springMVCソース分析--Model Factory

Model FactoryはModelを維持するためのもので、具体的には二つの機能が含まれています.
(1)Modelを初期化する
(2)プロセッサが実行後、Modelの対応するパラメータをSession Attributesに更新する
1、初期化Modelは@ModelAttributeと@Session Attributeに対する注釈の実行であり、実行する操作はinitModelに@Session Attributeの注釈を取得するパラメータの値と@ModelAttributeに注釈された関数を含む.

public void initModel(NativeWebRequest request, ModelAndViewContainer mavContainer, HandlerMethod handlerMethod)
			throws Exception {
		//    @SessionAttribute        ，    mavContainer 
		Map sessionAttributes = this.sessionAttributesHandler.retrieveAttributes(request);
		mavContainer.mergeAttributes(sessionAttributes);
		
		//     @ModelAttribute          Model
		invokeModelAttributeMethods(request, mavContainer);
		
		//      @ModelAttribute  @SessionAttribute      
		for (String name : findSessionAttributeArguments(handlerMethod)) {
			if (!mavContainer.containsAttribute(name)) {
				Object value = this.sessionAttributesHandler.retrieveAttribute(request, name);
				if (value == null) {
					throw new HttpSessionRequiredException("Expected session attribute '" + name + "'");
				}
				mavContainer.addAttribute(name, value);
			}
		}
	}

2、Modelを更新する操作は、udateModelにおいて、まず@Session Attributeのコメント値を更新し、Modelの値を更新します.

//  Model，         @SessionAttribute     value，    Model   
	public void updateModel(NativeWebRequest request, ModelAndViewContainer mavContainer) throws Exception {
		ModelMap defaultModel = mavContainer.getDefaultModel();
		if (mavContainer.getSessionStatus().isComplete()){
			this.sessionAttributesHandler.cleanupAttributes(request);
		}
		else {
			this.sessionAttributesHandler.storeAttributes(request, defaultModel);
		}
		if (!mavContainer.isRequestHandled() && mavContainer.getModel() == defaultModel) {
			updateBindingResult(request, defaultModel);
		}
	}

Model Factoryの完全なソースコードは以下の通りです.

public final class ModelFactory {

	private static final Log logger = LogFactory.getLog(ModelFactory.class);

	private final List modelMethods = new ArrayList();

	private final WebDataBinderFactory dataBinderFactory;

	private final SessionAttributesHandler sessionAttributesHandler;

	public ModelFactory(List invocableMethods, WebDataBinderFactory dataBinderFactory,
			SessionAttributesHandler sessionAttributesHandler) {

		if (invocableMethods != null) {
			for (InvocableHandlerMethod method : invocableMethods) {
				this.modelMethods.add(new ModelMethod(method));
			}
		}
		this.dataBinderFactory = dataBinderFactory;
		this.sessionAttributesHandler = sessionAttributesHandler;
	}

	public void initModel(NativeWebRequest request, ModelAndViewContainer mavContainer, HandlerMethod handlerMethod)
			throws Exception {
		//    @SessionAttribute        ，    mavContainer 
		Map sessionAttributes = this.sessionAttributesHandler.retrieveAttributes(request);
		mavContainer.mergeAttributes(sessionAttributes);
		
		//     @ModelAttribute          Model
		invokeModelAttributeMethods(request, mavContainer);
		
		//      @ModelAttribute  @SessionAttribute      
		for (String name : findSessionAttributeArguments(handlerMethod)) {
			if (!mavContainer.containsAttribute(name)) {
				Object value = this.sessionAttributesHandler.retrieveAttribute(request, name);
				if (value == null) {
					throw new HttpSessionRequiredException("Expected session attribute '" + name + "'");
				}
				mavContainer.addAttribute(name, value);
			}
		}
	}

	private void invokeModelAttributeMethods(NativeWebRequest request, ModelAndViewContainer mavContainer)
			throws Exception {

		while (!this.modelMethods.isEmpty()) {
			//     @ModelAttribute   
			InvocableHandlerMethod attrMethod = getNextModelMethod(mavContainer).getHandlerMethod();
			//     @ModelAttribute    value     
			String modelName = attrMethod.getMethodAnnotation(ModelAttribute.class).value();
			//        mavContainer    
			if (mavContainer.containsAttribute(modelName)) {
				continue;
			}
			
			//  @ModelAttribute     
			Object returnValue = attrMethod.invokeForRequest(request, mavContainer);

			if (!attrMethod.isVoid()){
				//  getNameForReturnValue     
				String returnValueName = getNameForReturnValue(returnValue, attrMethod.getReturnType());
				if (!mavContainer.containsAttribute(returnValueName)) {
					mavContainer.addAttribute(returnValueName, returnValue);
				}
			}
		}
	}
	//        ModelMethod
	private ModelMethod getNextModelMethod(ModelAndViewContainer mavContainer) {
		for (ModelMethod modelMethod : this.modelMethods) {
			if (modelMethod.checkDependencies(mavContainer)) {
				if (logger.isTraceEnabled()) {
					logger.trace("Selected @ModelAttribute method " + modelMethod);
				}
				this.modelMethods.remove(modelMethod);
				return modelMethod;
			}
		}
		ModelMethod modelMethod = this.modelMethods.get(0);
		if (logger.isTraceEnabled()) {
			logger.trace("Selected @ModelAttribute method (not present: " +
					modelMethod.getUnresolvedDependencies(mavContainer)+ ") " + modelMethod);
		}
		this.modelMethods.remove(modelMethod);
		return modelMethod;
	}
	//   @SessionAttribute      @ModelAttribute     
	private List findSessionAttributeArguments(HandlerMethod handlerMethod) {
		List result = new ArrayList();
		for (MethodParameter parameter : handlerMethod.getMethodParameters()) {
			if (parameter.hasParameterAnnotation(ModelAttribute.class)) {
				String name = getNameForParameter(parameter);
				//    @SessionAttribute     
				if (this.sessionAttributesHandler.isHandlerSessionAttribute(name, parameter.getParameterType())) {
					result.add(name);
				}
			}
		}
		return result;
	}
	//      
	public static String getNameForParameter(MethodParameter parameter) {
		ModelAttribute annot = parameter.getParameterAnnotation(ModelAttribute.class);
		String attrName = (annot != null) ? annot.value() : null;
		return StringUtils.hasText(attrName) ? attrName :  Conventions.getVariableNameForParameter(parameter);
	}
	//  @ModelAttribute     
	public static String getNameForReturnValue(Object returnValue, MethodParameter returnType) {
		ModelAttribute annotation = returnType.getMethodAnnotation(ModelAttribute.class);
		if (annotation != null && StringUtils.hasText(annotation.value())) {
			return annotation.value();
		}
		else {
			Method method = returnType.getMethod();
			Class> resolvedType = GenericTypeResolver.resolveReturnType(method, returnType.getContainingClass());
			return Conventions.getVariableNameForReturnType(method, resolvedType, returnValue);
		}
	}
	//  Model，         @SessionAttribute     value，    Model   
	public void updateModel(NativeWebRequest request, ModelAndViewContainer mavContainer) throws Exception {
		ModelMap defaultModel = mavContainer.getDefaultModel();
		if (mavContainer.getSessionStatus().isComplete()){
			this.sessionAttributesHandler.cleanupAttributes(request);
		}
		else {
			this.sessionAttributesHandler.storeAttributes(request, defaultModel);
		}
		if (!mavContainer.isRequestHandled() && mavContainer.getModel() == defaultModel) {
			updateBindingResult(request, defaultModel);
		}
	}
	//
	private void updateBindingResult(NativeWebRequest request, ModelMap model) throws Exception {
		List keyNames = new ArrayList(model.keySet());
		for (String name : keyNames) {
			Object value = model.get(name);

			if (isBindingCandidate(name, value)) {
				String bindingResultKey = BindingResult.MODEL_KEY_PREFIX + name;

				if (!model.containsAttribute(bindingResultKey)) {
					WebDataBinder dataBinder = dataBinderFactory.createBinder(request, value, name);
					model.put(bindingResultKey, dataBinder.getBindingResult());
				}
			}
		}
	}
	//
	private boolean isBindingCandidate(String attributeName, Object value) {
		if (attributeName.startsWith(BindingResult.MODEL_KEY_PREFIX)) {
			return false;
		}

		Class> attrType = (value != null) ? value.getClass() : null;
		if (this.sessionAttributesHandler.isHandlerSessionAttribute(attributeName, attrType)) {
			return true;
		}

		return (value != null && !value.getClass().isArray() && !(value instanceof Collection) &&
				!(value instanceof Map) && !BeanUtils.isSimpleValueType(value.getClass()));
	}


	private static class ModelMethod {

		private final InvocableHandlerMethod handlerMethod;

		private final Set dependencies = new HashSet();


		private ModelMethod(InvocableHandlerMethod handlerMethod) {
			this.handlerMethod = handlerMethod;
			for (MethodParameter parameter : handlerMethod.getMethodParameters()) {
				if (parameter.hasParameterAnnotation(ModelAttribute.class)) {
					this.dependencies.add(getNameForParameter(parameter));
				}
			}
		}

		public InvocableHandlerMethod getHandlerMethod() {
			return this.handlerMethod;
		}

		public boolean checkDependencies(ModelAndViewContainer mavContainer) {
			for (String name : this.dependencies) {
				if (!mavContainer.containsAttribute(name)) {
					return false;
				}
			}
			return true;
		}

		public List getUnresolvedDependencies(ModelAndViewContainer mavContainer) {
			List result = new ArrayList(this.dependencies.size());
			for (String name : this.dependencies) {
				if (!mavContainer.containsAttribute(name)) {
					result.add(name);
				}
			}
			return result;
		}

		@Override
		public String toString() {
			return this.handlerMethod.getMethod().toGenericString();
		}
	}

}