| Transaction.java |
/*
* GeoTools - The Open Source Java GIS Toolkit
* http://geotools.org
*
* (C) 2002-2008, Open Source Geospatial Foundation (OSGeo)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation;
* version 2.1 of the License.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*/
package org.geotools.data;
import java.io.IOException;
import java.util.Set;
/**
* The controller for Transaction with FeatureStore.
*
* <p>
* Shapefiles, databases, etc. are safely modified with the assistance of this
* interface. Transactions are also to provide authorization when working with
* locked features.
* </p>
*
* <p>
* All operations are considered to be working against a Transaction.
* Transaction.AUTO_COMMIT is used to represent an immidiate mode where
* requests are immidately commited.
* </p>
*
* <p>
* For more information please see DataStore and FeatureStore.
* </p>
*
* <p>
* Example Use:
* </p>
* <pre><code>
* Transaction t = new DefaultTransaction("handle");
* t.putProperty( "hint", new Integer(7) );
* try {
* SimpleFeatureStore road = (SimpleFeatureStore) store.getFeatureSource("road");
* FeatureStore river = (SimpleFeatureStore) store.getFeatureSource("river");
*
* road.setTransaction( t );
* river.setTransaction( t );
*
* t.addAuthorization( lockID ); // provide authoriztion
* road.removeFeatures( filter ); // operate against transaction
* river.removeFeature( filter ); // operate against transaction
*
* t.commit(); // commit operations
* }
* catch (IOException io){
* t.rollback(); // cancel operations
* }
* finally {
* t.close(); // free resources
* }
* </code></pre>
* <p>
* Example code walkthrough (from the perspective of Transaction):
* </p>
* <ol>
* <li>A new transaction is created (an instanceof DefaultTransaction with a handle)</li>
* <li>A hint is provided using Transaction.putProperty( key, value )</li>
* <li>Transaction is provided to two FeatureStores, this may result
* in Transaction.State instances being registered</li>
* <ul>
* <li>TransactionStateDiff (stored by DataStore):
* Used for in memory locking is used by many DataStore's
* (like ShapefileDataStore).
* Lazy creation by AbstractDataStore.state(transaction).
* </li>
* <li>JDBCTransactionState (stored by ConnectionPool):
* Used to manage connection rollback/commit.
* Lazy creation as part of JDBCDataStore.getConnection(transaction).
* </li>
* <li>InProcessLockingManager.FeatureLock (stored by LockingManger):
* Used for per transaction FeatureLocks, used to free locked features
* on Transaction commit/rollback.
* </li>
* </ul>
* These instances of Transaction state may make use of any hint provided
* to Transaction.putProperty( key, value ) when they are connected with
* Transaction.State.setTransaction( transaction ).
* <li>t.addAuthorization(lockID) is called, each Transaction.State has its
* addAuthroization(String) callback invoked with the value of lockID</li>
* <li>FeatureStore.removeFeatures methods are called on the two DataStores.
* <ul>
* <li>PostgisFeatureStore.removeFeatures(fitler) handles operation
* without delegation.
* </li>
* <li>Most removeFeature(filter) implementations use the implementation
* provided by AbstractFeatureStore which delegates to FeatureWriter.
* </li>
* </ul>
* Any of these operations may make use of the
* Transaction.putProperty( key, value ).
* <li>The transaction is commited, all of the Transaction.State methods have
* there Transaction.State.commit() methods called gicing them a chance
* to applyDiff maps, or commit various connections.
* </li>
* <li>The transaction is closed, all of the Transaction.State methods have
* there Transaction.State.setTransaction( null ) called, giving them a
* chance to clean up diffMaps, or return connections to the pool.
* </li>
* </ol>
* @author Jody Garnett
* @author Chris Holmes, TOPP
* @source $URL: http://svn.osgeo.org/geotools/tags/2.7-M3/modules/library/api/src/main/java/org/geotools/data/Transaction.java $
* @version $Id: Transaction.java 35372 2010-05-05 11:50:22Z mbedward $
*/
public interface Transaction {
/**
* Represents AUTO_COMMIT mode as opposed to operations with commit/rollback
* control under a user-supplied transaction.
*/
static final Transaction AUTO_COMMIT = new AutoCommitTransaction();
//
// External State
//
/**
* Retrive a Transaction property held by this transaction.
*
* <p>
* This may be used to provide hints to DataStore implementations, it
* operates as a blackboard for client, SimpleFeatureSource communication.
* </p>
*
* <p>
* If this proves successful addAuthorization/getAuthorization will be
* replaced with this mechanism.
* </p>
*/
Object getProperty(Object key);
/**
* List of Authorizations IDs held by this transaction.
*
* <p>
* This list is reset by the next call to commit() or rollback().
* </p>
*
* <p>
* Authorization IDs are used to provide FeatureLock support.
* </p>
*
* @return List of Authorization IDs
*/
Set<String> getAuthorizations();
/**
* Allows SimpleFeatureSource to squirel away information( and callbacks ) for
* later.
*
* <p>
* The most common example is a JDBC DataStore saving the required
* connection for later operations.
* </p>
* <pre><code>
* ConnectionState implements State {
* public Connection conn;
* public addAuthorization() {}
* public commit(){ conn.commit(); }
* public rollback(){ conn.rollback(); }
* }
* </code></pre>
*
* <p>
* putState will call State.setTransaction( transaction ) to allow State a
* chance to configure itself.
* </p>
*
* @param key Key used to externalize State
* @param state Externalized State
*/
void putState(Object key, State state);
/**
* Allows FeatureSources to clean up information ( and callbacks ) they
* earlier provided.
*
* <p>
* Care should be taken when using shared State to not remove State
* required by another FeatureSources.
* </p>
*
* <p>
* removeState will call State.setTransaction( null ) to allow State a
* chance cleanup after itself.
* </p>
*
* @param key Key that was used to externalize State
*/
void removeState(Object key);
/**
* Allows DataStores to squirel away information( and callbacks ) for
* later.
*
* <p>
* The most common example is a JDBC DataStore saving the required
* connection for later operations.
* </p>
*
* @return Current State externalized by key, or <code>null</code> if not
* found
*/
State getState(Object key);
//
// Flow Control
//
/**
* Makes all transactions made since the previous commit/rollback
* permanent.
*
* <p>
* FeatureSources will need to issue any changes notifications using a
* FeatureEvent.FEATURES_CHANGED to all FeatureSources with the same
* typeName and a different Transaction. FeatureSources with the same
* Transaction will of been notified of changes as the FeaureWriter made
* them.
* </p>
*
* @throws DataSourceException if there are any datasource errors.
*
* @see #setAutoCommit(boolean)
*/
void commit() throws IOException;
/**
* Undoes all transactions made since the last commit or rollback.
*
* <p>
* FeatureSources will need to issue any changes notifications using a
* FeatureEvent.FEATURES_CHANGED. This will need to be issued to all
* FeatureSources with the same typeName and Transaction.
* </p>
*
* @throws DataSourceException if there are problems with the datasource.
* @throws UnsupportedOperationException if the rollback method is not
* supported by this datasource.
*
* @see #setAutoCommit(boolean)
*/
void rollback() throws IOException;
//
// Locking Support
//
/**
* Provides an Authorization ID for this Transaction.
*
* <p>
* All proceeding modifyFeatures,removeFeature, unLockFeatures, refreshLock
* and ReleaseLock operations will make use of the provided authorization.
* </p>
*
* <p>
* Authorization is only maintained until the this Transaction is commited
* or rolledback.
* </p>
*
* <p>
* That is operations will only succeed if affected features either:
* </p>
*
* <ul>
* <li>
* not locked
* </li>
* <li>
* locked with the provided authID
* </li>
* </ul>
*
* <p>
* Authorization ID is provided as a String, rather than a FeatureLock, to
* account for across process lock use.
* </p>
*
* @param authID
*/
void addAuthorization(String authID) throws IOException;
/**
* Provides a Transaction property for this Transasction.
*
* <p>
* All proceeding SimpleFeatureSource (for FeatureReader/Writer) operations may
* make use of the provided property.
* </p>
*/
void putProperty(Object key, Object value) throws IOException;
/**
* Provides an opportunity for a Transaction to free an State it maintains.
* <p>
* This method should call State.setTransaction( null ) on all State it
* maintains.
* </p>
* <p>
* It is hoped that FeatureStore implementations that have externalized
* their State with the transaction take the opportunity to revert to
* Transction.AUTO_COMMIT.
* </p>
* @throws IOException
*/
void close() throws IOException;
/**
* DataStore implementations can use this interface to externalize the
* state they require to implement Transaction Support.
*
* <p>
* The commit and rollback methods will be called as required. The
* intension is that several DataStores can share common transaction state
* (example: Postgis DataStores sharing a connection to the same
* database).
* </p>
*
* @author jgarnett, Refractions Reasearch Inc.
* @version CVS Version
*
* @see org.geotools.data
*/
static public interface State {
/**
* Provides configuration information for Transaction.State
*
* <p>
* setTransaction is called with non null <code>transaction</code> when
* Transaction.State is <code>putState</code> into a Transaction. This
* tranasction will be used to determine correct event notification.
* </p>
*
* <p>
* setTransaction is called with <code>null</code> when removeState is
* called (usually during Transaction.close() ).
* </p>
*
* @param transaction
*/
void setTransaction(Transaction transaction);
/**
* Call back used for Transaction.setAuthorization()
*/
void addAuthorization(String AuthID) throws IOException;
/**
* Call back used for Transaction.commit()
*/
void commit() throws IOException;
/**
* Call back used for Transaction.rollback()
*/
void rollback() throws IOException;
}
}