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/*
* $Id: ActionDispatcher.java 471754 2006-11-06 14:55:09Z husted $
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.apache.struts.actions;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.struts.Globals;
import org.apache.struts.action.Action;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.util.MessageResources;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.HashMap;
/**
* Action helper class that dispatches to a public method in an
* Action.
This class is provided as an alternative mechanism to
* using DispatchAction and its various flavours and means Dispatch
* behaviour can be easily implemented into any Action without
* having to inherit from a particular super Action.
* To implement dispatch behaviour in an Action class,
* create your custom Action as follows, along with the methods you require
* (and optionally "cancelled" and "unspecified" methods):
*
* public class MyCustomAction extends Action {
*
* protected ActionDispatcher dispatcher
* = new ActionDispatcher(this, ActionDispatcher.MAPPING_FLAVOR);
*
* public ActionForward execute(ActionMapping mapping,
* ActionForm form,
* HttpServletRequest request,
* HttpServletResponse response)
* throws Exception {
* return dispatcher.execute(mapping, form, request, response);
* }
* }
*
*
*
* It provides three flavours of determing the name of the method:
*
*
*
* - {@link #DEFAULT_FLAVOR} - uses the parameter
* specified in the struts-config.xml to get the method name from the Request
* (equivalent to
DispatchAction except uses "method" as a
* default if the parameter is not specified in the
* struts-config.xml).
*
* - {@link #DISPATCH_FLAVOR}
* - uses the parameter specified in the struts-config.xml to get the method
* name from the Request (equivalent to
DispatchAction).
*
* - {@link #MAPPING_FLAVOR} - uses the parameter
* specified in the struts-config.xml as the method name (equivalent to
*
MappingDispatchAction).
*
*
* @version $Rev: 471754 $ $Date: 2006-11-06 08:55:09 -0600 (Mon, 06 Nov 2006) $
* @since Struts 1.2.7
*/
public class ActionDispatcher {
// ----------------------------------------------------- Instance Variables
/**
* Indicates "default" dispatch flavor.
*/
public static final int DEFAULT_FLAVOR = 0;
/**
* Indicates "mapping" dispatch flavor.
*/
public static final int MAPPING_FLAVOR = 1;
/**
* Indicates flavor compatible with DispatchAction.
*/
public static final int DISPATCH_FLAVOR = 2;
/**
* Commons Logging instance.
*/
protected static Log log = LogFactory.getLog(ActionDispatcher.class);
/**
* The message resources for this package.
*/
protected static MessageResources messages =
MessageResources.getMessageResources(
"org.apache.struts.actions.LocalStrings");
/**
* The associated Action to dispatch to.
*/
protected Action actionInstance;
/**
* Indicates dispatch flavor.
*/
protected int flavor;
/**
* The Class instance of this DispatchAction class.
*/
protected Class clazz;
/**
* The set of Method objects we have introspected for this class, keyed by
* method name. This collection is populated as different methods are
* called, so that introspection needs to occur only once per method
* name.
*/
protected HashMap methods = new HashMap();
/**
* The set of argument type classes for the reflected method call. These
* are the same for all calls, so calculate them only once.
*/
protected Class[] types =
{
ActionMapping.class, ActionForm.class, HttpServletRequest.class,
HttpServletResponse.class
};
// ----------------------------------------------------- Constructors
/**
* Construct an instance of this class from the supplied parameters.
*
* @param actionInstance The action instance to be invoked.
*/
public ActionDispatcher(Action actionInstance) {
this(actionInstance, DEFAULT_FLAVOR);
}
/**
* Construct an instance of this class from the supplied parameters.
*
* @param actionInstance The action instance to be invoked.
* @param flavor The flavor of dispatch to use.
*/
public ActionDispatcher(Action actionInstance, int flavor) {
this.actionInstance = actionInstance;
this.flavor = flavor;
clazz = actionInstance.getClass();
}
// --------------------------------------------------------- Public Methods
/**
* Process the specified HTTP request, and create the corresponding HTTP
* response (or forward to another web component that will create it).
* Return an ActionForward instance describing where and how
* control should be forwarded, or null if the response has
* already been completed.
*
* @param mapping The ActionMapping used to select this instance
* @param form The optional ActionForm bean for this request (if any)
* @param request The HTTP request we are processing
* @param response The HTTP response we are creating
* @return The forward to which control should be transferred, or
* null if the response has been completed.
* @throws Exception if an exception occurs
*/
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
// Process "cancelled"
if (isCancelled(request)) {
ActionForward af = cancelled(mapping, form, request, response);
if (af != null) {
return af;
}
}
// Identify the request parameter containing the method name
String parameter = getParameter(mapping, form, request, response);
// Get the method's name. This could be overridden in subclasses.
String name =
getMethodName(mapping, form, request, response, parameter);
// Prevent recursive calls
if ("execute".equals(name) || "perform".equals(name)) {
String message =
messages.getMessage("dispatch.recursive", mapping.getPath());
log.error(message);
throw new ServletException(message);
}
// Invoke the named method, and return the result
return dispatchMethod(mapping, form, request, response, name);
}
/**
* Dispatches to the target class' unspecified method, if
* present, otherwise throws a ServletException. Classes utilizing
* ActionDispatcher should provide an unspecified
* method if they wish to provide behavior different than throwing a
* ServletException.
*
* @param mapping The ActionMapping used to select this instance
* @param form The optional ActionForm bean for this request (if any)
* @param request The non-HTTP request we are processing
* @param response The non-HTTP response we are creating
* @return The forward to which control should be transferred, or
* null if the response has been completed.
* @throws Exception if the application business logic throws an
* exception.
*/
protected ActionForward unspecified(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
// Identify if there is an "unspecified" method to be dispatched to
String name = "unspecified";
Method method = null;
try {
method = getMethod(name);
} catch (NoSuchMethodException e) {
String message =
messages.getMessage("dispatch.parameter", mapping.getPath(),
mapping.getParameter());
log.error(message);
throw new ServletException(message);
}
return dispatchMethod(mapping, form, request, response, name, method);
}
/**
* Dispatches to the target class' cancelled method, if present,
* otherwise returns null. Classes utilizing ActionDispatcher
* should provide a cancelled method if they wish to provide
* behavior different than returning null.
*
* @param mapping The ActionMapping used to select this instance
* @param form The optional ActionForm bean for this request (if any)
* @param request The non-HTTP request we are processing
* @param response The non-HTTP response we are creating
* @return The forward to which control should be transferred, or
* null if the response has been completed.
* @throws Exception if the application business logic throws an
* exception.
*/
protected ActionForward cancelled(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
// Identify if there is an "cancelled" method to be dispatched to
String name = "cancelled";
Method method = null;
try {
method = getMethod(name);
} catch (NoSuchMethodException e) {
return null;
}
return dispatchMethod(mapping, form, request, response, name, method);
}
// ----------------------------------------------------- Protected Methods
/**
* Dispatch to the specified method.
*
* @param mapping The ActionMapping used to select this instance
* @param form The optional ActionForm bean for this request (if any)
* @param request The non-HTTP request we are processing
* @param response The non-HTTP response we are creating
* @param name The name of the method to invoke
* @return The forward to which control should be transferred, or
* null if the response has been completed.
* @throws Exception if the application business logic throws an
* exception.
*/
protected ActionForward dispatchMethod(ActionMapping mapping,
ActionForm form, HttpServletRequest request,
HttpServletResponse response, String name)
throws Exception {
// Make sure we have a valid method name to call.
// This may be null if the user hacks the query string.
if (name == null) {
return this.unspecified(mapping, form, request, response);
}
// Identify the method object to be dispatched to
Method method = null;
try {
method = getMethod(name);
} catch (NoSuchMethodException e) {
String message =
messages.getMessage("dispatch.method", mapping.getPath(), name);
log.error(message, e);
String userMsg =
messages.getMessage("dispatch.method.user", mapping.getPath());
throw new NoSuchMethodException(userMsg);
}
return dispatchMethod(mapping, form, request, response, name, method);
}
/**
* Dispatch to the specified method.
*
* @param mapping The ActionMapping used to select this instance
* @param form The optional ActionForm bean for this request (if any)
* @param request The non-HTTP request we are processing
* @param response The non-HTTP response we are creating
* @param name The name of the method to invoke
* @param method The method to invoke
* @return The forward to which control should be transferred, or
* null if the response has been completed.
* @throws Exception if the application business logic throws an
* exception.
*/
protected ActionForward dispatchMethod(ActionMapping mapping,
ActionForm form, HttpServletRequest request,
HttpServletResponse response, String name, Method method)
throws Exception {
ActionForward forward = null;
try {
Object[] args = { mapping, form, request, response };
forward = (ActionForward) method.invoke(actionInstance, args);
} catch (ClassCastException e) {
String message =
messages.getMessage("dispatch.return", mapping.getPath(), name);
log.error(message, e);
throw e;
} catch (IllegalAccessException e) {
String message =
messages.getMessage("dispatch.error", mapping.getPath(), name);
log.error(message, e);
throw e;
} catch (InvocationTargetException e) {
// Rethrow the target exception if possible so that the
// exception handling machinery can deal with it
Throwable t = e.getTargetException();
if (t instanceof Exception) {
throw ((Exception) t);
} else {
String message =
messages.getMessage("dispatch.error", mapping.getPath(),
name);
log.error(message, e);
throw new ServletException(t);
}
}
// Return the returned ActionForward instance
return (forward);
}
/**
* Introspect the current class to identify a method of the specified name
* that accepts the same parameter types as the execute
* method does.
*
* @param name Name of the method to be introspected
* @return The method with the specified name.
* @throws NoSuchMethodException if no such method can be found
*/
protected Method getMethod(String name)
throws NoSuchMethodException {
synchronized (methods) {
Method method = (Method) methods.get(name);
if (method == null) {
method = clazz.getMethod(name, types);
methods.put(name, method);
}
return (method);
}
}
/**
* Returns the parameter value as influenced by the selected {@link
* #flavor} specified for this ActionDispatcher.
*
* @param mapping The ActionMapping used to select this instance
* @param form The optional ActionForm bean for this request (if any)
* @param request The HTTP request we are processing
* @param response The HTTP response we are creating
* @return The ActionMapping parameter's value
* @throws Exception if an error occurs.
*/
protected String getParameter(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
String parameter = mapping.getParameter();
if ("".equals(parameter)) {
parameter = null;
}
if ((parameter == null) && (flavor == DEFAULT_FLAVOR)) {
// use "method" for DEFAULT_FLAVOR if no parameter was provided
return "method";
}
if ((parameter == null)
&& ((flavor == MAPPING_FLAVOR) || (flavor == DISPATCH_FLAVOR))) {
String message =
messages.getMessage("dispatch.handler", mapping.getPath());
log.error(message);
throw new ServletException(message);
}
return parameter;
}
/**
* Returns the method name, given a parameter's value.
*
* @param mapping The ActionMapping used to select this instance
* @param form The optional ActionForm bean for this request (if
* any)
* @param request The HTTP request we are processing
* @param response The HTTP response we are creating
* @param parameter The ActionMapping parameter's name
* @return The method's name.
* @throws Exception if an error occurs.
*/
protected String getMethodName(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response,
String parameter) throws Exception {
// "Mapping" flavor, defaults to "method"
if (flavor == MAPPING_FLAVOR) {
return parameter;
}
// default behaviour
return request.getParameter(parameter);
}
/**
* Returns true if the current form's cancel button was
* pressed. This method will check if the Globals.CANCEL_KEY
* request attribute has been set, which normally occurs if the cancel
* button generated by CancelTag was pressed by the user
* in the current request. If true, validation performed by
* an ActionForm's validate() method will
* have been skipped by the controller servlet.
*
* @param request The servlet request we are processing
* @return true if the current form's cancel button was
* pressed; false otherwise.
* @see org.apache.struts.taglib.html.CancelTag
*/
protected boolean isCancelled(HttpServletRequest request) {
return (request.getAttribute(Globals.CANCEL_KEY) != null);
}
}
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