 How do I write a J2EE/EJB Singleton?
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A day ago my application was one EAR, containing one WAR, one EJB
JAR, and a couple of utility JAR files. I had a POJO singleton class
in one of those utility files, it worked, and all was well with the
world:
EAR
|--- WAR
|--- EJB JAR
|---
Util 1 JAR
|--- Util 2 JAR
|--- etc.
Then I created a second WAR and found out (the hard way) that
each WAR has its own ClassLoader, so each WAR sees a different
singleton, and things break down from there. This is not so
good.
EAR
|--- WAR 1
|--- WAR 2
|---
EJB JAR
|--- Util 1 JAR
|--- Util 2 JAR
|---
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Related to : How do I write a J2EE/EJB Singleton?
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| J2EE/EJB + service locator: is it safe to cache EJB Home lookup result? |
| Programming Languages |
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In a J2EE application, we are using EJB2 in weblogic.
To avoid losing time building the initial context and looking up
EJB Home interface, I'm considering the Service Locator
Pattern.
But after a few search on the web I found that
even if this pattern is often recommended for the InitialContext
caching, there are some negative opinion about the EJB Home
caching.
Questions:
Is it safe to cache EJB Home
lookup result ?
What will happen if one my cluster node is no
more working ?
What will happen if I install a new version of the
EJB without refreshing the service locator's cache ?
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| How do I write a J2EE/EJB Singleton? |
| Programming Languages |
 |
A day ago my application was one EAR, containing one WAR, one EJB
JAR, and a couple of utility JAR files. I had a POJO singleton class
in one of those utility files, it worked, and all was well with the
world:
EAR
|--- WAR
|--- EJB JAR
|---
Util 1 JAR
|--- Util 2 JAR
|--- etc.
Then I created a second WAR and found out (the hard way) that
each WAR has its own ClassLoader, so each WAR sees a different
singleton, and things break down from there. This is not so
good.
EAR
|--- WAR 1
|--- WAR 2
|---
EJB JAR
|--- Util 1 JAR
|--- Util 2 JAR
|---
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| Singleton across classloaders/EJB:How to avoid multiple instance of JCS Cache due to multiple class loader/EJB's? |
| Programming Languages |
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I want to use JCS (Java Cache System) to cache ldap queries which
should be shared by multiple EJB's (class loaders) to avoid the
duplicate searches. I have created a singleton wrapper to create only
one instance of JCS cache but due to each EJB's having their own class
loader, it creates multiple instance of JCS cache so ldap search
results are not reused.
Is there any way to create a true
singleton which can be shared by multiple EJBs/Class loaders?
One
of my friend suggested to create a EJB wrapper on my singleton. Is it
right approach? Can't I implement without EJB? I saw and article about
how to implement "Absolute Singleton" but when I tried the solution
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| EJB help, very confused with gui's and JFrames with J2EE |
| Programming Languages |
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Hi im in need of some help with a J2EE application im
working on. I need to develop a JFrame front-end GUI client that will
talk to the server, however i am not sure how to use JFrame to invoke
methods on the server. This is mainly because im struggling to
understand how I can call a method on the client side that will call a
method on the server side when it appears to me that the client
doesn't have a handle on the server-side (If that makes sense?) I
have crawled the web for some examples(including sun) but I still
cannot find a tutorial. So I created a simple 'Tester' package
that had a stateless session bean
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| Familar with Java but not J2EE, JSP, EJB |
| Programming Languages |
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I'm looking for a good book to get started with J2EE, JSP,
EJB, and Struts. To be honest, I'm not really familar with those.
I'm fairly a newbie programmer when it comes to Java - by that, I
mean, I can implement data structures (binary trees, priority queues,
stacks, graphs, sorting routines, etc). I can do a bit of Java
applets. Thus far, I had been doing all my projects in Java using
JCreator, which many say is for beginners. So, I just downloaded
Oracle JDeveloper 10g as a new IDE for my Java projects. Now, at
the moment I'm relearning advanced methods of PHP like OOP and
networking
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| Which j2ee/j2se for EJB? |
| Programming Languages |
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hi all, I currently studying 2 books both by the 'head
first' series, jsp+servlets and EJB. i'm two thirds through the
servlets+jsp book and if anyone needs to learn this subject this is
the book, it's amazing!! I've just started reading the book on
EJB and i'm not sure which version of j2ee to get. the book says 1.3
not 1.4 but i can't find a link to it at sun?? Secondly the j2se i've
got is 1.5. The book states that there could be problems with this
later version?? Does this mean i'll have to downoad 1.3 or 1.4 or is
there a patch now for the server as the book was written a couple of
years ago?
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