> Hello,
>
> I have developed a Java web application based on Tomcat which reads shape
> files and imports the geometries into a PostGis database. When only a single
> user imports his data, then so far everything works very well. But if two or
> more concurrent users want to import their shape files, then the application
> crashes.
>
> The workflow is the following:
> A user loads a zip file up to the server. For each zip file, a random
> directory name is created and the zip file is stored in it. After that the
> file will get extracted and the shape file is imported into PostGis.
>
> The error scenario is the following:
> For example user1 loads geo1.zip and user2 loads geo2.zip up to the server.
> Then the two directories and files c:/abc/geo1.zip and c:/cba/geo2.zip are
> created on the server's filesystem. Then the bug comes: my shape file reader
> muddles up the directories and can't find the files because it puts the paths
> together in a wrong way, e.g. c:/abc/geo2.zip.
>
> I dont't understand why the path is created in this wrong way because the
> requests don't share the same instance of the class ShapeFileReader (which is
> indeed nod thread safe), they create all their own instance.
> Perhaps an expert of you can help me to find my mistake!
>
> Here is my code of the shape file reader:
> ###########################################
> public class ShapeFileReader {
>
> private static Logger logger = Logger.getLogger(ShapeFileReader.class);
> private URL shapeURL;
> private ShapefileDataStore store;
> private FeatureSource source;
> private FeatureResults fsShape;
> private FeatureReader reader;
>
> /**
> * This method initializes the object.
> * @param path The path to the shape file.
> */
> public synchronized void setShapeFilePath(String path) {
> File file = new File(path);
>
> try {
> this.shapeURL = file.toURL();
> this.store = new ShapefileDataStore(this.shapeURL);
> String name = store.getTypeNames()[0];
> this.source = this.store.getFeatureSource(name);
> this.fsShape = this.source.getFeatures();
> this.reader = this.fsShape.reader();
> } ...
/**
> * This method collects the geometry values from the shape file.
> * @see GeometryBean
> * @return A Vector of type <code>GeometryBean</code>
> */
> public synchronized Vector getGeometries() {
> Vector geometries = new Vector();
> try {
> this.reader = this.fsShape.reader();
>
> while (this.reader.hasNext()) {
> Feature feature = this.reader.next();
>
> MultiPolygon polygon = (MultiPolygon)
> feature.getDefaultGeometry();
> GeometryBean geometryBean = new GeometryBean();
> geometryBean.setMultiPolygon(polygon);
> geometries.add(geometryBean);
> }
> } ...
> return geometries;
> }
> ###########################################
>
> Here is the relevant code of the servlet which starts the import process:
> ###########################################
> public class ShapeImportServlet extends javax.servlet.http.HttpServlet
> implements javax.servlet.Servlet {
> protected void doPost(HttpServletRequest request, HttpServletResponse
> response) throws ServletException, IOException {
> // The information about the uploaded zip file, containing the
> directory name and the zip file name
> UploadDataBean uploadData = (UploadDataBean)
> session.getAttribute("uploadData");
> this.processImport(request, uploadData);
> ...
> }
> /**
> * This method extracts the necessary information out of the request
> and delegates
> * the database import to a dedicated importer thread. So the servlet
> can display
> * the results immediately while the importer thread does its job.
> * @param request HttpServletRequest.
> * @param uploadData Information about the data which should be
> uploaded.
> */
> private void processImport(HttpServletRequest request, UploadDataBean
> uploadData) > {
>
> String directory = uploadData.getDirectoryName() + "/";
>
> Map parameters = request.getParameterMap();
>
> Set set = parameters.keySet();
> Iterator iter = set.iterator();
>
> ArrayList filePaths = new ArrayList();
> ArrayList tableNames = new ArrayList();
>
> ArrayList params = new ArrayList();
>
> //Evaluate the request parameters
> for(Enumeration e=request.getParameterNames();
> e.hasMoreElements(); )
> {
> params.add((String)e.nextElement());
> }
>
> String[] parameterNames = new String[params.size()];
>
> for (int i = 0; i < parameterNames.length; i++) {
> parameterNames[i] = (String) params.get(i);
> }
>
> // Bring the parameter names in the right order to evaluate
> them correctly.
> // After sorting, the version, the pk ant the name match.
> Arrays.sort(parameterNames);
> for (int i = 0; i < parameterNames.length; i++) {
>
> tableNames.add(request.getParameter(parameterNames[i]));
> filePaths.add(directory + parameterNames[i]);
> }
> }
> if (workflow.equals("1")) {
> logger.info("User has chosen to process workflow 1");
> new Workflow1Thread(filePaths, tableNames, versions,
> pks, countryID).start();
> } else {
> System.out.println("---Begin DEBUG");
> for (int i = 0; i < filePaths.size(); i++) {
> System.out.print("filepath " +
> (String)filePaths.get(i) +
> " tableName "
> + (String) tableNames.get(i) +
> " version " +
> (String) versions.get(i) + "\n");
> }
> new Workflow2Thread(filePaths, tableNames, versions,
> pks, countryID).start();
> }
> }
> // This method in the workflow threads starts the reading and import of
> the shape files:
> protected void importGeometries() {
> // for every geometry table which should be imported
> for (int i = 0; i < this.pathToShapeFile.size(); i++) {
> // ShapeFileAccess mit Pfad zum File benutzen,
> um die Eintraege zu lesen
> shapeFileAccess.setShapeFilePath((String)
> this.pathToShapeFile.get(i)); // here the application gets a
> FileNotFoundException!!
> Vector geometries =
> shapeFileAccess.getGeometries();
> }
> }
> }
> ###########################################
> Regards,
> Thorsten
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