, MultipartRequest.class);
  5.         if (multipartRequest != null) {
  6.             bindMultipart(multipartRequest.getMultiFileMap(), mpvs);
  7.         }
  8.         else if (StringUtils.startsWithIgnoreCase(request.getContentType(), "multipart/")) {
  9.             HttpServletRequest httpServletRequest = WebUtils.getNativeRequest(request, HttpServletRequest.class);
  10.             if (httpServletRequest != null) {
  11.                 StandardServletPartUtils.bindParts(httpServletRequest, mpvs, isBindEmptyMultipartFiles());
  12.             }
  13.         }
  14.         addBindValues(mpvs, request);
  15.         doBind(mpvs);
  16.     }

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  1.     @Override
  2.     protected void doBind(MutablePropertyValues mpvs) {
  3.         checkFieldDefaults(mpvs);
  4.         checkFieldMarkers(mpvs);
  5.         adaptEmptyArrayIndices(mpvs);
  6.         super.doBind(mpvs);
  7.     }
  8.     protected void doBind(MutablePropertyValues mpvs) {
  9.         checkAllowedFields(mpvs);
  10.         checkRequiredFields(mpvs);
  11.         applyPropertyValues(mpvs);
  12.     }
  13. protected void applyPropertyValues(MutablePropertyValues mpvs) {
  14.     getPropertyAccessor().setPropertyValues(mpvs, isIgnoreUnknownFields(), isIgnoreInvalidFields());
  15. }
  1. public class BeanWrapperImpl extends AbstractNestablePropertyAccessor implements BeanWrapper {
  2.         @Override
  3.     public void setPropertyValues(PropertyValues pvs, boolean ignoreUnknown, boolean ignoreInvalid)
  4.             throws BeansException {
  5.         try {
  6.             for (PropertyValue pv : propertyValues) {
  7.                 // setPropertyValue may throw any BeansException, which won't be caught
  8.                 // here, if there is a critical failure such as no matching field.
  9.                 // We can attempt to deal only with less serious exceptions.
  10.                 try {
  11.                     setPropertyValue(pv);
  12.                 }
  13.             }
  14. }
  16.     @Override
  17.     public void setPropertyValue(PropertyValue pv) throws BeansException {
  18.         PropertyTokenHolder tokens = (PropertyTokenHolder) pv.resolvedTokens;
  19.         if (tokens == null) {
  20.             String propertyName = pv.getName();
  21.             AbstractNestablePropertyAccessor nestedPa;
  22.             try {
  23.                 nestedPa = getPropertyAccessorForPropertyPath(propertyName);
  24.             }
  25.             catch (NotReadablePropertyException ex) {
  26.                 throw new NotWritablePropertyException(getRootClass(), this.nestedPath + propertyName,
  27.                         "Nested property in path '" + propertyName + "' does not exist", ex);
  28.             }
  29.             tokens = getPropertyNameTokens(getFinalPath(nestedPa, propertyName));
  30.             if (nestedPa == this) {
  31.                 pv.getOriginalPropertyValue().resolvedTokens = tokens;
  32.             }
  33.             nestedPa.setPropertyValue(tokens, pv);
  34.         }
  35.         else {
  36.             setPropertyValue(tokens, pv);
  37.         }
  38.     }