/**
* Copyright 2011 Nube Technologies
*
* Licensed 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 co.nubetech.hiho.mapreduce.lib.db;
import java.io.IOException;
import java.io.StringWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import org.apache.hadoop.mapreduce.Job;
import org.apache.log4j.Logger;
import org.codehaus.jackson.JsonFactory;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.map.ObjectMapper;
import co.nubetech.hiho.mapreduce.lib.db.apache.DBConfiguration;
import co.nubetech.hiho.mapreduce.lib.db.apache.DBOutputFormat;
import co.nubetech.hiho.common.HIHOConf;
public class GenericDBOutputFormat extends DBOutputFormat {
final static Logger logger = Logger
.getLogger(co.nubetech.hiho.mapreduce.lib.db.GenericDBOutputFormat.class);
public static ArrayList<ColumnInfo> populateColumnInfo(
ResultSetMetaData meta) throws SQLException {
ArrayList<ColumnInfo> columns = new ArrayList<ColumnInfo>();
for (int i = 0; i < meta.getColumnCount(); ++i) {
ColumnInfo info = new ColumnInfo(i, meta.getColumnType(i + 1),
meta.getColumnName(i + 1));
columns.add(info);
}
return columns;
}
public static void setOutput(Job job, String tableName, String columnNames)
throws IOException{
job.setOutputFormatClass(GenericDBOutputFormat.class);
DBConfiguration dbConf = new DBConfiguration(job.getConfiguration());
dbConf.setOutputTableName(tableName);
dbConf.setOutputFieldNames(columnNames);
String dbDriver = job.getConfiguration().get(
DBConfiguration.DRIVER_CLASS_PROPERTY);
String connString = job.getConfiguration().get(
DBConfiguration.URL_PROPERTY);
String username = job.getConfiguration().get(
DBConfiguration.USERNAME_PROPERTY);
String password = job.getConfiguration().get(
DBConfiguration.PASSWORD_PROPERTY);
Connection conn;
PreparedStatement stmt;
try {
Class.forName(dbDriver).newInstance();
conn = DriverManager.getConnection(connString, username, password);
String query = "select " + columnNames + " from " + tableName;
stmt = conn.prepareStatement(query);
ResultSetMetaData meta = stmt.getMetaData();
ArrayList<ColumnInfo> columnInfo = populateColumnInfo(meta);
String jsonString = getJsonStringOfColumnInfo(columnInfo);
job.getConfiguration().set(HIHOConf.COLUMN_INFO, jsonString);
logger.debug("columnInfo is: " + job.getConfiguration().get(HIHOConf.COLUMN_INFO));
stmt.close();
conn.close();
} catch (Exception e) {
e.printStackTrace();
throw new IOException(e);
}
}
public static String getJsonStringOfColumnInfo(ArrayList<ColumnInfo> columnInfo) throws IOException {
ObjectMapper mapper = new ObjectMapper();
JsonFactory jsonFactory = new JsonFactory();
StringWriter writer = new StringWriter();
JsonGenerator jsonGenerator = jsonFactory.createJsonGenerator(writer);
mapper.writeValue(jsonGenerator, columnInfo);
String jsonString = writer.toString();
return jsonString;
}
}