I have found an error in the web.xml file, however, this DID NOT fix the
problem. Inside the web.xml file, there is the following snippet:
<init-param>
<description>
Default field used in standard Lucene QueryParser used
in UserQuery
tag</description>
<param-name>defaultStandardQueryParserField</param-name>
<param-value>jobDescription</param-value>
</init-param>
the <param-value> here should be IMHO "description", as neither the
query.xsl file, nor index.jsp file contain any tags/values called
"jobDescription", only "description". I hope the contributors to the Lucene
project take note of this, or please show me the error of my ways. Having
said that, as I mentioned earlier, despite making this correction, I am
still getting the above "NullPointerException". Can anyone see where I am
going wrong?
Thanks again to all who reply.
Sincerely;
Fayyaz
syedfa wrote:
>
> Dear fellow Java developers:
>
> I am trying to run the XML Query Parser example that comes with Lucene 3.0
> source distribution. I have the application structured identical to the
> one you download, and I am trying to run it in eclipse. When I launch the
> application, fill out the form that appears on index.jsp, and then submit
> it to search the index, I get the following error 505:
>
> javax.servlet.ServletException: Error processing query
>
> org.apache.lucene.xmlparser.webdemo.FormBasedXmlQueryDemo.doPost(FormBasedXmlQueryDemo.java:124)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
>
>
> root cause
>
> java.lang.NullPointerException
>
> org.apache.lucene.xmlparser.webdemo.FormBasedXmlQueryDemo.doPost(FormBasedXmlQueryDemo.java:107)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:710)
> javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
>
>
> I absolutely have no idea why this is happening, as I even structured the
> package of the servlet in eclipse identical to the way it is in the
> example. I have attached my entire servlet, "FormBasedXmlQueryDemo"
> below:
>
> public class FormBasedXmlQueryDemo extends HttpServlet {
> private static final long serialVersionUID = 1L;
>
> private QueryTemplateManager queryTemplateManager;
> private CorePlusExtensionsParser xmlParser;
> private IndexSearcher searcher;
> private Analyzer analyzer = new
> StandardAnalyzer(org.apache.lucene.util.Version.LUCENE_CURRENT);
>
> public FormBasedXmlQueryDemo() {
> super();
> // TODO Auto-generated constructor stub
> }
>
> @Override
> public void init(ServletConfig config) throws ServletException {
> // TODO Auto-generated method stub
> super.init(config);
>
> try{
>
> openExampleIndex();
>
> String xslFile=config.getInitParameter("xslFile");
> String defaultStandardQueryParserField =
> config.getInitParameter("defaultStandardQueryParserField");
> queryTemplateManager = new
> QueryTemplateManager(getServletContext().getResourceAsStream("/WEB-INF/" +
> xslFile));
> xmlParser = new
> CorePlusExtensionsParser(defaultStandardQueryParserField, analyzer);
>
> }catch(Exception e){
> throw new ServletException("Error loading query
> template", e);
> }
> }
>
> protected void doGet(HttpServletRequest request, HttpServletResponse
> response) throws ServletException, IOException {
>
> }
>
> @Override
> protected void doPost(HttpServletRequest request, HttpServletResponse
> response) throws ServletException, IOException {
> // TODO Auto-generated method stub
>
> Properties completedFormFields = new Properties();
> Enumeration pNames = request.getParameterNames();
>
> while (pNames.hasMoreElements()){
>
> String propName = (String) pNames.nextElement();
> String value = request.getParameter(propName);
>
> if ((value != null) && (value.trim().length()>0)){
> completedFormFields.setProperty(propName,
> value);
> }
> }
>
> try{
> org.w3c.dom.Document xmlQuery =
> queryTemplateManager.getQueryAsDOM(completedFormFields);
> Query query =
> xmlParser.getQuery(xmlQuery.getDocumentElement());
> TopDocs topDocs = searcher.search(query, 10);
>
> if (topDocs != null) {
> ScoreDoc[] sd = topDocs.scoreDocs;
> Document[] results = new Document[sd.length];
>
> for(int i = 0; i < results.length; i++){
>
> results[i] = searcher.doc(sd[i].doc);
> request.setAttribute("results",
> results);
> }
> }
>
> RequestDispatcher dispatcher =
> getServletContext().getRequestDispatcher("/index.jsp");
> dispatcher.forward(request, response);
> }
> catch(Exception e){
> throw new ServletException("Error processing query", e);
> }
> }
>
> private void openExampleIndex() throws CorruptIndexException,
> IOException
> {
>
>
> RAMDirectory rd = new RAMDirectory();
> IndexWriter writer = new IndexWriter(rd, analyzer,
> IndexWriter.MaxFieldLength.LIMITED);
> InputStream dataIn =
> getServletContext().getResourceAsStream("/WEB-INF/data.tsv");
> BufferedReader br = new BufferedReader(new
> InputStreamReader(dataIn));
> String line = br.readLine();
>
> while (line != null){
>
> line = line.trim();
> if (line.length() > 0){
>
> StringTokenizer st = new StringTokenizer(line,
> "\t");
> Document doc = new Document();
> doc.add(new
> Field("location",st.nextToken(),Field.Store.YES,
> Field.Index.ANALYZED_NO_NORMS));
> doc.add(new
> Field("salary",st.nextToken(),Field.Store.YES,
> Field.Index.ANALYZED_NO_NORMS));
> doc.add(new
> Field("type",st.nextToken(),Field.Store.YES,
> Field.Index.ANALYZED_NO_NORMS));
> doc.add(new
> Field("description",st.nextToken(),Field.Store.YES,
> Field.Index.ANALYZED));
> writer.addDocument(doc);
> }
>
> line = br.readLine();
> }
>
> writer.close();
> }
>
> }
>
>
>
> When I was tracing through the code, it appears that it was throwing the
> exception just as it tried to process the line:
>
> TopDocs topDocs = searcher.search(query, 10);
>
> Does anyone know where I am going wrong?
>
> Thanks in advance to all who reply.
>
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