/*******************************************************************************
* Copyright (c) 2000, 2015 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.ui.internal.navigator.extensions;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import org.eclipse.core.runtime.IConfigurationElement;
import org.eclipse.core.runtime.IExtension;
import org.eclipse.core.runtime.IExtensionPoint;
import org.eclipse.core.runtime.IExtensionRegistry;
import org.eclipse.core.runtime.Platform;
import org.eclipse.ui.internal.navigator.NavigatorPlugin;
/**
* Template implementation of a registry reader that creates objects representing registry contents.
* Typically, an extension contains one element, but this reader handles multiple elements per
* extension.
*
* To start reading the extensions from the registry for an extension point, call the method
* <code>readRegistry</code>.
*
* To read children of an IConfigurationElement, call the method <code>readElementChildren</code>
* from your implementation of the method <code>readElement</code>, as it will not be done by
* default.
* <p>
* <strong>EXPERIMENTAL</strong>. This class or interface has been added as part of a work in
* progress. There is a guarantee neither that this API will work nor that it will remain the same.
* Please do not use this API without consulting with the Platform/UI team.
* </p>
*
* @since 3.2
*/
public abstract class RegistryReader {
protected static final String TAG_DESCRIPTION = "description"; //$NON-NLS-1$
private boolean isInitialized;
private final String extensionPointId;
private final String pluginId;
private final IExtensionRegistry registry;
/**
* The constructor.
*/
protected RegistryReader(String aPluginId, String anExtensionPoint) {
this.registry = Platform.getExtensionRegistry();
this.pluginId = aPluginId;
this.extensionPointId = anExtensionPoint;
}
/**
* This method extracts description as a subelement of the given element.
*
* @return description string if defined, or empty string if not.
*/
protected String getDescription(IConfigurationElement config) {
IConfigurationElement[] children = config.getChildren(TAG_DESCRIPTION);
if (children.length >= 1) {
return children[0].getValue();
}
return "";//$NON-NLS-1$
}
/**
* Logs the error in the workbench log using the provided text and the information in the
* configuration element.
*/
protected static void logError(IConfigurationElement element, String text) {
IExtension extension = element.getDeclaringExtension();
StringBuffer buf = new StringBuffer();
buf.append("Plugin " + extension.getNamespaceIdentifier() + ", extension " + extension.getExtensionPointUniqueIdentifier());//$NON-NLS-2$//$NON-NLS-1$
buf.append("\n" + text);//$NON-NLS-1$
NavigatorPlugin.logError(0, buf.toString(), null);
}
/**
* Logs a very common registry error when a required attribute is missing.
*/
protected static void logMissingAttribute(IConfigurationElement element, String attributeName) {
logError(element, "Required attribute '" + attributeName + "' not defined");//$NON-NLS-2$//$NON-NLS-1$
}
/**
* Logs a very common registry error when a required child is missing.
*/
protected static void logMissingElement(IConfigurationElement element, String elementName) {
logError(element, "Required sub element '" + elementName + "' not defined");//$NON-NLS-2$//$NON-NLS-1$
}
/**
* Logs a registry error when the configuration element is unknown.
*/
protected static void logUnknownElement(IConfigurationElement element) {
logError(element, "Unknown extension tag found: " + element.getName());//$NON-NLS-1$
}
/**
* Apply a reproducable order to the list of extensions provided, such that the order will not
* change as extensions are added or removed.
*/
protected IExtension[] orderExtensions(IExtension[] extensions) {
// By default, the order is based on plugin id sorted
// in ascending order. The order for a plugin providing
// more than one extension for an extension point is
// dependent in the order listed in the XML file.
IExtension[] sortedExtension = new IExtension[extensions.length];
System.arraycopy(extensions, 0, sortedExtension, 0, extensions.length);
Comparator comparer = new Comparator() {
@Override
public int compare(Object arg0, Object arg1) {
String s1 = ((IExtension) arg0).getNamespaceIdentifier();
String s2 = ((IExtension) arg1).getNamespaceIdentifier();
return s1.compareToIgnoreCase(s2);
}
};
Collections.sort(Arrays.asList(sortedExtension), comparer);
return sortedExtension;
}
/**
* Implement this method to read element's attributes. If children should also be read, then
* implementor is responsible for calling <code>readElementChildren</code>. Implementor is
* also responsible for logging missing attributes.
*
* @return true if element was recognized, false if not.
*/
protected abstract boolean readElement(IConfigurationElement element);
/**
* Read the element's children. This is called by the subclass' readElement method when it wants
* to read the children of the element.
*/
protected void readElementChildren(IConfigurationElement element) {
readElements(element.getChildren());
}
/**
* Read each element one at a time by calling the subclass implementation of
* <code>readElement</code>.
*
* Logs an error if the element was not recognized.
*/
protected void readElements(IConfigurationElement[] elements) {
for (int i = 0; i < elements.length; i++) {
if (!readElement(elements[i])) {
logUnknownElement(elements[i]);
}
}
}
/**
* Read one extension by looping through its configuration elements.
*/
protected void readExtension(IExtension extension) {
readElements(extension.getConfigurationElements());
}
/**
* Start the registry reading process using the supplied plugin ID and extension point.
*/
public void readRegistry() {
if (isInitialized) {
return;
}
synchronized (this) {
if (!isInitialized) {
IExtensionPoint point = registry.getExtensionPoint(pluginId, extensionPointId);
if (point == null) {
return;
}
IExtension[] extensions = point.getExtensions();
extensions = orderExtensions(extensions);
for (IExtension extension : extensions) {
readExtension(extension);
}
isInitialized = true;
}
}
}
}