Java tutorial
/* * Copyright 2002-2015 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.web.servlet.mvc.multiaction; import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Map; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.springframework.beans.BeanUtils; import org.springframework.util.Assert; import org.springframework.util.ReflectionUtils; import org.springframework.validation.ValidationUtils; import org.springframework.validation.Validator; import org.springframework.web.HttpSessionRequiredException; import org.springframework.web.bind.ServletRequestDataBinder; import org.springframework.web.bind.support.WebBindingInitializer; import org.springframework.web.context.request.ServletWebRequest; import org.springframework.web.servlet.ModelAndView; import org.springframework.web.servlet.mvc.AbstractController; import org.springframework.web.servlet.mvc.LastModified; /** * {@link org.springframework.web.servlet.mvc.Controller Controller} * implementation that allows multiple request types to be handled by the same * class. Subclasses of this class can handle several different types of * request with methods of the form * * <pre class="code">public (ModelAndView | Map | String | void) actionName(HttpServletRequest request, HttpServletResponse response, [,HttpSession] [,AnyObject]);</pre> * * A Map return value indicates a model that is supposed to be passed to a default view * (determined through a {@link org.springframework.web.servlet.RequestToViewNameTranslator}). * A String return value indicates the name of a view to be rendered without a specific model. * * <p>May take a third parameter (of type {@link HttpSession}) in which an * existing session will be required, or a third parameter of an arbitrary * class that gets treated as the command (that is, an instance of the class * gets created, and request parameters get bound to it) * * <p>These methods can throw any kind of exception, but should only let * propagate those that they consider fatal, or which their class or superclass * is prepared to catch by implementing an exception handler. * * <p>When returning just a {@link Map} instance view name translation will be * used to generate the view name. The configured * {@link org.springframework.web.servlet.RequestToViewNameTranslator} will be * used to determine the view name. * * <p>When returning {@code void} a return value of {@code null} is * assumed meaning that the handler method is responsible for writing the * response directly to the supplied {@link HttpServletResponse}. * * <p>This model allows for rapid coding, but loses the advantage of * compile-time checking. It is similar to a Struts {@code DispatchAction}, * but more sophisticated. Also supports delegation to another object. * * <p>An implementation of the {@link MethodNameResolver} interface defined in * this package should return a method name for a given request, based on any * aspect of the request, such as its URL or an "action" parameter. The actual * strategy can be configured via the "methodNameResolver" bean property, for * each {@code MultiActionController}. * * <p>The default {@code MethodNameResolver} is * {@link InternalPathMethodNameResolver}; further included strategies are * {@link PropertiesMethodNameResolver} and {@link ParameterMethodNameResolver}. * * <p>Subclasses can implement custom exception handler methods with names such * as: * * <pre class="code">public ModelAndView anyMeaningfulName(HttpServletRequest request, HttpServletResponse response, ExceptionClass exception);</pre> * * The third parameter can be any subclass or {@link Exception} or * {@link RuntimeException}. * * <p>There can also be an optional {@code xxxLastModified} method for * handlers, of signature: * * <pre class="code">public long anyMeaningfulNameLastModified(HttpServletRequest request)</pre> * * If such a method is present, it will be invoked. Default return from * {@code getLastModified} is -1, meaning that the content must always be * regenerated. * * <p><b>Note that all handler methods need to be public and that * method overloading is <i>not</i> allowed.</b> * * <p>See also the description of the workflow performed by * {@link AbstractController the superclass} (in that section of the class * level Javadoc entitled 'workflow'). * * <p><b>Note:</b> For maximum data binding flexibility, consider direct usage of a * {@link ServletRequestDataBinder} in your controller method, instead of relying * on a declared command argument. This allows for full control over the entire * binder setup and usage, including the invocation of {@link Validator Validators} * and the subsequent evaluation of binding/validation errors. * * @author Rod Johnson * @author Juergen Hoeller * @author Colin Sampaleanu * @author Rob Harrop * @author Sam Brannen * @see MethodNameResolver * @see InternalPathMethodNameResolver * @see PropertiesMethodNameResolver * @see ParameterMethodNameResolver * @see org.springframework.web.servlet.mvc.LastModified#getLastModified * @see org.springframework.web.bind.ServletRequestDataBinder * @deprecated as of 4.3, in favor of annotation-driven handler methods */ @Deprecated public class MultiActionController extends AbstractController implements LastModified { /** Suffix for last-modified methods */ public static final String LAST_MODIFIED_METHOD_SUFFIX = "LastModified"; /** Default command name used for binding command objects: "command" */ public static final String DEFAULT_COMMAND_NAME = "command"; /** * Log category to use when no mapped handler is found for a request. * @see #pageNotFoundLogger */ public static final String PAGE_NOT_FOUND_LOG_CATEGORY = "org.springframework.web.servlet.PageNotFound"; /** * Additional logger to use when no mapped handler is found for a request. * @see #PAGE_NOT_FOUND_LOG_CATEGORY */ protected static final Log pageNotFoundLogger = LogFactory.getLog(PAGE_NOT_FOUND_LOG_CATEGORY); /** Object we'll invoke methods on. Defaults to this. */ private Object delegate; /** Delegate that knows how to determine method names from incoming requests */ private MethodNameResolver methodNameResolver = new InternalPathMethodNameResolver(); /** List of Validators to apply to commands */ private Validator[] validators; /** Optional strategy for pre-initializing data binding */ private WebBindingInitializer webBindingInitializer; /** Handler methods, keyed by name */ private final Map<String, Method> handlerMethodMap = new HashMap<String, Method>(); /** LastModified methods, keyed by handler method name (without LAST_MODIFIED_SUFFIX) */ private final Map<String, Method> lastModifiedMethodMap = new HashMap<String, Method>(); /** Methods, keyed by exception class */ private final Map<Class<?>, Method> exceptionHandlerMap = new HashMap<Class<?>, Method>(); /** * Constructor for {@code MultiActionController} that looks for * handler methods in the present subclass. */ public MultiActionController() { this.delegate = this; registerHandlerMethods(this.delegate); // We'll accept no handler methods found here - a delegate might be set later on. } /** * Constructor for {@code MultiActionController} that looks for * handler methods in delegate, rather than a subclass of this class. * @param delegate handler object. This does not need to implement any * particular interface, as everything is done using reflection. */ public MultiActionController(Object delegate) { setDelegate(delegate); } /** * Set the delegate used by this class; the default is {@code this}, * assuming that handler methods have been added by a subclass. * <p>This method does not get invoked once the class is configured. * @param delegate an object containing handler methods * @throws IllegalStateException if no handler methods are found */ public final void setDelegate(Object delegate) { Assert.notNull(delegate, "Delegate must not be null"); this.delegate = delegate; registerHandlerMethods(this.delegate); // There must be SOME handler methods. if (this.handlerMethodMap.isEmpty()) { throw new IllegalStateException("No handler methods in class [" + this.delegate.getClass() + "]"); } } /** * Set the method name resolver that this class should use. * <p>Allows parameterization of handler method mappings. */ public final void setMethodNameResolver(MethodNameResolver methodNameResolver) { this.methodNameResolver = methodNameResolver; } /** * Return the MethodNameResolver used by this class. */ public final MethodNameResolver getMethodNameResolver() { return this.methodNameResolver; } /** * Set the {@link Validator Validators} for this controller. * <p>The {@code Validators} must support the specified command class. */ public final void setValidators(Validator[] validators) { this.validators = validators; } /** * Return the Validators for this controller. */ public final Validator[] getValidators() { return this.validators; } /** * Specify a WebBindingInitializer which will apply pre-configured * configuration to every DataBinder that this controller uses. * <p>Allows for factoring out the entire binder configuration * to separate objects, as an alternative to {@link #initBinder}. */ public final void setWebBindingInitializer(WebBindingInitializer webBindingInitializer) { this.webBindingInitializer = webBindingInitializer; } /** * Return the WebBindingInitializer (if any) which will apply pre-configured * configuration to every DataBinder that this controller uses. */ public final WebBindingInitializer getWebBindingInitializer() { return this.webBindingInitializer; } /** * Registers all handlers methods on the delegate object. */ private void registerHandlerMethods(Object delegate) { this.handlerMethodMap.clear(); this.lastModifiedMethodMap.clear(); this.exceptionHandlerMap.clear(); // Look at all methods in the subclass, trying to find // methods that are validators according to our criteria Method[] methods = delegate.getClass().getMethods(); for (Method method : methods) { // We're looking for methods with given parameters. if (isExceptionHandlerMethod(method)) { registerExceptionHandlerMethod(method); } else if (isHandlerMethod(method)) { registerHandlerMethod(method); registerLastModifiedMethodIfExists(delegate, method); } } } /** * Is the supplied method a valid handler method? * <p>Does not consider {@code Controller.handleRequest} itself * as handler method (to avoid potential stack overflow). */ private boolean isHandlerMethod(Method method) { Class<?> returnType = method.getReturnType(); if (ModelAndView.class == returnType || Map.class == returnType || String.class == returnType || void.class == returnType) { Class<?>[] parameterTypes = method.getParameterTypes(); return (parameterTypes.length >= 2 && HttpServletRequest.class == parameterTypes[0] && HttpServletResponse.class == parameterTypes[1] && !("handleRequest".equals(method.getName()) && parameterTypes.length == 2)); } return false; } /** * Is the supplied method a valid exception handler method? */ private boolean isExceptionHandlerMethod(Method method) { return (isHandlerMethod(method) && method.getParameterTypes().length == 3 && Throwable.class.isAssignableFrom(method.getParameterTypes()[2])); } /** * Registers the supplied method as a request handler. */ private void registerHandlerMethod(Method method) { if (logger.isDebugEnabled()) { logger.debug("Found action method [" + method + "]"); } this.handlerMethodMap.put(method.getName(), method); } /** * Registers a last-modified handler method for the supplied handler method * if one exists. */ private void registerLastModifiedMethodIfExists(Object delegate, Method method) { // Look for corresponding LastModified method. try { Method lastModifiedMethod = delegate.getClass().getMethod( method.getName() + LAST_MODIFIED_METHOD_SUFFIX, new Class<?>[] { HttpServletRequest.class }); Class<?> returnType = lastModifiedMethod.getReturnType(); if (!(long.class == returnType || Long.class == returnType)) { throw new IllegalStateException("last-modified method [" + lastModifiedMethod + "] declares an invalid return type - needs to be 'long' or 'Long'"); } // Put in cache, keyed by handler method name. this.lastModifiedMethodMap.put(method.getName(), lastModifiedMethod); if (logger.isDebugEnabled()) { logger.debug("Found last-modified method for handler method [" + method + "]"); } } catch (NoSuchMethodException ex) { // No last modified method. That's ok. } } /** * Registers the supplied method as an exception handler. */ private void registerExceptionHandlerMethod(Method method) { this.exceptionHandlerMap.put(method.getParameterTypes()[2], method); if (logger.isDebugEnabled()) { logger.debug("Found exception handler method [" + method + "]"); } } //--------------------------------------------------------------------- // Implementation of LastModified //--------------------------------------------------------------------- /** * Try to find an XXXXLastModified method, where XXXX is the name of a handler. * Return -1 if there's no such handler, indicating that content must be updated. * @see org.springframework.web.servlet.mvc.LastModified#getLastModified(HttpServletRequest) */ @Override public long getLastModified(HttpServletRequest request) { try { String handlerMethodName = this.methodNameResolver.getHandlerMethodName(request); Method lastModifiedMethod = this.lastModifiedMethodMap.get(handlerMethodName); if (lastModifiedMethod != null) { try { // Invoke the last-modified method... Long wrappedLong = (Long) lastModifiedMethod.invoke(this.delegate, request); return (wrappedLong != null ? wrappedLong : -1); } catch (Exception ex) { // We encountered an error invoking the last-modified method. // We can't do anything useful except log this, as we can't throw an exception. logger.error("Failed to invoke last-modified method", ex); } } } catch (NoSuchRequestHandlingMethodException ex) { // No handler method for this request. This shouldn't happen, as this // method shouldn't be called unless a previous invocation of this class // has generated content. Do nothing, that's OK: We'll return default. } return -1L; } //--------------------------------------------------------------------- // Implementation of AbstractController //--------------------------------------------------------------------- /** * Determine a handler method and invoke it. * @see MethodNameResolver#getHandlerMethodName * @see #invokeNamedMethod * @see #handleNoSuchRequestHandlingMethod */ @Override protected ModelAndView handleRequestInternal(HttpServletRequest request, HttpServletResponse response) throws Exception { try { String methodName = this.methodNameResolver.getHandlerMethodName(request); return invokeNamedMethod(methodName, request, response); } catch (NoSuchRequestHandlingMethodException ex) { return handleNoSuchRequestHandlingMethod(ex, request, response); } } /** * Handle the case where no request handler method was found. * <p>The default implementation logs a warning and sends an HTTP 404 error. * Alternatively, a fallback view could be chosen, or the * NoSuchRequestHandlingMethodException could be rethrown as-is. * @param ex the NoSuchRequestHandlingMethodException to be handled * @param request current HTTP request * @param response current HTTP response * @return a ModelAndView to render, or {@code null} if handled directly * @throws Exception an Exception that should be thrown as result of the servlet request */ protected ModelAndView handleNoSuchRequestHandlingMethod(NoSuchRequestHandlingMethodException ex, HttpServletRequest request, HttpServletResponse response) throws Exception { pageNotFoundLogger.warn(ex.getMessage()); response.sendError(HttpServletResponse.SC_NOT_FOUND); return null; } /** * Invokes the named method. * <p>Uses a custom exception handler if possible; otherwise, throw an * unchecked exception; wrap a checked exception or Throwable. */ protected final ModelAndView invokeNamedMethod(String methodName, HttpServletRequest request, HttpServletResponse response) throws Exception { Method method = this.handlerMethodMap.get(methodName); if (method == null) { throw new NoSuchRequestHandlingMethodException(methodName, getClass()); } try { Class<?>[] paramTypes = method.getParameterTypes(); List<Object> params = new ArrayList<Object>(4); params.add(request); params.add(response); if (paramTypes.length >= 3 && HttpSession.class == paramTypes[2]) { HttpSession session = request.getSession(false); if (session == null) { throw new HttpSessionRequiredException( "Pre-existing session required for handler method '" + methodName + "'"); } params.add(session); } // If last parameter isn't of HttpSession type, it's a command. if (paramTypes.length >= 3 && HttpSession.class != paramTypes[paramTypes.length - 1]) { Object command = newCommandObject(paramTypes[paramTypes.length - 1]); params.add(command); bind(request, command); } Object returnValue = method.invoke(this.delegate, params.toArray(new Object[params.size()])); return massageReturnValueIfNecessary(returnValue); } catch (InvocationTargetException ex) { // The handler method threw an exception. return handleException(request, response, ex.getTargetException()); } catch (Exception ex) { // The binding process threw an exception. return handleException(request, response, ex); } } /** * Processes the return value of a handler method to ensure that it either returns * {@code null} or an instance of {@link ModelAndView}. When returning a {@link Map}, * the {@link Map} instance is wrapped in a new {@link ModelAndView} instance. */ @SuppressWarnings("unchecked") private ModelAndView massageReturnValueIfNecessary(Object returnValue) { if (returnValue instanceof ModelAndView) { return (ModelAndView) returnValue; } else if (returnValue instanceof Map) { return new ModelAndView().addAllObjects((Map<String, ?>) returnValue); } else if (returnValue instanceof String) { return new ModelAndView((String) returnValue); } else { // Either returned null or was 'void' return. // We'll assume that the handle method already wrote the response. return null; } } /** * Create a new command object of the given class. * <p>This implementation uses {@code BeanUtils.instantiateClass}, * so commands need to have public no-arg constructors. * Subclasses can override this implementation if desired. * @throws Exception if the command object could not be instantiated * @see org.springframework.beans.BeanUtils#instantiateClass(Class) */ protected Object newCommandObject(Class<?> clazz) throws Exception { if (logger.isDebugEnabled()) { logger.debug("Creating new command of class [" + clazz.getName() + "]"); } return BeanUtils.instantiateClass(clazz); } /** * Bind request parameters onto the given command bean * @param request request from which parameters will be bound * @param command command object, that must be a JavaBean * @throws Exception in case of invalid state or arguments */ protected void bind(HttpServletRequest request, Object command) throws Exception { logger.debug("Binding request parameters onto MultiActionController command"); ServletRequestDataBinder binder = createBinder(request, command); binder.bind(request); if (this.validators != null) { for (Validator validator : this.validators) { if (validator.supports(command.getClass())) { ValidationUtils.invokeValidator(validator, command, binder.getBindingResult()); } } } binder.closeNoCatch(); } /** * Create a new binder instance for the given command and request. * <p>Called by {@code bind}. Can be overridden to plug in custom * ServletRequestDataBinder subclasses. * <p>The default implementation creates a standard ServletRequestDataBinder, * and invokes {@code initBinder}. Note that {@code initBinder} * will not be invoked if you override this method! * @param request current HTTP request * @param command the command to bind onto * @return the new binder instance * @throws Exception in case of invalid state or arguments * @see #bind * @see #initBinder */ protected ServletRequestDataBinder createBinder(HttpServletRequest request, Object command) throws Exception { ServletRequestDataBinder binder = new ServletRequestDataBinder(command, getCommandName(command)); initBinder(request, binder); return binder; } /** * Return the command name to use for the given command object. * <p>Default is "command". * @param command the command object * @return the command name to use * @see #DEFAULT_COMMAND_NAME */ protected String getCommandName(Object command) { return DEFAULT_COMMAND_NAME; } /** * Initialize the given binder instance, for example with custom editors. * Called by {@code createBinder}. * <p>This method allows you to register custom editors for certain fields of your * command class. For instance, you will be able to transform Date objects into a * String pattern and back, in order to allow your JavaBeans to have Date properties * and still be able to set and display them in an HTML interface. * <p>The default implementation is empty. * <p>Note: the command object is not directly passed to this method, but it's available * via {@link org.springframework.validation.DataBinder#getTarget()} * @param request current HTTP request * @param binder new binder instance * @throws Exception in case of invalid state or arguments * @see #createBinder * @see org.springframework.validation.DataBinder#registerCustomEditor * @see org.springframework.beans.propertyeditors.CustomDateEditor */ protected void initBinder(HttpServletRequest request, ServletRequestDataBinder binder) throws Exception { if (this.webBindingInitializer != null) { this.webBindingInitializer.initBinder(binder, new ServletWebRequest(request)); } } /** * Determine the exception handler method for the given exception. * <p>Can return {@code null} if not found. * @return a handler for the given exception type, or {@code null} * @param exception the exception to handle */ protected Method getExceptionHandler(Throwable exception) { Class<?> exceptionClass = exception.getClass(); if (logger.isDebugEnabled()) { logger.debug("Trying to find handler for exception class [" + exceptionClass.getName() + "]"); } Method handler = this.exceptionHandlerMap.get(exceptionClass); while (handler == null && exceptionClass != Throwable.class) { if (logger.isDebugEnabled()) { logger.debug("Trying to find handler for exception superclass [" + exceptionClass.getName() + "]"); } exceptionClass = exceptionClass.getSuperclass(); handler = this.exceptionHandlerMap.get(exceptionClass); } return handler; } /** * We've encountered an exception thrown from a handler method. * Invoke an appropriate exception handler method, if any. * @param request current HTTP request * @param response current HTTP response * @param ex the exception that got thrown * @return a ModelAndView to render the response */ private ModelAndView handleException(HttpServletRequest request, HttpServletResponse response, Throwable ex) throws Exception { Method handler = getExceptionHandler(ex); if (handler != null) { if (logger.isDebugEnabled()) { logger.debug("Invoking exception handler [" + handler + "] for exception: " + ex); } try { Object returnValue = handler.invoke(this.delegate, request, response, ex); return massageReturnValueIfNecessary(returnValue); } catch (InvocationTargetException ex2) { logger.error("Original exception overridden by exception handling failure", ex); ReflectionUtils.rethrowException(ex2.getTargetException()); } catch (Exception ex2) { logger.error("Failed to invoke exception handler method", ex2); } } else { // If we get here, there was no custom handler or we couldn't invoke it. ReflectionUtils.rethrowException(ex); } throw new IllegalStateException("Should never get here"); } }