SequenceHandler.java
/*
** Module : SequenceHandler.java
** Abstract : Interface for all sequence handler implementations.
**
** Copyright (c) 2012-2025, Golden Code Development Corporation.
**
** -#- -I- --Date-- ----------------------------Description--------------------------------------
** 001 OM 20121128 Created initial version.
** 002 OM 20130801 Added synchronization for access to un-atomic db sequence functionality.
** 003 EVL 20160223 Javadoc fixes to make compatible with Oracle Java 8 for Solaris 10.
** 004 ECF 20160501 Replaced direct SQL use with a more efficient implementation.
** 005 GBB 20230512 Logging methods replaced by CentralLogger/ConversionStatus.
** 006 OM 20250110 Added sequence support for multi-tenant databases.
** 007 ICP 20250129 Used int64.of to leverage caches instances.
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program 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 Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
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** Affero GPL version 3 and may not be removed by you.
**
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*/
package com.goldencode.p2j.persist.sequence;
import java.math.*;
import java.util.logging.*;
import com.goldencode.p2j.util.*;
import com.goldencode.p2j.util.logging.*;
/**
* This class defines 3 sequence primitives for sequence <code>CURRENT-VALUE</code>,
* <code>NEXT-VALUE</code> functions and <code>CURRENT-VALUE</code> statement and an utility
* <code>contains</code> method. The access to these methods is synchronized so for a database
* only one thread can execute a primitive on a sequence. The
* {@link com.goldencode.p2j.persist.SequenceManager SequenceManager} is
* responsible for instantiating only one <code>SequenceHandler</code> per database.
* <p>
* Implementations of this class will use different strategies for handling 4GL sequences,
* depending on the native support from the respective database system. They will override the
* four protected <code>safeXXX</code> methods. It is guaranteed that when they are executed,
* the database-level lock has been acquired. Because that, it is recommended that these methods
* should be fast and should not acquire other locks to prevent possible dead-locks.
*/
public class SequenceHandler
{
/** Logger (safe as a JVM-wide value rather than as context-local). */
private static final CentralLogger LOG = CentralLogger.get(SequenceHandler.class);
/** The database logical name on which this handler will work with. */
private String database;
/**
* The only constructor takes the name of the database as argument.
*
* @param ldbName
* The database logical name on which this handler will work with.
*/
public SequenceHandler(String ldbName)
{
database = ldbName;
/* start(); */
}
/**
* Queries the current value of a sequence. The base class always returns unknown value.
* <p>
* This method will acquire the lock for modifying sequences on this database and then will
* call the protected overridable safe version form derived classes.
*
* @param seqName
* The name of the sequence.
* @param tenantId
* The tenant id. If present (not null) it is checked. If not it is computed as
* {@code tenant-id(ldbName}).
*
* @return The (new) value of the sequence, as requested.
*/
public final int64 getCurrentValue(String seqName, Long tenantId)
{
synchronized(this)
{
return safeGetCurrentValue(seqName, database, tenantId);
}
}
/**
* Computes and returns the next value of a sequence. The base class always returns unknown
* value.
* <p>
* This method will acquire the lock for modifying sequences on this database and then will
* call the protected overridable safe version form derived classes.
*
* @param seqName
* The name of the sequence.
* @param tenantId
* The tenant id. If present (not null) it is checked. If not it is computed as
* {@code tenant-id(ldbName}).
*
* @return The (new) value of the sequence, as requested.
*/
public final int64 getNextValue(String seqName, Long tenantId)
{
synchronized(this)
{
return safeGetNextValue(seqName, database, tenantId);
}
}
/**
* Initialize (reset) the current value of a sequence. The base class does nothing.
* <p>
* This method will acquire the lock for modifying sequences on this database and then will
* call the protected overridable safe version form derived classes.
*
* @param seqName
* The name of the sequence.
* @param newVal
* The value the sequence will be reset to.
* @param tenantId
* The tenant id. If present (not null) it is checked. If not it is computed as
* {@code tenant-id(ldbName}).
*/
public final void setValue(String seqName, long newVal, Long tenantId)
{
synchronized(this)
{
safeSetValue(seqName, database, newVal, tenantId);
}
}
/**
* Test whether the database contains a sequence. This is useful to identify the correct
* database/sequences when a 4GL static function / statement is called without the database
* parameter.
* <p>
* This method will acquire the lock for modifying sequences on this database and then will
* call the protected overridable safe version form derived classes.
*
* @param seqName
* The name of the sequence.
*
* @return false
*/
public final boolean contains(String seqName)
{
synchronized(this)
{
return safeContains(seqName, database);
}
}
/**
* Extract the int64 value from a query result set.
*
* @param result
* Single result of a sequence query. May be {@code null}.
*
* @return The value at position 0 wrapped as as int64.
*/
protected static int64 getResultValue(Object result)
{
if (result == null)
{
return int64.UNKNOWN;
}
if (result instanceof Long)
{
// deprecated ?
return int64.of((Long) result);
}
else if (result instanceof BigInteger)
{
return int64.of(((BigInteger) result).longValue());
}
else
{
// don't know how to cast the result:
LOG.logp(Level.WARNING, SequenceHandler.class.getName(), "getResultValue()",
"Cannot handle " + result.getClass() + "result type.");
return int64.UNKNOWN;
}
}
/**
* Queries the current value of a sequence. The base class always returns unknown value.
* <p>
* This method should be called only in a safe environment, where the database-level lock for
* access to sequences has already been acquired.
*
* @param seqName
* The name of the sequence.
* @param ldbName
* The database to which the sequence belongs to. If is null then the first connected
* database is assumed.
* @param tenantId
* The tenant id. If present (not null) it is checked. If not it is computed as
* {@code tenant-id(ldbName}).
*
* @return The current value of the sequence, as requested.
*/
protected int64 safeGetCurrentValue(String seqName, String ldbName, Long tenantId)
{
return int64.UNKNOWN;
}
/**
* Computes and returns the next value of a sequence. The base class always returns unknown
* value.
* <p>
* This method should be called only in a safe environment, where the database-level lock for
* access to sequences has already been acquired.
*
* @param seqName
* The name of the sequence.
* @param ldbName
* The database to which the sequence belongs to. If is null then
* the first connected database is assumed.
* @param tenantId
* The tenant id. If present (not null) it is checked. If not it is computed as
* {@code tenant-id(ldbName}).
*
* @return The new value of the sequence, as requested.
*/
protected int64 safeGetNextValue(String seqName, String ldbName, Long tenantId)
{
return int64.UNKNOWN;
}
/**
* Initialize (reset) the current value of a sequence. The base class does nothing.
* <p>
* This method should be called only in a safe environment, where the database-level lock for
* access to sequences has already been acquired.
*
* @param seqName
* The name of the sequence.
* @param ldbName
* The database to which the sequence belongs to. If is null then
* the first connected database is assumed.
* @param newVal
* The value the sequence will be reset to.
* @param tenantId
* The tenant id. If present (not null) it is checked. If not it is computed as
* {@code tenant-id(ldbName}).
*/
protected void safeSetValue(String seqName, String ldbName, long newVal, Long tenantId)
{
}
/**
* Test whether the database contains a sequence. This is useful to identify the correct
* database/sequences when a 4GL static function / statement is called without the database
* parameter.
* The base class always returns false.
* <p>
* This method should be called only in a safe environment, where the database-level lock for
* access to sequences has already been acquired.
*
* @param seqName
* The name of the sequence.
* @param ldbName
* The database to which the sequence belongs to. If is null then the first connected
* database is assumed.
*
* @return false
*/
protected boolean safeContains(String seqName, String ldbName)
{
return false;
}
}