dbcontext.java

velocity 的脚本语言的全部代码集合

/*
 * Copyright 2000-2001,2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.sql.*;
import java.io.Serializable;
import java.io.*;

import org.apache.velocity.context.AbstractContext;
import org.apache.velocity.context.Context;

/**
 *   Example context impl that uses a database to store stuff :)
 *
 *   yes, this is silly
 *
 *   expects a mysql db test with table 
 * 
 *  CREATE TABLE contextstore (
 *    k varchar(100),
 *    val blob
 *  );
 *
 *  very fragile, crappy code.... just a demo!
 *
 * @author <a href="mailto:[e-mail]">Geir Magnusson Jr.</a>
 * @version $Id: DBContext.java,v 1.2.14.1 2004/03/04 00:18:29 geirm Exp $
 */

public class DBContext extends AbstractContext
{
    Connection conn = null;

    public DBContext()
    {
        super();
        setup();
    }

    public DBContext( Context inner )
    {
        super( inner );
        setup();
    }

    /**
     *  retrieves a serialized object from the db
     *  and returns the living instance to the
     *  caller.
     */
    public Object internalGet( String key )
    {
        try 
        {
            String data = null;

            String sql = "SELECT k, val FROM contextstore WHERE k ='"+key+"'";
            
            Statement s = conn.createStatement();

            ResultSet rs = s.executeQuery( sql );

            if(rs.next())
               data = rs.getString("val");
            
            rs.close();
            s.close();
            
            ObjectInputStream in = new ObjectInputStream(  new ByteArrayInputStream( data.getBytes() ));

            Object o =  in.readObject();

            in.close();

            return o;
        }        
        catch(Exception e)
        {
            System.out.println("internalGet() : " + e );
        }

        return null;
    }

    /**
     *  Serializes and stores an object in the database.
     *  This is really a hokey way to do it, and will
     *  cause problems.  The right way is to use a 
     *  prepared statement...
     */
    public Object internalPut( String key, Object value )
    {
        try 
        {    
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ObjectOutputStream out = new ObjectOutputStream( baos );
            
            out.writeObject( value );
            String data = baos.toString();

            out.close();
            baos.close();
          
            Statement s = conn.createStatement();

            s.executeUpdate( "DELETE FROM contextstore WHERE k = '" + key + "'" );
            s.executeUpdate( "INSERT INTO contextstore (k,val) values ('"+key+"','" + data + "')" );

            s.close();            
        }        
        catch(Exception e)
        {
            System.out.println("internalGet() : " + e );
        }

        return null;
    }

    /**
     *  Not implementing. Not required for Velocity core
     *  operation, so not bothering.  As we say above :
     *  "very fragile, crappy code..."
     */
    public  boolean internalContainsKey(Object key)
    {
        return false;
    }
    
    /**
     *  Not implementing. Not required for Velocity core
     *  operation, so not bothering.  As we say above :
     *  "very fragile, crappy code..."
     */
    public  Object[] internalGetKeys()
    {
        return null;
    }

    /**
     *  Not implementing. Not required for Velocity core
     *  operation, so not bothering.  As we say above :
     *  "very fragile, crappy code..."
     */
    public  Object internalRemove(Object key)
    {
        return null;
    }


    private void setup()
    {
        try
        {
            Class.forName("org.gjt.mm.mysql.Driver").newInstance();
            conn = DriverManager.getConnection("jdbc:mysql://localhost/test?user=root");
        }
        catch (Exception e) 
        {
            System. out.println(e);
        }
      
        return;
    }
}