model/org/eclipse/jdt/core/IOpenable.java

/**********************************************************************
Copyright (c) 2000, 2001, 2002 IBM Corp. and others.
All rights reserved.   This program and the accompanying materials
are made available under the terms of the Common Public License v0.5
which accompanies this distribution, and is available at
http://www.eclipse.org/legal/cpl-v05.html
 
Contributors:
     IBM Corporation - initial API and implementation
**********************************************************************/
package org.eclipse.jdt.core;

import org.eclipse.core.runtime.IProgressMonitor;

/**
 * Common protocol for Java elements that must be opened before they can be 
 * navigated or modified. Opening a textual element (such as a compilation unit)
 * involves opening a buffer on its contents.  While open, any changes to the buffer
 * can be reflected in the element's structure; 
 * see <code>isConsistent</code> and <code>makeConsistent(IProgressMonitor)</code>.
 * <p>
 * To reduce complexity in clients, elements are automatically opened
 * by the Java model as element properties are accessed. The Java model maintains
 * an LRU cache of open elements, and automatically closes elements as they
 * are swapped out of the cache to make room for other elements. Elements with
 * unsaved changes are never removed from the cache, and thus, if the client
 * maintains many open elements with unsaved
 * changes, the LRU cache can grow in size (in this case the cache is not
 * bounded). However, as elements are saved, the cache will shrink back to its
 * original bounded size.
 * </p>
 * <p>
 * To open an element, all openable parent elements must be open.
 * The Java model automatically opens parent elements, as it automatically opens elements.
 * Opening an element may provide access to direct children and other descendants,
 * but does not automatically open any descendents which are themselves <code>IOpenable</code>.
 * For example, opening a compilation unit provides access to all its constituent elements,
 * but opening a package fragment does not open all compilation units in the package fragment.
 * </p>
 * <p>
 * This interface is not intended to be implemented by clients.
 * </p>
 */
public interface IOpenable {

/**
 * Closes this element and its buffer (if any).
 * Closing an element which is not open has no effect.
 *
 * <p>Note: although <code>close</code> is exposed in the API, clients are
 * not expected to open and close elements - the Java model does this automatically
 * as elements are accessed.
 *
 * @exception JavaModelException if an error occurs closing this element
 */
public void close() throws JavaModelException;
/**
 * Returns the buffer opened for this element, or <code>null</code>
 * if this element does not have a buffer.
 *
 * @exception JavaModelException if this element does not exist or if an
 *		exception occurs while accessing its corresponding resource.
 */
public IBuffer getBuffer() throws JavaModelException;
/**
 * Returns <code>true</code> if this element is open and:
 * <ul>
 * <li>its buffer has unsaved changes, or
 * <li>one of its descendants has unsaved changes, or
 * <li>a working copy has been created on one of this
 * element's children and has not yet destroyed
 * </ul>
 *
 * @exception JavaModelException if this element does not exist or if an
 *		exception occurs while accessing its corresponding resource.
 */
boolean hasUnsavedChanges() throws JavaModelException;
/**
 * Returns whether the element is consistent with its underlying resource or buffer.
 * The element is consistent when opened, and is consistent if the underlying resource
 * or buffer has not been modified since it was last consistent.
 *
 * <p>NOTE: Child consistency is not considered. For example, a package fragment
 * responds <code>true</code> when it knows about all of its
 * compilation units present in its underlying folder. However, one or more of
 * the compilation units could be inconsistent.
 *
 * @exception JavaModelException if this element does not exist or if an
 *		exception occurs while accessing its corresponding resource.
 *
 * @see IOpenable#makeConsistent
 */
boolean isConsistent() throws JavaModelException;
/**
 * Returns whether this openable is open. This is a handle-only method.
 */
boolean isOpen();
/**
 * Makes this element consistent with its underlying resource or buffer 
 * by updating the element's structure and properties as necessary.
 *
 * @exception JavaModelException if the element is unable to access the contents
 * 		of its underlying resource. Reasons include:
 * <ul>
 *  <li>This Java element does not exist (ELEMENT_DOES_NOT_EXIST)</li>
 * </ul>
 * @see IOpenable#isConsistent
 */
void makeConsistent(IProgressMonitor progress) throws JavaModelException;
/**
 * Opens this element and all parent elements that are not already open.
 * For compilation units, a buffer is opened on the contents of the underlying resource.
 *
 * <p>Note: although <code>open</code> is exposed in the API, clients are
 * not expected to open and close elements - the Java model does this automatically
 * as elements are accessed.
 *
 * @exception JavaModelException if an error occurs accessing the contents
 * 		of its underlying resource. Reasons include:
 * <ul>
 *  <li>This Java element does not exist (ELEMENT_DOES_NOT_EXIST)</li>
 * </ul>
 */
public void open(IProgressMonitor progress) throws JavaModelException;
/**
 * Saves any changes in this element's buffer to its underlying resource
 * via a workspace resource operation. This has no effect if the element has no underlying
 * buffer, or if there are no unsaved changed in the buffer.
 * <p>
 * The <code>force</code> parameter controls how this method deals with
 * cases where the workbench is not completely in sync with the local file system.
 * If <code>false</code> is specified, this method will only attempt
 * to overwrite a corresponding file in the local file system provided
 * it is in sync with the workbench. This option ensures there is no 
 * unintended data loss; it is the recommended setting.
 * However, if <code>true</code> is specified, an attempt will be made
 * to write a corresponding file in the local file system, 
 * overwriting any existing one if need be.
 * In either case, if this method succeeds, the resource will be marked 
 * as being local (even if it wasn't before).
 * <p>
 * As a result of this operation, the element is consistent with its underlying 
 * resource or buffer. 
 *
 * @exception JavaModelException if an error occurs accessing the contents
 * 		of its underlying resource. Reasons include:
 * <ul>
 *  <li>This Java element does not exist (ELEMENT_DOES_NOT_EXIST)</li>
 *  <li>This Java element is read-only (READ_ONLY)</li>
 * </ul>
 */
public void save(IProgressMonitor progress, boolean force) throws JavaModelException;
}