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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

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package java.sql;

/**

 * The interface used for the custom mapping of an SQL user-defined type (UDT) to

 * a class in the Java programming language. The class object for a class

 * implementing the <code>SQLData</code> interface will be entered in the

 * appropriate <code>Connection</code> object's type map along with the SQL

 * name of the UDT for which it is a custom mapping.

 * <P>

 * Typically, a <code>SQLData</code> implementation

 * will define a field for each attribute of an SQL structured type or a

 * single field for an SQL <code>DISTINCT</code> type. When the UDT is

 * retrieved from a data source with the <code>ResultSet.getObject</code>

 * method, it will be mapped as an instance of this class.  A programmer

 * can operate on this class instance just as on any other object in the

 * Java programming language and then store any changes made to it by

 * calling the <code>PreparedStatement.setObject</code> method,

 * which will map it back to the SQL type.

 * <p>

 * It is expected that the implementation of the class for a custom

 * mapping will be done by a tool.  In a typical implementation, the

 * programmer would simply supply the name of the SQL UDT, the name of

 * the class to which it is being mapped, and the names of the fields to

 * which each of the attributes of the UDT is to be mapped.  The tool will use

 * this information to implement the <code>SQLData.readSQL</code> and

 * <code>SQLData.writeSQL</code> methods.  The <code>readSQL</code> method

 * calls the appropriate <code>SQLInput</code> methods to read

 * each attribute from an <code>SQLInput</code> object, and the

 * <code>writeSQL</code> method calls <code>SQLOutput</code> methods

 * to write each attribute back to the data source via an

 * <code>SQLOutput</code> object.

 * <P>

 * An application programmer will not normally call <code>SQLData</code> methods

 * directly, and the <code>SQLInput</code> and <code>SQLOutput</code> methods

 * are called internally by <code>SQLData</code> methods, not by application code.

 *

 * @since 1.2

 */

public interface SQLData {

 /**

  * Returns the fully-qualified

  * name of the SQL user-defined type that this object represents.

  * This method is called by the JDBC driver to get the name of the

  * UDT instance that is being mapped to this instance of

  * <code>SQLData</code>.

  *

  * @return the type name that was passed to the method <code>readSQL</code>

  *            when this object was constructed and populated

  * @exception SQLException if there is a database access error

  * @exception SQLFeatureNotSupportedException if the JDBC driver does not support

  * this method

  * @since 1.2

  */

  String getSQLTypeName() throws SQLException;

 /**

  * Populates this object with data read from the database.

  * The implementation of the method must follow this protocol:

  * <UL>

  * <LI>It must read each of the attributes or elements of the SQL

  * type  from the given input stream.  This is done

  * by calling a method of the input stream to read each

  * item, in the order that they appear in the SQL definition

  * of the type.

  * <LI>The method <code>readSQL</code> then

  * assigns the data to appropriate fields or

  * elements (of this or other objects).

  * Specifically, it must call the appropriate <i>reader</i> method

  * (<code>SQLInput.readString</code>, <code>SQLInput.readBigDecimal</code>,

  * and so on) method(s) to do the following:

  * for a distinct type, read its single data element;

  * for a structured type, read a value for each attribute of the SQL type.

  * </UL>

  * The JDBC driver initializes the input stream with a type map

  * before calling this method, which is used by the appropriate

  * <code>SQLInput</code> reader method on the stream.

  *

  * @param stream the <code>SQLInput</code> object from which to read the data for

  * the value that is being custom mapped

  * @param typeName the SQL type name of the value on the data stream

  * @exception SQLException if there is a database access error

  * @exception SQLFeatureNotSupportedException if the JDBC driver does not support

  * this method

  * @see SQLInput

  * @since 1.2

  */

  void readSQL (SQLInput stream, String typeName) throws SQLException;

  /**

  * Writes this object to the given SQL data stream, converting it back to

  * its SQL value in the data source.

  * The implementation of the method must follow this protocol:<BR>

  * It must write each of the attributes of the SQL type

  * to the given output stream.  This is done by calling a

  * method of the output stream to write each item, in the order that

  * they appear in the SQL definition of the type.

  * Specifically, it must call the appropriate <code>SQLOutput</code> writer

  * method(s) (<code>writeInt</code>, <code>writeString</code>, and so on)

  * to do the following: for a Distinct Type, write its single data element;

  * for a Structured Type, write a value for each attribute of the SQL type.

  *

  * @param stream the <code>SQLOutput</code> object to which to write the data for

  * the value that was custom mapped

  * @exception SQLException if there is a database access error

  * @exception SQLFeatureNotSupportedException if the JDBC driver does not support

  * this method

  * @see SQLOutput

  * @since 1.2

  */

  void writeSQL (SQLOutput stream) throws SQLException;

}