IExecutableExtension.java

/*******************************************************************************
 * Copyright (c) 2000, 2006 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 * 
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.core.runtime;

import org.eclipse.core.runtime.CoreException;

/**
 * Interface for executable extension classes that require access to 
 * their configuration element, or implement an extension adapter.
 * <p>
 * Extension adapters are typically required in cases where the extension
 * implementation does not follow the interface rules specified
 * by the provider of the extension point. In these
 * cases, the role of the adapter is to map between the extension point
 * interface, and the actual extension implementation. In general, adapters
 * are used when attempting to plug-in existing Java implementations, or
 * non-Java implementations (e.g., external executables).
 * </p><p>
 * This interface can be used without OSGi running.
 * </p><p>
 * Clients may implement this interface.
 * </p>
 * 
 * @see IConfigurationElement#createExecutableExtension(String)
 */
public interface IExecutableExtension {
	/**
	 * This method is called by the implementation of the method
	 * <code>IConfigurationElement.createExecutableExtension</code>
	 * on a newly constructed extension, passing it its relevant configuration 
	 * information. Most executable extensions only make use of the first 
	 * two call arguments.
	 * <p>
	 * Regular executable extensions specify their Java implementation 
	 * class name as an attribute of the configuration element for the 
	 * extension. For example
	 * <pre>
	 *     <action run="com.example.BaseAction"/>
	 * </pre>
	 * In the above example, this method would be called with a reference
	 * to the <code><action></code> element (first argument), and
	 * <code>"run"</code> as the name of the attribute that defined
	 * this executable extension (second argument).
	 * </p>
	 * <p>
	 * The last parameter is for the specific use of extension adapters
	 * and is typically not used by regular executable extensions.
	 * </p>
	 * <p>
	 * There are two supported ways of associating additional
	 * adapter-specific data with the configuration in a way that
	 * is transparent to the extension point implementor:
	 * </p>
	 * <p>
	 * (1) by specifying adapter data as part of the implementation
	 * class attribute value. The Java class name can be followed
	 * by a ":" separator, followed by any adapter data in string
	 * form. For example, if the extension point specifies an attribute
	 * <code>"run"</code> to contain the name of the extension implementation,
	 * an adapter can be configured as
	 * <pre>
	 *     <action run="com.example.ExternalAdapter:./cmds/util.exe -opt 3"/>
	 * </pre>
	 * </p>
	 * <p>
	 * (2) by converting the attribute used to specify the executable
	 * extension to a child element of the original configuration element,
	 * and specifying the adapter data in the form of xml markup.
	 * Using this form, the example above would become
	 * <pre>
	 *     <action>
	 *         <<it>run</it> class="com.xyz.ExternalAdapter">
	 *             <parameter name="exec" value="./cmds/util.exe"/>
	 *             <parameter name="opt"  value="3"/>
	 *         </<it>run</it>>
	 *     </action>
	 * </pre>
	 * </p>
	 * <p>
	 * Form (2) will typically only be
	 * used for extension points that anticipate the majority of
	 * extensions configured into it will in fact be in the form
	 * of adapters.
	 * </p>
	 * <p>
	 * In either case, the specified adapter class is instantiated using its
	 * 0-argument public constructor. The adapter data is passed as the
	 * last argument of this method. The data argument is defined as Object.
	 * It can have the following values:
	 * <ul>
	 * <li><code>null</code>, if no adapter data was supplied</li>
	 * <li>in case (1), the initialization data
	 *		string is passed as a <code>String</code></li>
	 * <li>in case (2), the initialization data is passed
	 *		as a <code>Hashtable</code> containing the actual
	 *		parameter names and values (both <code>String</code>s)</li>
	 * </ul>
	 * </p>
	 *
	 * @param config the configuration element used to trigger this execution. 
	 *		It can be queried by the executable extension for specific
	 *		configuration properties
	 * @param propertyName the name of an attribute of the configuration element
	 *		used on the <code>createExecutableExtension(String)</code> call. This
	 *		argument can be used in the cases where a single configuration element
	 *		is used to define multiple executable extensions.
	 * @param data adapter data in the form of a <code>String</code>, 
	 *		a <code>Hashtable</code>, or <code>null</code>.
	 * @exception CoreException if error(s) detected during initialization processing
	 * @see IConfigurationElement#createExecutableExtension(String)
	 */
	public void setInitializationData(IConfigurationElement config, String propertyName, Object data) throws CoreException;
}