/*
 * Copyright 2002-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */


package org.springframework.data.document.web.bind.annotation.support;

import java.lang.annotation.Annotation;
import java.lang.reflect.*;
import java.util.*;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.BeanUtils;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.core.*;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.http.*;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.ui.ExtendedModelMap;
import org.springframework.ui.Model;
import org.springframework.util.*;
import org.springframework.validation.BindException;
import org.springframework.validation.BindingResult;
import org.springframework.validation.Errors;
import org.springframework.web.HttpMediaTypeNotSupportedException;
import org.springframework.web.bind.WebDataBinder;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.bind.annotation.support.HandlerMethodInvocationException;
import org.springframework.web.bind.annotation.support.HandlerMethodResolver;
import org.springframework.web.bind.support.*;
import org.springframework.web.context.request.NativeWebRequest;
import org.springframework.web.context.request.WebRequest;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.multipart.MultipartRequest;

/**
 * Support class for invoking an annotated handler method. Operates on the introspection results of a {@link
 * HandlerMethodResolver} for a specific handler type.
 * <p/>
 * <p>Used by {@link org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter} and {@link
 * org.springframework.web.portlet.mvc.annotation.AnnotationMethodHandlerAdapter}.
 *
 * @author Juergen Hoeller
 * @author Arjen Poutsma
 * @see #invokeHandlerMethod
 * @since 2.5.2
 */
public class HandlerMethodInvoker {

  private static final String MODEL_KEY_PREFIX_STALE = SessionAttributeStore.class.getName() + ".STALE.";

  /**
   * We'll create a lot of these objects, so we don't want a new logger every time.
   */
  private static final Log logger = LogFactory.getLog(HandlerMethodInvoker.class);

  private final HandlerMethodResolver methodResolver;

  private final WebBindingInitializer bindingInitializer;

  private final SessionAttributeStore sessionAttributeStore;

  private final ParameterNameDiscoverer parameterNameDiscoverer;

  private final WebArgumentResolver[] customArgumentResolvers;

  private final HttpMessageConverter[] messageConverters;

  private final SimpleSessionStatus sessionStatus = new SimpleSessionStatus();


  public HandlerMethodInvoker(HandlerMethodResolver methodResolver) {
    this(methodResolver, null);
  }

  public HandlerMethodInvoker(HandlerMethodResolver methodResolver, WebBindingInitializer bindingInitializer) {
    this(methodResolver, bindingInitializer, new DefaultSessionAttributeStore(), null, null, null);
  }

  public HandlerMethodInvoker(HandlerMethodResolver methodResolver, WebBindingInitializer bindingInitializer,
                              SessionAttributeStore sessionAttributeStore, ParameterNameDiscoverer parameterNameDiscoverer,
                              WebArgumentResolver[] customArgumentResolvers, HttpMessageConverter[] messageConverters) {

    this.methodResolver = methodResolver;
    this.bindingInitializer = bindingInitializer;
    this.sessionAttributeStore = sessionAttributeStore;
    this.parameterNameDiscoverer = parameterNameDiscoverer;
    this.customArgumentResolvers = customArgumentResolvers;
    this.messageConverters = messageConverters;
  }


  public final Object invokeHandlerMethod(Method handlerMethod, Object handler,
                                          NativeWebRequest webRequest, ExtendedModelMap implicitModel) throws Exception {

    Method handlerMethodToInvoke = BridgeMethodResolver.findBridgedMethod(handlerMethod);
    try {
      boolean debug = logger.isDebugEnabled();
      for (String attrName : this.methodResolver.getActualSessionAttributeNames()) {
        Object attrValue = this.sessionAttributeStore.retrieveAttribute(webRequest, attrName);
        if (attrValue != null) {
          implicitModel.addAttribute(attrName, attrValue);
        }
      }
      for (Method attributeMethod : this.methodResolver.getModelAttributeMethods()) {
        Method attributeMethodToInvoke = BridgeMethodResolver.findBridgedMethod(attributeMethod);
        Object[] args = resolveHandlerArguments(attributeMethodToInvoke, handler, webRequest, implicitModel);
        if (debug) {
          logger.debug("Invoking model attribute method: " + attributeMethodToInvoke);
        }
        String attrName = AnnotationUtils.findAnnotation(attributeMethod, ModelAttribute.class).value();
        if (!"".equals(attrName) && implicitModel.containsAttribute(attrName)) {
          continue;
        }
        ReflectionUtils.makeAccessible(attributeMethodToInvoke);
        Object attrValue = attributeMethodToInvoke.invoke(handler, args);
        if ("".equals(attrName)) {
          Class resolvedType = GenericTypeResolver.resolveReturnType(attributeMethodToInvoke, handler.getClass());
          attrName = Conventions.getVariableNameForReturnType(attributeMethodToInvoke, resolvedType, attrValue);
        }
        if (!implicitModel.containsAttribute(attrName)) {
          implicitModel.addAttribute(attrName, attrValue);
        }
      }
      Object[] args = resolveHandlerArguments(handlerMethodToInvoke, handler, webRequest, implicitModel);
      if (debug) {
        logger.debug("Invoking request handler method: " + handlerMethodToInvoke);
      }
      ReflectionUtils.makeAccessible(handlerMethodToInvoke);
      return handlerMethodToInvoke.invoke(handler, args);
    } catch (IllegalStateException ex) {
      // Internal assertion failed (e.g. invalid signature):
      // throw exception with full handler method context...
      throw new HandlerMethodInvocationException(handlerMethodToInvoke, ex);
    } catch (InvocationTargetException ex) {
      // User-defined @ModelAttribute/@InitBinder/@RequestMapping method threw an exception...
      ReflectionUtils.rethrowException(ex.getTargetException());
      return null;
    }
  }

  public final void updateModelAttributes(Object handler, Map<String, Object> mavModel,
                                          ExtendedModelMap implicitModel, NativeWebRequest webRequest) throws Exception {

    if (this.methodResolver.hasSessionAttributes() && this.sessionStatus.isComplete()) {
      for (String attrName : this.methodResolver.getActualSessionAttributeNames()) {
        this.sessionAttributeStore.cleanupAttribute(webRequest, attrName);
      }
    }

    // Expose model attributes as session attributes, if required.
    // Expose BindingResults for all attributes, making custom editors available.
    Map<String, Object> model = (mavModel != null ? mavModel : implicitModel);
    if (model != null) {
      try {
        String[] originalAttrNames = model.keySet().toArray(new String[model.size()]);
        for (String attrName : originalAttrNames) {
          Object attrValue = model.get(attrName);
          boolean isSessionAttr = this.methodResolver.isSessionAttribute(
              attrName, (attrValue != null ? attrValue.getClass() : null));
          if (isSessionAttr) {
            if (this.sessionStatus.isComplete()) {
              implicitModel.put(MODEL_KEY_PREFIX_STALE + attrName, Boolean.TRUE);
            } else if (!implicitModel.containsKey(MODEL_KEY_PREFIX_STALE + attrName)) {
              this.sessionAttributeStore.storeAttribute(webRequest, attrName, attrValue);
            }
          }
          if (!attrName.startsWith(BindingResult.MODEL_KEY_PREFIX) &&
              (isSessionAttr || isBindingCandidate(attrValue))) {
            String bindingResultKey = BindingResult.MODEL_KEY_PREFIX + attrName;
            if (mavModel != null && !model.containsKey(bindingResultKey)) {
              WebDataBinder binder = createBinder(webRequest, attrValue, attrName);
              initBinder(handler, attrName, binder, webRequest);
              mavModel.put(bindingResultKey, binder.getBindingResult());
            }
          }
        }
      } catch (InvocationTargetException ex) {
        // User-defined @InitBinder method threw an exception...
        ReflectionUtils.rethrowException(ex.getTargetException());
      }
    }
  }


  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;
      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 ("Valid".equals(paramAnn.annotationType().getSimpleName())) {
          validate = true;
        }
      }

      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) {
        Object argValue = resolveCommonArgument(methodParam, webRequest);
        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)) {
            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)) {
            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, !assignBindingResult);
        }
        args[i] = binder.getTarget();
        if (assignBindingResult) {
          args[i + 1] = binder.getBindingResult();
          i++;
        }
        implicitModel.putAll(binder.getBindingResult().getModel());
      }
    }

    return args;
  }

  protected void initBinder(Object handler, String attrName, WebDataBinder binder, NativeWebRequest webRequest)
      throws Exception {

    if (this.bindingInitializer != null) {
      this.bindingInitializer.initBinder(binder, webRequest);
    }
    if (handler != null) {
      Set<Method> initBinderMethods = this.methodResolver.getInitBinderMethods();
      if (!initBinderMethods.isEmpty()) {
        boolean debug = logger.isDebugEnabled();
        for (Method initBinderMethod : initBinderMethods) {
          Method methodToInvoke = BridgeMethodResolver.findBridgedMethod(initBinderMethod);
          String[] targetNames = AnnotationUtils.findAnnotation(initBinderMethod, InitBinder.class).value();
          if (targetNames.length == 0 || Arrays.asList(targetNames).contains(attrName)) {
            Object[] initBinderArgs =
                resolveInitBinderArguments(handler, methodToInvoke, binder, webRequest);
            if (debug) {
              logger.debug("Invoking init-binder method: " + methodToInvoke);
            }
            ReflectionUtils.makeAccessible(methodToInvoke);
            Object returnValue = methodToInvoke.invoke(handler, initBinderArgs);
            if (returnValue != null) {
              throw new IllegalStateException(
                  "InitBinder methods must not have a return value: " + methodToInvoke);
            }
          }
        }
      }
    }
  }

  private Object[] resolveInitBinderArguments(Object handler, Method initBinderMethod,
                                              WebDataBinder binder, NativeWebRequest webRequest) throws Exception {

    Class[] initBinderParams = initBinderMethod.getParameterTypes();
    Object[] initBinderArgs = new Object[initBinderParams.length];

    for (int i = 0; i < initBinderArgs.length; i++) {
      MethodParameter methodParam = new MethodParameter(initBinderMethod, i);
      methodParam.initParameterNameDiscovery(this.parameterNameDiscoverer);
      GenericTypeResolver.resolveParameterType(methodParam, handler.getClass());
      String paramName = null;
      boolean paramRequired = false;
      String paramDefaultValue = null;
      String pathVarName = null;
      Annotation[] paramAnns = methodParam.getParameterAnnotations();

      for (Annotation paramAnn : paramAnns) {
        if (RequestParam.class.isInstance(paramAnn)) {
          RequestParam requestParam = (RequestParam) paramAnn;
          paramName = requestParam.value();
          paramRequired = requestParam.required();
          paramDefaultValue = parseDefaultValueAttribute(requestParam.defaultValue());
          break;
        } else if (ModelAttribute.class.isInstance(paramAnn)) {
          throw new IllegalStateException(
              "@ModelAttribute is not supported on @InitBinder methods: " + initBinderMethod);
        } else if (PathVariable.class.isInstance(paramAnn)) {
          PathVariable pathVar = (PathVariable) paramAnn;
          pathVarName = pathVar.value();
        }
      }

      if (paramName == null && pathVarName == null) {
        Object argValue = resolveCommonArgument(methodParam, webRequest);
        if (argValue != WebArgumentResolver.UNRESOLVED) {
          initBinderArgs[i] = argValue;
        } else {
          Class paramType = initBinderParams[i];
          if (paramType.isInstance(binder)) {
            initBinderArgs[i] = binder;
          } else if (BeanUtils.isSimpleProperty(paramType)) {
            paramName = "";
          } else {
            throw new IllegalStateException("Unsupported argument [" + paramType.getName() +
                "] for @InitBinder method: " + initBinderMethod);
          }
        }
      }

      if (paramName != null) {
        initBinderArgs[i] =
            resolveRequestParam(paramName, paramRequired, paramDefaultValue, methodParam, webRequest, null);
      } else if (pathVarName != null) {
        initBinderArgs[i] = resolvePathVariable(pathVarName, methodParam, webRequest, null);
      }
    }

    return initBinderArgs;
  }

  @SuppressWarnings("unchecked")
  private Object resolveRequestParam(String paramName, boolean required, String defaultValue,
                                     MethodParameter methodParam, NativeWebRequest webRequest, Object handlerForInitBinderCall)
      throws Exception {

    Class<?> paramType = methodParam.getParameterType();
    if (Map.class.isAssignableFrom(paramType) && paramName.length() == 0) {
      return resolveRequestParamMap((Class<? extends Map>) paramType, webRequest);
    }
    if (paramName.length() == 0) {
      paramName = getRequiredParameterName(methodParam);
    }
    Object paramValue = null;
    MultipartRequest multipartRequest = webRequest.getNativeRequest(MultipartRequest.class);
    if (multipartRequest != null) {
      List<MultipartFile> files = multipartRequest.getFiles(paramName);
      if (!files.isEmpty()) {
        if (files.size() == 1 && !paramType.isArray() && !Collection.class.isAssignableFrom(paramType)) {
          paramValue = files.get(0);
        } else {
          paramValue = files;
        }
      }
    }
    if (paramValue == null) {
      String[] paramValues = webRequest.getParameterValues(paramName);
      if (paramValues != null) {
        if (paramValues.length == 1 && !paramType.isArray() && !Collection.class.isAssignableFrom(paramType)) {
          paramValue = paramValues[0];
        } else {
          paramValue = paramValues;
        }
      }
    }
    if (paramValue == null) {
      if (defaultValue != null) {
        paramValue = resolveDefaultValue(defaultValue);
      } else if (required) {
        raiseMissingParameterException(paramName, paramType);
      }
      paramValue = checkValue(paramName, paramValue, paramType);
    }
    WebDataBinder binder = createBinder(webRequest, null, paramName);
    initBinder(handlerForInitBinderCall, paramName, binder, webRequest);
    return binder.convertIfNecessary(paramValue, paramType, methodParam);
  }

  private Map resolveRequestParamMap(Class<? extends Map> mapType, NativeWebRequest webRequest) {
    Map<String, String[]> parameterMap = webRequest.getParameterMap();
    if (MultiValueMap.class.isAssignableFrom(mapType)) {
      MultiValueMap<String, String> result = new LinkedMultiValueMap<String, String>(parameterMap.size());
      for (Map.Entry<String, String[]> entry : parameterMap.entrySet()) {
        for (String value : entry.getValue()) {
          result.add(entry.getKey(), value);
        }
      }
      return result;
    } else {
      Map<String, String> result = new LinkedHashMap<String, String>(parameterMap.size());
      for (Map.Entry<String, String[]> entry : parameterMap.entrySet()) {
        if (entry.getValue().length > 0) {
          result.put(entry.getKey(), entry.getValue()[0]);
        }
      }
      return result;
    }
  }

  @SuppressWarnings("unchecked")
  private Object resolveRequestHeader(String headerName, boolean required, String defaultValue,
                                      MethodParameter methodParam, NativeWebRequest webRequest, Object handlerForInitBinderCall)
      throws Exception {

    Class<?> paramType = methodParam.getParameterType();
    if (Map.class.isAssignableFrom(paramType)) {
      return resolveRequestHeaderMap((Class<? extends Map>) paramType, webRequest);
    }
    if (headerName.length() == 0) {
      headerName = getRequiredParameterName(methodParam);
    }
    Object headerValue = null;
    String[] headerValues = webRequest.getHeaderValues(headerName);
    if (headerValues != null) {
      headerValue = (headerValues.length == 1 ? headerValues[0] : headerValues);
    }
    if (headerValue == null) {
      if (defaultValue != null) {
        headerValue = resolveDefaultValue(defaultValue);
      } else if (required) {
        raiseMissingHeaderException(headerName, paramType);
      }
      headerValue = checkValue(headerName, headerValue, paramType);
    }
    WebDataBinder binder = createBinder(webRequest, null, headerName);
    initBinder(handlerForInitBinderCall, headerName, binder, webRequest);
    return binder.convertIfNecessary(headerValue, paramType, methodParam);
  }

  private Map resolveRequestHeaderMap(Class<? extends Map> mapType, NativeWebRequest webRequest) {
    if (MultiValueMap.class.isAssignableFrom(mapType)) {
      MultiValueMap<String, String> result;
      if (HttpHeaders.class.isAssignableFrom(mapType)) {
        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;
    }
  }

  /**
   * Resolves the given {@link RequestBody @RequestBody} annotation.
   */
  protected Object resolveRequestBody(MethodParameter methodParam, NativeWebRequest webRequest, Object handler)
      throws Exception {

    return readWithMessageConverters(methodParam, createHttpInputMessage(webRequest), methodParam.getParameterType());
  }

  private HttpEntity resolveHttpEntityRequest(MethodParameter methodParam, NativeWebRequest webRequest)
      throws Exception {

    HttpInputMessage inputMessage = createHttpInputMessage(webRequest);
    Class<?> paramType = getHttpEntityType(methodParam);
    Object body = readWithMessageConverters(methodParam, inputMessage, paramType);
    return new HttpEntity<Object>(body, inputMessage.getHeaders());
  }

  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);
  }

  private Class<?> getHttpEntityType(MethodParameter methodParam) {
    Assert.isAssignable(HttpEntity.class, methodParam.getParameterType());
    ParameterizedType type = (ParameterizedType) methodParam.getGenericParameterType();
    if (type.getActualTypeArguments().length == 1) {
      Type typeArgument = type.getActualTypeArguments()[0];
      if (typeArgument instanceof Class) {
        return (Class<?>) typeArgument;
      } else if (typeArgument instanceof GenericArrayType) {
        Type componentType = ((GenericArrayType) typeArgument).getGenericComponentType();
        if (componentType instanceof Class) {
          // Surely, there should be a nicer way to do this
          Object array = Array.newInstance((Class<?>) componentType, 0);
          return array.getClass();
        }
      }
    }
    throw new IllegalArgumentException(
        "HttpEntity parameter (" + methodParam.getParameterName() + ") is not parameterized");

  }

  private Object resolveCookieValue(String cookieName, boolean required, String defaultValue,
                                    MethodParameter methodParam, NativeWebRequest webRequest, Object handlerForInitBinderCall)
      throws Exception {

    Class<?> paramType = methodParam.getParameterType();
    if (cookieName.length() == 0) {
      cookieName = getRequiredParameterName(methodParam);
    }
    Object cookieValue = resolveCookieValue(cookieName, paramType, webRequest);
    if (cookieValue == null) {
      if (defaultValue != null) {
        cookieValue = resolveDefaultValue(defaultValue);
      } else if (required) {
        raiseMissingCookieException(cookieName, paramType);
      }
      cookieValue = checkValue(cookieName, cookieValue, paramType);
    }
    WebDataBinder binder = createBinder(webRequest, null, cookieName);
    initBinder(handlerForInitBinderCall, cookieName, binder, webRequest);
    return binder.convertIfNecessary(cookieValue, paramType, methodParam);
  }

  /**
   * Resolves the given {@link CookieValue @CookieValue} annotation.
   * <p>Throws an UnsupportedOperationException by default.
   */
  protected Object resolveCookieValue(String cookieName, Class paramType, NativeWebRequest webRequest)
      throws Exception {

    throw new UnsupportedOperationException("@CookieValue not supported");
  }

  private Object resolvePathVariable(String pathVarName, MethodParameter methodParam,
                                     NativeWebRequest webRequest, Object handlerForInitBinderCall) throws Exception {

    Class<?> paramType = methodParam.getParameterType();
    if (pathVarName.length() == 0) {
      pathVarName = getRequiredParameterName(methodParam);
    }
    String pathVarValue = resolvePathVariable(pathVarName, paramType, webRequest);
    WebDataBinder binder = createBinder(webRequest, null, pathVarName);
    initBinder(handlerForInitBinderCall, pathVarName, binder, webRequest);
    return binder.convertIfNecessary(pathVarValue, paramType, methodParam);
  }

  /**
   * Resolves the given {@link PathVariable @PathVariable} annotation.
   * <p>Throws an UnsupportedOperationException by default.
   */
  protected String resolvePathVariable(String pathVarName, Class paramType, NativeWebRequest webRequest)
      throws Exception {

    throw new UnsupportedOperationException("@PathVariable not supported");
  }

  private String getRequiredParameterName(MethodParameter methodParam) {
    String name = methodParam.getParameterName();
    if (name == null) {
      throw new IllegalStateException(
          "No parameter name specified for argument of type [" + methodParam.getParameterType().getName() +
              "], and no parameter name information found in class file either.");
    }
    return name;
  }

  private Object checkValue(String name, Object value, Class paramType) {
    if (value == null) {
      if (boolean.class.equals(paramType)) {
        return Boolean.FALSE;
      } else if (paramType.isPrimitive()) {
        throw new IllegalStateException("Optional " + paramType + " parameter '" + name +
            "' is not present but cannot be translated into a null value due to being declared as a " +
            "primitive type. Consider declaring it as object wrapper for the corresponding primitive type.");
      }
    }
    return value;
  }

  private WebDataBinder resolveModelAttribute(String attrName, MethodParameter methodParam,
                                              ExtendedModelMap implicitModel, NativeWebRequest webRequest, Object handler) throws Exception {

    // Bind request parameter onto object...
    String name = attrName;
    if ("".equals(name)) {
      name = Conventions.getVariableNameForParameter(methodParam);
    }
    Class<?> paramType = methodParam.getParameterType();
    Object bindObject;
    if (implicitModel.containsKey(name)) {
      bindObject = implicitModel.get(name);
    } else if (this.methodResolver.isSessionAttribute(name, paramType)) {
      bindObject = this.sessionAttributeStore.retrieveAttribute(webRequest, name);
      if (bindObject == null) {
        raiseSessionRequiredException("Session attribute '" + name + "' required - not found in session");
      }
    } else {
      bindObject = BeanUtils.instantiateClass(paramType);
    }
    WebDataBinder binder = createBinder(webRequest, bindObject, name);
    initBinder(handler, name, binder, webRequest);
    return binder;
  }


  /**
   * Determine whether the given value qualifies as a "binding candidate", i.e. might potentially be subject to
   * bean-style data binding later on.
   */
  protected boolean isBindingCandidate(Object value) {
    return (value != null && !value.getClass().isArray() && !(value instanceof Collection) &&
        !(value instanceof Map) && !BeanUtils.isSimpleValueType(value.getClass()));
  }

  protected void raiseMissingParameterException(String paramName, Class paramType) throws Exception {
    throw new IllegalStateException("Missing parameter '" + paramName + "' of type [" + paramType.getName() + "]");
  }

  protected void raiseMissingHeaderException(String headerName, Class paramType) throws Exception {
    throw new IllegalStateException("Missing header '" + headerName + "' of type [" + paramType.getName() + "]");
  }

  protected void raiseMissingCookieException(String cookieName, Class paramType) throws Exception {
    throw new IllegalStateException(
        "Missing cookie value '" + cookieName + "' of type [" + paramType.getName() + "]");
  }

  protected void raiseSessionRequiredException(String message) throws Exception {
    throw new IllegalStateException(message);
  }

  protected WebDataBinder createBinder(NativeWebRequest webRequest, Object target, String objectName)
      throws Exception {

    return new WebRequestDataBinder(target, objectName);
