genericresultdescription.java

derby database source code.good for you.

/*

   Derby - Class org.apache.derby.impl.sql.GenericResultDescription

   Copyright 1997, 2004 The Apache Software Foundation or its licensors, as applicable.

   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.

 */

package org.apache.derby.impl.sql;

import org.apache.derby.iapi.sql.ResultColumnDescriptor;
import org.apache.derby.iapi.sql.ResultDescription;

import org.apache.derby.iapi.services.sanity.SanityManager;

import org.apache.derby.iapi.services.io.StoredFormatIds;
import org.apache.derby.iapi.services.io.FormatIdUtil;
import org.apache.derby.iapi.services.io.Formatable;

import java.io.ObjectOutput;
import java.io.ObjectInput;
import java.io.IOException;
/**
 * GenericResultDescription: basic implementation of result
 * description, used in conjunction with the other 
 * implementations in this package.  This implementation 
 * of ResultDescription may be used by anyone.
 *
 * @author ames
 */
public final class GenericResultDescription
	implements ResultDescription, Formatable
{

	/********************************************************
	**
	**	This class implements Formatable. That means that it
	**	can write itself to and from a formatted stream. If
	**	you add more fields to this class, make sure that you
	**	also write/read them with the writeExternal()/readExternal()
	**	methods.
	**
	**	If, inbetween releases, you add more fields to this class,
	**	then you should bump the version number emitted by the getTypeFormatId()
	**	method.
	**
	********************************************************/

	private ResultColumnDescriptor[] columns;
	private String statementType;
	
	/**
	 * Niladic constructor for Formatable
	 */
	public GenericResultDescription()
	{
	}

	/**
	 * Build a GenericResultDescription from columns and type
	 *
	 * @param columns an array of col descriptors
	 * @param statementType the type
	 */
	public GenericResultDescription(ResultColumnDescriptor[] columns, 
					String statementType) 
	{
		this.columns = columns;
		this.statementType = statementType;
	}

	/**
	 * Build a GenericResultDescription 
	 *
	 * @param rd the result description
	 * @param theCols the columns to take from the input rd
	 */
	public GenericResultDescription
	(
		ResultDescription	rd, 
		int[]				theCols
	) 
	{
		if (SanityManager.DEBUG)
		{
			SanityManager.ASSERT(theCols != null, "theCols argument to GenericResultDescription is null");
		}

		this.columns = new ResultColumnDescriptor[theCols.length];
		for (int i = 0; i < theCols.length; i++)
		{
			columns[i] = rd.getColumnDescriptor(theCols[i]);
		}
		this.statementType = rd.getStatementType();
	}

	//
	// ResultDescription interface
	//
	/**
	 * @see ResultDescription#getStatementType
	 */
	public String	getStatementType() {
		return statementType;
	}

	/**
	 * @see ResultDescription#getColumnCount
	 */
	public int	getColumnCount() 
	{
		return (columns == null) ? 0 : columns.length;
	}

	public ResultColumnDescriptor[] getColumnInfo() {
		return columns;
	}

	/**
	 * position is 1-based.
	 * @see ResultDescription#getColumnDescriptor
	 */
	public ResultColumnDescriptor getColumnDescriptor(int position) {
		return columns[position-1];
	}

	/**
	 * Get a new result description that has been truncated
	 * from input column number.   If the input column is
	 * 5, then columns 5 to getColumnCount() are removed.
	 * The new ResultDescription points to the same
	 * ColumnDescriptors (this method performs a shallow
	 * copy.
	 *
	 * @param truncateFrom the starting column to remove
	 *
	 * @return a new ResultDescription
	 */
	public ResultDescription truncateColumns(int truncateFrom)	
	{
		if (SanityManager.DEBUG) 
		{
			if (!(truncateFrom > 0 && columns != null))
			{
				SanityManager.THROWASSERT("bad truncate value: "+truncateFrom+" is too low");
			}
			if (truncateFrom > columns.length)
			{
				SanityManager.THROWASSERT("bad truncate value: "+truncateFrom+" is too high");
			}
		}
		ResultColumnDescriptor[] newColumns = new ResultColumnDescriptor[truncateFrom-1];
		System.arraycopy(columns, 0, newColumns, 0, newColumns.length);
		return new GenericResultDescription(newColumns, statementType);
	}


	//////////////////////////////////////////////
	//
	// FORMATABLE
	//
	//////////////////////////////////////////////
	/**
	 * Write this object out
	 *
	 * @param out write bytes here
	 *
 	 * @exception IOException thrown on error
	 */
	public void writeExternal(ObjectOutput out) throws IOException
	{
		int len = (columns == null) ? 0 : columns.length;

		out.writeObject(statementType);
		out.writeInt(len);
		while(len-- > 0)
		{
			/*
			** If we don't have a GenericColumnsDescriptor, 
			** create one now and use that to write out.
			** Do this to avoid writing out query tree
			** implementations of ResultColumnDescriptor
			*/
			if (!(columns[len] instanceof 
						GenericColumnDescriptor))
			{
				columns[len] = new GenericColumnDescriptor(columns[len]);
			}
			out.writeObject(columns[len]);
		}
	}

	/**
	 * Read this object from a stream of stored objects.
	 *
	 * @param in read this.
	 *
	 * @exception IOException					thrown on error
	 * @exception ClassNotFoundException		thrown on error
	 */
	public void readExternal(ObjectInput in)
		throws IOException, ClassNotFoundException
	{
		int len;

		columns = null;
		statementType = (String)in.readObject();
		len = in.readInt();
		if (len > 0)
		{
			columns = new GenericColumnDescriptor[len];
			while(len-- > 0)
			{
				columns[len] = (ResultColumnDescriptor)in.readObject();
			}
		}
	}
	
	/**
	 * Get the formatID which corresponds to this class.
	 *
	 *	@return	the formatID of this class
	 */
	public	int getTypeFormatId()	{ return StoredFormatIds.GENERIC_RESULT_DESCRIPTION_V01_ID; }


	
	public String toString()
	{
		if (SanityManager.DEBUG)
		{
			StringBuffer colStr = new StringBuffer();
			for (int i = 0; i < columns.length; i++)
			{
				colStr.append("column["+i+"]\n");
				colStr.append(columns[i].toString());
			}	
			return "GenericResultDescription\n" +
					"\tStatementType = "+statementType+"\n" +
					"\tCOLUMNS\n" + colStr.toString();
		}
		else
		{
			return "";
		}
	}
}