Hello, I searched around these mail archives for posts about NullPointerExceptions, but I wasn't able to find a solution to my problem below. Any advice on how to find a solution would be greatly appreciated.
Here is the message I receive from XMLDBException.GetMessage() call: Failed to execute command 'GetResource' on server: http://localhost:8080/xindice/, message: java.lang.Exception: java.lang.NullPointerException I'm using the following versions: Xindice: 1.1b4 Tomcat: 5.0.25 JVM: 1.4.2_01-b06 OS: Linux 2.4.18-14 Here is the sequence that causes this error: 1. User updates web form and post to my Servlet 2. My servlet does a GetResource() to pull the current version of the XML data. 3. My servlet updates the XML data. 4. My servlet does a createResource() and storeResource() to update the XML data back into Xindice. 5. ... later user repeats steps 1 to 4. Each time the user updates the form to Add/Update/Delete data. About one in every ten cycles the NullPointException will be thrown when I perform the GetResource(). I tried having my code sleep for 2 seconds after the first GetResource() failed and then retry to call, but that only solves the problem once in awhile. My XML data is usually somewhere in the 5 - 200 Kb range. A posting said a storeResource should take about 3ms/KB, so I thought sleeping for 2 seconds should have been enough delay for any of my files. Thanks for the help, -Nate Here is some code snippets. I create a singleton that owns this class, so there is only one of these (currently). Therefore EnableDatabase() is only executed once the first time that object is used. /* * XindiceGateway.java * * Created on August 25, 2004, 9:31 PM */ package org.test.gateways; import java.util.Vector; import org.apache.log4j.Logger; import org.apache.xindice.client.xmldb.services.CollectionManager; import org.apache.xindice.xml.dom.DOMParser; import org.test.commands.DatabaseCommand; import org.w3c.dom.Node; import org.xmldb.api.base.*; import org.xmldb.api.modules.*; import org.xmldb.api.*; /** * * @author stoddarn */ public class XindiceGateway { // Log4j Logger static Logger m_logger = Logger.getLogger(XindiceGateway.class); // Static mutex on the database static String m_databaseMutex = new String ("mutex"); private boolean m_databaseRegistered = false; // Static XINDICE data private static String XINDICE_DB_DRIVER = new String("org.apache.xindice.client.xmldb.DatabaseImpl"); // The root to the database private static String XINDICE_DB_ROOT = new String("xmldb:xindice://localhost:8080/db/"); // LINUX Penguin // Xindice API version private static String XINDICE_API_VERSION = new String ("1.0"); // Xindice file setup private static String XINDICE_COMPRESSION_ENABLED = new String ("true"); private static String XINDICE_FILTER_CLASS = new String("org.apache.xindice.core.filer.BTreeFiler"); /** Make sure the database is registered */ protected void EnableDatabase () throws ClassNotFoundException, InstantiationException, IllegalAccessException, XMLDBException { // If the database isn't already registered if (! m_databaseRegistered) { m_databaseRegistered = true; m_logger.info("Enabling Xindice Database"); Class c = Class.forName(XINDICE_DB_DRIVER); Database database = (Database) c.newInstance(); DatabaseManager.registerDatabase(database); // Update the CodeReview paths boolean baseCollectionFound = false; boolean projectListingsCollectionFound = false; boolean projectListingsFileFound = false; boolean projectsCollectionFound = false; // Check for "test" String [] baseCollection = ListCollections(""); // Loop to see if there is a match for (int bcItr = 0; !baseCollectionFound && bcItr < baseCollection.length; bcItr++) { if (baseCollection[bcItr].equals("test")) { baseCollectionFound = true; } } // If the baseCollection is missing add it if (!baseCollectionFound) { m_logger.info("Create codereview collection required"); CreateCollection("", "test"); } // Check for "projectlistings" and "projects" String [] testCollection = ListCollections("test"); // Loop to see if there is a match for project listings and projects for (int crItr = 0; (!projectListingsCollectionFound || !projectsCollectionFound) && crItr < testCollection.length; crItr++) { if (testCollection[crItr].equals("projectlistings")) { projectListingsCollectionFound = true; } else if (testCollection[crItr].equals("projects")) { projectsCollectionFound = true; } } // If the baseCollection is missing add it if (!projectListingsCollectionFound) { m_logger.info("Create projectlistings collection required"); CreateCollection("test", "projectlistings"); } // If the baseCollection is missing add it if (!projectsCollectionFound) { m_logger.info("Create projects collection required"); CreateCollection("test", "projects"); } } } /** Add documents to a collection */ public void AddDocument(String collectionName, String documentName, String documentXML) { Collection col = null; String[] documents = null; synchronized (m_databaseMutex) { try { EnableDatabase(); // Get the collection col = DatabaseManager.getCollection(XINDICE_DB_ROOT + collectionName); XMLResource document = (XMLResource) col.createResource(documentName, "XMLResource"); document.setContent(documentXML); col.storeResource(document); } catch (XMLDBException e) { m_logger.error("AddDocument: XML:DB Exception occured: " + e.getMessage()); } catch (Exception e) { m_logger.error("AddDocument: Other Exception occured"); } finally { // If the colletion was created, then make sure we close it if (col != null) { try { // Close the collection col.close(); } catch (Exception e) { // Catch any issues with closing the exception. m_logger.error("Unable to close collection. " + e.getMessage()); } } } } } /** Read a document */ public String ReadDocument(String collectionName, String documentName) { Collection col = null; String returnString = null; synchronized (m_databaseMutex) { try { EnableDatabase(); col = DatabaseManager.getCollection(XINDICE_DB_ROOT + collectionName); XMLResource document = (XMLResource) col.getResource(documentName); returnString = (String)document.getContent(); } catch (XMLDBException e) { m_logger.error("ReadDocument (" + collectionName + "/" + documentName + "): " + e.getMessage()); } catch (Exception e) { m_logger.error("ReadDocument (" + collectionName + "/" + documentName + "): " + e.getMessage()); } finally { // If the colletion was created, then make sure we close it if (col != null) { try { // Close the collection col.close(); } catch (Exception e) { // Catch any issues with closing the exception. m_logger.error("Unable to close collection. " + e.getMessage()); } } } } return (returnString); } /** Creates a new instance of XindiceGateway */ public XindiceGateway() { } }
