RMI and concurrency (newbie)

Hi
I have a simple question related to RMI and concurrency.
I have a server and several clients calling remote objects concurrently.
How is concurrency usually handled when one used RMI ?
Can we make use of "synchronized" on some method of the remote objects ?
I have read about risk related to performance and worse, some problems of deadlock if the synchronize is not well organized.
Is there other ways to deal with that ?
Thanks in advance for providinge me any information or suggestion.

RMI is inherently multithreaded. If you have specific remote resources that you want protected from concurrency, then define all of the accessor methods to be synchronized. (I don't think you can get away with making the remote methods synchronized; I would instead figure out what which resources I want to protect, and only protect those particular objects.)
Could there be problems? Maybe. But these are absolutely standard coding techniques.

Similar Messages

Connection to CRX via RMI and getting WeakReference value..... with an exception!

Hi there,
I have the following problem.
I opened a ticket in Day Care Support system, about CRX users/group membership that got lost while synchronization with our LDAP server.
Although when the user and the group had been created (and therefore taken from that same LDAP server), the membership was good.... but after some time the membership got lost......
So what i am trying to do now is a Java program that connects to CRX via RMI.
And gets the list of all the users from a group (aka membership).
The idea is to monitor the membership each seconds.
But when trying to get the property "rep:members" of the group, I have the following exception :
javax.jcr.ValueFormatException: Unknown value type 10
          at org.apache.jackrabbit.rmi.server.ServerObject.getRepositoryException(ServerObject.java:13 9)
          at org.apache.jackrabbit.rmi.server.ServerProperty.getValues(ServerProperty.java:71)
          at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
          at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
          at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
          at java.lang.reflect.Method.invoke(Method.java:611)
          at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:322)"
I searched a little bit and found that "10" is the number for type WeakReference.
That's normal to me because memberships are stored in the group as a list reference to users linked to that group....
Anyways, what's not normal to me is that when the type is "10" the API does not let me get the Value (cf. ServerProperty.getValues() method)
Here is the program:
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import javax.imageio.spi.ServiceRegistry;
import javax.jcr.Node;
import javax.jcr.NodeIterator;
import javax.jcr.Property;
import javax.jcr.PropertyIterator;
import javax.jcr.Repository;
import javax.jcr.RepositoryException;
import javax.jcr.RepositoryFactory;
import javax.jcr.Session;
import javax.jcr.SimpleCredentials;
import javax.jcr.Value;
public class Test {
          public static void main(String[] args) {
                    String uri = "rmi://sma11c02.............:1234/crx";
                    String username = "admin";
                    char[] password = {....................};
                    String workspace = "crx.default";
                    String nodePath = "/home/groups/a";
                    Repository repository = null;
                    Session session = null;
                    try {
                              // Connection to repository via RMI
                                        Map<String, String> jcrParameters = new HashMap<String, String>();
                                        jcrParameters.put("org.apache.jackrabbit.repository.uri", uri);
                                        Iterator<RepositoryFactory> iterator = ServiceRegistry.lookupProviders(RepositoryFactory.class);
                                        while (null == repository && iterator.hasNext()) {
                                                  repository = iterator.next().getRepository(jcrParameters);
                              if (repository == null) {
                                        throw new IllegalStateException("Problem with connection to the repository...");
                              // Creation of a session to the workspace
                              session = repository.login(new SimpleCredentials(username, password), workspace);
                              if (session == null) {
                                        throw new IllegalStateException("Problem with creation of session to the workspace...");
                              // Get the targetted node
                              Node node = session.getNode(nodePath);
                              System.out.println("Node : " + node.getName());
                              System.out.println();
                              PropertyIterator properties = node.getProperties();
                              System.out.println("List of properties for this node :");
                              while (properties.hasNext()) {
                                        Property property = properties.nextProperty();
                                        System.out.print("\t"+property.getName() + " : ");
                                        if (property.isMultiple()) {
                                                  Value[] values = property.getValues();
                                                  for (int i = 0; i < values.length; i++) {
                                                            System.out.print(values[i]);
                                                            if (i+1 != values.length) {
                                                                      System.out.print(", ");
                                                  System.out.println();
                                        } else {
                                                  Value value = property.getValue();
                                                  System.out.println(value);
                              System.out.println();
                              NodeIterator kids = node.getNodes();
                              System.out.println("List of children nodes for this node :");
                              while (kids.hasNext()) {
                                        Node kid = kids.nextNode();
                                        System.out.println("\tChild node : "+kid.getName());
                                        PropertyIterator kidProperties = kid.getProperties();
                                        System.out.println("List of properties for this child :");
                                        while (kidProperties.hasNext()) {
                                                  Property property = kidProperties.nextProperty();
                                                  System.out.print("\t"+property.getName() + " : ");
                                                  if (property.isMultiple()) {
                                                            Value[] values = property.getValues();
                                                            for (int i = 0; i < values.length; i++) {
                                                                      System.out.print(values[i]);
                                                                      if (i+1 != values.length) {
                                                                                System.out.print(", ");
                                                            System.out.println();
                                                  } else {
                                                            Value value = property.getValue();
                                                            System.out.println(value);
                                        System.out.println();
                    } catch (RepositoryException e) {
                              e.printStackTrace();
                    } finally {
                              if (session != null) {
                                        session.logout();
Here is the output of the below program:
Node : a
List of properties for this node :
          jcr:createdBy : admin
          jcr:mixinTypes : mix:lockable
          jcr:created : 2011-10-25T16:58:48.140+02:00
          jcr:primaryType : rep:AuthorizableFolder
List of children nodes for this node :
          Child node : administrators
List of properties for this child :
          jcr:createdBy : admin
          rep:principalName : administrators
          rep:members : javax.jcr.ValueFormatException: Unknown value type 10
          at org.apache.jackrabbit.rmi.server.ServerObject.getRepositoryException(ServerObject.java:13 9)
          at org.apache.jackrabbit.rmi.server.ServerProperty.getValues(ServerProperty.java:71)
          at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
          at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
          at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
          at java.lang.reflect.Method.invoke(Method.java:611)
          at sun.rmi.server.UnicastServerRef.dispatch(UnicastServerRef.java:322)
          at sun.rmi.transport.Transport$1.run(Transport.java:171)
          at java.security.AccessController.doPrivileged(AccessController.java:284)
          at sun.rmi.transport.Transport.serviceCall(Transport.java:167)
          at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:547)
          at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:802)
          at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:661)
          at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:897)
          at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:919)
          at java.lang.Thread.run(Thread.java:736)
          at sun.rmi.transport.StreamRemoteCall.exceptionReceivedFromServer(Unknown Source)
          at sun.rmi.transport.StreamRemoteCall.executeCall(Unknown Source)
          at sun.rmi.server.UnicastRef.invoke(Unknown Source)
          at org.apache.jackrabbit.rmi.server.ServerProperty_Stub.getValues(Unknown Source)
          at org.apache.jackrabbit.rmi.client.ClientProperty.getValues(ClientProperty.java:173)
          at Test.main(Test.java:96)
Here is the list of jar files i'm using with this program:
          2862818581          61388           crx-rmi-2.2.0.jar
          732434195           335603           jackrabbit-jcr-commons-2.4.0.jar
          1107929681           411330           jackrabbit-jcr-rmi-2.4.0.jar
          3096295771           69246           jcr-2.0.jar
          1206850944           367444           log4j-1.2.14.jar
          685167282           25962           slf4j-api-1.6.4.jar
          2025068856           9748           slf4j-log4j12-1.6.4.jar
Finally, we are using CQ 5.4 (CRX 2.2) with the latest hotfix and under Websphere 7.0
Best regards,
Vincent FINET

Je suis absent(e) du bureau jusqu'au 17/04/2012
Je suis absent.
Je répondrai à votre sollicitation à mon retour le 17 avril 2012.
Cordialement,
Vincent FINET
Remarque : ceci est une réponse automatique à votre message "[CQ5]
Connection to CRX via RMI and getting WeakReference value..... with an
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What is the difference between RMI and JAX-RPC?

Dear All
First of all my understanding of RMI and JAX-RPC:
RMI is JAVA only version of RPC. It can't talk to any other language.
JAX-RPC is a part of JWSDP and if you implement your client and server with JAX-RPC, client written in any language can talk with JAX-RPC implementation.
What else makes them different and am I right with my understanding?
Finally, I would like to develop clients which will have a java class, say httpserver.java, which will act like a http server, listens to a http port. Now, Two such client will run in two different PC and I want to call a module from one client to another which should be accessible via my httpserver.java. For that which should be my choice RMI or JAX-RPC? Can I achive it with http get-post method, as I am expecting to read some value of variables from one client to the another.
Say class A has variable a, aa, aaa and clas B has variable b, bb, bbb. Now I want to read the value of b, bb, bbb from class A. How do I do that when class B is listening to a http port with my httpserver.java class.
Lastly, say B is listening to a http port and I want to send a file to B from A. How can I do that? Remember, B didn�t ask for that. How can A send a file to B when B is listening to a http port with my httpserver.java.
With regards
Mohammed Jubaer Arif
Mobile: +61-0411215302
Personal Web: http://www.geocities.com/jubairarifctg/
Org. Web.: http://www.geocities.com/halimschamber/

simply put, RMI allows you to (semi) transparently treat remote objects as if they were local, and your distributed application can be written (more or less) like a "normal" java app. Sockets just give you a "raw" connection to work with, and you get to build up your application from that.
I hope that helped
Lee

Please help: RMI and Swing/AWT issue

Hi guys, I've been having a lot of trouble trying to get a GUI application to work with RMI. I'd appreciate any help. Here's the story:
I wrote a Java application and its GUI using Netbeans. In a nutshell, the application is about performing searches. I am now at the point where I need exterior programs to use my application's search capabilities, thus needing RMI. Such exterior programs are to call methods currently implemented in my application.
I implemented RMI, and got the client --> server communication working. However, the GUI just breaks. It starts outputting exceptions, gets delayed, doesn't update properly, some parts of it stop working.... basically hysterical behavior.
Now take a look at this line within my server class:
Naming.rebind("SearchProgram", mySearchProgram);
If I take it out, RMI obviously does not work... but the application and its GUI work flawlessly. If I put it in, the RMI calls work, but the GUI's above symptoms occur again. Among the symptoms are null pointer exceptions which all look similar, are related to "AWT-EventQueue-0", and keep ocurring. Here's just snippet of the errors outputted:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.metal.MetalScrollBarUI.getPreferredSize(MetalScrollBarUI.java:102)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1615)
at javax.swing.JScrollBar.getMinimumSize(JScrollBar.java:704)
at javax.swing.ScrollPaneLayout.minimumLayoutSize(ScrollPaneLayout.java:624)
at java.awt.Container.minimumSize(Container.java:1598)
at java.awt.Container.getMinimumSize(Container.java:1583)
at javax.swing.JComponent.getMinimumSize(JComponent.java:1697)
at java.awt.BorderLayout.minimumLayoutSize(BorderLayout.java:634)
at java.awt.Container.minimumSize(Container.java:1598)
at java.awt.Container.getMinimumSize(Container.java:1583)
at javax.swing.JComponent.getMinimumSize(JComponent.java:1697)
at java.awt.BorderLayout.minimumLayoutSize(BorderLayout.java:634)
at java.awt.Container.minimumSize(Container.java:1598)
at java.awt.Container.getMinimumSize(Container.java:1583)
at javax.swing.JComponent.getMinimumSize(JComponent.java:1697)
at javax.swing.BoxLayout.checkRequests(BoxLayout.java:433)
at javax.swing.BoxLayout.layoutContainer(BoxLayout.java:375)
at java.awt.Container.layout(Container.java:1401)
at java.awt.Container.doLayout(Container.java:1390)
at java.awt.Container.validateTree(Container.java:1473)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validate(Container.java:1448)
at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:379)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:113)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:461)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.basic.BasicMenuItemUI.getPreferredMenuItemSize(BasicMenuItemUI.java:400)
at javax.swing.plaf.basic.BasicMenuItemUI.getPreferredSize(BasicMenuItemUI.java:310)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1615)
at javax.swing.BoxLayout.checkRequests(BoxLayout.java:434)
at javax.swing.BoxLayout.preferredLayoutSize(BoxLayout.java:251)
at javax.swing.plaf.basic.DefaultMenuLayout.preferredLayoutSize(DefaultMenuLayout.java:38)
at java.awt.Container.preferredSize(Container.java:1558)
at java.awt.Container.getPreferredSize(Container.java:1543)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1617)
at javax.swing.JRootPane$RootLayout.layoutContainer(JRootPane.java:910)
at java.awt.Container.layout(Container.java:1401)
at java.awt.Container.doLayout(Container.java:1390)
at java.awt.Container.validateTree(Container.java:1473)
at java.awt.Container.validate(Container.java:1448)
at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:379)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:113)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:461)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
There are no complaints about anything within my code, it's all GUI related whenever I make a bind() or rebind() call.
Again, any help here would be great... cause this one's just beating me.
Thanks!

Maybe you want to change that worker thread to
not do RMI but anything else (dummy data) to see if it really is RMI, I doubt it, I think you are updating some structures that have to do with swing GUI and hence you will hang.
Just check this out.

RMI and Swing Events

Hi,
I have a problem, integrating an application with RMI and a Client side with swing.
I have un RMI object that does something, and in any time I want to inform to the client side rmi... I did something like:
// This is the REmote implementation
public MyRemoteImpl extends Activatable implements MyRemote{
EventListenerList listeners;
// code for activation, etc.......
public void addListener(MyListener l){
    // add the listener in the list...
public void fireEvent(String msgEvent){
    // in each listener that is MyListener, .doEvent(String msg)
// Methods that calls fireEvent...
// Mylistener interface..
public MyListener implements EventListener{
public void doEvent(String msg);
// The swing client side.
public MyClient extends JPanel implements MyListener{
MyRemote rem=null;
// In the start of ui.. Ido:
rem.addListener(this);
public void doEvent(String msg){
    // Puts the message at one component....
}The problem is that when the doEvent of the Swing side is called, it is executing in the rmid... And the UI is not updated...
What I do wrong??
Thanks and Best Regards.

I wrote an application that does something similar, it receives some event and modifies a JTree accordingly. You should try using the java.awt.EventQueue.invokeLater(Runnable) method. Something like this:
public void doEvent(String msg) {
    // Determine what changes need to be made
    java.awt.EventQueue.invokeLater(new Runnable() {
        public void run() {
            // Only the GUI component modification calls need to go here
}

RMI and native code

Hi
Can anybody send me a sample code(HelloWorld type)that is based on RMI and uses native code(eg. win32).
SANJAY

If you're trying to do anything with native code, then you should be familiar with JNI API, windows or not.
Check out the JNI tutorials on this site and i'm sure they'll provide you with JNI tutorials and samples.

Rmi and http

i know this might sound silly but i am new to rmi ( to java too )
i want to understand the difference between rmi and other protocols such as http,ftp and so.
now what i think i know - and sometimes think im not sure i know or
perhaps im sure i know nothing about - is that rmi is java specific and can only work with java while http is different if im not wrong.. and rmi does not require http r8?
so how can rmi work over http or ftp ..,( can it in the 1st place ?)

Which version of WLS you are using?
Applet should also need to satisfy the version requirements similar to
standalone java client. With WLS 5.1, it may work. But, it will not work
with 6.* servers.
Again, the JRE versions in the Netscape and IExplorer are different. So the
applet, working in IE may not work on Netscape. It is better to test a
sample application, than taking assumptions.
Cheers,
..maruthi
"Andrea Musumeci" <[email protected]> wrote in message
news:3cb1dcba$[email protected]..
can an applet written in java 1.1.x work in a browser using weblogic rmiwithout a plugin? I need to create a java chat applet with callback. Tnx in
advance

Does ATS load testing support Java RMI and T3 protocol?

Hi Experts,
Does ATS load testing support Java RMI and T3 protocol or EJB(J2EE)?
Thanks!

Joseph,
Oracle Application Testing Suite is mainly used for testing of applications from a end user perspective and offers an intuitive capture/replay for web, Siebel, EBS, JDE, Fusion apps or SOA based application through WebServices WSDL imports.
The scripting environment (Oracle OpenScript) does not support script creation by recording JAVA RBI or T3 protocol as we lack a recorder for it, but the scrips are created as pure JAVA code so you could use the JAVA language to write a small RMI cor T3 client for your testing.
We have customers that have used Application Testing Suite to test non-UI based testing, like: JMS, FTP, Tuxedo and others, but it require a bit of coding.
Please let me know if you would like to know more or discuss your options
regards
Mikael Fries
Principal Product Manager / Oracle

Standard Java RMI and WLS5.1?

I would surmise that the problem you are seeing is the result of the fact
that we do not except standard Java RMI calls using the functionality in the
JDK. You must use the WebLogic implementation of RMI. It is exactly the
same in terms of APIs, but we have gone through and optimize the underlying
protocol.
Please see the documentation for more details.
We offer both RMI over IIOP and RMI over T3.
Thanks,
Michael
Michael Girdley
Product Manager, WebLogic Server & Express
BEA Systems Inc
Mario Felarca <[email protected]> wrote in message
news:[email protected]..
Hello,
I was trying to get a simple callback demo working using standard java
RMI and the WLS5.1. Unfortunately, although things seemed to compile
and launch smoothly, when the client started up and tried to talk to the
WLS I would get the following error:
weblogic.rmi.server.ExportException: A description for CallbackImpl was
found but it could not be read due to: [Failed to find a stub for [class
CallbackImpl] implements at least one interface [interface Callback]
which extends Remote.]
weblogic.rmi.StubNotFoundException: Failed to find a stub for [class
CallbackImpl] implements at least one interface [interface Callback]
which extends Remote.
I tried determining if this was a classpath problem, but all my efforts
kept producing this result.
On the flip side, if I retool my objects slightly in order to make them
use weblogic.rmi.*, then everything works perfectly.
Is there a tradeoff to using weblogic.rmi over java.rmi?
Also, does anyone have any ideas as to what might be causing my error
when using standard rmi?
Thanks so much in advance,
Mario-

Weak and concurrent hash map for caching

Hello,
I have written a very simple cache class with both weakness and concurrency benefits. This class is intended to be used as a weak cache in "hot redeploy" capable servers (JBoss or any other).
My implementation uses the (problematic) "double-check" pattern with a reentrant lock and encapsulates a WeakHashMap with WeakReference values (to avoid circular key/value references). Here is the code:
public interface ValueCreator<V> {
     public V create();
public class WeakCache<K, V> {
     private final Lock lock = new ReentrantLock();
     private final Map<K, WeakReference<V>> weakMap;
     public WeakCache() {
          this(16);
     public WeakCache(int initialCapacity) {
          this(initialCapacity, 0.75F);
     public WeakCache(int initialCapacity, float loadFactor) {
          weakMap = new WeakHashMap<K, WeakReference<V>>(initialCapacity, loadFactor);
     public V get(K key, ValueCreator<V> creator) {
          WeakReference<V> ref = weakMap.get(key);
          if (ref == null) {
               lock.lock();
               try {
                    ref = weakMap.get(key);
                    if (ref == null) {
                         ref = new WeakReference<V>(creator.create());
                         weakMap.put(key, ref);
               } finally {
                    lock.unlock();
          return ref.get();
     }One usage of this cache is for session ejb3 lookup:
private static final WeakCache<Class, Object> LOOKUP_CACHE = new WeakCache<Class, Object>();
public static <T> T lookup(final Class<T> serviceClass) {
     T service = (T)LOOKUP_CACHE.get(serviceClass,
          new ValueCreator<Object>() {
               public T create() {
                    String lookup = "myapp/" + serviceClass.getSimpleName() + "/local";
                    try {
                         return (T)(new InitialContext()).lookup(lookup);
                    } catch (NamingException e) {
                         throw new RuntimeException("Could not lookup EJB " + serviceClass + ": " + lookup, e);
     return service;
...2 questions:
1. Is there any issue with concurrent access to this cache ?
2. What happens exactly when the garbage collector wants to free memory with a map with both weak keys and values ?
Some limited tests show that the behavior of this cache fits my needs: the lookup cache is cleared on redeploy and it keeps its key/values pairs otherwise.
Thanks for any comments.
Message was edited by:
fwolff999

I know that DCL is broken under certain circumstances (but I have read it may work with modern JVM and the use of volatile variables for example).
So: is it broken with this specific implementation and if so, what should be done to make it work ?
The getter method is potentially setting a value (like in ConcurrentHashMap.putIfAbsent) and it uses a ValueCreator in order to actually create the value only if it is not already present in the map.

RMI and Netbeans

hello,
i have develop a simple application using RMI. It was running perfectly from command prompt.
Then i imported the project into netbeans 6.1. Then when i run it the server looks running normally but when a client try to connect to the server it given an error
java.rmi.UnmarshalException: error unmarshalling return; nested exception is:
java.lang.ClassNotFoundException: ........(No security manager: RMI class loader disabled)
Can someone help suggest a solution
Thanks

Hi!
Please tell me how could you get netbeans 6.1 to recognise an RMI project.
I have too, tried to import some old java files (two rmi interface files a server implementation and an applet) into netbeans 6.1. As far as i can tell it completely refuses to work with RMI, and i have not found ANY support on the internet so far, to how to do it, or any working rmi modules for netbeans 6.1 ...
Years old rmi developement, what worked nicely under windows 95 (good old days lol) does not wish to work for me now...
Should I return to use age old enviroments, or what?
I would deeply appreciate any help from You, or anyone able.
Thanks!

Rmi and wireless

Hello!
I'm using the RMIAdapter sample of Oracle to check the basic mechanism of rmi and wireless.
Does anybody now, if there are some known problems with wireless regarding this subject?
I have written both: the adapter and the client code. So far so good. But when I try to point a masterservice
to this adapter, there are some strange results:
If I define the RMI Service URL in this way: rmi://localhost:port, ASW accepts the input, but using the
service returns an IllegalArgumentException in the logfile.
If I define the RMI Service URL with its ServiceName (= rmi://localhost:port/ServiceName, ASW doesn't accept
the input.
So my question is: where's the error? As far as I know, a "correct" RMI URL consists of the following parts:
rmi://<hostname>[:<port>]/servicename. It would be the second above-mentioned trial.
Why does ASW rejects this kind of RMI Service URL?
So it would be great, if someone could help me out with the RMI magic of ASW.
Thanks a lot in advance,
Heike Skok

Hello Heike,
Here are the values for the RMIAdapter Init Parameters:
RMI Server URL: rmi://localhost:2099/Sample
Remote interface: oracle.panama.adapter.rmi.SampleInterface
(assuming that you didn't make any changes in the sample source code).
Here are some steps that the documentation does not describe in details (assuming that developers are familiar with RMI).
1. I copied SampleInterface.class and SampleImpl.class in $ORACLE_HOME/wireless/server/classes/oracle/panama/adapter/rmi directory
2. I ran
rmic -d . oracle.panama.adapter.rmi.SampleImpl
from $ORACLE_HOME/wireless/server/classes directory to generate SampleImpl_Stub.class and SampleImpl_Skel.class
3. I ran
java oracle.panama.adapter.rmi.SampleImpl
from $ORACLE_HOME/wireless/server/classes directory to start my RMI server.
You have to start the remote RMI server first before you can create the MasterService. The RMIAdapter will connect to the remote RMI server during initialization. The remote RMI server will print out
"Sample bound in registry" if started correctly.
If you have problems with the RMI registry then you may have to change JAVA_HOME\jre\lib\security\java.policy file and add the following:
grant {
permission java.net.SocketPermission "*:1024-65535",
"connect,accept";
permission java.net.SocketPermission "*:80", "connect";
After doing all that I was able to successfully run RMIAdapter based services.
Thanks,
Hristo Tonev

Can we use applets as user interfaces with sockets, RMI and J2EE

Dear Sir or Madam,
Since I am a TA for software architecture class, some one ask me the following question: I think the answer is "No" based on the document on http://java.sun.com/sfaq/
How I answer the quesions? Looking forward your help!!!
1.You may have 2 applets and 2 html files. One applet with one html file may stay at a client PC and run on this PC, and the other applet with the other html file may stay at a server PC and run on this PC. In this case, all the applets are run locally.
2.Could applets works with sockets, RMI and J2EE?
3.Can we use applets as user interfaces with sockets, RMI and J2EE?
Thank you very much!
Best regards,
Jing

The scenario you paint doesn't quite make sense. The "server PC" wouldn't be running an applet, normally, since applets are by definition in a web browser page, and most likely involve user interaction, and "server processes" generally are done without user interaction.
The security rules around applets are that -- by default -- applets can connect with sockets ONLY to the server from whence the applet was loaded. RMI uses sockets (J2EE is too broad a spec) and hence RMI calls would also be limited to the server from whence the applet was loaded. Within that limitation, an applet could open all the sockets it wants, so long as they are all on the server from whence the applet was loaded.
If you want two applets on two different systems to communicate with each other, the simplest way is to have them rendevous through a server process on the server(s) from whence each applet was loaded. Maybe it's PC-a <-> server-a <-> server-b <-> PC-b ...? Or maybe PC-a and PC-b both are talking to the same server.
The limitation is rooted in the security subsystem. You can specify a policy file and override anything in the security subsystem. That does mean signing the applet and then cajoling the user into agreeing to grant greater levels of security than the default. In such a case you can open sockets more broadly and then PC-a could talk directly to PC-b without going through any servers.
- David

Difference between multiple employment and concurrent employment

hi,
What is the difference between multiple employment and concurrent employment.
Regards,
Chandra

Hi
Multiple employment is one person working woth more than one company with different EE iD.
Person who has more than one personnel assignment with one enterprise or several affiliated enterprises in an cocurerent employee.
Please go thru the link.
http://help.sap.com/saphelp_47x200/helpdata/en/54/f535c614aa7a46800915c6f0dbc071/frameset.htm
Ravee
+91.99206.33669

How to create a thread safe and concurrent web part

Hi,
I am creating a sharepoint web part.
The web part will store the information in the sharepoint list.
The web part is going to be used by 300 users all at the same time at the same moment.
Each 300 users trying to update list clicking button on my web part almost every 20 seconds.
I am worried will the sharepoint List be able to handle so many concurrent updates.
How should I design my webpart so that such issues do not arise and my webpart is also fast.
Regards
Vinod

Hi,
Per my understanding, there might be a concern about the performance and concurrent operation in your Visual Web Part.
By default, there is already a built-in system in SharePoint handling the concurrent operation in a list, if the workload is not so high, it would be OK for the commonly use in
your scenario.
If there would be a requirement about creating a “fast” web part,
a possible solution can be like this:
In the web part, users click button to submit the specific update requirements with some data to server. In server side, we can create an application to handle the requests(add/update/delete
item) from users sequentially one after one.
By doing this, in client side, the web part will only responsible for submitting user request with simple data, all the time consuming jobs will be split into small tasks and being
executed sequentially in server side.
Also, here are two links below about some useful tips in developing web part which would be helpful to you:
https://msdn.microsoft.com/en-us/library/dd583135%28v=office.11%29.aspx?f=255&MSPPError=-2147217396
http://apmblog.dynatrace.com/2010/03/18/how-to-avoid-the-top-5-sharepoint-performance-mistakes/
Thanks
Patrick Liang
TechNet Community Support
Please remember to mark the replies as answers if they help, and unmark the answers if they provide no help. If you have feedback for TechNet Support, contact
[email protected]

RMI and concurrency (newbie)

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