Dynamic loading in Java

I was asked following in the interview-
What things are dynamically loaded in Java?
How can we change this behaviour so as to load things
statically?
Can anybody clarify this for me or give some reference
URLs etc?
Sounds like an absurdly general question to me.
For example shared libraries are loaded dynamically. And there is no way to do it statically unless one modifies the jvm.
Or using Class.forName() loads a class dynamically. Statically one could create a null reference which would be a 'static' load. Of course that is a rather tentative definition because java is still going to load it when the method is reached rather than on start up.
Or one could say that the core jvm is statically loaded, for example the system class loader, since it is implemented in C (but of course it actually exists in a shared library so it is loaded dynamically as well by the OS.) All other classes are loaded dynamically and again it requires changing the JVM to alter the behavior.

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URLClassLoader + dynamically loading signed jar files

I have an applet that does not know all of the jar files it will need to load at startup.
I would like to dynamically load these signed jar files using the URLClassLoader, however it does not recognize these jar files as being signed and I get java.security.AccessControlException: access denied errors.
Any suggestions?
Thanks!

Try this classloader for loading the jars, it should to the trick:
import java.net.URL;
import java.net.URLClassLoader;
import java.net.URLStreamHandlerFactory;
import java.security.AllPermission;
import java.security.CodeSource;
import java.security.PermissionCollection;
import java.security.Permissions;
public class AllPermissionsClassLoader extends URLClassLoader {
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Dynamic Load Plan creation using scripting

Hello All,
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ODI SDK apis allows dynamic creation of Loadplans. Oracle Fusion Middleware Java API Reference for Oracle Data Integrator
Studio too uses these APIs for LP related operations so you should be able to do using these whatever studio allows.
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Is there a way to make this work?

To answer my own question -- no
A reference from http://access1.sun.com/techarticles/DR-article.html says:
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Dynamic loading tree and data grid

Hi All,
I new to java as well as JSF. I am very impressed with the jsf and Sun Java Creator IDE. I made a sample project.
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To dynamically load a Basic Table (ui:table) from a database, see http://developers.sun.com/prodtech/javatools/jscreator/learning/tutorials/2/databoundcomponents.html
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A tutorial for dynamically creating a tree from a database is work in progress.
Hope this helps,
Chris

Dynamically loading client proxy no longer works

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Are you running SP2 R2? This worked for me as well until I upgraded to SCCM 2007 SP2 R2. I am focusing on the "~Doing Account Cleanup" errors in the ccm.log which should happen every 30 days, not every 20 minutes. Those errors have to be related to client push problems. Also, thanks for the reboot suggestion. I realize anytime a computer object is added to a domain security group that has is a member of a local group on the client, that a reboot is necessary on client systems in order to receive a new Kerberos access token but in the case of my test systems, I have explicitly added the computer account to the local administrators group so a reboot is not required. I have a test site in a completely different forest and it behaves almost the same way (doesn't run the "~Doing Account Cleanup" every 20 minutes) but still fails to install the client using the site server's computer account. Must be me!!!

Dynamic binding in java

I have say 2 classes - A and B which has the method doSomething()
I have an array of objects - Object[] obj wihch has both A and B.
How can i invoke doSomethin() of the respective class without any hard coding or typechecking inside the loop.

Reflection is not the way to go (though its the
answer for the way you framed your question.) The
proper way is to create an interface and implement
that interface on both of those objects. Then cast
to the interface.
interface Aninterface {
public void doSomething();
class A implements Aninterface {
public void doSomething(){
//something in A fashion
class B implements Aninterface {
public void doSomething(){
//something in B fashion
class Mainclass {
public static void main(String [] params) {
Aninterface [] objs = getObjects();
objs[0].doSomething();
objs[1].doSomething();
Aninterface [] getObjects() {
Classloader cl = new URLClassloader(new []
URL{new URL("path.to.jar.with.classes")};
Class a = cl.loadclass("A");
Class b = cl.loadclass("B");
return new Aninterface [] {(Aninterface
)a.newInstance(),(Aninterface )b.newInstance()};
}This is the proper way of handling dynamic class
loading in Java. The getObjects method would load
those classes dynamically as needed. It only knows
the classes by their interface Aninterface. The
actual classes A and B are never imported into the
main program and are not on the classpath at compile
time.why is that more 'proper' than using reflection? it's the better solution, if you're in a position to do so, but we can't always dictate that classes will implement a particular interface, especially if we're working with third-party code

How to dynamically load static (inner) class

I have an urgnent question, any comments would be appricated.
I have a static inner class definition.
Class myObject
public static class innerObject
I want to dynamically load the static innerObject class such as
Class c = Class.forName ( "myObject.innerObject" );
innerObject t = ( innerObject ) c.newInstance();
I can't do this as it give me ClassNotFound Exception, Do I need to load myObject first? any comments?
The other alternative is that to define my myObject as having a static variable referencing the static class.
Class myObject
staic innerObject m_inner = new innerObject();
public static class innerObject
Is there any option in java allowing me to load a static variable?
Many thanks
Jay

I can't do this as it give me ClassNotFound Exception,Use "myObject$innerObject" instead of "myObject.innerObject".
Is there any option in java allowing me to load a
static variable?What do you mean by that?

How to Dynamically Load jvm.dll without setting PATH

Please help, invoking CreateJavaVM via a function pointer is returning -3, but I'm not sure why.
When my PATH is setup up to include the jvm.dll and I invoke JNI_CreateJavaVM() directly, it works fine. But I want it to work regardless of my PATH setting, so I am trying to use LoadLibrary and dynamically load the jvm.dll and then a function pointer to invoke CreateJavaVM().
The LoadLibrary returns non-NULL result, the GetProcAccress() returns non-null, but when I invoke the pointer to the CreateJavaVM call, it returns -3. I know -3 is JNI_EVERSION error, but any ideas what is wrong with the code below, such that it would give me this error?
Currently my code is as follows:
typedef jint (JNICALL CreateJavaVM_t)(JavaVM **pvm, void **env, void *args);
JavaVM *m_jvm;
JNIEnv *m_env;
SetDllDirectory(L"C:\\Program Files\\Java\\jdk1.6.0_20\\jre\\bin\\client");
HINSTANCE hVM = LoadLibrary(L"jvm.dll");
if ( hVM == NULL ) {
// report error
CreateJavaVM_t *pfnCreateJavaVM = (CreateJavaVM_t*)GetProcAddress(hVM, "JNI_CreateJavaVM");
#ifdef JNI_VERSION_1_6
char cpChars[1024] = {0};
sprintf_s(cpChars, "-Djava.class.path=%s", classPath); // classpath is defined elsewhere
JavaVMOption options[1];
options[0].optionString = cpChars;
JavaVMInitArgs vm_args;
vm_args.version = JNI_VERSION_1_6;
vm_args.options = options;
vm_args.nOptions = 1;
vm_args.ignoreUnrecognized = JNI_TRUE;
pin_ptr<JNIEnv*> env = &m_env;
pin_ptr<JavaVM*> jvm = &m_jvm;
int result = pfnCreateJavaVM(jvm, (void**)env, &vm_args);
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Thanks in advance,
Bill

wkoscho wrote:
For some reason, pfnCreateJavaVM is returning -3, but I'm not sure why? Any ideas what is wrong with this code, such that it would give me a -3?As an experiment try using a different jvm.dll from a different location. From my box there are several different jvm.dll under my jdk install dir.

Dynamically loading jar files

Hi
In my application I need to dynamically create objects of types specified by string which is passed as parameter. I am able to do this if the class is inside the same jar. But I need to load the class from any jar name specified. How do i go about doing this? Is there a way to dynamically loading jar files?

It's easy. You use [url http://java.sun.com/j2se/1.5.0/docs/api/java/net/URLClassLoader.html]URLClassLoader:String jarPath = ...;
String className = ...;
URLClassLoader ucl = new URLClassLoader(new URL[] { new File(jarPath).toURL() });
Class cls = Class.forName(className, true, ucl);
...Regards

How to load a java script in oracle database

Is it possible to load d java script in Oracle database. while the object type is
java resource ..

RENUJP wrote:
I meant to load a javascript to oracle database not to oracle appliocation.
like loadjava....
I can load a javascript to oracle database.. but i can't call it...Please re-read the comments above, especially the part about this not being a javascript nor oracle forum. Exactly what part about this information don't you understand?

I am running 10.5.8, and just updated my java to java 5 update10. Now my firefox is missing the Java plugin, and I can't load any Java applet at all. When I try it with Safari, it hangs when certain Java applet loads. HELP!!!

Suddenly my Java plugin is missing and i can't load any Java with Firefox at all, even though i have it enabled in the browser! i've tried loading in java embedding plugin, but it doesn't work. what should i do???

It's not in Tools> Add-ons >plugins? Should be Java Plug-in 2 for NPAPI browsers 13.5.0. What are you seeing there? I don't think it's called the embedding plugin any longer.
Might try getting the Firefox 5 standalone application. Trash the current one and replace it. Doing this won't affect your Profile or any settings.
http://www.mozilla.com/en-US/firefox/all.html
If it's enabled, how can it be missing?
If this doesn't work, ask here. No need to register. Make sure you put (Mac) in the title.
http://forums.mozillazine.org/viewforum.php?f=38
Message was edited by: WZZZ
EDIT. Oops, may be different for 10.5.8. Was thinking recent Java update for 10.6. But try installing a new app anyway. In the past, this got me the latest Java plugin.

Anyway to have JDeveloper dynamically load BC4J components in memory?

We are dealing with a large BC4J based application that contains large amount of application modules. So far, 300 application modules and total 4000 BC4J objects have been created. The size of the application still keeps growing daily... may up to twenty times than what we are having right now.
While the application size growing, some unusual problem comes out. The biggest problem is that it makes JDeveloper very sluggish. It takes 15 minutes to just open JDeveloper and may need a few minutes to open the application module editor. (FYI: in our team, most developers have 1G memory and 1.8G CPU or up.) This is probably still OK for right now, but it will become a big problem later when the project size grows.
When we analysis the project structure, we know that most of time, developer does not need to load all the application modules. For example, we have a core package that contains about 30 application modules. This core package needs to be shared and should be loaded. But, the other nine packages contain about 30 application modules each do not need to be loaded into memory at the same time in most cases. Since BC4J is XML based, we could not find a way to just partially load those application modules, especially when theres cross references between them.
When we check the project.jpr file, looks like all BC4J objects are referenced there. We have 40K lines in our project.jpr file now. When open JDeveloper, we believe JDeveloper will try to load all referenced BC4J XML content into memory. This consumes 500M memory and makes the overall performance very sluggish. The situation may become even worse when the project size keeps growing. For example, we cannot have 5000M (5G) memory in a development machine for 3000 application modules.
We do know that by checking out the "ScanSource Paths to Determins Project Contents" in the Input Paths of Project Settings, we can short the JDevelopers open time, but this will not give BC4J relationship information and some other useful information Not a practical solution.
So, any idea to make JDeveloper dynamically loaded BC4J based on need?
Weve tried a few ways. One is to partition the application into different project and import the core one into the other projects. Only open the project in workspace when need. But this is not officially documented by Oracle and we are not sure whether it is possible/correct or not. Another thought is to remove the NOT-CURRENTLY-USED package from the project. But JDeveloper only support file level remove.
Any help on this dilemma will be highly appreciated.
Thanks,
Charles

The package is the unit of loading in the IDE for ADF business components.
To edit components, they must belong to the project.
To refer to components in a read-only way, they can be imported. This allows other editable or read-only components to refer to them without allowing the imported components to be edited.
Both editable and imported components need to be loaded in memory to use them, so you can save memory at design time by creating projects that leave out as many packages as possible.
Is there a way we can get your existing project in house to study its design time performance?

Dynamic load of images in to established Timeline effect

Is it possible to dynamicly load images in to an already
established timeline effect?
Steps I've done.
Stuffed a JPG in to the library by draging and dropping it in
to the SWFs library.
Dropped the JPG on to the main stage
Right clicked the image then going down to Timeline effects
and choosing an effect.
Completing any changes in effects dialogue box and then
clicking OK.
Play the movie, and pat myself on the back that it worked.
So then, how can I get Actionscript to load an image
dynamically in to that same Timeline effect and have it do the
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hii
Can u mention the error message getting while the status become RED??
As what I understand, this may be the issue of invalid characteristics inPSA Data Records or also there may be records that does not support the lower case or upper case data.
So just check the data in PSA Level
Thanks
Neha

Spry Tabbed panels + Progressive Enhancement and Dynamic Loading of Content With Spry

Is there any way to combine tabbed panels together with "Progressive Enhancement and Dynamic Loading of Content With Spry"?
Visit: http://labs.adobe.com/technologies/spry/articles/best_practices/progressive_enhancement.ht ml#updatecontent
And click on the "Using Spry.Utils.updateContent()"
The 3rd example shows how to use a fade transition whenever the content changes.
I already have tabbed panels. My menu contains buttons (on tabs) and my Content div contains the panels.
Tabs code;
<ul class="TabbedPanelsTabGroup">
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                    <td style="padding-right:0px" title ="Home">
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                    </tr>
               </table>
          </li>
etc
etc
etc
and the panel code:
<div class="TabbedPanelsContent" id="Home">
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</div>
I hoped i can use the example code from the link into my tabbed panels.
I thought this code:
onclick="FadeAndUpdateContent('event', 'data/AquoThonFrag.html'); return false;"
could be added to the tab code like this:
<a href="javascript:TabbedPanels1.showPanel(1);" onclick="FadeAndUpdateContent('event', 'data/AquoThonFrag.html'); return false;" title="Home" style="background-image:url(/Buttons/Home.png);width:172px;height:75px;display:block;"><br/></a>
But the content doesnt fade...
I know i need to change the header etc.
The following is from the link:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:spry="http://ns.adobe.com/spry">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Aquo Events</title>
<script src="../../../includes/SpryEffects.js" type="text/javascript"></script>
<script src="../../../includes/SpryData.js" type="text/javascript"></script>
<script type="text/javascript">

</script>
<style type="text/css">
/* IE HACK to prevent bad rendering when fading. */
#event { background-color: white; }
</style>
</head>
So i changed my header etc, put the SpryEffects.js and SpryData.js into position and nothing changed...
Is there a way to keep my tabbed panel (or change as less as possible) and let
A. The fade work
B. The loading work.
The problem now is that it loads all pages instead of only the home. Therefore i wanted this Progressive Enhancement.
And the fading part is just because its nice...

It doesnt show in the post but off course i changed this link;
"data/AquoThonFrag.html"
into;
"javascript:TabbedPanels1.showPanel(1);"
I must say i dont know if this even works...

Dynamic loading in Java

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