/*******************************************************************************
* Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.internal.history;
import java.io.*;
import org.eclipse.persistence.platform.server.ServerPlatform;
import org.eclipse.persistence.queries.*;
import org.eclipse.persistence.exceptions.*;
import org.eclipse.persistence.history.*;
import org.eclipse.persistence.internal.helper.*;
import org.eclipse.persistence.internal.sessions.*;
/**
* INTERNAL:
* <b>Purpose</b>: Allows the reading of objects as of a past time.
* <p>
* <b>Description</b>: All queries executed through this special lightweight
* session will return results as of a past time. Objects read will be cached
* in a special isolated cache.
* <p>
* <b>Responsibilities</b>:
* <ul>
* <li> Execute all read queries as of a past time.
* <li> Insure that all objects read are cached in an Identity map completely isolated from that of its parent.
* <li> Once a query has been uniquely prepared to read past objects, execute the call on the parent session.
* </ul>
* <p>
* @author Stephen McRitchie
* @since OracleAS TopLink 10<i>g</i> (10.1.3)
* @see org.eclipse.persistence.sessions.Session#acquireHistoricalSession
*/
public class HistoricalSession extends AbstractSession {
protected final AbstractSession parent;
protected final AsOfClause asOfClause;
/**
* INTERNAL:
* Create and return a new Historical Session.
*/
public HistoricalSession(AbstractSession parent, AsOfClause clause) {
super();
this.asOfClause = clause;
this.parent = parent;
// As a lightweight session copy over all fields, do not clone them.
this.project = parent.getProject();
this.queries = parent.getQueries();
this.profiler = parent.getProfiler();
this.isInProfile = parent.isInProfile();
this.isLoggingOff = parent.isLoggingOff();
this.sessionLog = parent.getSessionLog();
if (parent.hasEventManager()) {
this.eventManager = parent.getEventManager().clone(this);
}
this.exceptionHandler = parent.getExceptionHandler();
this.descriptors = parent.getDescriptors();
}
/**
* INTERNAL:
* Acquires a special historical session for reading objects as of a past time.
*/
public org.eclipse.persistence.sessions.Session acquireHistoricalSession(org.eclipse.persistence.history.AsOfClause clause) throws ValidationException {
throw ValidationException.cannotAcquireHistoricalSession();
}
/**
* INTERNAL:
* A UnitOfWork can not be acquired from a Historical Session.
*/
public UnitOfWorkImpl acquireUnitOfWork() {
throw ValidationException.operationNotSupported(Helper.getShortClassName(getClass()) + ".acquireUnitOfWork");
}
/**
* INTERNAL:
* No transactions should be used inside a HistoricalSession.
*/
public void beginTransaction() throws DatabaseException, ConcurrencyException {
throw ValidationException.operationNotSupported(Helper.getShortClassName(getClass()) + ".beginTransaction");
}
/**
* INTERNAL:
* No transactions should be used inside a HistoricalSession.
*/
public void commitTransaction() throws DatabaseException, ConcurrencyException {
throw ValidationException.operationNotSupported(Helper.getShortClassName(getClass()) + ".commitTransaction");
}
/**
* INTERNAL:
* Gets the session which this query will be executed on.
* Generally will be called immediately before the call is translated,
* which is immediately before session.executeCall.
* <p>
* Since the execution session also knows the correct datasource platform
* to execute on, it is often used in the mappings where the platform is
* needed for type conversion, or where calls are translated.
* <p>
* Is also the session with the accessor. Will return a ClientSession if
* it is in transaction and has a write connection.
* @return a session with a live accessor
* @param query may store session name or reference class for brokers case
*/
public AbstractSession getExecutionSession(DatabaseQuery query) {
return getParent().getExecutionSession(query);
}
/**
* ADVANCED:
* Answers a read-only data object, which knows whether it is
* a wall-clock time or a system change number.
*/
public AsOfClause getAsOfClause() {
return asOfClause;
}
/**
* PUBLIC:
* Answers the value this Session is As Of.
* Equivalent to getAsOfClause().getValue().
*/
public Object getAsOfValue() {
return getAsOfClause().getValue();
}
/**
* INTERNAL:
* Returns the parent Session.
*/
public AbstractSession getParent() {
return parent;
}
/**
* INTERNAL:
* Marked internal as this is not customer API but helper methods for
* accessing the server platform from within TopLink's other sessions types
* (ie not DatabaseSession)
*/
public ServerPlatform getServerPlatform(){
return getParent().getServerPlatform();
}
/**
* ADVANCED:
* Answers if all objects are to be read as of a past time. Only true if
* this is a special historical session.
* @see #getAsOfClause
*/
public boolean hasAsOfClause() {
return ((asOfClause != null) && (asOfClause.getValue() != null));
}
/**
* INTERNAL:
* Return the results from executing the database query.
* the arguments should be a database row with raw data values.
* No modify queries are allowed through a HistoricalSession.
*/
public Object internalExecuteQuery(DatabaseQuery query, AbstractRecord databaseRow) throws DatabaseException {
if (!query.isReadQuery()) {
throw QueryException.invalidQueryOnHistoricalSession(query);
} else {
return super.internalExecuteQuery(query, databaseRow);
}
}
/**
* INTERNAL:
* Historical session are never in a transaction.
*/
public boolean isInTransaction() {
return false;
}
/**
* INTERNAL:
* Return if this session is a historical session.
*/
public boolean isHistoricalSession() {
return true;
}
/**
* INTERNAL:
* A call back to do session specific preparation of a query.
* <p>
* The call back occurs immediately before we clone the query for execution,
* meaning that if this method needs to clone the query then the caller will
* determine that it doesn't need to clone the query twice.
*/
public DatabaseQuery prepareDatabaseQuery(DatabaseQuery query) {
DatabaseQuery clonedQuery = (DatabaseQuery)query.clone();
clonedQuery.setIsExecutionClone(true);
clonedQuery.setIsPrepared(false);
return clonedQuery;
}
/**
* INTERNAL:
* No transactions should be used inside a HistoricalSession.
*/
public void rollbackTransaction() throws DatabaseException, ConcurrencyException {
throw ValidationException.operationNotSupported(Helper.getShortClassName(getClass()) + ".rollbackTransaction");
}
public String toString() {
StringWriter writer = new StringWriter();
writer.write(getSessionTypeString());
writer.write("(");
writer.write(getAsOfClause().toString());
writer.write(")");
return writer.toString();
}
}