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7DBWritable (Hadoop 0.20.1 API)
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91org.apache.hadoop.mapred.lib.db</FONT>
92<BR>
93Interface DBWritable</H2>
94<DL>
95<DT><B>All Known Implementing Classes:</B> <DD><A HREF="../../../../../../org/apache/hadoop/mapred/lib/db/DBInputFormat.NullDBWritable.html" title="class in org.apache.hadoop.mapred.lib.db">DBInputFormat.NullDBWritable</A></DD>
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99<DT><PRE>public interface <B>DBWritable</B></DL>
100</PRE>
101
102<P>
103Objects that are read from/written to a database should implement
104 <code>DBWritable</code>. DBWritable, is similar to <A HREF="../../../../../../org/apache/hadoop/io/Writable.html" title="interface in org.apache.hadoop.io"><CODE>Writable</CODE></A> 
105 except that the <A HREF="../../../../../../org/apache/hadoop/mapred/lib/db/DBWritable.html#write(java.sql.PreparedStatement)"><CODE>write(PreparedStatement)</CODE></A> method takes a
106 <A HREF="http://java.sun.com/javase/6/docs/api/java/sql/PreparedStatement.html?is-external=true" title="class or interface in java.sql"><CODE>PreparedStatement</CODE></A>, and <A HREF="../../../../../../org/apache/hadoop/mapred/lib/db/DBWritable.html#readFields(java.sql.ResultSet)"><CODE>readFields(ResultSet)</CODE></A> 
107 takes a <A HREF="http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html?is-external=true" title="class or interface in java.sql"><CODE>ResultSet</CODE></A>.
108 <p>
109 Implementations are responsible for writing the fields of the object
110 to PreparedStatement, and reading the fields of the object from the
111 ResultSet.
112 
113 <p>Example:</p>
114 If we have the following table in the database :
115 <pre>
116 CREATE TABLE MyTable (
117   counter        INTEGER NOT NULL,
118   timestamp      BIGINT  NOT NULL,
119 );
120 </pre>
121 then we can read/write the tuples from/to the table with :
122 <p><pre>
123 public class MyWritable implements Writable, DBWritable {
124   // Some data     
125   private int counter;
126   private long timestamp;
127       
128   //Writable#write() implementation
129   public void write(DataOutput out) throws IOException {
130     out.writeInt(counter);
131     out.writeLong(timestamp);
132   }
133       
134   //Writable#readFields() implementation
135   public void readFields(DataInput in) throws IOException {
136     counter = in.readInt();
137     timestamp = in.readLong();
138   }
139       
140   public void write(PreparedStatement statement) throws SQLException {
141     statement.setInt(1, counter);
142     statement.setLong(2, timestamp);
143   }
144       
145   public void readFields(ResultSet resultSet) throws SQLException {
146     counter = resultSet.getInt(1);
147     timestamp = resultSet.getLong(2);
148   }
149 }
150 </pre></p>
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168<CODE>&nbsp;void</CODE></FONT></TD>
169<TD><CODE><B><A HREF="../../../../../../org/apache/hadoop/mapred/lib/db/DBWritable.html#readFields(java.sql.ResultSet)">readFields</A></B>(<A HREF="http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html?is-external=true" title="class or interface in java.sql">ResultSet</A>&nbsp;resultSet)</CODE>
170
171<BR>
172&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Reads the fields of the object from the <A HREF="http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html?is-external=true" title="class or interface in java.sql"><CODE>ResultSet</CODE></A>.</TD>
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176<CODE>&nbsp;void</CODE></FONT></TD>
177<TD><CODE><B><A HREF="../../../../../../org/apache/hadoop/mapred/lib/db/DBWritable.html#write(java.sql.PreparedStatement)">write</A></B>(<A HREF="http://java.sun.com/javase/6/docs/api/java/sql/PreparedStatement.html?is-external=true" title="class or interface in java.sql">PreparedStatement</A>&nbsp;statement)</CODE>
178
179<BR>
180&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Sets the fields of the object in the <A HREF="http://java.sun.com/javase/6/docs/api/java/sql/PreparedStatement.html?is-external=true" title="class or interface in java.sql"><CODE>PreparedStatement</CODE></A>.</TD>
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196<A NAME="write(java.sql.PreparedStatement)"><!-- --></A><H3>
197write</H3>
198<PRE>
199void <B>write</B>(<A HREF="http://java.sun.com/javase/6/docs/api/java/sql/PreparedStatement.html?is-external=true" title="class or interface in java.sql">PreparedStatement</A>&nbsp;statement)
200           throws <A HREF="http://java.sun.com/javase/6/docs/api/java/sql/SQLException.html?is-external=true" title="class or interface in java.sql">SQLException</A></PRE>
201<DL>
202<DD>Sets the fields of the object in the <A HREF="http://java.sun.com/javase/6/docs/api/java/sql/PreparedStatement.html?is-external=true" title="class or interface in java.sql"><CODE>PreparedStatement</CODE></A>.
203<P>
204<DD><DL>
205<DT><B>Parameters:</B><DD><CODE>statement</CODE> - the statement that the fields are put into.
206<DT><B>Throws:</B>
207<DD><CODE><A HREF="http://java.sun.com/javase/6/docs/api/java/sql/SQLException.html?is-external=true" title="class or interface in java.sql">SQLException</A></CODE></DL>
208</DD>
209</DL>
210<HR>
211
212<A NAME="readFields(java.sql.ResultSet)"><!-- --></A><H3>
213readFields</H3>
214<PRE>
215void <B>readFields</B>(<A HREF="http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html?is-external=true" title="class or interface in java.sql">ResultSet</A>&nbsp;resultSet)
216                throws <A HREF="http://java.sun.com/javase/6/docs/api/java/sql/SQLException.html?is-external=true" title="class or interface in java.sql">SQLException</A></PRE>
217<DL>
218<DD>Reads the fields of the object from the <A HREF="http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html?is-external=true" title="class or interface in java.sql"><CODE>ResultSet</CODE></A>.
219<P>
220<DD><DL>
221<DT><B>Parameters:</B><DD><CODE>resultSet</CODE> - the <A HREF="http://java.sun.com/javase/6/docs/api/java/sql/ResultSet.html?is-external=true" title="class or interface in java.sql"><CODE>ResultSet</CODE></A> to get the fields from.
222<DT><B>Throws:</B>
223<DD><CODE><A HREF="http://java.sun.com/javase/6/docs/api/java/sql/SQLException.html?is-external=true" title="class or interface in java.sql">SQLException</A></CODE></DL>
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