SQLDatapublic interface SQLData 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. |
| Methods Summary |
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| public java.lang.String | getSQLTypeName()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.
| | public void | readSQL(java.sql.SQLInput stream, java.lang.String typeName)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.
| | public void | writeSQL(java.sql.SQLOutput stream)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.
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