java.sql.SQLData Maven / Gradle / Ivy
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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} interface will be entered in the
* appropriate {@code Connection} object's type map along with the SQL
* name of the UDT for which it is a custom mapping.
*
* Typically, a {@code SQLData} implementation
* will define a field for each attribute of an SQL structured type or a
* single field for an SQL {@code DISTINCT} type. When the UDT is
* retrieved from a data source with the {@code 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 {@code 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 {@code SQLData.readSQL} and
* {@code SQLData.writeSQL} methods. The {@code readSQL} method
* calls the appropriate {@code SQLInput} methods to read
* each attribute from an {@code SQLInput} object, and the
* {@code writeSQL} method calls {@code SQLOutput} methods
* to write each attribute back to the data source via an
* {@code SQLOutput} object.
*
* An application programmer will not normally call {@code SQLData} methods
* directly, and the {@code SQLInput} and {@code SQLOutput} methods
* are called internally by {@code SQLData} 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}.
*
* @return the type name that was passed to the method {@code readSQL}
* when this object was constructed and populated
* @throws SQLException if there is a database access error
* @throws 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 {@code readSQL} then
* assigns the data to appropriate fields or
* elements (of this or other objects).
* Specifically, it must call the appropriate reader method
* ({@code SQLInput.readString}, {@code 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
* {@code SQLInput} reader method on the stream.
*
* @param stream the {@code SQLInput} 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
* @throws SQLException if there is a database access error
* @throws 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 {@code SQLOutput} writer
* method(s) ({@code writeInt}, {@code 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.
*
* @param stream the {@code SQLOutput} object to which to write the data for
* the value that was custom mapped
* @throws SQLException if there is a database access error
* @throws SQLFeatureNotSupportedException if the JDBC driver does not support
* this method
* @see SQLOutput
* @since 1.2
*/
void writeSQL (SQLOutput stream) throws SQLException;
}