DBWritable (Hadoop 0.20.2-cdh3u5 API)
Date: 2012-10-05

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## org.apache.hadoop.mapreduce.lib.db
Interface DBWritable

All Known Subinterfaces:
  DBWritable

All Known Implementing Classes:
  DBInputFormat.NullDBWritable, DBInputFormat.NullDBWritable

    public interface DBWritable

Objects that are read from/written to a database should implement `DBWritable`. DBWritable, is similar to `Writable` except that the `write(PreparedStatement)` method takes a `PreparedStatement`, and `readFields(ResultSet)` takes a `ResultSet`.

Implementations are responsible for writing the fields of the object to PreparedStatement, and reading the fields of the object from the ResultSet.

Example:

If we have the following table in the database :

     CREATE TABLE MyTable (
       counter        INTEGER NOT NULL,
       timestamp      BIGINT  NOT NULL,
     );

then we can read/write the tuples from/to the table with :

     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);
       }
     }

Method Summary
`void` | `readFields(ResultSet resultSet)` Reads the fields of the object from the `ResultSet`.
`void` | `write(PreparedStatement statement)` Sets the fields of the object in the `PreparedStatement`.

Method Detail

### write

    void write(PreparedStatement statement)
               throws SQLException

  Sets the fields of the object in the `PreparedStatement`.

  Parameters:
    `statement` - the statement that the fields are put into.
  Throws:
    `SQLException`

### readFields

    void readFields(ResultSet resultSet)
                    throws SQLException

  Reads the fields of the object from the `ResultSet`.

  Parameters:
    `resultSet` - the `ResultSet` to get the fields from.
  Throws:
    `SQLException`

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