Question about EJB and thread safe coding - asking again!

sorry everyone, no one seems to be interested in helping me on this, so i post it again.
i have a question about the EJB and thread safe coding. when we build EJBs, do we need to worry about thread safe issue? i know that EJBs are single threaded, and the container manages the thread for us. maybe i am wrong about this. if i wasnot, how can we program the EJB so that two or more instance of EJB are not going to have deadlock problem when accessing data resources. do we need to put syncronization in ours beans, do we even need to worry about creating a thread safe EJB? thanks in advance. the question really bothers me a lot lately.

sorry everyone, no one seems to be interested in
helping me on this, so i post it again.Excellent plan. Why not search a little bit on your own instead of waiting for your personal forum slaves to answer your call. See below.
i have a question about the EJB and thread safe
coding. when we build EJBs, do we need to worry about
thread safe issue? Read this: http://forum.java.sun.com/thread.jsp?forum=13&thread=562598&tstart=75&trange=15
i know that EJBs are single
threaded, and the container manages the thread for us.
maybe i am wrong about this. if i wasnot, how can we
program the EJB so that two or more instance of EJB
are not going to have deadlock problem when accessing
data resources. do we need to put syncronization in
ours beans, do we even need to worry about creating a
thread safe EJB? thanks in advance. the question
really bothers me a lot lately.
Java's Thread Tutorial
JavaWorld: Introduction to Java threads
IBM: Introduction to Java threads
Google: java+threads+tutorial

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Specification/Architectural question about EJBs and XML

Hello,
My problem is as follows: I would like for a session ejb to retrieve information from xml files (other that the ejb DDs of course...). I prefer the XML-file solution to the relational-database solution as it is more lightweight. (We haven't got the resources nor the skill to administrate a native xml database.) Am I allowed to read from the filesystem? What is the best architectural solution you would advise bearing in mind I need the information contained in the xml files to be available in java (in the session bean). Ideally I would drop xml files in a directory and they would automatically be parsed and taken into account by an ejb.
I am available to provide more details if needed.
Any clue welcome,
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Hello,
My problem is as follows: I would like for a session ejb to retrieve information from xml files (other that the ejb DDs of course...). I prefer the XML-file solution to the relational-database solution as it is more lightweight. (We haven't got the resources nor the skill to administrate a native xml database.) Am I allowed to read from the filesystem? What is the best architectural solution you would advise bearing in mind I need the information contained in the xml files to be available in java (in the session bean). Ideally I would drop xml files in a directory and they would automatically be parsed and taken into account by an ejb.
I am available to provide more details if needed.
Any clue welcome,
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In my Company we have some problems with the
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Hi,
You said that you are using the T.codes VK31 or VK32.
These transaction codes are used to enter condition records for standard condition types. As you can see a grid left side having all the standard condition types like price, discounts, taxes, frieghts.
Pl check using T.code VK11 OR VK12 (change mode)
Here you can enter the required condition type, in the intial screen. (like PR00, MWST, K004, K005 .....etc)
After giving the condition type, press enter or click on Combinations icon on top of the screen. Then you can see all the condition tables which you maintained for that condition type. Like as you said table 118, table 5, table 6 and table 4.
You can select any table and press enter, then you can go into the screen in which you have all the field cataglogues you maintained for that table. For example you selected combination of Customer/Material (table 5) then after you press enter then you can see customer field on top, and material fields.
You can give all the required values and save the conditon record.
Hope this is clear.
REWARD IF HELPFUL.
Regards,
praveen

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Discussion of hacked phones is prohibited on these forums. Sorry, you'll need to go elsewhere to get support for a j'broke iPhone.

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Hi All
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i cant say for hp's
havent worked on any in a while
recent machines have been coupleof dell's , vaio & emachine
which dells do offer it at least the ones i tried , my laptop does(dell)
all home pc's are built by me which do offer to boot individual drives
what hp you getting it may tell in specs
are both discs sata? if so it might not offer this option with 2 drives of same interface
check your power supply alot of these preconfigured machines put cheap under reated power supplies in there
& will burn your motherboard i just replaced PS(250 watt) & mobo(845gvsr) in an emachines <cheap stuff<
i hope you researched the pc before buying ie : mobo, power supply are the biggest concerns
i find it much more benificial to build my own machine gives me peace at mind. the cost is sometimes more in $ but not always , your biggest expense is time researching hardware
if you live in usa the best places to start looking are bensbargains.net & pricewatch.com
i am not affiliated with either & niether sell the hardware they are just advertisers a place to buy
for costomized machines that i would trust is unitedmicro.com theyll asemble & test before shipping
i have gotten 2 machines so far from them with NO PROBLEMS with hardware (knock knock)
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I have a Macbook Pro june 2011... I have 8GB ram but I only have 256mb VRAM...
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Is there any way to upgrade my VRAM, so that I can play games on steam?
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I have a quad core i7 Processor.
My graphcics card is the AMD Radeon HD 6490M.
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The only two items that a user can change on a MBP are the RAM and HDD (Retinas not included). You have what the unit came with and the only way you will be able to change that is to purchase a MBP with superior graphics
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Ciao.

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For what it's worth, I also see a timeout on the first [ Search Online ] click, after about half a minute delay. Second click turns up results immediately. This happens each time Lens Correction is started, even without restarting Photoshop, and in both 32 and 64 bit versions. Also note that I started with one profile listed by default (though from the wrong camera) for my 40D with 28-135 zoom.
I alsow noticed that I was seeing progress bar activity in the Lens Correction dialog while I was typing this (even though Lens Correction was NOT the active window) every time I hit the 'L' key. Strange.
Windows 7 x64.
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FileWriter file = new FileWriter ("$HOME/.netrc");
2- .netrc file must have the following permissions: -rw- --- --- but when i create the .netrc file the following permissions are on default: -rw- r-- r--, how can i change this permissions? (In java code, i can't use chmod.....)
3- Are there any way to pass parameters to a .netrc file? If i get to do this i needn't change the permissions because i can't modify or create/destroy this file.
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1- .netrc file is in $HOME directory but i can't
access to this directory from java code. The
following line producesan Exception (directory
doesn't exists)
FileWriter file = new FileWriter ("$HOME/.netrc");$HOME would have to be replaced by a shell, I don't
think you can use it as part of a legal path.
Instead, use System.getProperty("user.home");
Ok, thanks
2- .netrc file must have the followingpermissions:
-rw- --- --- but when i create the .netrc file the
following permissions are on default: -rw- r--r--,
how can i change this permissions? (In java code,i
can't use chmod.....)Yes, you can: Runtime.exec("chmod ...");
I need to use estrictly the .netrc with -rw- --- --- permissions
Yes, i can use Runtime.exec ("chmod ..."); but i don't like very much this solution because is a slow solution, am i right?
3- Are there any way to pass parameters to a.netrc
file? If i get to do this i needn't change the
permissions because i can't modify orcreate/destroy
this file.I don't think so. Why do you need the .netrc file in
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Are i++, i-- atomic and thread safe for int i

I want to minimize the sync time multiple threads take to contend for a shared pool, which is implemented as a FIFO. My plan is to:
1. Use a int variable "count" to trace the free obj count. Hence eliminates the need of synchonized methods size() and isEmpty()
2. Increment & decrement count when implemeting push() and pop()
3. Minimize the number of statements in synchonized block as possible within push() and pop(), which in this case, excludes count++ and count-- provided these operations are atomic and thread safe
Have I lost something ?

So, may I make a conclusion.
To minimize contention, I use FIFO instead LIFO or stack and build it from scratch without extending from existing Collection-related class
1 public class FIFO {
2 . . private volatile int count;
3 . . private Object head, tail;
4 . . public Object pop() {
5 . . . .synchonized (tail) {
6 . . . . .if (count >= 3) {
7 . . . . . .Object tail_origin = tail;
8 . . . . . .// Re-organizing the linked list skipped
9 . . . . . .synchonized (this) {
10 . . . . . . count--;
11 . . . . . }
12 . . . . . return tail_origin;
13 . . . . }
14 . . . . else {
15 . . . . . throw new PoolEmptyException();
16 . . . . }
17 . . . }
18 . . }
19 . . public void push(Object o) {
20 . . . synchronized (head) {
21 . . . . . // Re-organizing the linked list skipped
22 . . . . . head = o;
23 . . . . . synchonized (this) {
24 . . . . . . count++;
25 . . . . . }
26 . . . }
27 . . }
28 . . public int sizeOf() {
29 . . . return count;
30 . . }
31 }
1. The reason I choose FIFO is to avoid the contention between push() and pop() -- they are NOT declared as synchonized, instead they only lock head and tail respectively. (Sorry I borrow the name push and pop from stack)
2. pop() only works when count >= 3 to avoid head == tail after pop() and hence a further call to push() block concurrent call to pop() and vice versa (see line 5 and 20)
3. The goal is to minimize the time and scope of contention. In line 9 and 23, I lock the whole pool object only when modify count, which is not atomic.
4. This pool is used for a thread pool supporting many concurrent short-lived HTTP request
Have I missed something ?
Thanks a lot!

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A very basic question about storage and safety:
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1. Upload the digital files from my camcorder to my Desktop *(as opposed to iMovie)*
2. Duplicate that footage/clips.
3. Put the duplicate clips/footage into a folder labeled with the name of that footage (like "Fun At the Dentist" or "Jimmy Learns How to Yodel").
4. Drag the folder with the footage/clips into my external hard drive into a pre-existing folder titled "Backups/duplicates of all of my raw footage/clips." This big granddaddy folder will house all of the child folders of different movies.
5 Then, open up iMovie '11 and import the raw footage/clips from my Desktop rather than from my camcorder.
6. Then I want to make a duplicate of my finished movie and put it in my external hard drive in a "Finished Movies" folder.
I know that the original raw unedited footage will always be in iMovies '11 but I want the original to also exist immediately accessible in my external hard drive.
QUESTION:
Is this viable? Is it wise? (I know it goes an extra unnecessary step, but aside from that.)
*Do you have any precautionary advice?* Should I do something in my iMovies '11 preferences? What?
In earlier years with iMovie '04 or '06 (cannot recall) I made many novice errors and ended up losing audio to my finished movie. I also lost footage.
This time around with iMovie '11 I don't to make such novice, ignorant errors.
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Yes I'm sure it will work great for you.
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Hi,
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1) Do I need to have ASM instance running on each node ? ( most likely yes... but want to make sure )
2) can I share oracle_home between ASM instance and database instance ? what is the best choice ?
3) I'm planning to use shared disks for all files, all databases.... what are the pros/cons ?
4) what should be the installation procedure ? Meaning, first create ASM instance on each node, then install cluster software, build RAC databases...... can someone explain..
5) I believe RMAN is the only option for backup since I'm using ASM, correct ?
I'm a newbie to RAC and ASM..
Thanks,

user4866039 wrote:
1) Do I need to have ASM instance running on each node ? ( most likely yes... but want to make sure )yes.
2) can I share oracle_home between ASM instance and database instance ? what is the best choice ?in 10g you can, in 11gr2 you cannot. and it might be better to seperate them because it will give you more flexibility with patching.
3) I'm planning to use shared disks for all files, all databases.... what are the pros/cons ?if you share your oracle_home you won't be able to do rolling updates. so i recommend to keep oracle_homes local.
4) what should be the installation procedure ? Meaning, first create ASM instance on each node, then install cluster software, build RAC databases...... can someone explain..follow the install guide for your respective version. for 10g you'd install clusterware first, then asm and database is last.
5) I believe RMAN is the only option for backup since I'm using ASM, correct ?pretty much. you could stop your database and dump the raw devices or use asmcmd/asmftp but rman is definitely the best choice
Bjoern

Urgent: Question about Censoring and replacing

Hello, guys.
This is my very first time writting a java program. Please tell me what I have done wrong as this is my first time?
My question is to write a program that asks the user for a word to replace in some text, and the word to replace it with. The program then reads a line of text from the user and echoes the line back to screen replacing all occurrences of the first word with the second word. It only replaces the word being censored when it occurs independently in a line (i.e. not as a part of another word).
Like:
Enter word to censor: dumb
Enter word to replace it: xxxxx
Enter line of text to censor:
The guy is dumb but his friend is even dumber.
The guys is xxxxx but his friend is even dumber.
Please look at my code now and tell me what is wrong?
public class censor
   public static void main(String args[])
       String sentence = "Please type a word which you like to censor"
       String ac = string sentence;
       String[] temp = null;
       temp = sentence.split(" ");
       for (int j = 0; j < temp.length; j++ )
           if (temp[j].equals("bridge"))
               string sentence = "Censored";
           System.out.println(sentence + " " + string sentence);
} Edited by: G on Apr 13, 2008 4:04 AM
Edited by: KevinGupta on Apr 13, 2008 4:05 AM

Hey guys,
I'm getting an error where I have added the "ERROR LINE" next to the line where im getting an error..
What I'm trying to do ?: I'm trying to make it like
Enter word to censor: dumb
Enter word to replace it: xxxxx
Enter line of text to censor: The guy is dumb dumb dumb dumb and his friend is dumber.
So, this code should replace ALL "dumb" with xxxxx NOT the dumber. But when I try to run this code only one dumb changes to xxxx not all ? So, please help on that. Also, this code doesnt work when I try to write " LIke ThaT " It gives me an exception error ?
{color:#ff0000}Look at the error below (underneath the code){color}
import java.util.*;
public class LineCensor
public static void main(String [] args)
System.out.print("Enter a word to censor: ");
Scanner keyboard = new Scanner(System.in);
String word = keyboard.nextLine();
System.out.print("Enter a word to replace it: ");
String wordC = keyboard.nextLine();
System.out.println("Enter line of text to censor: ");
String phrase = keyboard.nextLine();
String wordLowered = word.toLowerCase();
String phraseLowered = phrase.toLowerCase();
int location = phrase.indexOf(word);
String string1 = phraseLowered.substring(location,(location +
wordLowered.length()));
String string2 = phraseLowered.substring(0, location);
String string3 = phraseLowered.substring(location+word.length());
System.out.println(string2+wordC+string3);
string2 = string2.toLowerCase();
for (int i=0; i < phrase.length; i++)
(phrase.equals());                        <-------- ERROR LINE.
phrase = wordC;
System.out.println(+i);
}ERROR:
The error is:
LineCensor.java:28: not a statement
(phrase.equals());
^
1 error ANOTher ErroR
Enter a word to censor: CaT
Enter a word to replace it: xxxx
Enter line of text to censor:
The cAT wAs CuRioUs abOuT otHER CAT's strings
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1
at java.lang.String.substring(String.java:1932)
at LineCensor.main(LineCensor.java:17) This error is coming up because of lower and high caps typing. This shouldnt be happening no matter how I type the sentence/word.
Please help ?
Edited by: kabootar on Apr 16, 2008 3:20 AM
Edited by: kabootar on Apr 16, 2008 3:21 AM

Question about "synchronized" and "wait"

Hello, everyone!
I have seen a piece of code like this,
synchronized (lock)
//do operation 1
lock.wait();
//do operation 2
I think in the above piece of code, when a thead finished operation 1, it will release the lock and let other threads waiting for the lock have chance to run the same block of code. Am I correct?
If I am correct, I have a further question, a "synchronized" block means a set of operations that can not be interrupted, but when invoke "wait" method, the thread running in the "synchronized" block will be terminated (interrupted) by release the lock and other threads will have chance to enter the "synchronized" block. In short, the execution inside the "synchronized" block will be interrupted. So, I wonder whether the above piece of code is correct and conforms to the principle of "synchronized". And what is its real use?
Thanks in advance,
George

Thanks, pkwooster buddy!You're welcome
I just wondered whether "wait inside a synchronized
block" technology is thread safe. Please look at the
following example,wait and synchronized are thread safe.
public class Foo {
int mVal= 0;
public final Object mLock = ...;
public void doIt() {
synchronized(mLock) {
mVal = ...;
mLock.wait();
if (mVal == ...) {
// do something
} else {
// do something else
}If we have two threads, T1 and T2, enter the block in
their respective order, and T1 is woken up first, T2
may have tampered with T1's execution path because T2
changed mVal while T1 was asleep. So T2 manipulate
instance field mVal is a side-effect.when you do the wait() you give up the lock and the other threads get a chance to run. When you exit the wait() you get the new value of the myVal variable which may have been changed. This is exactly what you want. To make that not thread save you could do
int temp = myVal;
wait();
if(temp == ...)in this case the variable temp contains the old vale of myVal.
>
I think the most safest way is never wait inside a
synchronized block, but it is less efficient. What do
you think about the trick of wait inside a
synchronized block? I think you are very experienced
in thread field from your kind reply.
Thanks in advance,
Georgewait(), notify() and notifyAll() are very useful. You need them when you want threads to cooperate in an predictable manner. I recommend that you review the section on consumer and producer classes and wait and notify in the Threads Tutorial. It gives good examples. For a practical example of this you could also take a look at my Multithreaded Server Example. It implements a simple chat server that switches String messages. Look especially at the send(), doSend() and popMessage() methods in the StreamConnection class. These allow the receive thread of one user to send messages out using the send thread of another user. If you have questions about that example, please post the questions on that topic.
Hope this helps.

Question about EJB and thread safe coding - asking again!

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