2 Replies Latest reply on Feb 6, 2002 6:56 PM by dennis

    ejb dom

    dennis Newbie

      Writing a MBean is a lot more simple than writing a EJB ;)
      Simply write a class and its MBean interface and it starts. Look at ... all Jboss to find example.
      I don't use cluster and don't know exactly how to handle this problem in JMX. (BTW is the marc/juha book on JMX out ?). For the moment I would simply deploy my MBean in all the servers I am running. For example I use 2 servers at devel time on for tomcat 3.2 and one for ejb, ... Both runs the MBean.
      I could use the RMI connector (I tries it without problems) but it is a jboss specific so I prefer not using it anymore.
      What took me long time to catch is the fact that MBean is not just there for JBoss. It is also there for a lot of configuration issue that users face in any project. IMHO, using env definition in ejb is less and less a good option for "configuration" stuff.

      Example :

      public class EISIntegratorLoader
      extends FileLoader
      implements EISIntegratorLoaderMBean{

      // ----------------------------------------------------------------- Logging
      transient static Category cat=Category.getInstance(EISIntegratorLoader.class);

      private String fileName;
      private boolean started;
      private Map mapping = new Hashtable();

      public String getName(){
      if (cat.isDebugEnabled()) cat.debug("getName()");
      return "SecureActionLoader";
      }

      public String getConfigFile(){
      if (cat.isDebugEnabled()) cat.debug("getConfigFile()");
      return fileName;
      }

      public void setConfigFile(String fileName)
      throws FileNotFoundException{
      if (cat.isDebugEnabled()) cat.debug("setConfigFile("+fileName+")");
      this.fileName = fileName;
      Document doc = extractDoc(findFile(fileName));
      List list = doc.getRootElement().getChildren("mapping");
      //List list = doc.getMixedContent();
      if (cat.isDebugEnabled()) cat.debug("MAPPING Number = "+list.size());
      Iterator i = list.iterator();
      while (i.hasNext()){
      Element el = (Element)i.next();
      String source = el.getChildText("source");
      String destination = el.getChildText("destination");
      if (!mapping.containsKey(source)){
      mapping.put(source,destination);
      if (cat.isDebugEnabled()) cat.debug("MAPPING : "+source+" ==> "+destination);
      }
      }
      }

      public Map getMapping(){
      if (cat.isDebugEnabled()) cat.debug("getMapping");
      return this.mapping;
      }

      public void start() throws Exception{
      cat.info("start()");
      started = true;
      }

      public void stop(){
      cat.info("stop()");
      started = false;
      }

      // ----------------------------------------------------------------- Private

      /** This will build the Document object
      * @param url the URL for the XML configuration file
      * @return a {@link Document} representing the actions
      * definition
      */
      private Document extractDoc(URL url){
      if (cat.isDebugEnabled()) cat.debug("Executing extractDoc");
      SAXBuilder builder = new SAXBuilder();
      if (cat.isDebugEnabled()) cat.debug("Builder="+builder);
      // build the document
      Document doc;
      try{
      doc = builder.build(url);
      if (cat.isDebugEnabled()) cat.debug("Doc="+doc);
      } catch (Exception e){
      cat.debug("Exception",e);
      throw new IllegalStateException("JDOMException"+e.getMessage());
      }
      Document actionDoc = new Document(doc.getRootElement().getChild("mappings"));
      return actionDoc;
      }

      The interface is

      public String getConfigFile();
      public void setConfigFile(String fileName) throws FileNotFoundException;

      public Document getDocument();

      public void start() throws Exception;
      public void stop() throws Exception;


      With FileLoader being

      protected URL findFile(String fileName) throws IllegalStateException {
      Class confClass = this.getClass();
      ClassLoader loader = confClass.getClassLoader();
      URL fileURL = loader.getResource(fileName);

      // Was the resource found?
      if (fileURL == null) {
      cat.error("Can't find the file: '" + fileName + "'");
      throw new IllegalStateException("Can't locate file: '" + fileName + "'");
      }
      else {
      return fileURL;
      }
      }

      The call is done like this (in j2ee pattern singleton ServiceLocator) :

      private ServiceLocator() {
      if (cat.isDebugEnabled()) cat.debug("Constructor");
      try{
      if (useCache) cache = new Hashtable();
      // Get the JNDI Initial Context (local and remote)
      initial = new InitialContext();
      if (cat.isDebugEnabled()) cat.debug("InitialContext="+initial);
      // Get the Deployment Description
      ArrayList servers = MBeanServerFactory.findMBeanServer(null);
      if (cat.isDebugEnabled()) cat.debug("List of MBean Server = " + servers);

      if (servers == null || servers.size() == 0) {
      // Try to connect remotely (TestSecAConfigurator will do that)
      // Remove it for jboss 3.0 compatibility
      //JMXConnector server = new RMIClientConnectorImpl(InetAddress.getLocalHost().getHostName());
      //ObjectName objName = new ObjectName("HubMethods:service=EISIntegratorLoader");
      //mapping = (Map) server.getAttribute(objName, "Mapping");
      mapping = new FastHashMap();
      } else {
      try{
      MBeanServer server = (MBeanServer) servers.get(0);
      ObjectName objName = new ObjectName("HubMethods:service=EISIntegratorLoader");
      mapping = (Map) server.getAttribute(objName, "Mapping");
      }catch (Exception e){
      cat.warn("EISIntegratorLoader MBean could not be accessed "+e.getMessage());
      mapping = new FastHashMap();
      }
      }
      if (cat.isDebugEnabled()) cat.debug("Mapping Size : "+mapping.size());

      }catch (Exception e){
      cat.error("Exception",e);
      }
      }

        • 1. Re: ejb dom
          Åsmund Hjulstad Newbie

          I have a very strong feeling you will encounter severe performance problems with this approach.

          Even though the invocation stack in 3.0 is a lot faster than it was in the beginning, you just can't beat method invocation on the target class directly.

          Storing a document-fragment in an entity-bean, however...

          Åsmund Hjulstad

          • 2. Re: ejb dom
            dennis Newbie

            those problems could be solved by not letting the container manage any relationship i think , correct me if i'am wrong. It was just a tought that crossed my mind but never left also , i'am just going to try and see how it behaves. Imagine a gigabytes large clustered persistant ejb-dom with xpath over ejb-ql , what could you do with that if it would really work ?