airnowgrib2tojson.AirNowGRIB2toJSON.java Source code

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Here is the source code for airnowgrib2tojson.AirNowGRIB2toJSON.java

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/*
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package airnowgrib2tojson;

import java.io.BufferedOutputStream;
import org.apache.commons.net.ftp.FTPClient;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.net.SocketException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.List;
import java.util.TimeZone;
import org.apache.commons.net.ftp.FTP;
import ucar.ma2.Array;
import ucar.ma2.Index;
import ucar.nc2.dataset.CoordinateAxis;
import ucar.nc2.dataset.VariableDS;
import ucar.nc2.dt.GridCoordSystem;
import ucar.nc2.dt.GridCoordSystem.*;
import ucar.nc2.dt.GridDatatype;
import ucar.nc2.dt.grid.GridDataset;

/**
 *
 * @author Thomas Leschik
 */
public class AirNowGRIB2toJSON {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {

        SimpleDateFormat GMT = new SimpleDateFormat("yyMMddHH");
        GMT.setTimeZone(TimeZone.getTimeZone("GMT-2"));

        System.out.println(GMT.format(new Date()));

        FTPClient ftpClient = new FTPClient();
        FileOutputStream fos = null;

        try {
            //Connecting to AirNow FTP server to get the fresh AQI data  
            ftpClient.connect("ftp.airnowapi.org");
            ftpClient.login("pixelshade", "GZDN8uqduwvk");
            ftpClient.enterLocalPassiveMode();
            ftpClient.setFileType(FTP.BINARY_FILE_TYPE);

            //downloading .grib2 file
            File of = new File("US-" + GMT.format(new Date()) + "_combined.grib2");
            OutputStream outstr = new BufferedOutputStream(new FileOutputStream(of));
            InputStream instr = ftpClient
                    .retrieveFileStream("GRIB2/US-" + GMT.format(new Date()) + "_combined.grib2");
            byte[] bytesArray = new byte[4096];
            int bytesRead = -1;
            while ((bytesRead = instr.read(bytesArray)) != -1) {
                outstr.write(bytesArray, 0, bytesRead);
            }

            //Close used resources
            ftpClient.completePendingCommand();
            outstr.close();
            instr.close();

            // logout the user 
            ftpClient.logout();

        } catch (SocketException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                //disconnect from AirNow server
                ftpClient.disconnect();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        try {
            //Open .grib2 file
            final File AQIfile = new File("US-" + GMT.format(new Date()) + "_combined.grib2");
            final GridDataset gridDS = GridDataset.open(AQIfile.getAbsolutePath());

            //The data type needed - AQI; since it isn't defined in GRIB2 standard,
            //Aerosol type is used instead; look AirNow API documentation for details.
            GridDatatype AQI = gridDS.findGridDatatype("Aerosol_type_msl");

            //Get the coordinate system for selected data type;
            //cut the rectangle to work with - time and height axes aren't present in these files
            //and latitude/longitude go "-1", which means all the data provided.
            GridCoordSystem AQIGCS = AQI.getCoordinateSystem();
            List<CoordinateAxis> AQI_XY = AQIGCS.getCoordinateAxes();
            Array AQIslice = AQI.readDataSlice(0, 0, -1, -1);

            //Variables for iterating through coordinates
            VariableDS var = AQI.getVariable();
            Index index = AQIslice.getIndex();

            //Variables for counting lat/long from the indices provided
            double stepX = (AQI_XY.get(2).getMaxValue() - AQI_XY.get(2).getMinValue()) / index.getShape(1);
            double stepY = (AQI_XY.get(1).getMaxValue() - AQI_XY.get(1).getMinValue()) / index.getShape(0);
            double curX = AQI_XY.get(2).getMinValue();
            double curY = AQI_XY.get(1).getMinValue();

            //Output details
            OutputStream ValLog = new FileOutputStream("USA_AQI.json");
            Writer ValWriter = new OutputStreamWriter(ValLog);

            for (int j = 0; j < index.getShape(0); j++) {
                for (int i = 0; i < index.getShape(1); i++) {
                    float val = AQIslice.getFloat(index.set(j, i));

                    //Write the AQI value and its coordinates if it's present by i/j indices
                    if (!Float.isNaN(val))
                        ValWriter.write("{\r\n\"lat\":" + curX + ",\r\n\"lng\":" + curY + ",\r\n\"AQI\":" + val
                                + ",\r\n},\r\n");

                    curX += stepX;
                }
                curY += stepY;
                curX = AQI_XY.get(2).getMinValue();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}