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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
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 */

package java.sql;

/**
 * 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. */ public interface SQLData { /** * 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. * * @return a string with UDT type name for this object mapping, passed to * {@code readSQL} when the object was created. * @throws SQLException * if a database error occurs. */ public String getSQLTypeName() throws SQLException; /** * 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. * * @param stream * the {@code SQLInput} stream from which the type map data is * read for the custom mapping. * @param typeName * the SQL type name for the type which is being mapped. * @throws SQLException * if a database error occurs. * @see SQLInput */ public void readSQL(SQLInput stream, String typeName) throws SQLException; /** * 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.
  • *
* * @param stream * the {@code SQLOutput} stream to use to write out the data for * the custom mapping. * @throws SQLException * if a database error occurs. * @see SQLOutput */ public void writeSQL(SQLOutput stream) throws SQLException; }




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