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package org.apache.velocity.example;
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.velocity.context.AbstractContext;
import org.apache.velocity.context.Context;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
/**
* 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:geirm@optonline.net">Geir Magnusson Jr.</a>
* @version $Id$
*/
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.
*/
@Override
public Object internalGet(String key )
{
try
{
String sql = "SELECT val FROM contextstore WHERE k ='"+key+"'";
Statement s = conn.createStatement();
ResultSet rs = s.executeQuery( sql );
Object o = null;
ObjectInputStream in = null;
if(rs.next())
{
in = new ObjectInputStream( rs.getBinaryStream(1) );
o = in.readObject();
in.close();
}
rs.close();
s.close();
return o;
}
catch(Exception e)
{
System.out.println("internalGet() : " + e );
e.printStackTrace();
}
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...
*/
@Override
public Object internalPut(String key, Object value )
{
try
{
Statement s = conn.createStatement();
s.executeUpdate( "DELETE FROM contextstore WHERE k = '" + key + "'" );
s.close();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
ObjectOutputStream out = new ObjectOutputStream( baos );
out.writeObject( value );
byte buf[] = baos.toByteArray();
out.close();
baos.close();
ByteArrayInputStream bais = new ByteArrayInputStream(buf);
PreparedStatement ps = conn.prepareStatement( "INSERT INTO contextstore (k,val) values ('"+key+"', ?)");
ps.setBinaryStream(1, bais, buf.length);
ps.executeUpdate();
ps.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..."
*/
@Override
public boolean internalContainsKey(String key)
{
return false;
}
/**
* Not implementing. Not required for Velocity core
* operation, so not bothering. As we say above :
* "very fragile, crappy code..."
*/
@Override
public String[] internalGetKeys()
{
return null;
}
/**
* Not implementing. Not required for Velocity core
* operation, so not bothering. As we say above :
* "very fragile, crappy code..."
*/
@Override
public Object internalRemove(String key)
{
return null;
}
private void setup()
{
try
{
Class.forName("com.mysql.cj.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost/test?user=YOUR_DB_USER&password=YOUR_DB_PASSWORD");
}
catch (Exception e)
{
System. out.println(e);
}
}
}
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