| /** |
| * 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 |
| * limitations under the License. |
| */ |
| package org.apache.hadoop.mapreduce.lib.db; |
| |
| import java.sql.PreparedStatement; |
| import java.sql.ResultSet; |
| import java.sql.SQLException; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.apache.hadoop.io.Writable; |
| |
| /** |
| * Objects that are read from/written to a database should implement |
| * <code>DBWritable</code>. DBWritable, is similar to {@link Writable} |
| * except that the {@link #write(PreparedStatement)} method takes a |
| * {@link PreparedStatement}, and {@link #readFields(ResultSet)} |
| * takes a {@link ResultSet}. |
| * <p> |
| * Implementations are responsible for writing the fields of the object |
| * to PreparedStatement, and reading the fields of the object from the |
| * ResultSet. |
| * |
| * <p>Example:</p> |
| * If we have the following table in the database : |
| * <pre> |
| * CREATE TABLE MyTable ( |
| * counter INTEGER NOT NULL, |
| * timestamp BIGINT NOT NULL, |
| * ); |
| * </pre> |
| * then we can read/write the tuples from/to the table with : |
| * <p><pre> |
| * public class MyWritable implements Writable, DBWritable { |
| * // Some data |
| * private int counter; |
| * private long timestamp; |
| * |
| * //Writable#write() implementation |
| * public void write(DataOutput out) throws IOException { |
| * out.writeInt(counter); |
| * out.writeLong(timestamp); |
| * } |
| * |
| * //Writable#readFields() implementation |
| * public void readFields(DataInput in) throws IOException { |
| * counter = in.readInt(); |
| * timestamp = in.readLong(); |
| * } |
| * |
| * public void write(PreparedStatement statement) throws SQLException { |
| * statement.setInt(1, counter); |
| * statement.setLong(2, timestamp); |
| * } |
| * |
| * public void readFields(ResultSet resultSet) throws SQLException { |
| * counter = resultSet.getInt(1); |
| * timestamp = resultSet.getLong(2); |
| * } |
| * } |
| * </pre></p> |
| */ |
| @InterfaceAudience.Public |
| @InterfaceStability.Stable |
| public interface DBWritable { |
| |
| /** |
| * Sets the fields of the object in the {@link PreparedStatement}. |
| * @param statement the statement that the fields are put into. |
| * @throws SQLException |
| */ |
| public void write(PreparedStatement statement) throws SQLException; |
| |
| /** |
| * Reads the fields of the object from the {@link ResultSet}. |
| * @param resultSet the {@link ResultSet} to get the fields from. |
| * @throws SQLException |
| */ |
| public void readFields(ResultSet resultSet) throws SQLException ; |
| } |