trigger.java

hsql是很有名的嵌入式数据库

/* Copyright (c) 2001-2005, The HSQL Development Group
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 *
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package org.hsqldb;

// fredt@users 20030727 - signature altered to support update triggers
/*

Contents of row1[] and row2[] in each type of trigger.

BEFORE INSERT
 - row1[] contains single String object = "Statement-level".

AFTER INSERT
 - row1[] contains single String object = "Statement-level".

BEFORE UPDATE
 - row1[] contains single String object = "Statement-level".

AFTER UPDATE
 - row1[] contains single String object = "Statement-level".

BEFORE DELETE
 - row1[] contains single String object = "Statement-level".

AFTER DELETE
 - row1[] contains single String object = "Statement-level".

BEFORE INSERT FOR EACH ROW
 - row2[] contains data about to be inserted and this can
be modified within the trigger such that modified data gets written to the
database.

AFTER INSERT FOR EACH ROW
 - row2[] contains data just inserted into the table.

BEFORE UPDATE FOR EACH ROW
 - row1[] contains currently stored data and not the data that is about to be
updated.

 - row2[] contains the data that is about to be updated.

AFTER UPDATE FOR EACH ROW
 - row1[] contains old stored data.
 - row2[] contains the new data.

BEFORE DELETE FOR EACH ROW
 - row1[] contains row data about to be deleted.

AFTER DELETE FOR EACH ROW
 - row1[] contains row data that has been deleted.

List compiled by Andrew Knight (quozzbat@users)
*/

/**
 * The interface an HSQLDB TRIGGER must implement
 *
 * @author Peter Hudson
 * @version 1.7.2
 * @since 1.7.0
 */
public interface Trigger {

    // indexes into the triggers list
    int INSERT_AFTER      = 0;
    int DELETE_AFTER      = 1;
    int UPDATE_AFTER      = 2;
    int INSERT_BEFORE     = INSERT_AFTER + TriggerDef.NUM_TRIGGER_OPS;
    int DELETE_BEFORE     = DELETE_AFTER + TriggerDef.NUM_TRIGGER_OPS;
    int UPDATE_BEFORE     = UPDATE_AFTER + TriggerDef.NUM_TRIGGER_OPS;
    int INSERT_AFTER_ROW  = INSERT_AFTER + 2 * TriggerDef.NUM_TRIGGER_OPS;
    int DELETE_AFTER_ROW  = DELETE_AFTER + 2 * TriggerDef.NUM_TRIGGER_OPS;
    int UPDATE_AFTER_ROW  = UPDATE_AFTER + 2 * TriggerDef.NUM_TRIGGER_OPS;
    int INSERT_BEFORE_ROW = INSERT_BEFORE + 2 * TriggerDef.NUM_TRIGGER_OPS;
    int DELETE_BEFORE_ROW = DELETE_BEFORE + 2 * TriggerDef.NUM_TRIGGER_OPS;
    int UPDATE_BEFORE_ROW = UPDATE_BEFORE + 2 * TriggerDef.NUM_TRIGGER_OPS;

    /**
     * The method invoked upon each triggered action. <p>
     *
     * When UPDATE triggers are fired, oldRow contains the
     * existing values of the table row and newRow contains the
     * new values.<p>
     *
     * For INSERT triggers, oldRow is null and newRow contains the
     * table row to be inserted.
     *
     * For DELETE triggers, newRow is null and oldRow contains the
     * table row to be deleted.
     *
     * type contains the integer index id for trigger type, e.g.
     * TriggerDef.INSERT_AFTER (fredt@users)
     *
     * @param trigName the name of the trigger
     * @param tabName the name of the table upon which the
     *      triggered action is occuring
     * @param oldRow the old row
     * @param newRow the new row
     */
    void fire(int type, String trigName, String tabName, Object[] oldRow,
              Object[] newRow);
}