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/**
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* '$RCSfile$'
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* Purpose: An abstract class that encapsulates access to any RDBMS.
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* This allows to swap easily between databases without any
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* modification to the application.
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* Copyright: 2000 Regents of the University of California and the
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* National Center for Ecological Analysis and Synthesis
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* Authors: Jivka Bojilova
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*
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* '$Author: jones $'
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* '$Date: 2006-11-10 10:25:38 -0800 (Fri, 10 Nov 2006) $'
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* '$Revision: 3077 $'
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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package edu.ucsb.nceas.dbadapter;
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import java.sql.*;
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import edu.ucsb.nceas.metacat.MetaCatUtil;
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/**
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* Java offers uniform database access through the use of JDBC.
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* But many databases still use different SQL implementations and
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* conventions. Thus this class offers extended programming interface
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* that all subclasses should implement to gain access to different
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* databases.
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*
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* To add a new database adapter class you must create a new class
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* <dbname>Adapter that extends edu.ucsb.nceas.dbadapter.AbstarctDatabase
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* (where dbname is the name of the database or database driver you wish
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* to add to your application). AbstarctDatabase is an abstract class,
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* thus the subclasses need to implement the abstract methods.
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*/
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public abstract class AbstractDatabase {
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/**
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* Unique ID generator
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*
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* @param conn db connection in which the unique id was generated
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* @param tableName the table which unique id was generate
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* @exception SQLException <br/> any SQLException that can be thrown
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* during the db operation
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* @return return the generated unique id as a long type
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*/
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public abstract long getUniqueID(Connection conn, String tableName)
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throws SQLException;
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/**
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* The function name that gets the current date and time
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* from the database server
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*
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* @return return the current date and time function name
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*/
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public abstract String getDateTimeFunction();
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/**
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* The function name that is used to return non-NULL value
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*
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* @return return the non-NULL function name
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*/
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public abstract String getIsNULLFunction();
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/**
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* The character that the specific database implementation uses to
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* indicate string literals in SQL. This will usually be a single
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* qoute (').
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*
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* @return return the string delimiter
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*/
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public abstract String getStringDelimiter();
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/**
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* MSSQL didn't support to_date function which to transfer a text string
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* to date type. But Oracle and Postsql do.
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*/
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public String toDate(String dateString, String format)
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{
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return "to_date(" + "'"+ dateString + "', '" + format + "')";
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}
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/**
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* Syntax for doing a left join
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* Add 'a.' in front of the fields for first table and
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* 'b.' in front of the fields for the second table
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*
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* @param selectFields fields that you want to be selected
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* @param tableA first table in the join
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* @param tableB second table in the join
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* @param joinCriteria the criteria based on which the join will be made
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* @param nonJoinCriteria all other criterias
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* @return return the string for teh select query
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*/
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public abstract String getLeftJoinQuery(String selectFields, String tableA,
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String tableB, String joinCriteria, String nonJoinCriteria);
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/**
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* Instantiate a class using the name of the class at runtime
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*
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* @param className the fully qualified name of the class to instantiate
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*/
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static public Object createObject(String className) throws Exception {
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Object object = null;
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try {
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Class classDefinition = Class.forName(className);
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object = classDefinition.newInstance();
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} catch (InstantiationException e) {
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throw e;
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} catch (IllegalAccessException e) {
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throw e;
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} catch (ClassNotFoundException e) {
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throw e;
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}
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return object;
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}
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/**
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* the main routine used to test the dbadapter utility.
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*/
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static public void main(String[] args) {
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// Determine our db adapter class and
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// create an instance of that class
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try {
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String dbAdapter = MetaCatUtil.getOption("dbAdapter");
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AbstractDatabase dbAdapterObj = (AbstractDatabase)createObject(dbAdapter);
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// test if they work correctly
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String date = dbAdapterObj.getDateTimeFunction();
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} catch (Exception e) {
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System.out.println(e);
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}
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}
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/**
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* This method will return the sql command to get document list in xml_document
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* in replication. Because it involes outer join, so this method is very flexible.
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* @return
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*/
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public abstract String getReplicationDocumentListSQL();
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}
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