/*

   Derby - Class org.apache.derby.impl.jdbc.EmbedResultSetMetaData40

   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.

 */
package org.apache.derby.impl.jdbc;

import java.sql.SQLException;

import org.apache.derby.iapi.reference.SQLState;
import org.apache.derby.iapi.sql.ResultColumnDescriptor;
/**
 * ResultSetMetaData implementation for JDBC 4.
   <P>
   EmbedResultSetMetaData40 objects are shared across multiple threads
   by being stored in the ResultDescription for a compiled plan.
   If the required api for ResultSetMetaData ever changes so
   that it has a close() method, a getConnection() method or
   any other Connection or ResultSet specific method then
   this sharing must be removed.
 */
public class EmbedResultSetMetaData40 extends EmbedResultSetMetaData {
    
    public EmbedResultSetMetaData40(ResultColumnDescriptor[] columnInfo) {
        super(columnInfo);
    }
    
    /**
     * Returns false unless <code>interfaces</code> is implemented 
     * 
     * @param  interfaces             a Class defining an interface.
     * @return true                   if this implements the interface or 
     *                                directly or indirectly wraps an object 
     *                                that does.
     * @throws java.sql.SQLException  if an error occurs while determining 
     *                                whether this is a wrapper for an object 
     *                                with the given interface.
     */
    public boolean isWrapperFor(Class<?> interfaces) throws SQLException {
        return interfaces.isInstance(this);
    }
    
    /**
     * Returns <code>this</code> if this class implements the interface
     *
     * @param  interfaces a Class defining an interface
     * @return an object that implements the interface
     * @throws SQLException if no object if found that implements the 
     * interface
     */
   public <T> T unwrap(java.lang.Class<T> interfaces) 
                            throws SQLException{
        //Derby does not implement non-standard methods on 
        //JDBC objects
        //hence return this if this class implements the interface 
        //or throw an SQLException
        try {
            return interfaces.cast(this);
        } catch (ClassCastException cce) {
            throw Util.generateCsSQLException(SQLState.UNABLE_TO_UNWRAP,
                    interfaces);
        }
    }
}
