xdocs/howto/action-event-howto.xml - turbine-core - Git at Google

 <?xml version="1.0"?>
 <!--
 /*
  * Copyright 2001-2004 The Apache Software Foundation.
  *
  * 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.
  */
  -->

 <document>

  <properties>
   <title>Action Events Howto</title>
  </properties>

 <body>

 <section name="Action Events">

 <p>
 Turbine has a very useful feature that makes handling form submission
 much more painless for the developer. In order to understand this, you
 need to be familiar with the way that Turbine handles Actions. What happens
 is that when a URI has the action= variable defined, a class is executed
 before all of your other Screen classes by your Page class. So, consider
 the following URI (I'm using the <a href="velocity-site-howto.html">
 VelocitySite Howto
 </a> example):
 </p>

 <p>
 http://www.server.com/servlet/Turbine/template/AddUser/action/NewUser
 What happens is that Turbine will first execute the Java class file Action
 named NewUser. Then, any class that extends the ActionEvent class instead
 of the Action class will be able to take advantage of what happens next...
 </p>

 <source><![CDATA[
 public class NewUser extends VelocityAction
 {
     public void doAdd (RunData data, Context context) throws Exception
     {
         // put code here to add the user to the system
         context.put ("username", username );
         data.setMessage("User Added!");
     }

     public void doPerform(RunData data, Context context) throws Exception
     {
         data.setMessage("Button not found!");
     }
 }
 ]]></source>

 <p>
 Then, write your HTML tags specially like this:
 </p>

 <source><![CDATA[
 <input type="submit" name="eventSubmit_doAdd" value="Add User">
 ]]></source>

 <p>
 When your Action is executed, an "event" is sent to it by attempting
 to execute a "doAdd()" method in your Action. The cool thing about this
 is that each of your "actions" that are performed within your Action class
 now are componentized into a single method that can be javadoc'ed individually.
 </p>

 <p>
 This new functionality does not mean that you should write all of your
 actions in one single class, what it means is that if you have a screen
 with many buttons on it that are very specific to that screen, it might
 be a good idea to place all those methods into a single class. This allows
 you to do it easily and also prevents you from having to do a "if then
 elseif" tree to figure out which button was clicked.
 </p>

 <p>
 For a catchall, the doPerform() method will be executed if no other
 method or button could be found.
 </p>

 <p>
 Because ParameterParser makes all the key values lowercase, we have
 to do some work to format the string into a method name. For example, a
 button name eventSubmit_doDelete gets converted into eventsubmit_dodelete.
 Thus, we need to form some sort of naming convention so that dodelete can
 be turned into doDelete.
 </p>

 <p>
 Thus, the convention is this:
 <ul>
     <li>
         The variable name MUST have the prefix "eventSubmit_".</li>

     <li>
         The variable name after the prefix MUST begin with the letters "do".</li>

     <li>
         The first letter after the "do" will be capitalized and the rest will be
         lowercase</li>
 </ul>
 </p>

 <p>
 If you follow these conventions, then you should be ok with your method
 naming in your Action class.
 </p>

 <p>
 There is a property in the TurbineResources.properties file, called "action.eventsubmit.needsvalue".
 If you set this to "true", only the events that contain a non-empty, non-zero value will be
 executed. This is useful if you have a form with multiple, different events, that need to be executed
 and the form is submitted by client-side code, e.g. JavaScript.
 </p>
 <p>
 If you want to trigger an action event from an html link, versus a button, then just add a parameter with the name eventSubmit_doMyaction.
 The value can be anything as the name is all that is important.
 </p>
 </section>

 </body>
 </document>
	<?xml version="1.0"?>
	<!--
	/*
	* Copyright 2001-2004 The Apache Software Foundation.
	*
	* 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.
	*/
	-->

	<document>

	<properties>
	<title>Action Events Howto</title>
	</properties>

	<body>

	<section name="Action Events">

	<p>
	Turbine has a very useful feature that makes handling form submission
	much more painless for the developer. In order to understand this, you
	need to be familiar with the way that Turbine handles Actions. What happens
	is that when a URI has the action= variable defined, a class is executed
	before all of your other Screen classes by your Page class. So, consider
	the following URI (I'm using the <a href="velocity-site-howto.html">
	VelocitySite Howto
	</a> example):
	</p>

	<p>
	http://www.server.com/servlet/Turbine/template/AddUser/action/NewUser
	What happens is that Turbine will first execute the Java class file Action
	named NewUser. Then, any class that extends the ActionEvent class instead
	of the Action class will be able to take advantage of what happens next...
	</p>

	<source><![CDATA[
	public class NewUser extends VelocityAction
	{
	public void doAdd (RunData data, Context context) throws Exception
	{
	// put code here to add the user to the system
	context.put ("username", username );
	data.setMessage("User Added!");
	}

	public void doPerform(RunData data, Context context) throws Exception
	{
	data.setMessage("Button not found!");
	}
	}
	]]></source>

	<p>
	Then, write your HTML tags specially like this:
	</p>

	<source><![CDATA[
	<input type="submit" name="eventSubmit_doAdd" value="Add User">
	]]></source>

	<p>
	When your Action is executed, an "event" is sent to it by attempting
	to execute a "doAdd()" method in your Action. The cool thing about this
	is that each of your "actions" that are performed within your Action class
	now are componentized into a single method that can be javadoc'ed individually.
	</p>

	<p>
	This new functionality does not mean that you should write all of your
	actions in one single class, what it means is that if you have a screen
	with many buttons on it that are very specific to that screen, it might
	be a good idea to place all those methods into a single class. This allows
	you to do it easily and also prevents you from having to do a "if then
	elseif" tree to figure out which button was clicked.
	</p>

	<p>
	For a catchall, the doPerform() method will be executed if no other
	method or button could be found.
	</p>

	<p>
	Because ParameterParser makes all the key values lowercase, we have
	to do some work to format the string into a method name. For example, a
	button name eventSubmit_doDelete gets converted into eventsubmit_dodelete.
	Thus, we need to form some sort of naming convention so that dodelete can
	be turned into doDelete.
	</p>

	<p>
	Thus, the convention is this:
	<ul>
	<li>
	The variable name MUST have the prefix "eventSubmit_".</li>

	<li>
	The variable name after the prefix MUST begin with the letters "do".</li>

	<li>
	The first letter after the "do" will be capitalized and the rest will be
	lowercase</li>
	</ul>
	</p>

	<p>
	If you follow these conventions, then you should be ok with your method
	naming in your Action class.
	</p>

	<p>
	There is a property in the TurbineResources.properties file, called "action.eventsubmit.needsvalue".
	If you set this to "true", only the events that contain a non-empty, non-zero value will be
	executed. This is useful if you have a form with multiple, different events, that need to be executed
	and the form is submitted by client-side code, e.g. JavaScript.
	</p>
	<p>
	If you want to trigger an action event from an html link, versus a button, then just add a parameter with the name eventSubmit_doMyaction.
	The value can be anything as the name is all that is important.
	</p>
	</section>

	</body>
	</document>