Converting PostGres db table into Json:

PostGres to Json:
my table at localhost:

required library: http://wiki.fasterxml.com/JacksonDownload
Code:

package com.oe.basic;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import java.sql.ResultSetMetaData;
import java.util.HashMap;
import java.util.Map;

import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;

public class PostgresJson
{
public static void main(String[] args) throws SQLException, JsonGenerationException, JsonMappingException, IOException
{
   Connection conn = null;
Statement stmt=null;
ResultSet rs = null;
String url = "jdbc:postgresql://localhost/testdb?user=postgres&password=password";
String sql = "select * from sample_d";
try
{
try {
Class.forName("org.postgresql.Driver");
} catch (ClassNotFoundException e)
 {
e.printStackTrace();
 } //Check for driver

// DriverManager.getConnection(url).createStatement().executeQuery(sql)
conn = DriverManager.getConnection(url); //connection
System.out.println("Opened database successfully");
stmt =conn.createStatement(); //connection to statement
rs = stmt.executeQuery(sql);
//-----------------------------------------------------------------------------------------------

               List<Map<String, Object>>  contents = getEntitiesFromResultSet(rs);  //get list of mapped string to object
               ObjectMapper mapper = new ObjectMapper();   // Jack json library

               String json = mapper.writeValueAsString(contents); //ObjectMapper().writeValueAsString(contents);
               System.out.println(json);
               /*Final Output: [{"age":25,"name":"Dinesh"},
                * {"age":29,"name":"Aarya"},
                * {"age":26,"name":"arjun"},
                * {"age":30,"name":"Drona"}]
                * */

    } catch (SQLException e) {
               throw (e);
      } finally {
               if (rs != null) {
                   rs.close();
               }
         }
}
//--------------------------------------------------------------
    protected static List<Map<String, Object>> getEntitiesFromResultSet(ResultSet resultSet) throws SQLException
    {
        ArrayList<Map<String, Object>> entities = new ArrayList<Map<String, Object>>();
        while (resultSet.next()) {
            entities.add(getEntityFromResultSet(resultSet)); //add map into List
        }
        //System.out.println(entities);
        return entities;
        /* output:[{age=25, name=Dinesh},
         *  {age=29, name=Aarya},
         *  {age=26, name=arjun},
         *  {age=30, name=Drona}]
        */
    }

private static Map<String, Object> getEntityFromResultSet(ResultSet rs1) throws SQLException
{
ResultSetMetaData metaData = rs1.getMetaData(); //get meta data from resultset
       int columnCount = metaData.getColumnCount(); // get no. of columns by getColumnCount() function in metadata
       Map<String,Object> resultsMap = new HashMap<String,Object>(); // init hashmap
       for (int i = 1; i <= columnCount; ++i) {
           String columnName = metaData.getColumnName(i).toLowerCase(); //get column data
           Object object = rs1.getObject(i);
           resultsMap.put(columnName, object);
       } //runs until column count
      // System.out.println(columnCount);
       return resultsMap;
       /* output:
       *  {age=25, name=Dinesh}
*{age=29, name=Aarya}
* {age=26, name=arjun}
* {age=30, name=Drona}
**/
}
}