typedescriptor.java

derby database source code.good for you.

/*

   Derby - Class org.apache.derby.catalog.TypeDescriptor

   Copyright 1998, 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.catalog;

/**
 *
 * An interface for describing types in Cloudscape systems.
 *	
 *	
 *	<p>The values in system catalog DATATYPE columns are of type
 *	TypeDescriptor.
 */

public interface TypeDescriptor
{
	///////////////////////////////////////////////////////////////////////
	//
	//	CONSTANTS
	//
	///////////////////////////////////////////////////////////////////////


	/**
	  The return value from getMaximumWidth() for types where the maximum
	  width is unknown.
	 */

	public	static	int MAXIMUM_WIDTH_UNKNOWN = -1;


	///////////////////////////////////////////////////////////////////////
	//
	//	METHODS
	//
	///////////////////////////////////////////////////////////////////////

	/**
	 * Get the jdbc type id for this type.  JDBC type can be
	 * found in java.sql.Types. 
	 *
	 * @return	a jdbc type, e.g. java.sql.Types.DECIMAL 
	 *
	 * @see java.sql.Types
	 */
	public int getJDBCTypeId();

	/**
	  Returns the maximum width of the type.  This may have
	  different meanings for different types.  For example, with char,
	  it means the maximum number of characters, while with int, it
	  is the number of bytes (i.e. 4).

	  @return	the maximum length of this Type; -1 means "unknown/no max length"
	  */
	public	int			getMaximumWidth();


	/**
	  Returns the maximum width of the type IN BYTES.  This is the
	  maximum number of bytes that could be returned for this type
	  if the corresponding getXXX() method is used.  For example,
	  if we have a CHAR type, then we want the number of bytes
	  that would be returned by a ResultSet.getString() call.

	  @return	the maximum length of this Type IN BYTES;
				-1 means "unknown/no max length"
	  */
	public	int			getMaximumWidthInBytes();


	/**
	  Returns the number of decimal digits for the type, if applicable.
	 
	  @return	The number of decimal digits for the type.  Returns
	 		zero for non-numeric types.
	  */
	public	int			getPrecision();


	/**
	  Returns the number of digits to the right of the decimal for
	  the type, if applicable.
	 
	  @return	The number of digits to the right of the decimal for
	 		the type.  Returns zero for non-numeric types.
	  */
	public	int			getScale();


	/**
	  Gets the nullability that values of this type have.
	  

	  @return	true if values of this type may be null. false otherwise
	  */
	public	boolean		isNullable();

	/**
	  Gets the name of this type.
	  

	  @return	the name of this type
	  */
	public	String		getTypeName();


	/**
	  Converts this type descriptor (including length/precision)
	  to a string suitable for appearing in a SQL type specifier.  E.g.
	 
	 			VARCHAR(30)

	  or

	             java.util.Hashtable 
	 
	 
	  @return	String version of type, suitable for running through
	 			a SQL Parser.
	 
	 */
	public 	String		getSQLstring();

}