Spring Framework example source code file (MultiActionController.java)
The Spring Framework MultiActionController.java source code
/*
* Copyright 2002-2008 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.ServletRequest;
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);
*
* 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 void a return value of 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 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);
*
* The third parameter can be any subclass or {@link Exception} or
* {@link RuntimeException}.
*
* <p>There can also be an optional xxxLastModified method for
* handlers, of signature:
*
* <pre class="code">public long anyMeaningfulNameLastModified(HttpServletRequest request)
*
* 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>Note that all handler methods need to be public and that
* method overloading is <i>not allowed.
*
* <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>Note: 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
*/
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 handlerMethodMap = new HashMap();
/** LastModified methods, keyed by handler method name (without LAST_MODIFIED_SUFFIX) */
private final Map lastModifiedMethodMap = new HashMap();
/** Methods, keyed by exception class */
private final Map exceptionHandlerMap = new HashMap();
/**
* 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 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 (int i = 0; i < methods.length; i++) {
// We're looking for methods with given parameters.
Method method = methods[i];
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 Controller.handleRequest itself
* as handler method (to avoid potential stack overflow).
*/
private boolean isHandlerMethod(Method method) {
Class returnType = method.getReturnType();
if (ModelAndView.class.equals(returnType) || Map.class.equals(returnType) || String.class.equals(returnType) ||
void.class.equals(returnType)) {
Class[] parameterTypes = method.getParameterTypes();
return (parameterTypes.length >= 2 &&
HttpServletRequest.class.equals(parameterTypes[0]) &&
HttpServletResponse.class.equals(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.equals(returnType) || Long.class.equals(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)
*/
public long getLastModified(HttpServletRequest request) {
try {
String handlerMethodName = this.methodNameResolver.getHandlerMethodName(request);
Method lastModifiedMethod = (Method) this.lastModifiedMethodMap.get(handlerMethodName);
if (lastModifiedMethod != null) {
try {
// Invoke the last-modified method...
Long wrappedLong = (Long) lastModifiedMethod.invoke(this.delegate, new Object[] {request});
return (wrappedLong != null ? wrappedLong.longValue() : -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
*/
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 = (Method) this.handlerMethodMap.get(methodName);
if (method == null) {
throw new NoSuchRequestHandlingMethodException(methodName, getClass());
}
try {
Class[] paramTypes = method.getParameterTypes();
List params = new ArrayList(4);
params.add(request);
params.add(response);
if (paramTypes.length >= 3 && paramTypes[2].equals(HttpSession.class)) {
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 &&
!paramTypes[paramTypes.length - 1].equals(HttpSession.class)) {
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.
*/
private ModelAndView massageReturnValueIfNecessary(Object returnValue) {
if (returnValue instanceof ModelAndView) {
return (ModelAndView) returnValue;
}
else if (returnValue instanceof Map) {
return new ModelAndView().addAllObjects((Map) 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 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 (int i = 0; i < this.validators.length; i++) {
if (this.validators[i].supports(command.getClass())) {
ValidationUtils.invokeValidator(this.validators[i], command, binder.getBindingResult());
}
}
}
binder.closeNoCatch();
}
/**
* Create a new binder instance for the given command and request.
* <p>Called by bind. Can be overridden to plug in custom
* ServletRequestDataBinder subclasses.
* <p>The default implementation creates a standard ServletRequestDataBinder,
* and invokes <code>initBinder. Note that 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));
}
initBinder((ServletRequest) request, binder);
}
/**
* Initialize the given binder instance, for example with custom editors.
* @deprecated as of Spring 2.0:
* use <code>initBinder(HttpServletRequest, ServletRequestDataBinder) instead
*/
protected void initBinder(ServletRequest request, ServletRequestDataBinder binder) throws Exception {
}
/**
* Determine the exception handler method for the given exception.
* <p>Can return 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 = (Method) this.exceptionHandlerMap.get(exceptionClass);
while (handler == null && !exceptionClass.equals(Throwable.class)) {
if (logger.isDebugEnabled()) {
logger.debug("Trying to find handler for exception superclass [" + exceptionClass.getName() + "]");
}
exceptionClass = exceptionClass.getSuperclass();
handler = (Method) 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, new Object[] {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");
}
}
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