X-Git-Url: https://gerrit.simantics.org/r/gitweb?a=blobdiff_plain;ds=sidebyside;f=bundles%2Forg.simantics.db%2Fsrc%2Forg%2Fsimantics%2Fdb%2Frequest%2FAsyncRead.java;fp=bundles%2Forg.simantics.db%2Fsrc%2Forg%2Fsimantics%2Fdb%2Frequest%2FAsyncRead.java;h=99d59792aacc775587a5f53748f9b442b41be1ab;hb=969bd23cab98a79ca9101af33334000879fb60c5;hp=0000000000000000000000000000000000000000;hpb=866dba5cd5a3929bbeae85991796acb212338a08;p=simantics%2Fplatform.git
diff --git a/bundles/org.simantics.db/src/org/simantics/db/request/AsyncRead.java b/bundles/org.simantics.db/src/org/simantics/db/request/AsyncRead.java
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+/*******************************************************************************
+ * Copyright (c) 2007, 2010 Association for Decentralized Information Management
+ * in Industry THTH ry.
+ * 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:
+ * VTT Technical Research Centre of Finland - initial API and implementation
+ *******************************************************************************/
+package org.simantics.db.request;
+
+ import org.simantics.db.AsyncReadGraph;
+import org.simantics.db.Session;
+import org.simantics.db.exception.CancelTransactionException;
+import org.simantics.db.procedure.AsyncProcedure;
+
+/**
+ * TODO: fix this documentation, it is completely out-of-date!
+ *
+ * The GraphRequest
interface is used to create transaction
+ * requests to Simantics database implementations. Both read and write
+ * transaction requests use the same interface.
+ *
+ *
+ * The actual work carried out by the implemented request should be done in the
+ * perform
method. It receives a Graph
instance as
+ * the only argument which is the interface for actually reading and writing the
+ * graph data model.
+ *
+ *
+ * Transaction requests can be made to the database by creating your own
+ * GraphRequest
instance and putting it in the request queue of
+ * the database session through the {@link Session} interface. The database
+ * session is responsible for executing the queued requests in a thread of its
+ * choice, or possibly/preferably multiple threads. The database session can
+ * allow multiple read-only requests to occur simultaneously, but read-write
+ * requests require exclusive database access. In other words only one
+ * read-write request can be in execution simultaneously.
+ *
+ *
+ * This interface also has two callbacks -
+ * Perform receives an object instance implementing the
+ * The general contract of the method handleException
for
+ * allowing handling any exceptions thrown by perform
and
+ * requestCompleted
for performing actions after a request has
+ * been successfully completed.
+ *
+ * @author Antti Villberg
+ * @see AsyncReadGraph
+ * @see AsyncProcedure
+ * @see Session
+ */
+public interface AsyncReadGraphRequest
is serviced by the database session
+ * the method perform
is invoked.
+ *
+ * Graph
+ * interface which provides the only way to read/write the graph data model.
+ * The Graph instance must only be valid during the execution of the
+ * perform
method and therefore should not be stored for use
+ * outside of its execution.
+ *
+ * perform
is that it may
+ * take any action whatsoever which involves reading or writing the data
+ * model through the received Graph instance.
+ *
+ * @param g an interface for reading and writing the data model
+ * @return the result status of the request which affects how the
+ * transaction proceeds, see GraphRequestStatus for more information
+ * @throws Exception when anything goes wrong inside the request thread
+ * @throws CancelTransactionException to indicate that the request needs to
+ * be cancelled and any changes rolled back
+ */
+ void perform(AsyncReadGraph graph, AsyncProcedure