SQLDatapublic interface SQLData | An interface for the custom mapping of an SQL User Defined Type (UDT)
to a Java class. The Java class object is added to the connection's type map
paired with the SQL name of the corresponding UDT.
Usually within an implementation of {@code SQLData}, there is a corresponding
field for every attribute of an SQL type, but only one field, if the type is
SQL {@code DISTINCT}. When the UDT is returned within a {@code ResultSet}, it
is accessed with the {@link ResultSet#getObject} method and is returned as an
object which is an instance of the class defined by the {@code SQLData}
mapping. The application can use this object just like any other Java object
and can store changes back into the database using the
{@link PreparedStatement#setObject} method which performs the reverse mapping
into the SQL {@code UDT}.
Normally the implementation of a custom mapping is generated by
a tool requiring the name of the SQL {@code 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 {@code
SQLData}, {@code readSQL}, and {@code writeSQL} methods. {@code readSQL} reads
attributes from an {@code SQLInput} object, and {@code writeSQL} writes them.
This is done via {@code SQLInput} and {@code SQLOutput} method calls
respectively.
Ordinarily an application would not call {@code SQLData} methods directly.
Similarly {@code SQLInput} and {@code SQLOutput} methods are not usually
called directly.
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| Methods Summary |
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| public java.lang.String | getSQLTypeName()Gets the SQL name of the User Defined Type (UDT) that this object
represents. This method, usually invoked by the JDBC driver, retrieves
the name of the UDT instance associated with this {@code SQLData} object.
| | public void | readSQL(java.sql.SQLInput stream, java.lang.String typeName)Reads data from the database into this object. This method follows these
steps:
- Utilize the passed input stream to read the attributes or entries of
the SQL type
- This is carried out by reading each entry from the input stream,
ordered as they are in the SQL definition.
- Assign the data to the appropriate fields or elements. This is done
by calling the relevant reader method for the type involved (e.g. {@code
SQLInput.readString}, {@code 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 {@code readSQL} is called.
| | public void | writeSQL(java.sql.SQLOutput stream)Writes the object to a supplied {@code SQLOutput} data stream, writing it
out as an SQL value to the data source.
This method follows the following steps:
- Write each attribute of the SQL type to the output stream.
- Write each item by calling a method on the output stream, in the
order they appear in the SQL definition of the type. Use the appropriate
{@code SQLOutput} methods (e.g. {@code writeInt}, {@code 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.
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