rpersistantmap.java

与postgresql数据库结合的数据库水印软件包

/*
 * 
 * Copyright 2003,2004 The Watermill Team
 *
 * This file is part of Watermill.
 *
 *    Watermill is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    Watermill 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 General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with Watermill; if not, write to the Free Software
 *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */
package Watermill.relational;

import java.io.*;
import java.sql.*;
import Watermill.kernel.*;

public class RPersistantMap extends PersistantMap {
    private Connection connection;
    private String tableName;

    public RPersistantMap(Connection c,String tableName){
	connection=c;
	this.tableName=tableName;
	if (!tableExists())
	    createTable();
    }

    public void add(String key,Object o){
	try {
	    ByteArrayOutputStream baos = new ByteArrayOutputStream();
	    ObjectOutputStream oout = new ObjectOutputStream(baos);
	    oout.writeObject(o);
	    oout.close();
	  
	    String query="insert into "+tableName+" values (?,?)";
	    Msg.debug(query);
	    PreparedStatement ps= connection.prepareStatement(query);
	  
	    ps.setString(1,key);
	    ps.setBytes(2, baos.toByteArray());
	    ps.executeUpdate();
	}
	catch (Exception e){
	    e.printStackTrace();
	    Msg.fatal("problem in persistant storage:"+e.getMessage());
	}
    }

    public boolean tableExists(){
	Statement stm=null;
	
	try {
	    stm=connection.createStatement();
	    stm.execute("select count(*) from "+tableName);
	}
	catch (SQLException se){
	    return false;
	}
	return true;
    }

    public void createTable(){

	Statement stm=null;

	try {
	    stm=connection.createStatement();
	    stm.execute("DROP TABLE "+tableName);
	}
	catch (SQLException se){
	    Msg.debug("table does not exists");
	}
	try {
	    stm.execute("CREATE TABLE "+tableName+" (key text PRIMARY KEY,data bytea)");
	    Msg.debug("cpt2");
	}
	catch (SQLException e){
	    Msg.debug("cpt3"+e.getMessage());
	    Msg.fatal(e);
	}
	
    }

    public void dropAll(){
	Statement stm=null;
	
	try {
	    stm=connection.createStatement();
	    stm.execute("drop table "+tableName);
	    createTable();
	}
	catch (SQLException se){
	    Msg.debug(se);
	}
    }
	
    public Object get(String key){
	try {
	    Statement stm=connection.createStatement();
	    String query="select data from "+tableName+" where key='"+key+"'";
	    Msg.debug(query);
	    
	    ResultSet rs=stm.executeQuery(query);
	    rs.next();
	    byte[] buf = rs.getBytes(1);
	    if (buf != null) {
		ObjectInputStream objectIn = new ObjectInputStream(new ByteArrayInputStream(buf));
		return objectIn.readObject();
	    }
	    else {
		Msg.fatal("Persistant storage: incorrect format.");
		return null;
	    }
	}
	catch (Exception e){
	    Msg.fatal(e);
	    return null;
	}
    }
}