HTTPConnection.java

package eu.simstadt.nf4j.async;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.StringReader;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.nio.file.Files;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
import java.util.Optional;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import eu.simstadt.nf4j.Job;
import eu.simstadt.nf4j.FailedTransmissionException;
import eu.simstadt.nf4j.InvalidJobDescriptorException;
import eu.simstadt.nf4j.JobStatus;
import eu.simstadt.nf4j.Connector;

/**
 * NFConnector lets you communicate with your novaFACTORY (nF) server instance. It supports nF version 6.3.1.1.
 * For more technical details about the NFConnector interface @see NFConnector.
 * 
 * Please note, that this connector doesn't act asynchronously. This connector is safe, but will block your main
 * application. You may rather want to use the asynchronous job implementations. 
 * 
 * @author Marcel Bruse
 * 
 * @param <I> The import job descriptor implementation for this connector.
 * @param <E> The export job descriptor implementation for this connector.
 */
public class HTTPConnection implements Connector<AsyncImportJob, AsyncExportJob> {

	/** Supported version of the novaFACTORY. */
	public static final String NOVA_FACTORY_VERSION = "6.3.1.1";
	
	/** The default context of the nF web application. It is part of any request URL directed at the nF server. */
	public static final String DEFAULT_CONTEXT = "novaFACTORY";
	
	/** The default port number of the nF web application. */
	public static final int DEFAULT_PORT = 80;
	
	/** The default protocol for requests. */
	public static final String DEFAULT_PROTOCOL = "http";
	
	/** The standard char set for requests. */
	public static final String DEFAULT_CHARSET = "UTF-8";
	
	/** The standard line separator required for file transmission via multipart/form-data. */
	public static final String CRLF = "\r\n";
	
	/** The name of nF's remote order servlet. */
	public static final String REMOTE_ORDER_SERVLET = "RemoteOrder";
	
	/** The name of nF's remote status servlet. */
	public static final String REMOTE_STATUS_SERVLET = "RemoteStatus";
	
	/** The name of nF's remote import servlet. */
	public static final String REMOTE_IMPORT_SERVLET = "RemoteImport";
	
	/** Default parser error message. */
	public static final String XML_PARSER_ERROR = "Request failed due to an unknown XML parser error.";
	
	/** Default IO exception occurred message. */
	public static final String IO_EXCEPTION_OCCURRED = 
			"Request failed due to an IO exception. Check the host and port.";
	
	/** Default malformed URL message. */
	public static final String MALFORMED_URL = "Request failed due to a malformed URL.";
	
	/** Default unknown error message. */
	public static final String UNKNOWN_ERROR_OCCURRED = "An unknown error occurred.";
	
	/** The server or host name of the nF server. */
	private String server;
	
	/** The port of the nF server. */
	private int port;
	
	/** The protocol of the data connection. */
	private String protocol;
	
	/** The context of the nF web application. It is part of any request URL directed at the nF server. */
	private String context;
	
	/**
	 * Constructs your Connector instance.
	 * 
	 * @param server The host name of the nF server with which you want to establish a data connection.
	 */
	public HTTPConnection(String server) {
		this(server, DEFAULT_PORT, DEFAULT_CONTEXT, DEFAULT_PROTOCOL);
	}
	
	/**
	 * Constructs your Connector instance.
	 * 
	 * @param server The host name of the nF server with which you want to establish a data connection.
	 * @param port The port of the nF web application.
	 * @param context The context of the nF web application. It is part of any request URL directed at the nF server.
	 */
	public HTTPConnection(String server, int port, String context, String protocol) {
		this.server = server;
		this.port = port;
		this.context = context;
		this.protocol = protocol;
	}

	/**
	 * Callers of this NFConnector want to know the actual version of the novaFACTORY and the versions of its
	 * HTTP/FTP/WPS/etc. interfaces against which this interface has been implemented.
	 * 
	 * The NovaFACTORY interfaces may change over time. Such changes force the SimStadt programmers to
	 * implement different versions of this NFConnector interface while keeping old implementations in order to 
	 * ensure backward compatibility.
	 * 
	 * @return The supported version of the novaFACTORY.
	 */
	@Override
	public String supportsNFVersion() {
		return NOVA_FACTORY_VERSION;
	}
	
	/**
	 * Returns the status of any existing nF export job.
	 * 
	 * @param jobId The id of the export job for which you want to request the status.
	 * @return The status of any existing nF export job.
	 * @throws IOException An error occurred during the request. This could be a malformed URL or a network failure.
	 */
	@Override
	public AsyncExportJob requestExportJob(int jobId) throws FailedTransmissionException {
		AsyncExportJob result = new AsyncExportJob(jobId, this);
		try {
			List<String> parameters = Arrays.asList(buildParameter("jobid", jobId));
			getJobFromResponse(result, getResponse(buildURL(REMOTE_STATUS_SERVLET, parameters)));
		} catch (MalformedURLException ex) {
			result.getStatus().setMessage(MALFORMED_URL);
			throw new FailedTransmissionException(ex.getMessage());
		} catch (IOException ex) {
			result.getStatus().setMessage(IO_EXCEPTION_OCCURRED);
			throw new FailedTransmissionException(ex.getMessage());
		} catch (ParserConfigurationException | SAXException ex) {
			result.getStatus().setMessage(XML_PARSER_ERROR);
			throw new FailedTransmissionException(ex.getMessage());
		}
		return result;
	}
	
	/**
	 * Returns the status of any existing nF import job.
	 * 
	 * @param jobId The id of the import job for which you want to request the status.
	 * @return The status of any existing nF import job.
	 * @throws IOException An error occurred during the request. This could be a malformed URL or a network failure.
	 */
	@Override
	public AsyncImportJob requestImportJob(int jobId) throws FailedTransmissionException {
		AsyncImportJob result = new AsyncImportJob(jobId, this);
		try {
			List<String> parameters = Arrays.asList(
					buildParameter("jobid", jobId),
					buildParameter("request", "status"));
			getJobFromResponse(result, getResponse(buildURL(REMOTE_IMPORT_SERVLET, parameters)));
		} catch (MalformedURLException ex) {
			result.getStatus().setMessage(MALFORMED_URL);
			throw new FailedTransmissionException(ex.getMessage());
		} catch (IOException ex) {
			result.getStatus().setMessage(IO_EXCEPTION_OCCURRED);
			throw new FailedTransmissionException(ex.getMessage());
		} catch (ParserConfigurationException | SAXException ex) {
			result.getStatus().setMessage(XML_PARSER_ERROR);
			throw new FailedTransmissionException(ex.getMessage());
		}
		return result;
	}
	
	/**
	 * Downloads the result for a given nF export job and hands over the corresponding file handle.
	 * 
	 * @param jobId The id of the export job for which the result should be loaded.
	 * @return A file handle to the result of the nF export job. 
	 */
	@Override
	public File requestExportJobResult(AsyncExportJob job) throws FailedTransmissionException {
		if (!job.hasFinished()) {
			throw new FailedTransmissionException("Job is not finished yet!");
		}
		File result = null;
		try {
			List<String> parameters = Arrays.asList(
					buildParameter("request", "downloadJob"),
					buildParameter("mode", 0),
					buildParameter("jobId", job.getId()));
			result = downloadFile(buildURL(REMOTE_ORDER_SERVLET, parameters));
		} catch (MalformedURLException ex) {
			throw new FailedTransmissionException(ex.getMessage());
		} catch (IOException ex) {
			throw new FailedTransmissionException(ex.getMessage());
		}
		return result;
	}
	
	/**
	 * Builds a simple parameter string for a HTTP GET request string.
	 * 
	 * @param key The parameter name.
	 * @param value The value of the parameter.
	 * @return The HTTP GET request parameter as concatenated key and value.
	 */
	private String buildParameter(String key, Object value) {
		return key + "=" + value;
	}
	
	/**
	 * Builds a HTTP GET request URL out of the used protocol, nF server, port, context, servlet and existing
	 * parameters.
	 * 
	 * @param servlet One of the supported nF servlets RemoteOrder, RemoteStatus or RemoteImport.
	 * @param parameters List of parameters to be send to the servlet.
	 * @return The built URL instance.
	 * @throws MalformedURLException You will get some of this, if you mess up any part of the URL.
	 */
	private URL buildURL(String servlet, List<String> parameters) throws MalformedURLException {
		String url = String.format("%s://%s:%s/%s/%s", protocol, server, port, context, servlet);
		if (Objects.nonNull(parameters) && !parameters.isEmpty()) {
			url += "?" + String.join("&", parameters);
		}
		return new URL(url);
	}
	
	/**
	 * Requests a response from the given URL. The response is expected to be returned as nF XML report.
	 * 
	 * @param url The URL of the nF servlet with all its necessary parameters. Read the nF handbook for more
	 * details about the usage of nF servlets.
	 * @return The response is expected to be a XML report, which will then be returned as a String.
	 * @throws IOException You will get some of this, if anything goes wrong with your data connection to your
	 * nF instance.
	 */
	private String getResponse(URL url) throws UnsupportedEncodingException, IOException {
		HttpURLConnection httpConnection = (HttpURLConnection) url.openConnection();
		httpConnection.setRequestProperty("Accept-Charset", DEFAULT_CHARSET);
		return getResponse(httpConnection);
	}
	
	/**
	 * Requests a response from the given HTTP connection. The response is expected to be a XML document. 
	 * 
	 * @param httpConnection The HTTP Connection to the nF servlet. Read the nF handbook for more details
	 * about the usage of the nF servlets.
	 * @return The response is expected to be a XML report, which will then be returned as a String.
	 * @throws UnsupportedEncodingException You will get some of this, if your connection uses wrong encodings.
	 * @throws IOException You will get some of this, if anything goes wrong with your data connection to your
	 * nF instance.
	 */
	private String getResponse(HttpURLConnection httpConnection) throws UnsupportedEncodingException, IOException {
		String xml = "";
		if (httpConnection.getResponseCode() == HttpURLConnection.HTTP_OK) {
			String contentType = httpConnection.getHeaderField("Content-Type");
			String charset = null;
			for (String param : contentType.replace(" ", "").split(";")) {
				if (param.startsWith("charset=")) {
					charset = param.split("=", 2)[1];
					break;
				}
			}
			InputStream response = httpConnection.getInputStream();
			if (Objects.nonNull(charset)) {
				BufferedReader reader = new BufferedReader(new InputStreamReader(response, charset));
				String line;
				while ((line = reader.readLine()) != null) {
					xml += line;
				}			
			}
			response.close();
		} else {
			throw new IOException();
		}
		return xml;
	}
	
	/**
	 * If everything works as expected, then nF's servlets will respond with XML reports to your requests. The job
	 * id and status will be extracted from the response string. The id of the passed job instance will be updated.
	 * The XML reports have a certain structure. Read the nF manual for more information about the XML reports and
	 * have a look at the DTD of the XML reports.
	 * 
	 * @param xml A XML string that is supposed to be a XML document.
	 * @param An empty job status object about to be filled with the actual result. It will be UNKOWN if there was
	 * no XML report in the response. 
	 * @throws ParserConfigurationException Something went wrong.
	 * @throws SAXException Some parse error.
	 * @throws IOException Some parse error.
	 */
	private void getJobFromResponse(Job job, String xml)
			throws ParserConfigurationException, SAXException, IOException, FailedTransmissionException {		
		SAXParserFactory saxFactory = SAXParserFactory.newInstance();
		SAXParser parser = saxFactory.newSAXParser();
		StringReader reader = new StringReader(xml);
		ReportHandler handler = new ReportHandler();
		parser.parse(new InputSource(reader), handler);
		if (Objects.nonNull(handler.statusId)) {
			job.setStatusForCode(handler.statusId);
		}
		if (Objects.nonNull(handler.jobId)) {
			job.setId(handler.jobId);
		}
		if (Objects.nonNull(handler.serviceException)) {
			throw new FailedTransmissionException(handler.serviceException);
		}
	}
	
	/**
	 * Downloads a (zipped) CityGML file from the nF server. The file will be the result of an export job.
	 *  
	 * @param url The URL of the remote order servlet that points at the CityGML file on the nF server. 
	 * @return Returns a handle to the downloaded (zipped) CityGML file. Will be null if no file has been
	 * downloaded (due to errors).
	 * @throws IOException Something went wrong with your data connection. Check your server and the port.
	 */
	private File downloadFile(URL url) throws IOException {
		File handle = null;
		HttpURLConnection httpConnection = (HttpURLConnection) url.openConnection();
		httpConnection.setRequestProperty("Accept-Charset", DEFAULT_CHARSET);
		if (httpConnection.getResponseCode() == HttpURLConnection.HTTP_OK) {
			String filename = "result.gml";
            String disposition = httpConnection.getHeaderField("Content-Disposition");
            if (disposition != null) {
                int index = disposition.indexOf("filename=");
                if (index > -1) {
                    filename = disposition.
                    		substring(index + 9, disposition.length()).
                    		replaceAll("\"", "").
                    		replaceAll(";", "");
                }
            }
            InputStream inputStream = httpConnection.getInputStream();
            FileOutputStream outputStream = new FileOutputStream(filename);
            int bytesRead = -1;
            byte[] buffer = new byte[4096];
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                outputStream.write(buffer, 0, bytesRead);
            }
            outputStream.close();
            inputStream.close();
            handle = new File(filename);
		} else {
			throw new IOException();
		}
		return handle;
	}

	/**
	 * Sends an export job to the nF. This job will be enqueued in the queue of export jobs.
	 * 
	 * @param file The XML file which describes the nF export job.
	 * @return Returns the status of the export job you just sent.
	 * @throws InvalidJobDescriptorException 
	 */
	@Override
	public void sendAndUpdateExportJob(AsyncExportJob job) 
			throws InvalidJobDescriptorException, FailedTransmissionException {
		JobFileBuilderImpl jobFileBuilder = new JobFileBuilderImpl();
		File exportJobFile = jobFileBuilder.buildExportJobFile(job.getDescriptor());
		try {
			URL url = buildURL(REMOTE_ORDER_SERVLET, null);
			HttpURLConnection connection = (HttpURLConnection) url.openConnection();
			connection.setRequestMethod("POST");
			connection.setRequestProperty("Connection", "Keep-Alive");
			connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
			connection.setDoOutput(true); // Sends export job file
			connection.setDoInput(true);  // Expects XML response 
			connection.connect();
			OutputStream os = connection.getOutputStream();
			PrintWriter writer = new PrintWriter(new OutputStreamWriter(os, DEFAULT_CHARSET), true);
			Files.copy(exportJobFile.toPath(), os);
			os.flush();
			writer.append(CRLF).flush();
			getJobFromResponse(job, getResponse(connection));
			if (job.getId() > 0) {
				job.setStatus(JobStatus.SENT, Optional.empty());
			} else {
				throw new FailedTransmissionException("Job didn't receive an id from the nF server.");
			}
		} catch (MalformedURLException ex) {
			job.getStatus().setMessage(MALFORMED_URL);
			throw new FailedTransmissionException(ex.getMessage());
		} catch (IOException ex) {
			job.getStatus().setMessage(IO_EXCEPTION_OCCURRED);
			throw new FailedTransmissionException(ex.getMessage());
		} catch (ParserConfigurationException | SAXException ex) {
			job.getStatus().setMessage(XML_PARSER_ERROR);
			throw new FailedTransmissionException(ex.getMessage());
		}
	}

	/**
	 * Sends an import job to nF. The given import job file has to be a zip file and has to obey the internal
	 * structure defined in the nF manuals. Short description:
	 * 
	 * Import jobs enable you to add, alter and delete CityGML top level objects (like buildings) in the nF.
	 * Every import job file has to contain a start file. Start files control the import process through their
	 * file names and their contents. The name of a start file has the following structure
	 * 
	 *     <Product>_<Tile>.start
	 * 
	 * The start file should contain the level to which your manipulated CityGML should be imported. Your CityGML
	 * file and the ZIP archive has to be named after the following naming convention:
	 * 
	 *     <Product>_<Tile>_<Level>_<Operation>.gml
	 *    
	 * Here operation can be ...
	 * - 'REP': Replaces whole existing buildings only,
	 * - 'REPUPD': Replaces whole existing buildings and adds new buildings, 
	 * - 'UPD': Update, same as REP,
	 * - 'CHG': Change, same as REPUPD,
	 * - 'DEL': Deletes the geometry of a particular LOD,
	 * - 'DELALL': Deletes a whole building
	 * 
	 * @param file The nF import job as a prepared ZIP file. It has to contain the CityGML file and the start file.
	 * @return Returns the job status of your import job.
	 * @throws FailedTransmissionException 
	 */
	@Override
	public void sendAndUpdateImportJob(AsyncImportJob job) 
			throws InvalidJobDescriptorException, FailedTransmissionException {
		if (job.getStatus() != JobStatus.LOCAL) {
			throw new FailedTransmissionException("Job cannot be sent twice!");
		}
		JobFileBuilderImpl jobFileBuilder = new JobFileBuilderImpl();
		File importJobFile = jobFileBuilder.buildImportJobFile(job.getDescriptor());
		try {
			String product = job.getDescriptor().getProduct();
			List<String> parameters = Arrays.asList(
					buildParameter("request", "imp"),    // trigger import
					buildParameter("pdctKrz", product),  // the nF product to import to
					buildParameter("createjob", "1"));   // force nF to create an import job with a job number
			URL url = buildURL(REMOTE_IMPORT_SERVLET, parameters);
			HttpURLConnection connection = (HttpURLConnection) url.openConnection();
			connection.setRequestMethod("POST");
			connection.setRequestProperty("Content-Type", "application/zip");
			connection.setRequestProperty("Accept", "*/*");
			connection.setRequestProperty("", "");
			connection.setDoOutput(true); // Sends export job file
			connection.setDoInput(true);  // Expects XML response
			connection.connect();
			OutputStream os = connection.getOutputStream();
			PrintWriter writer = new PrintWriter(new OutputStreamWriter(os, DEFAULT_CHARSET), true);
			Files.copy(importJobFile.toPath(), os);
			os.flush();
			writer.append(CRLF).flush();
			getJobFromResponse(job, getResponse(connection));
			if (job.getId() > 0) {
				job.setStatus(JobStatus.SENT, Optional.empty());
			} else {
				throw new FailedTransmissionException("Job didn't receive an id from the nF server.");
			}
		} catch (MalformedURLException ex) {
			job.getStatus().setMessage(MALFORMED_URL);
			throw new FailedTransmissionException(ex.getMessage());
		} catch (IOException ex) {
			job.getStatus().setMessage(IO_EXCEPTION_OCCURRED);
			throw new FailedTransmissionException(ex.getMessage());
		} catch (SAXException | ParserConfigurationException ex) {
			job.getStatus().setMessage(XML_PARSER_ERROR);
			throw new FailedTransmissionException(ex.getMessage());
		}
	}
	
}