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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 SQLData interface will be entered in the
appropriate Connection object's type map along with the SQL
name of the UDT for which it is a custom mapping.


Typically, a SQLData implementation
will define a field for each attribute of an SQL structured type or a
single field for an SQL DISTINCT type. When the UDT is
retrieved from a data source with the ResultSet.getObject
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 PreparedStatement.setObject method,
which will map it back to the SQL type.


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 SQLData.readSQL and
SQLData.writeSQL methods.  The readSQL method
calls the appropriate SQLInput methods to read
each attribute from an SQLInput object, and the
writeSQL method calls SQLOutput methods
to write each attribute back to the data source via an
SQLOutput object.


An application programmer will not normally call SQLData methods
directly, and the SQLInput and SQLOutput methods
are called internally by SQLData methods, not by application code.

Since:1.2
/**
 * 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
SQLData.

Throws:
Returns:the type name that was passed to the method readSQL
           when this object was constructed and populated
Since:1.2
/**
  * 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:

    

  • 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.

  • The method readSQL then
assigns the data to appropriate fields or
elements (of this or other objects).
Specifically, it must call the appropriate reader method
(SQLInput.readString, SQLInput.readBigDecimal,
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.


The JDBC driver initializes the input stream with a type map
before calling this method, which is used by the appropriate
SQLInput reader method on the stream.

Params:
  • stream – the SQLInput object from which to read the data for
the value that is being custom mapped
  • typeName – the SQL type name of the value on the data stream
Throws:
See Also:
Since:1.2
/**
  * 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:

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 SQLOutput writer
method(s) (writeInt, writeString, 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.

Params:
  • stream – the SQLOutput object to which to write the data for
the value that was custom mapped
Throws:
See Also:
Since:1.2
/**
  * 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;
}