Migrated source code from Simantics SVN

[simantics/platform.git] / bundles / org.simantics.db / src / org / simantics / db / request / DelayedWrite.java

diff --git a/bundles/org.simantics.db/src/org/simantics/db/request/DelayedWrite.java b/bundles/org.simantics.db/src/org/simantics/db/request/DelayedWrite.java
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+/*******************************************************************************\r
+ * Copyright (c) 2007, 2010 Association for Decentralized Information Management\r
+ * in Industry THTH ry.\r
+ * All rights reserved. This program and the accompanying materials\r
+ * are made available under the terms of the Eclipse Public License v1.0\r
+ * which accompanies this distribution, and is available at\r
+ * http://www.eclipse.org/legal/epl-v10.html\r
+ *\r
+ * Contributors:\r
+ *     VTT Technical Research Centre of Finland - initial API and implementation\r
+ *******************************************************************************/\r
+package org.simantics.db.request;\r
+\r
+import java.util.Map;\r
+\r
+import org.simantics.db.ChangeSetIdentifier;\r
+import org.simantics.db.Session;\r
+import org.simantics.db.VirtualGraph;\r
+import org.simantics.db.WriteGraph;\r
+import org.simantics.db.exception.CancelTransactionException;\r
+import org.simantics.db.exception.DatabaseException;\r
+\r
+/**\r
+ * The <code>GraphRequest</code> interface is used to create transaction\r
+ * requests to Simantics database implementations. Both read and write\r
+ * transaction requests use the same interface.\r
+ * \r
+ * <p>\r
+ * The actual work carried out by the implemented request should be done in the\r
+ * <code>perform</code> method. It receives a <code>Graph</code> instance as\r
+ * the only argument which is the interface for actually reading and writing the\r
+ * graph data model.\r
+ * \r
+ * <p>\r
+ * Transaction requests can be made to the database by creating your own\r
+ * <code>GraphRequest</code> instance and putting it in the request queue of\r
+ * the database session through the {@link Session} interface. The database\r
+ * session is responsible for executing the queued requests in a thread of its\r
+ * choice, or possibly/preferably multiple threads. The database session can\r
+ * allow multiple read-only requests to occur simultaneously, but read-write\r
+ * requests require exclusive database access. In other words only one\r
+ * read-write request can be in execution simultaneously.\r
+ * \r
+ * <p>\r
+ * This interface also has two callbacks - <code>handleException</code> for\r
+ * allowing handling any exceptions thrown by <code>perform</code> and\r
+ * <code>requestCompleted</code> for performing actions after a request has\r
+ * been successfully completed.\r
+ * \r
+ * <p>\r
+ * Clients of this interface are encouraged to extend the provided abstract\r
+ * implementations or this class or extend their own helper implementations for\r
+ * ones particular needs. The provided abstract implementations are:\r
+ * <ul>\r
+ * <li>{@link ReadGraphRequestAdapter} provides default implementations for\r
+ * everything except {@link #perform(WriteGraph)}.</li>\r
+ * <li>{@link SimpleGraphRequest} replaces {@link #perform(WriteGraph)} with\r
+ * {@link SimpleGraphRequest#run(WriteGraph)} for easier request implementation in\r
+ * simple cases.</li>\r
+ * <li>{@link GraphRequestWithResult} makes it easier for the user to return\r
+ * a single result Object from the request.</li>\r
+ * </ul>\r
+ * \r
+ * @author Tuukka Lehtonen\r
+ * @see ReadGraphRequestAdapter\r
+ * @see GraphRequestRunner\r
+ * @see GraphRequestStatus\r
+ * @see GraphRequestWithResult\r
+ * @see Session\r
+ * @see SimpleGraphRequest\r
+ */\r
+public interface DelayedWrite extends WriteTraits {\r
+\r
+    /**\r
+     * When a <code>GraphRequest</code> is serviced by the database session\r
+     * the method <code>perform</code> is invoked.\r
+     * \r
+     * <p>\r
+     * Perform receives an object instance implementing the <code>Graph</code>\r
+     * interface which provides the only way to read/write the graph data model.\r
+     * The Graph instance must only be valid during the execution of the\r
+     * <code>perform</code> method and therefore should not be stored for use\r
+     * outside of its execution.\r
+     * \r
+     * <p>\r
+     * The general contract of the method <code>perform</code> is that it may\r
+     * take any action whatsoever which involves reading or writing the data\r
+     * model through the received Graph instance.\r
+     * \r
+     * @param g an interface for reading and writing the data model\r
+     * @return the result status of the request which affects how the\r
+     *         transaction proceeds, see GraphRequestStatus for more information\r
+     * @throws Exception when anything goes wrong inside the request thread\r
+     * @throws CancelTransactionException to indicate that the request needs to\r
+     *         be cancelled and any changes rolled back\r
+     */\r
+    void perform(WriteGraph graph) throws DatabaseException;\r
+    \r
+    ChangeSetIdentifier getIdentifier();\r
+    \r
+    VirtualGraph getProvider();\r
+    \r
+    void fillMetadata(Map<String, String> metadata);\r
+}\r