Date: 2004-09-19T08:09:20
Editor: MichaelMcGrady <[EMAIL PROTECTED]>
Wiki: Apache Struts Wiki
Page: StrutsCatalogMultipleButtonSolutions
URL: http://wiki.apache.org/struts/StrutsCatalogMultipleButtonSolutions
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##language:en
== Table of Contents ==
{{{
1 Table of Contents
2 PROBLEM: Universal Button Solutions: SOLUTIONS: DispatchUtil, (new)
DispatchAction, ButtonTagUtil
3 Uses
3.1 Action Class Code
3.2 Mulitiple Image Tags
3.3 Link Tags
3.4 Submit Tags
3.5 File Browse Tags
3.6 Button Tags
3.7 struts-config.xml Uses
3.7.1 MappingDispatchAction
3.7.2 LookupDispatchAction
4 SOLUTION ONE: DispatchUtil Code
5 (new) DispatchAction
5.1 Discussion
5.2 SOLUTION TWO: (new) DispatchAction Code
6 POJO: Solution for Tags without Dispatch, without Reflection, without
ActionMapping or Even without Struts
6.1 Discussion
6.2 SOLUTION THREE: ButtonTagUtil Code
7 Links
8 Comments (Peanut Gallery)
}}}
== Universal Button Utility for Struts ==
There is a persistent problem in web applications in handling multiple buttons, and
this is especially a problem when the buttons are images.
Struts has provided a solution for this with DispatchAction and its progeny. I have
found this solution to be too heavy, too complicated, and too obtuse. So, I have
engendered my own.
The principle reason for this class is the problem with <input type='image'
name='whatever'> tags in HTML. Those tag send the values in the name attribute as
''whatever.x=9'' and ''whatever.y=26''. DispatchAction and its progeny provide a
melange of solutions but no common way to deal with ''<a href='whatever.do'>'',
''<input type='submit'>'', ''<input type='image'>'', ''<input type='file'>'', or
whatever. This class, DispatchUtil does that. If you prefer to use a subclass, just
provide the functionality in this class in a class extending Action. Herbert Rabago
came up with the idea of providing the functionality in a utility class and I really
like that idea. So, here we go.
== Uses ==
'''N.B. the uses of "dispatch".''' If you do not like using "dispatch", then you can
rewrite the code in the getMethodName(...) method. Essentially, you will need to
replace ".dispatch" with something else in the tag names which you can identify in the
enumeration. You have to use a suffix with this logic. But, if you want a prefix,
e.g. "dispatch.update" or "method.update", then you will have to change the logic too.
Suffix logic seems to best fit the existing methods in String. Otherwise, I would
have used a prefix. You may want to anyway.
=== Action Class Code to Use ===
In all the following tag uses, you use the Action class code in execute(...) or
process(...) as given directly below.
{{{
ActionForward = forward = new
DispatchUtil().dispatch(this,mapping,form,request,response);
}}}
=== Multiple Image Tags ===
Multiple image tags are the primary reason for this class. Integrating this into a
common solution is the difficulty.
{{{
<input type='image' name='update.dispatch' src='update.gif'>
<input type='image' name='delete.dispatch' src='delete.gif'>
}}}
=== Link Tags ===
{{{
<a href='profile.do?update.dispatch=whatever'>
<a href='profile.do?delete.dispatch=whatever'>
}}}
=== Submit Tags ===
{{{
<input type='submit' name='update.dispatch' value='whatever'>
<input type='submit' name='delete.dispatch' value='whatever'>
}}}
=== File Browse Tags ===
{{{
<input type='file' name='update.dispatch'>
<input type='file' name='delete.dispatch'>
}}}
=== Button Tags ===
{{{
<input type='button' name='update.dispatch' value='whatever'>
<input type='button' name='delete.dispatch' value='whatever'>
}}}
=== struts-config.xml Uses ===
If you like to do things the way they are done with DispatchActions and use Struts xml
for commands, then the following are possibilities. '''Please note that you never
have to do this. Struts xml configuration is wholly voluntary for this solution.'''
If you want the sort of behavior you get with MappingDispatchAction using
DispatchUtil, then you do as we indicate. This does not mean, of course, that you
have to use MappingDispatchAction. DispatchUtil completely absorbs all the
functionality of the DispatchActions. You will see, further, that no
struts-config.xml configuration is required at all for LookupDispatchActions.
==== MappingDispatchAction ====
This solution depends not on the value of the name attributes in the html tags, but
strictly on the value of the path attributes in the html tags, anytime
/updateProfile.do is called in the example below, any name attributes will be
overridden and the value of the ActionMapping property called "parameter" will be
operative instead.
{{{<action path="/updateProfile"
type="org.example.ProfileAction"
parameter="update.dispatch"
name="profileForm"
validate="true"
input="/editProfile.jsp"
scope="request">
<forward name="success" path="/updatedProfile.jsp"/>
</action>
<action path="/deleteSubscription"
type="org.example.ProfileAction"
name="profileForm"
scope="request"
input="/subscription.jsp"
parameter="delete.dispatch">
<forward name="success" path="/deletedSubscription.jsp"/>
</action>
}}}
==== LookupDispatchAction ====
This solution depends not on the value of the path attribute or the parameter property
in the ActionMapping, notice that no parameter attribute exists below, but strictly on
the values of the name attributes as indicated in our section on the tags. In other
words, we don't have to configure struts-config.xml for what used to be
LookupDispatchActions.
{{{
<action path="/updateProfile"
type="org.example.ProfileAction"
name="profileForm"
validate="true"
input="/editProfile.jsp"
scope="request">
<forward name="success" path="/updatedProfile.jsp"/>
</action>
<action path="/deleteSubscription"
type="org.example.ProfileAction"
name="profileForm"
scope="request"
input="/subscription.jsp"
<forward name="success" path="/deletedSubscription.jsp"/>
</action>
}}}
== Code ==
{{{
package com.crackwillow.struts.util.dispatch;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Enumeration;
import java.util.HashMap;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
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;
public class DispatchUtil {
protected static Log log =
LogFactory.getLog(DispatchUtil.class);
protected static MessageResources messages = MessageResources.getMessageResources
("org.apache.struts.actions.LocalStrings");
protected HashMap methods = new HashMap();
protected Class [] types = { ActionMapping.class,
ActionForm.class,
HttpServletRequest.class,
HttpServletResponse.class };
public ActionForward dispatch(Action action,
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
String methodName = getMethodName(request,mapping);
Class clazz = action.getClass();
if ("execute".equals(methodName) || "perform".equals(methodName)){
// Prevent recursive calls
String message = messages.getMessage("dispatch.recursive", mapping.getPath());
log.error(message);
throw new ServletException(message);
}
return dispatchMethod(action,clazz,mapping, form, request, response, methodName);
}
protected ActionForward dispatchMethod(Action action,
Class clazz,
ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response,
String name)
throws Exception {
if (name == null) {
return this.unspecified(mapping, form, request, response);
}
Method method = null;
try {
method = getMethod(clazz,name);
} catch(NoSuchMethodException nsme) {
String message = messages.getMessage("dispatch.method", mapping.getPath(), name);
log.error(message, nsme);
throw nsme;
}
ActionForward forward = null;
try {
Object args[] = { mapping, form, request, response };
forward = (ActionForward)method.invoke(action, args);
} catch(ClassCastException cce) {
String message = messages.getMessage("dispatch.return", mapping.getPath(), name);
log.error(message, cce);
throw cce;
} catch(IllegalAccessException iae) {
String message = messages.getMessage("dispatch.error", mapping.getPath(), name);
log.error(message, iae);
throw iae;
} catch(InvocationTargetException ite) {
Throwable t = ite.getTargetException();
if (t instanceof Exception) {
throw ((Exception) t);
} else {
String message = messages.getMessage("dispatch.error", mapping.getPath(),
name);
log.error(message, ite);
throw new ServletException(t);
}
}
return (forward);
}
protected static String getMethodName(HttpServletRequest request, ActionMapping
mapping) {
String methodName = null;
String buttonValue = null;
String paramProperty = mapping.getParameter();
if((paramProperty != null)) {
methodName = paramProperty.substring(0,paramProperty.indexOf('.'));
} else {
Enumeration enum = request.getParameterNames();
while(enum.hasMoreElements()) {
buttonValue = (String)enum.nextElement();
StdOut.log("log.dispatch","DispatchUtil buttonValue = " + buttonValue);
if(buttonValue.indexOf(".dispatch") >= 0) {
methodName = buttonValue;
break;
}
}
}
return methodName.substring(0,methodName.indexOf('.'));
}
protected Method getMethod(Class clazz,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);
}
}
protected ActionForward unspecified(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
String message = messages.getMessage( "dispatch.parameter", mapping.getPath(),
getMethodName(request,mapping));
log.error(message);
throw new ServletException(message);
}
}
}}}
== (new) DispatchAction ==
=== Discussion ===
If, rather than having a utility class provide the functionality, you prefer an Action
class. Here is a redoing of the DispatchAction class to let you do that. You use
this class for '''ALL''' the progeny of DispatchAction class, i.e. this class replaces
completely DispatchAction, LookupDispatchAction, and MappingDispatchAction. You can
alter this class to get whatever subsidiary functionality you might want and which
some might consider essential.
=== Code ===
{{{
package com.crackwillow.struts.action;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Enumeration;
import java.util.HashMap;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
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;
public abstract class DispatchAction
extends Action {
protected Class clazz = this.getClass();
protected static Log log =
LogFactory.getLog(SimpleDispatchAction.class);
protected static MessageResources messages = MessageResources.getMessageResources
("org.apache.struts.actions.LocalStrings");
protected HashMap methods = new HashMap();
protected Class[] types = { ActionMapping.class,
ActionForm.class,
HttpServletRequest.class,
HttpServletResponse.class };
public ActionForward execute(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
String name = getMethodName(request,mapping);
if ("execute".equals(name) || "perform".equals(name)){
// Prevent recursive calls
String message = messages.getMessage("dispatch.recursive", mapping.getPath());
log.error(message);
throw new ServletException(message);
}
return dispatchMethod(mapping, form, request, response, name);
}
protected ActionForward dispatchMethod(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response,
String name)
throws Exception {
if (name == null) {
return this.unspecified(mapping, form, request, response);
}
Method method = null;
try {
method = getMethod(name);
} catch(NoSuchMethodException nsme) {
String message = messages.getMessage("dispatch.method", mapping.getPath(), name);
log.error(message, nsme);
throw nsme;
}
ActionForward forward = null;
try {
Object args[] = {mapping, form, request, response};
forward = (ActionForward) method.invoke(this, args);
} catch(ClassCastException cce) {
String message = messages.getMessage("dispatch.return", mapping.getPath(), name);
log.error(message, cce);
throw cce;
} catch(IllegalAccessException iae) {
String message = messages.getMessage("dispatch.error", mapping.getPath(), name);
log.error(message, iae);
throw iae;
} catch(InvocationTargetException ite) {
Throwable t = ite.getTargetException();
if (t instanceof Exception) {
throw ((Exception) t);
} else {
String message = messages.getMessage("dispatch.error", mapping.getPath(),
name);
log.error(message, ite);
throw new ServletException(t);
}
}
return (forward);
}
protected static String getMethodName(HttpServletRequest request, ActionMapping
mapping) {
String methodName = null;
String buttonValue = null;
String paramProperty = mapping.getParameter();
if((paramProperty != null)) {
methodName = paramProperty.substring(0,paramProperty.indexOf('.'));
} else {
Enumeration enum = request.getParameterNames();
while(enum.hasMoreElements()) {
buttonValue = (String)enum.nextElement();
StdOut.log("log.dispatch","DispatchUtil buttonValue = " + buttonValue);
if(buttonValue.indexOf(".dispatch") >= 0) {
methodName = buttonValue;
break;
}
}
}
return methodName.substring(0,methodName.indexOf('.'));
}
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);
}
}
protected ActionForward unspecified(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
String message = messages.getMessage( "dispatch.parameter", mapping.getPath(),
getMethodName(request,mapping));
log.error(message);
throw new ServletException(message);
}
protected ActionForward cancelled(ActionMapping mapping,
ActionForm form,
HttpServletRequest request,
HttpServletResponse response)
throws Exception {
return null;
}
}
}}}
== POJO: Solution for Tags without Dispatch, without Reflection, without ActionMapping
or Even without Struts ==
=== Discussion ===
You can use the same strategy to determine what button tag has been clicked without
employing Struts. The best way to do this, in my opinion, in the following solution.
=== Code ===
{{{
public class ButtonTagUtil {
public static String getName(HttpServletRequest request) {
String methodName = null;
String buttonValue = null;
Enumeration enum = request.getParameterNames();
while(enum.hasMoreElements()) {
buttonValue = (String)enum.nextElement();
if(buttonValue.indexOf(".dispatch") >= 0) {
methodName = buttonValue;
break;
}
}
return methodName.substring(0,methodName.indexOf('.'));
}
}
}}}
=== Links ===
StrutsCatalogMultipleImageTagsSimplified
StrutsCatalogInstrumentableForms
StrutsCatalogSimpleDispatchAction
StrutsCatalogMappedBeans
StrutsCatalogHidingImagesAndOtherResourcesUnderWEBINF
== Comments (Please Put Comments Here) ==
If your comments are extensive, you might want to provide a link instead of adding to
this already incredibly verbose presentation.
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