public interface SQLData
Usually within an implementation of SQLData
, there is a corresponding
field for every attribute of an SQL type, but only one field, if the type is
SQL DISTINCT
. When the UDT is returned within a ResultSet
, it
is accessed with the ResultSet.getObject(int)
method and is returned as an
object which is an instance of the class defined by the SQLData
mapping. The application can use this object just like any other Java object
and can store changes back into the database using the
PreparedStatement.setObject(int, java.lang.Object)
method which performs the reverse mapping
into the SQL UDT
.
Normally the implementation of a custom mapping is generated by
a tool requiring the name of the SQL UDT
, the name
of the class which it is going to be mapped to, and the field names to which
the UDT attributes are mapped. The tool can then implement the SQLData
, readSQL
, and writeSQL
methods. readSQL
reads
attributes from an SQLInput
object, and writeSQL
writes them.
This is done via SQLInput
and SQLOutput
method calls
respectively.
Ordinarily an application would not call SQLData
methods directly.
Similarly SQLInput
and SQLOutput
methods are not usually
called directly.
Modifier and Type | Method and Description |
---|---|
String |
getSQLTypeName()
Gets the SQL name of the User Defined Type (UDT) that this object
represents.
|
void |
readSQL(SQLInput stream,
String typeName)
Reads data from the database into this object.
|
void |
writeSQL(SQLOutput stream)
Writes the object to a supplied
SQLOutput data stream, writing it
out as an SQL value to the data source. |
String getSQLTypeName() throws SQLException
SQLData
object.readSQL
when the object was created.SQLException
- if a database error occurs.void readSQL(SQLInput stream, String typeName) throws SQLException
SQLInput.readString
, SQLInputreadBigDecimal
). If the type is
distinct, then read its only data entry. For structured types, read every
entry.
The supplied input stream is typically initialized by the calling JDBC
driver with the type map before readSQL
is called.
stream
- the SQLInput
stream from which the type map data is
read for the custom mapping.typeName
- the SQL type name for the type which is being mapped.SQLException
- if a database error occurs.SQLInput
void writeSQL(SQLOutput stream) throws SQLException
SQLOutput
data stream, writing it
out as an SQL value to the data source.
This method follows the following steps:
SQLOutput
methods (e.g. writeInt
, writeString
).
Write a single data element for a distinct type. For a structured type,
write a value for each attribute of the the SQL type.stream
- the SQLOutput
stream to use to write out the data for
the custom mapping.SQLException
- if a database error occurs.SQLOutput