thoerup/traininfoservice/LocateStations.java

package dk.thoerup.traininfoservice;

import java.io.IOException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import dk.thoerup.traininfoservice.DBConnection;

/**
 * Servlet implementation class LocateStations
 */
public class LocateStations extends HttpServlet {
        private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public LocateStations() {
        super();
        // TODO Auto-generated constructor stub
    }

        protected String getStations(Connection conn, double latitude, double longitude) throws SQLException {
                //inner select is workaround from not being able to use a calculated column directly in where clause
                final String SQL = "SELECT * FROM ( "+
                                                   "               SELECT name,latitude,longitude,address,stationcode, " + 
                                                   "                     earth_distance( ll_to_earth(latitude,longitude), ll_to_earth(?,?))::int AS calcdist " + 
                                                   "               FROM trainstations " +
                                                   "       ) AS trainstations2 " +
                                               "ORDER BY calcdist ASC " + 
                                               "LIMIT 4 ";
                
                System.out.println(SQL);
                
                PreparedStatement stmt = null;
                ResultSet res = null;
                
                StringBuffer buff = new StringBuffer();
                
                buff.append("<?xml version=\"1.0\" ?>\n");
                buff.append("<stations>\n");
                try
                {
                        stmt = conn.prepareStatement(SQL);
                        stmt.setDouble(1, latitude);
                        stmt.setDouble(2, longitude);
                        
                        res = stmt.executeQuery();
                        
                        while (res.next()) {
                                buff.append("<station>\n");

                                buff.append("<name>").append( res.getString(1) ) .append("</name>\n");
                                buff.append("<latitude>").append( res.getDouble(2) ) .append("</latitude>\n");
                                buff.append("<longitude>").append( res.getDouble(3) ) .append("</longitude>\n");                                
                                buff.append("<address>").append( res.getString(4) ) .append("</address>\n");    
                                buff.append("<stationcode>").append( res.getString(5) ) .append("</stationcode>\n");
                                buff.append("<calcdist>").append( res.getDouble(6) ) .append("</calcdist>\n");
                                
                                buff.append("</station>\n");                            
                        }
                } finally {
                        if (res != null && !res.isClosed())
                                res.close();
                        if (stmt != null && !stmt.isClosed())
                                stmt.close();
                }
                buff.append("</stations>\n");
                return buff.toString();
        }

        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
                
                double latitude = Double.parseDouble( request.getParameter("latitude") );
                double longitude = Double.parseDouble( request.getParameter("longitude") );
                                
                Connection conn = null;
                try {
                        conn = DBConnection.getConnection();
                        
                        String xml = getStations(conn, latitude, longitude);
                        
                        response.setContentType("text/xml");
                        response.getWriter().print(xml);
                        
                        conn.close();
                        conn = null;
                        
                } catch (Exception e) {
                        throw new ServletException(e);
                } finally {
                        try {
                                if (conn != null)
                                        conn.close();
                        } catch (Throwable t) {}
                }
        }

}
1	package dk.thoerup.traininfoservice;
2
3	import java.io.IOException;
4	import java.sql.Connection;
5	import java.sql.PreparedStatement;
6	import java.sql.ResultSet;
7	import java.sql.SQLException;
8
9	import javax.servlet.ServletException;
10	import javax.servlet.http.HttpServlet;
11	import javax.servlet.http.HttpServletRequest;
12	import javax.servlet.http.HttpServletResponse;
13
14	import dk.thoerup.traininfoservice.DBConnection;
15
16	/**
17	* Servlet implementation class LocateStations
18	*/
19	public class LocateStations extends HttpServlet {
20	private static final long serialVersionUID = 1L;
21
22	/**
23	* @see HttpServlet#HttpServlet()
24	*/
25	public LocateStations() {
26	super();
27	// TODO Auto-generated constructor stub
28	}
29
30	protected String getStations(Connection conn, double latitude, double longitude) throws SQLException {
31	//inner select is workaround from not being able to use a calculated column directly in where clause
32	final String SQL = "SELECT * FROM ( "+
33	" SELECT name,latitude,longitude,address,stationcode, " +
34	" earth_distance( ll_to_earth(latitude,longitude), ll_to_earth(?,?))::int AS calcdist " +
35	" FROM trainstations " +
36	" ) AS trainstations2 " +
37	"ORDER BY calcdist ASC " +
38	"LIMIT 4 ";
39
40	System.out.println(SQL);
41
42	PreparedStatement stmt = null;
43	ResultSet res = null;
44
45	StringBuffer buff = new StringBuffer();
46
47	buff.append("<?xml version=\"1.0\" ?>\n");
48	buff.append("<stations>\n");
49	try
50	{
51	stmt = conn.prepareStatement(SQL);
52	stmt.setDouble(1, latitude);
53	stmt.setDouble(2, longitude);
54
55	res = stmt.executeQuery();
56
57	while (res.next()) {
58	buff.append("<station>\n");
59
60	buff.append("<name>").append( res.getString(1) ) .append("</name>\n");
61	buff.append("<latitude>").append( res.getDouble(2) ) .append("</latitude>\n");
62	buff.append("<longitude>").append( res.getDouble(3) ) .append("</longitude>\n");
63	buff.append("<address>").append( res.getString(4) ) .append("</address>\n");
64	buff.append("<stationcode>").append( res.getString(5) ) .append("</stationcode>\n");
65	buff.append("<calcdist>").append( res.getDouble(6) ) .append("</calcdist>\n");
66
67	buff.append("</station>\n");
68	}
69	} finally {
70	if (res != null && !res.isClosed())
71	res.close();
72	if (stmt != null && !stmt.isClosed())
73	stmt.close();
74	}
75	buff.append("</stations>\n");
76	return buff.toString();
77	}
78
79	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
80
81	double latitude = Double.parseDouble( request.getParameter("latitude") );
82	double longitude = Double.parseDouble( request.getParameter("longitude") );
83
84	Connection conn = null;
85	try {
86	conn = DBConnection.getConnection();
87
88	String xml = getStations(conn, latitude, longitude);
89
90	response.setContentType("text/xml");
91	response.getWriter().print(xml);
92
93	conn.close();
94	conn = null;
95
96	} catch (Exception e) {
97	throw new ServletException(e);
98	} finally {
99	try {
100	if (conn != null)
101	conn.close();
102	} catch (Throwable t) {}
103	}
104	}
105
106	}