TriggerManagerHandle.java
/*
** Module : TriggerManagerHandle.java
** Abstract : A handle for avoiding accessing the TriggerManager via static API.
**
** Copyright (c) 2023, Golden Code Development Corporation.
**
** -#- -I- --Date-- -------------------------------------- Description --------------------------------------
** 001 OM 20230915 Added support for generic session triggers.
** 002 OM 20231127 Removed unused 'override' parameter. Updated javadoc.
*/
/*
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** published by the Free Software Foundation, either version 3 of the
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** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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**
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**
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**
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*/
package com.goldencode.p2j.persist.trigger;
/**
* A handle for avoiding accessing the TriggerManager directly via its public API. Objects of this class can
* be used for setting up generic triggers in a similar manner how session triggers are registered from
* converted code.
* <p>
* The generic triggers are Java callback methods which are invoked BEFORE the session database triggers, but
* they are configured for <strong>all</strong> tables (we may add a mask/regex pattern to filter only
* specific tables) of a database. The implementer is responsible to write the code for handling the event at
* a lower level, including table filtering (for the moment) but must take care of full 4GL state:
* transactions, locking, buffers, undo ability.
*/
public class TriggerManagerHandle
{
/** The manager instance. Uses lazy instantiation. */
private DatabaseTriggerManager manager = null;
/** Default c'tor does nothing */
public TriggerManagerHandle()
{
}
/**
* Register a generic trigger for a specific event. When such trigger is registered, it will be fired for
* all events of that type, of all tables from specified database before any other configured session or
* schema trigger. The execution of the latter two is unaffected of the presence or execution of the
* generic trigger.
*
* @param eventName
* The event as case-insensitive string.
* @param database
* The database to apply to. (In future revisions, this parameter might be replaced by a table
* mask / pattern.)
* @param triggerClassName
* The trigger class which implements the method for handling the respective event in a generic
* manner.
*
* @return {@code null} if the operation is successful and a short description of the problem otherwise.
*/
public String registerGenericTrigger(String eventName, String database, String triggerClassName)
{
return getManager().registerGenericTrigger(eventName, database, triggerClassName);
}
/**
* Register a generic trigger for a ASSIGN event. When such trigger is registered, it will be fired for all
* ASSIGN events, of all tables from specified database BEFORE any other configured session or schema
* triggers. The execution of the latter two is unaffected of the presence or execution of the generic
* trigger.
*
* @param eventName
* The event as case-insensitive string.
* @param database
* The database to apply to. (In future revisions, this parameter might be replaced by a table
* mask / pattern.)
* @param triggerClassName
* The trigger class which implements the method for handling the respective event in a generic
* manner.
* @param property
* The <strong>property</strong> name of the affected field. (Also subject for replacing with a
* mask / pattern.)
*
* @return {@code null} if the operation is successful and a short description of the problem otherwise.
*/
public String registerGenericTrigger(String eventName,
String database,
String triggerClassName,
String property)
{
return getManager().registerGenericTrigger(eventName, database, triggerClassName, property);
}
/**
* Unregister a previously set generic trigger given the event type and database/.
* This is the equivalent of {@code ON <event> OF <table> REVERT} but for generic triggers.
*
* @param eventName
* The event as case-insensitive string.
* @param database
* The database to apply to. In future revisions, this parameter might be replaced by a table
* pattern.
*
* @return {@code null} if the operation is successful and a short description of the problem otherwise.
*/
public String deregisterGenericTrigger(String eventName, String database)
{
return getManager().deregisterGenericTrigger(eventName, database);
}
/**
* Unregister a session database trigger for the given event type and buffer class.
* This is the equivalent of {@code ON Assign OF <table> REVERT} but for generic triggers.
*
* @param eventName
* The event as case-insensitive string. Recommended {@code ASSIGN} but this variant of the method
* ignores the parameter.
* @param database
* The database to apply to. In future revisions, this parameter might be replaced by a table
* pattern.
* @param property
* The property that is deregistered from {@code ASSIGN} trigger.
*
* @return {@code null} if the operation is successful and a short description of the problem otherwise.
*/
public String deregisterGenericTrigger(String eventName, String database, String property)
{
return getManager().deregisterGenericAssignTrigger(database, property);
}
/**
* Obtain and caches the manager instance locally.
*
* @return the manager instance.
*/
private DatabaseTriggerManager getManager()
{
if (manager == null)
{
manager = DatabaseTriggerManager.get();
}
return manager;
}
}