Question on thread safety with Sevlet action method

I have an application that runs well but seems to have trouble with multiple users and I suspect that there is some thread safety issue involved.
It is a Struts application and I have all of my execute methods of the Acton classes are all synchronized which I thought would take care of any cross user issues but it does not seem to have done that.
The Action classes do have some instance variables which may be the problem as well as possibly a few utility string classes with static methods that are not synchornized. I keep some db connection cached in the session object but this should not be shared between users.
My question is, with the execute method synchronized how or where could I be getting crosstalk between users (each with their own sessions)?
I was thinking of packaging my Action class as seperate object with the actual Action class just allocate what I need (messages and locale) and pass them through a freshly instantiated "old action class". That should solve any instance variable cross talk.
I am assuming that any local variables in the execute method would not have any exposure as they should be thread specific and allocated on the runtime stack for that thread call.
Am I missing anything important?
Thanks in advance
---John Putnam

     * Creates a new instance of a {@link javax.xml.parsers.DocumentBuilder}
     * using the currently configured parameters.
    public DocumentBuilder newDocumentBuilder()
        throws ParserConfigurationException
        /** Check that if a Schema has been specified that neither of the schema properties have been set. */
        if (grammar != null && attributes != null) {
            if (attributes.containsKey(JAXPConstants.JAXP_SCHEMA_LANGUAGE)) {
                throw new ParserConfigurationException(
                        SAXMessageFormatter.formatMessage(null,
                        "schema-already-specified", new Object[] {JAXPConstants.JAXP_SCHEMA_LANGUAGE}));
            else if (attributes.containsKey(JAXPConstants.JAXP_SCHEMA_SOURCE)) {
                throw new ParserConfigurationException(
                        SAXMessageFormatter.formatMessage(null,
                        "schema-already-specified", new Object[] {JAXPConstants.JAXP_SCHEMA_SOURCE}));
        try {
            return new DocumentBuilderImpl(this, attributes, features, fSecureProcess);
        } catch (SAXException se) {
            // Handles both SAXNotSupportedException, SAXNotRecognizedException
            throw new ParserConfigurationException(se.getMessage());
    }It appears to be thread-safe. The 'attributes' and 'features' instances variables are hashtables, which are synchronized. Unless you are modifying DocumentBuilderFactory itself in another thread (say, changing whether it is namespace aware), I do not see any issues with a simple call to newDocumentBuilder().
- Saish

Similar Messages

Urgent question about Thread-safety

Hi all,
the new tiger release provides an "isReachable()" method for the "InetAddress" object.
I've found, this method is not thread-safe (see the source and output below).
It returns true for all threads, when multiple threads using this method with different adresses are running at a time and one of the addresses is reachable. This happens only on WinXp. Running on Linux, the output is like expected.
I've tried to report this as a bug. But the gurus answered, taking care of thread safety would be a "programmers task".
My question is, what can I do, to be thread-safe in my case?
W.U.
import java.util.*;
import java.net.*;
public class IsReachableTest_1 extends Thread{
    static volatile int inst=1;
    static final String NET_ADDR="192.168.111.";
    int instance=inst++;
    public void run(){
        for(int i=19;i<23;i++){
            try{
                long start=System.nanoTime();
                if(InetAddress.getByName(NET_ADDR+i).isReachable(1000))
                    System.out.println(""+instance+"--host found at:"+NET_ADDR+i+"--time:"+(System.nanoTime()-start)/1000000);
                else
                    System.out.println(""+instance+"--no host at:"+NET_ADDR+i);
            }catch(Exception e){System.out.println(""+instance+"--ERROR "+e.toString());}
        System.out.println(""+instance+"--done.");
    public static void main(String[] args) {
        System.out.println(
            System.getProperty("java.vendor")+" "+
            System.getProperty("java.version")+" running on "+
            System.getProperty("os.name")+" "+
            System.getProperty("os.version"));
        Vector v=new Vector();
        System.out.println("\nTest 1: One after another:");
        for(int i=0;i<10;i++){
            IsReachableTest_1 t;
            t=new IsReachableTest_1();
            t.start();
            try{
                t.join();
            }catch(Exception e){System.out.println("MAIN1: "+e.toString());}
        System.out.println("\nTest 2: All together:");
        inst=1;
        for(int i=0;i<10;i++){
            IsReachableTest_1 t;
            t=new IsReachableTest_1();
            t.start();
            v.addElement(t);
        for(Iterator i=v.iterator();i.hasNext();)
            try{
                ((IsReachableTest_1)i.next()).join();
            }catch(Exception e){System.out.println("MAIN2: "+e.toString());}
            System.out.println("\nALL DONE");
And here is the output, when running on WinXp:
Sun Microsystems Inc. 1.5.0-beta running on Windows XP 5.1
Test 1: One after another:
1--no host at:192.168.111.19
1--no host at:192.168.111.20
1--host found at:192.168.111.21--time:2
1--no host at:192.168.111.22
1--done.
2--no host at:192.168.111.19
2--no host at:192.168.111.20
2--host found at:192.168.111.21--time:4
2--no host at:192.168.111.22
2--done.
3--no host at:192.168.111.19
3--no host at:192.168.111.20
3--host found at:192.168.111.21--time:1
3--no host at:192.168.111.22
3--done.
4--no host at:192.168.111.19
4--no host at:192.168.111.20
4--host found at:192.168.111.21--time:1
4--no host at:192.168.111.22
4--done.
5--no host at:192.168.111.19
5--no host at:192.168.111.20
5--host found at:192.168.111.21--time:3
5--no host at:192.168.111.22
5--done.
6--no host at:192.168.111.19
6--no host at:192.168.111.20
6--host found at:192.168.111.21--time:1
6--no host at:192.168.111.22
6--done.
7--no host at:192.168.111.19
7--no host at:192.168.111.20
7--host found at:192.168.111.21--time:1
7--no host at:192.168.111.22
7--done.
8--no host at:192.168.111.19
8--no host at:192.168.111.20
8--host found at:192.168.111.21--time:1
8--no host at:192.168.111.22
8--done.
9--no host at:192.168.111.19
9--no host at:192.168.111.20
9--host found at:192.168.111.21--time:1
9--no host at:192.168.111.22
9--done.
10--no host at:192.168.111.19
10--no host at:192.168.111.20
10--host found at:192.168.111.21--time:1
10--no host at:192.168.111.22
10--done.
Test 2: All together:
1--no host at:192.168.111.19
2--no host at:192.168.111.19
3--no host at:192.168.111.19
4--no host at:192.168.111.19
5--no host at:192.168.111.19
6--no host at:192.168.111.19
7--no host at:192.168.111.19
8--no host at:192.168.111.19
9--no host at:192.168.111.19
10--no host at:192.168.111.19
2--no host at:192.168.111.20
3--no host at:192.168.111.20
6--host found at:192.168.111.20--time:924 <----- this host does not exist!!
5--host found at:192.168.111.20--time:961 <----- this host does not exist!!
10--host found at:192.168.111.20--time:778 <----- this host does not exist!!
9--host found at:192.168.111.20--time:815 <----- this host does not exist!!
2--host found at:192.168.111.21--time:37
7--host found at:192.168.111.20--time:888 <----- this host does not exist!!
8--host found at:192.168.111.20--time:852 <----- this host does not exist!!
4--host found at:192.168.111.20--time:997 <----- this host does not exist!!
1--host found at:192.168.111.20--time:1107 <----- this host does not exist!!
3--host found at:192.168.111.21--time:38
6--host found at:192.168.111.21--time:1
5--host found at:192.168.111.21--time:1
10--host found at:192.168.111.21--time:2
2--host found at:192.168.111.22--time:3 <----- this host does not exist!!
9--host found at:192.168.111.21--time:2
7--host found at:192.168.111.21--time:1
4--host found at:192.168.111.21--time:3
1--host found at:192.168.111.21--time:39
2--done.
1--host found at:192.168.111.22--time:5 <----- this host does not exist!!
1--done.
10--host found at:192.168.111.22--time:40 <----- this host does not exist!!
3--host found at:192.168.111.22--time:192 <----- this host does not exist!!
6--host found at:192.168.111.22--time:75 <----- this host does not exist!!
8--host found at:192.168.111.21--time:230
5--host found at:192.168.111.22--time:155 <----- this host does not exist!!
4--host found at:192.168.111.22--time:78 <----- this host does not exist!!
9--host found at:192.168.111.22--time:77 <----- this host does not exist!!
7--host found at:192.168.111.22--time:76 <----- this host does not exist!!
10--done.
6--done.
4--done.
5--done.
3--done.
7--done.
9--done.
8--no host at:192.168.111.22
8--done.
ALL DONE

I created this test (it's basically the same as your class):
import java.util.*;
import java.net.*;
public class IsReachableTest_2 implements Runnable {
    private final String[] addresses = new String[] {
         "www.sun.com",
         "129.42.16.99" // www.ibm.com which is not reachable
    public void run(){
        try {
            for (int i = 0; i < addresses.length; i++) {
                final long start = System.nanoTime();
                final String address = addresses;
     if (InetAddress.getByName(address).isReachable(5000)) {
     System.out.println(Thread.currentThread().getName() + ": Host found at: " + address +
          " --time: " + (System.nanoTime() - start) / 1000);
     } else System.out.println("no host at: " + address);
} catch(Exception e){
e.printStackTrace();
System.out.println("Thread " + Thread.currentThread().getName() + " DONE");
public static void main(String[] args) {
System.out.println(
     System.getProperty("java.vendor") +
     " " +
     System.getProperty("java.version") +
     " running on " +
     System.getProperty("os.name") +
     " " +
     System.getProperty("os.version")
for (int i = 0; i < 10; i++) {
     final Thread t = new Thread(new IsReachableTest_2(), "THREAD " + (i+1));
     t.start();
And I get:
Sun Microsystems Inc. 1.5.0-beta running on Windows 2000 5.0
THREAD 1: Host found at: www.sun.com --time: 217653
THREAD 3: Host found at: www.sun.com --time: 214404
THREAD 6: Host found at: www.sun.com --time: 214900
THREAD 4: Host found at: www.sun.com --time: 215901
THREAD 5: Host found at: www.sun.com --time: 216666
THREAD 10: Host found at: www.sun.com --time: 216620
THREAD 9: Host found at: www.sun.com --time: 217405
THREAD 2: Host found at: www.sun.com --time: 220705
THREAD 7: Host found at: www.sun.com --time: 220845
THREAD 8: Host found at: www.sun.com --time: 221384
no host at: 129.42.16.99
Thread THREAD 4 DONE
no host at: 129.42.16.99
Thread THREAD 6 DONE
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
no host at: 129.42.16.99
Thread THREAD 5 DONE
Thread THREAD 10 DONE
Thread THREAD 9 DONE
Thread THREAD 7 DONE
Thread THREAD 3 DONE
Thread THREAD 1 DONE
Thread THREAD 2 DONE
Thread THREAD 8 DONE
HOWEVER: I was getting some strange results every so often. Results like:
Sun Microsystems Inc. 1.5.0-beta running on Windows 2000 5.0
THREAD 3: Host found at: www.sun.com --time: 261132
THREAD 9: Host found at: www.sun.com --time: 264183
THREAD 2: Host found at: www.sun.com --time: 266447
THREAD 6: Host found at: www.sun.com --time: 266596
THREAD 8: Host found at: www.sun.com --time: 267192
THREAD 5: Host found at: www.sun.com --time: 268610
THREAD 4: Host found at: www.sun.com --time: 269849
THREAD 1: Host found at: www.sun.com --time: 280978
THREAD 7: Host found at: www.sun.com --time: 272589
THREAD 10: Host found at: www.sun.com --time: 273162
THREAD 3: Host found at: 129.42.16.99 --time: 13657
Thread THREAD 3 DONE
THREAD 4: Host found at: 129.42.16.99 --time: 4123
THREAD 2: Host found at: 129.42.16.99 --time: 9439
THREAD 5: Host found at: 129.42.16.99 --time: 6681
THREAD 8: Host found at: 129.42.16.99 --time: 7655
THREAD 6: Host found at: 129.42.16.99 --time: 8627
THREAD 9: Host found at: 129.42.16.99 --time: 10586
Thread THREAD 4 DONE
Thread THREAD 2 DONE
Thread THREAD 5 DONE
Thread THREAD 8 DONE
Thread THREAD 6 DONE
Thread THREAD 9 DONE
no host at: 129.42.16.99
Thread THREAD 7 DONE
no host at: 129.42.16.99
no host at: 129.42.16.99
Thread THREAD 10 DONE
Thread THREAD 1 DONE
Usually the first run after I had compiled the class (!?) This isn't a thread safety problem.

Dumb question about Thread Safety in Servlets

Hi all
I wrote this Client API for sending requests and receiving responses to / from a multivalue database. The API is called by my Servlet. Now it seems my API is not thread safe because when several people open up the servlet at the same time, the API gets totally confused. When the API calls are inside a synchronized(){} it works just fine, but obviously at a big performance hit. Is that the wrong way of doing it??
However when I was doing the ACID test locally on my machine, by opening two command prompts and excuting the same java program (with the same code in it as the servlet, but standalone) my API worked just fine. How come?
Any insights appreciated as I am just learning about thread safety now (the hard way :-( )
cheers
Dejan

Does this help
Are you using one connection to the database shared by all instances
of your servlet
And is this connection create in the init method of the servlet and stored
in the servlet context.
Problem 4 people try and use your servlet at the same time, each servlet trys to
create a connection to the database and then store it in the servlet context and
this causes a problem.
Solution create a listener to create the connection and store it in the servlet context
when the servlet is created.
If this is your problem it is not advisable to use only one connection to the db
try using db pooling

Problem with seting action method to a Hyperlink object

Hi there,
as the subject says, I have a problem wih setting the action method of a Hyperlink object. Here is how the program is organized:
I have an external bean which generates an ArrayList of Hyperlink objects. In the backing bean of my web page I call a method from the above mentioned external bean to generate the list of hyperlink objects. After that in the page bean I insert the hyperlink objects in GridPanel component. So far everything works fine, but the action method of the Hyperlink objects is not called and I can't understant why.
Here is how I add the objects to the GridPanel component:
private void populateGridPanel()
        Hyperlink hyper;
        for(int i=0; i< checkboxList.size(); i++)
                hyper = (Hyperlink) hyperlinkList.get(i);
                vehicleGridPanel.getChildren().add(hyper);
    }All properties of the Hyperlink objects are set in the external bean not in the page bean, here is how:
//action method executed when the hyperlink is clicked
MethodBinding mb = (MethodBinding) FacesContext.getCurrentInstance().getApplication().createMethodBinding("#{Page1.hyperlink_action}", null);
veHyperlink.setAction(mb);The populateGridPanel() method is called in the init() method of the page bean, after the initialization of all other components.
An interesting fact is that if I manually drag-n-drop a hyperlink object to my page and programatically set its action method with the code above everything works fine. But using the same code for the dynamically generated hyperlink objects inserted in the grid panel doesn't work.
Any kind of help is highly appreciated.
Thanks!
Message was edited by:
panayot

I got this use case to work as follows:
1. Drag a Grid Panel and set its columns property to 1.
2. Drag a Message Group.
3. Use the following code in Page1:
public void prerender() {
populateGridPanel();
private void populateGridPanel() {
if (gridPanel1.getChildren().size() > 0) {return;}
for (int i = 0; i < 3; i++) {
Hyperlink veHyperlink = new Hyperlink();
//action method executed when the hyperlink is clicked
MethodBinding mb = (MethodBinding) FacesContext.getCurrentInstance().getApplication().createMethodBinding("#{Page1.hyperlink_action}", null);
veHyperlink.setAction(mb);
veHyperlink.setText("dynamic hyperlink " + i);
veHyperlink.setId("dynamicHyperlink" + i);
gridPanel1.getChildren().add(veHyperlink);
public void hyperlink_action() {
info("Yup it worked at: " + new java.util.Date());
4. Fix imports, Run, and then click on the hyperlinks.

How do I gain type safety with a generic method taking a class object?

How do I achieve type safety with the following code without getting a compile error?
import java.util.ArrayList;
import java.util.List;
public class Main {
    public static void main(String[] args) throws Exception {
        ListenerHolder th = new ListenerHolder();
        List<TestObject<String>> list = createTestObjectList();
        /* *** compiler error here *** */
        th.addListener(TestObject.class, list);
    private final static List<TestObject<String>> createTestObjectList() {
        List<TestObject<String>> list = new ArrayList<TestObject<String>>();
        return list;
    private final static class ListenerHolder {
            /* *** my generic method *** */
            public <T> void addListener(Class<T> listenerType, List<T> listener) { }
    private final static class TestObject<T> { }
}The compiler error is:
C:\java\Main.java:11: <T>addListener(java.lang.Class<T>,java.util.List<T>) in Main.ListenerHolder cannot be applied to (java.lang.Class<Main.TestObject>,java.util.List<Main.TestObject<java.lang.String>>)
Thanks in advance,
Dan

dandubois wrote:
Thanks for the help, that is exactly what I wanted to know.
It didn't occur to me that TestObject<T> would in some respects be considered as an 'extends' of TestObject as I know the compiler converts them all back to plain TestObjects.Maybe I should have written TestObject<?>, to make it more obvious. There's some supertype/subtype relation diagram in the Generics FAQ somewhere, if you need more detailed information.
In the end, I think jtahlborn's solution might be more appropriate in the described scenario, so you should go for it.

Help please with my action method

Hello everybody,
Actually I'm working in a CRM 4.0 development project and I'm totally new in ABAP Programming.
My question is the following:
I have to develop an action method which delete several partner functions from partner tab in a sales order (for all included items and always the same partner functions, ZO1, ZO2 and ZO3 for example).
Which is the best way to do it? Maybe using CRM_ORDER_MAINTAIN function?
Could anybody help me posting some example code or any guideline?
Thanks in advance.

hi, I think you need a way to delete partner of SD.
I do the similar functionality for PO, so I think the situation is same.
I think some FM can be helpful to you.
try this:
SD_SALESDOCUMENT_CHANGE
it has a TABLE parameter PARTNERCHANGES and PARTNERS.
Hope it will be helpful
thanks

Issue with JSF action method and Popup

All,
I have command Button, which has an action method. And my onclick function opens new popup. Once I close the popup, it has to return some values to the parent page and then my action method has to be executed.
Issue is if I close the popup, nothing is happening in parent page.
In my JavaScript if I return true, popup is opening and my action method is executing. But my expected behavior is after closing popup then only my action has to be executed.
Thanks,
Dhana

Hi all,
I came back to this today (after almost 2 years)... the current version of facestrace doesn't require a taglib at all: http://code.google.com/p/primefaces/downloads/list
Just drop it in WEB-INF/lib, add *.jsf to the url mappings for the faces servlet. Then whenever you add trace=true to your URL, you get a nice dump of information there.
Best,
John

Thread safety with newDocumentBuilder()

Hello,
I have the following class 'ParserService'. Just one instance of this class exists, and it's created in the servlet init method calling "new ParserService()".
After this, all incoming requests (threads executing service method) call the 'parse' method
public class ParserService
private DocumentBuilderFactory dbfDom;
// Constructor.
public ParserService()
this.dbfDom = DocumentBuilderFactory.newInstance();
this.dbfDom.setNamespaceAware(true);
this.dbfDom.setCoalescing(true);
// ---------------- DOM PARSER ------------------------------------------------------------------------------
public Document parse(String strDocument) throws ProxyServletException
try
   return (this.dbfDom.newDocumentBuilder().parse(new InputSource(new StringReader(strDocument))));
catch (ProxyServletException pse) { throw pse; }
catch (Exception e)                { throw new ProxyServletException(GenericConstants.PARSER_PARSE, e); }
}The question is if 'newDocumentBuilder()' is thread safe. Can I call the 'newDocumentBuilder()' method from different threads using the only factory 'this.dbfDom'?
Thanks in advance,
Joan.

     * Creates a new instance of a {@link javax.xml.parsers.DocumentBuilder}
     * using the currently configured parameters.
    public DocumentBuilder newDocumentBuilder()
        throws ParserConfigurationException
        /** Check that if a Schema has been specified that neither of the schema properties have been set. */
        if (grammar != null && attributes != null) {
            if (attributes.containsKey(JAXPConstants.JAXP_SCHEMA_LANGUAGE)) {
                throw new ParserConfigurationException(
                        SAXMessageFormatter.formatMessage(null,
                        "schema-already-specified", new Object[] {JAXPConstants.JAXP_SCHEMA_LANGUAGE}));
            else if (attributes.containsKey(JAXPConstants.JAXP_SCHEMA_SOURCE)) {
                throw new ParserConfigurationException(
                        SAXMessageFormatter.formatMessage(null,
                        "schema-already-specified", new Object[] {JAXPConstants.JAXP_SCHEMA_SOURCE}));
        try {
            return new DocumentBuilderImpl(this, attributes, features, fSecureProcess);
        } catch (SAXException se) {
            // Handles both SAXNotSupportedException, SAXNotRecognizedException
            throw new ParserConfigurationException(se.getMessage());
    }It appears to be thread-safe. The 'attributes' and 'features' instances variables are hashtables, which are synchronized. Unless you are modifying DocumentBuilderFactory itself in another thread (say, changing whether it is namespace aware), I do not see any issues with a simple call to newDocumentBuilder().
- Saish

A question about thread safety and the Acrobat SDK

Hi All,
On page 12 of this FAQ: http://www.adobe.com/devnet/acrobat/pdfs/Acrobat_SDK_developer_faq.pdf
It says that Use of any Acrobat product in a multithreaded way is technically impossible.
I'm currently writing a command line application to perform some basic data gathering on a PDF file. The Application only makes use of a PDDoc object, and never calls on any other kind of object (i.e. AVDoc).
The application itself is not multithreaded. All of the logic runs in a single thread.
However, the application will be called (via the command line) from another application that /is/ multithreaded. I think that this might be fine, but I wasn't sure. In this case, would this count as a single thread, but spread across multiple processes? And if that is the case, would that be OK with the SDK?
Or would having multiple invocations/calls into the Acrobat DLLs cause the same issue as a multi-threaded application?
Unfortunately, I haven't done a lot of work with threads before. This might be a very silly question.

The application would be called from a perl script that is used to automate several tasks. The app is a console application, written in C# w/ the Acrobat COM components, and Visual Studio 2005.
The console application uses the Acrobat SDK to instantiate a PDDoc object, open a PDF, and get information about the document. It then returns results back to the console.
So, the perl script just calls: "C:\pdfinfo.exe -f=myPdf.pdf" and pipes the result to a log file.
In this case, it never creates a new instance of the Acrobat application, but it does use the SDK.
The reason that I was concerned was that the perl script is multi-threaded. I wasn't sure if acrobat was just sensitive to multiple threads inside a single process, or if it was unable to handle multiple processes as well.
PDL's answer suggests that I should be fine as long as a new process is started each time. This is good to hear.

Question about 360 movieclip with cursor action

Hello Flash Forum
We have a question about a 360 flash / movieclip which comes
to a halt or jumps to whereever the cursor is moved horizontally
while any vertical movements is ignored. We are having difficulties
to implement this and would like to ask whether someone can point
us into the right direction in Flash 8 - read somewhere that this
is extremely easy in Flash 8 but we cannot find out how!?
An example would be:
http://www.kswiss.com/cgi-bin/kswiss/store/product_detail.html?mv_arg=x&pid=01190:177
and then chosing 'Go 360'
Thank you for any assistance and/or direction.
Alex

Alex, took a look at your sample - looks to me like
start_drag and stop_drag on mouse_over. Hope this helps. ash

CommandButton action method invoked multiple times in standalone OC4J

Hi,
We've developed an application in JDeveloper 10.1.3.3.0 (ADF Business Components version 10.1.3.41.57). In one page we have a commandButton with an action method:
<af:commandButton action="#{MyBean.myActionMethod}"
blocking="false"
textAndAccessKey="#{nls['MY_LABEL']}"
id="myButtonId" >
<f:actionListener type="oracle.jheadstart.controller.jsf.listener.ResetBreadcrumbStackActionListener"/>
</af:commandButton>
This method is defined in a managed bean:
public String myActionMethod() {
/* some code */
return "indexPage";
There is a navigation-rule for outcome "indexPage". When we run our application in the JDeveloper embedded OC4J instance and click on the commandButton, the action method is invoked once and then the .jspx in the navigation-rule is navigated to.
We deployed our application to a standalone OC4J instance. Both embedded and standalone OC4J have version: Oracle Containers for J2EE 10g (10.1.3.3.0) (build 070610.1800.23513)
When we run our application in the standalone OC4J and click on the commandButton, the action method is repeatedly invoked in a seemingly infinite loop.
We'd appreciate it if someone could shed some light on the matter. Please note that we cannot use <redirect /> in our navigation-rule for "indexPage" because in production we have an Oracle webcache server upstream of our OC4J. Users can only submit HTTPS requests to the webcache, which in turn forwards these requests as HTTP requests.
Kind regards,
Ibrahim

Dear All,
We'd really appreciate it if somebody would suggest some possible causes even if these might seem fare-fetched. Perhaps compare certain .jar files or something to that effect.
Anything ????
Thanks and regards,
Ibrahim

MessageFormat.format - Thread safety - vital question

Hello Forum
This question is especially on the function *"public static String format(String pattern, Object... arguments)"* in Message format class. No information is given in Javadoc for this function regarding thread safety. However a generic message for the entire class is given in the javadoc stating that the - *"Message formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally."*
It is for this reason I believe the code scanning tools like Fortify catch this function as having lack of thread safety for web applications.
However, if you look at the decompiled source of the function - no shared object is being accessed. The decompiled source of this function is below -
+public static String format(String pattern, Object ... arguments) {+
MessageFormat temp = new MessageFormat(pattern);
return temp.format(arguments);
+}+
Here no shared object is being accessed, a new object is created within the static method and the same is used for formatting. This decompiled version indicates that this method is actually thread safe (since no shared object is present and each method stack in each thread will have its own copy of MessageFormat. No sharing happens).
Could you tell us if this is the case in the current scenario. This particular format method is actually thread safe when compared to other format methods.
regards
Phani Lanka

user10855645 wrote:
Hello Forum
This question is especially on the function *"public static String format(String pattern, Object... arguments)"* in Message format class. No information is given in Javadoc for this function regarding thread safety. However a generic message for the entire class is given in the javadoc stating that the - *"Message formats are not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally."*Doesn't sound like much of a question. They're not threadsafe, so use separate instances for separate threads, or use appropriate synchronization. Open and shut.
However, if you look at the decompiled source of the function......you're doing it wrong. The implementation is the wrong place to look, and you can't rely on that. Go by the documentation, not by the implementation.
And you're confused as well. The docs for that method say: "Creates a MessageFormat..." So you have your answer right there.
Here no shared object is being accessed, a new object is created within the static method and the same is used for formatting. This decompiled version indicates that this method is actually thread safeWrong. The documentation indicates that it's threadsafe. The deompiled code only tell you what that particular implementation is doing.
I'm not sure what you're concerned or confused about in the first place. The docs for the class say "use a separate instance for each thread," and the docs for that method say, "creates a new instance." So where's the confusion?

Auto-re-action method Question (Please Urgent)

Hi, all
I have very quick question about Auto-re-action method CCMS, I setup method for "server dialog response time" and changed threshold value to become red and alert create, when I double click on it it shows 10 Alerts with status "Action_Faled" its suposed to be "Action Required" or Action-Running...
Background job has been created, do you know how do i trace that why it does't work
Even SMTP works fine, and internal mail works fine...
Thanks a lot

please let me know where should I post it
i am working XI 3.0

Thread Safety Issue with DOM

I am parsing an XML into a DOM object using the Xerces parser that is packaged with JDK 1.5.
First, I create a new instance of the DocumentBuilderFactory and then using the factory, create a new DocumentBuilder. I then parse the XML using the DocumentBuilder to obtain a DOM object.
Somehow, I am seeing the same DOM object being used for different XMLs.
Is there a thread safety issue with the Xerces parser?

certainly, Xerces parser is not thread safe. You have to provide thread safety by making sure that only one thread is allowed to access DocumentBuilder object.

Reflection objects and thread safety

Hi,
I believe that I saw that Field and Method objects are thread-safe (i.e., can safely have methods called against a single object instance concurrently from multiple threads), but am having trouble finding such a description in the JDK javadocs static that fact.
I'm assuming that all thread-specific 'state' would be managed by the Object target passed to methods like invoke()/get()/set() and not on the actual Field and Method objects themselves. Ideally, i'd like to only have to look up fields and methods only once reflectively, and thereafter just use the same reflection object instances to access their target objects at runtime as a performance optimizations - possibly in different threads and at the same time - without having to pay the cost of looking it up again. I should be able to do that providing Method.invoke() is thread safe. Otherwise, i'd probably be forced to call Class.getMethod() to get a new Method object to use against each object instance, which would be more costly both from a memory standpoint (more Method objects) and a lookup-cost perspective.
Given that lots of existing performance-critical enterprise infrastructure code, such as OR database APIs, IoC frameworks and J2EE containers use reflection to decouple the generic code from any app specific code (from a compile time perspective) as an alternative to code generation, it's surprising that there's no obvious statement about thread safety in these classes. If I look at the source code for Method, it appears to be thread safe, but I can only get so far with this analysis, as the critical code in Method appears to be implemented using a class named 'sun.reflect.MethodAccessor', whose source I don't have access to.
I know it's possible to invoke a method against multiple objects by calling Method.invoke() against each of the target objects in question. However, there's no mention as to whether it's safe to use a single Method object instance to invoke a method against multiple target object instances at the same time (i.e., from different threads running in parallel). This would fail, for instance, if the Method object had data members that were used to communicate information between internal calls without any synchronization, as the values might be used by one thread while another was changing them.
Just to clarify (as i've seen some confusion in other forum discussions on this topic):
I completely understand that the thread safety of a target object's method (read, small 'm') is entirely dependent upon it's implementation and not the mechanism by which it's invoked - i.e., whether a method is invoked by an explicit compiled-in call against an instance of the target object in some Java source file, or indirectly via Method object-based reflection, is immaterial the the method's thread safety.
What i'm asking about is the thread safety of the Method.invoke() call itself (read, big 'M'). Same question wrt Field.get()/.set() as well. These calls should be thread-safe if they're stateless wrt the Method and Field object instances that they are invoked against.

In general, if a Java API is silent about multi-threading, it is intended to be thread-safe. See the javadoc for HashMap for an example of an explicit warning.
It is true that Java code can have bugs that show up only on unusual implementations of the Java memory model, such as relaxed memory model machines. Most (if not all) implementations of the JDK have been deployed principally on platforms with strong memory models. (Perhaps not coincidentally, those are also the machines that have market share.) There are even bugs found occasionally in the JDK core, so draw your own conclusions about the bug-tail of our software stack on systems with relaxed memory models!
One of the more likely bugs to run into on highly optimized systems is failure of timely initialization of non-final fields in objects which are shared in an unsynchronized manner. See http://www.cs.umd.edu/~pugh/java/memoryModel/jsr-133-faq.html#finalRight and related pages. JDK core programmers (at Sun, to my personal knowledge) take care not to write code with such bugs, but application programmers might.
And, yes, caching your own Method objects is a good idea, if only because their lookup is generally cumbersome and slow. If you are very performance sensitive, you'll end up generating bytecode "shim" between your callers and the desired target methods. I expect that the http://openjdk.java.net/projects/mlvm/ (an openjdk project we are just starting) will provide some relief for this; stay tuned.
Finally, since Method objects have no state to speak of (except their "accessible" bit, which is an ahead-of-time configuration), it would be really, really surprising if they could create a race condition of some sort. If you expect race conditions in formally stateless data structures, you are certifiably paranoid. (A normal state on some platforms, hopefully not on Java.)
For more information about method calls, including reflective methods, see my blog post: http://blogs.sun.com/jrose/entry/anatomy_of_a_call_site
Best wishes...

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