Loading a class from specified classpath

Hello,
I would like to create an instance of a class in a specific directory.
So, I am doing this way :
System.setProperty("java.class.path", classPath.getAbsolutePath());
Class object = Class.forName(name);
Object instance = object.newInstance();It works perfectly when running in my IDE (Eclipse).
But when I am running my application through a JAR, I encountered the following error :
ClassNotfoundException
I don't understand why an exception is thrown whereas I defined correctly my classpath.
Could you help me ?

When running from an executable jar the normal class path is ignore in favour of thejar and any Class-Path specified in the jar's manifest.
What you want is a URLClassLoader. Bascially:
URLClassLoader cl = new URLClassLoader(new URL[]{classPath.toURL()});
Class clazz = cl.loadClass(fullName);(Catch assorted exceptions)
There should not be a class of the given name in the jar, or libraries it references (if there is, that will be loaded in preference).

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Problem loading modified classes from CLASSPATH using system class loader

Hi,
I am facing problem to load the modified classes from CLASSPATH.
I have set my CLASSPATH to a directory whose classes will be modified frequently. After the server(web/app) is started, the system class loader, using which am trying to load the classes from the directory where the CLASSPATH is set, am not able to load the modified files without the server restart.
Do I need to have a custom class loader to fix this.
Please help me.
Thanks,
Sureddy

Do I need to have a custom class loader to fix this.Yes.

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Hi,
I am deploying an .ear file, which has one .war file in it. The war file, has
infobus.jar, inside it under \WEB-INF\lib. Whenever in my servlet code I try to
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But if I put the infobus.jar on system classpath , everything works out fine.
Can somebody tell me, what is going on

Gseel is right: you try to instantiate an EJB with the BDK.
Enterprise Java Beans are totally different from graphical/GUI beans. EJBs are thought for dealing with business logic like accessing a database, ldap directory and so on. They run on a application server (simply speaking - a java enabled webserver) and do some processing to handle user requests. Enterprise Java Beans usually don't interact directly with the user, they only do the work in the background and forward their results, which are then rendered for the user. Typically they are employed for handling web requests (a user with a browser), but they can also be used for awt/swing applications. Though - let me repeat - they don't appear visually on the screen.
The only similarities between those two bean types are the following: they have getter/setter methods for their properties, they implement Serializeable (or a sub-interface like Externalizable, Remote) and they have a default no-argument constructor.
If you want to run your been you need an application server (your bean is pre-packaged for the Bea Weblogic app-server). If you want to do something graphical, you'll need to search for GUI beans.
dani3l

Problem in loading a class from server

hello,
Please help me ,i m using this code to load a class from server and this code load this successfully but i don't how to make object of class that is just loaded.
i want to load the class and use its method in my program please help me i m in very critical position.
pelase help me give me hint
import java.sql.*;
import java.net.*;
import java.io.*;
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String str = "FinalMyConnection";
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also load all required parser and sax classes into oracle,i.e.,
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Loading a class not on classpath

how can we load a class not on classpath?

uddinr0121 wrote:
try this
private void addArchive(File jarFile) throws IOException {
URL u = jarFile.toURI().toURL();
URLClassLoader sysloader = (URLClassLoader) ClassLoader.getSystemClassLoader();
Class<?> sysclass = URLClassLoader.class;
try {
Method method = sysclass.getDeclaredMethod("addURL", parameters);
method.setAccessible(true);
method.invoke(sysloader, new Object[]{u});
} catch (Throwable t) {
t.printStackTrace();
}this will add the jar file to the classpath after which you should be able to invoke using Class.forName()
hope this helpsThat's a horrible solution, when you can just create a new URLClassLoader and use that to load the class.
Adding it to the system classpath with reflection trickery is not really a clean solution to that.

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hi all!
Does anyone know how to load java class from jsp page?
I try to load java class from jsp page.
Is it possible to load java class fom jsp page?
thanks and have a good day!

What I mean is How to load/open java class file from jsp page?
I think we can open Applet from jsp page by using
<applet code=helloApplet.class width=100 height=100>
</applet>
but, how to open java class which is an application made by Frame?
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I have a class object for my .class file. It thougth it would be loaded to the classpath dynamcially by resolveClass(Class c), but still i am not able to add my class to the VM's classpath.
Can anybody help,
Thanks in advance
Amir

how do you get that Class object?
If you use Class.forName(java.lang.String), the class loads itself, if found in classpath.
If the class is dynamicaly generated, and you have the the file, or the bytes that form the class, you may invoke
ClassLoader.defineClass(String name, byte[] b, int off, int len)
I have no idea if my answer is anywhere near what you expect...

Is there a restriction on loading "javax" classes from WEB-INF/lib?

I'm having trouble with a webapp in WL 10MP1 that is having trouble loading classes from the "jsr311-api-1.0.jar" in my WEB-INF/lib. Even though I have no trouble with it in Eclipse (no compile errors), classes from that jar fail with "NoClassDefFound" exceptions. I have a feeling it might be the fact that the packages in that jar start with "javax". Assuming that's the case, is there anything I can do to fix this?
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Note that I've tried two other strategies that both result in the same failed state.
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Similarly, I tried copying the jars into $DOMAIN_HOME/lib, and that fails to find "org.apache.commons.logging.LogFactory". I could continue down this path, but it doesn't seem likely to succeed. Eventually, I'll get to a point where it just can't find the classes specific to my application, which I certainly can't copy into $DOMAIN_HOME/lib.
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How to load a class from its name.

Hi,
In my program, I want users can write their own classes, these classes need to implement an interface and name of class will be stored in database. I use Class.forName() to load these classes but I cannot type-cast to interface. Please help me.
Here is the code in my program:
public interface A {
public void doSomething();
public class test {
public static void main(String[] args) {
A clazz = (A)Class.forName("MyClass"); // error here
A.doSomething();
}

Hai,
Refine your test class as follows:
public class test
public static void main(String arg[])
try
Class clazz = Class.forName("MyClass");
Object obj = clazz.newInstance();
((MyClass)obj).doSomething();
catch(Exception ex)
System.out.println(ex);
Regards
Raja.

How to load a class from a jar not in the classpath

I have a gazillion jars of class files that I want to access dynamically in an application. I don't want to list every jar. The jars also contain images. With images you can explicitly point to the jar with and load the image with createImage....
"jar:file:/C:/myjarlocation/myjar.jar!/pathtoimage/image.gif"
Is there a similar string you can use when creating classes on the fly in a classloader with getClass().forName("classname") ??

Hm, if you are not in an EJB container or some other environment that won't let you create a classloader, you might create a new URLClassLoader with a path pointing to those JARs. You will probably want to use your normal application class loader as the parent loader, so any referenced common class definitions are found during the load.
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URL u = new URL(this.getCodeBase(), "../something.jpg");
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System.out.println(this.getCodeBase().toString());

Unable to load Java classes from byte arrays.

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Hi. I am new to Java. I am trying to load a java object from a subdirectory. Is that possible? Thanks in advance!

Thanks for the quick reply!
I tried this:
set CLASSPATH =
Data;Application;Entertainment;MiniGames;
but it doesn't seem to work...
The actual subdirectory is
\Data\Application\Entertainment\MiniGames
I am new to Java, so please bear with me with my
stupidity... please advice again.
Thanks in advanceClasspath needs to contain the actual directory paths, not a relative path. So it should be something like .;c:\Data\Application\Entertainment\MiniGames

Load a class from strea

Hi i have a strange problem:i save a class object in a database blob then i want to read the object and set them in to the class path.Is possible?

i save a class object in a database blob then i want to read the object Do you save a Class or an instance of that Class?
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Loading all classes on classpath

Hello!
I'm trying to create some kind of "Package browser" which I can use for selecting a class that exists on the classpath.
I've come up with a solution that reads the classpath property and then looks up the classes by searching each directory and jar-file for class files. These are presented in a JTree. This solution has a drawback though. When using Visual Age for Java, my app won't find any class files on the classpath as these are not added to the local file system. It seems Visual Age has it's own ClassLoader which loads classes from it's own repository rather than from the file system.
Now I wonder, is there another way to load all classes from the classpath?
Regards,
Pelle Poluha

Visual Age uses the "system" classpath alright. When I add another directory to the classpath using VA, my "package browser" recognizes this but shows an empty directory. And it is empty on my local file system. What I can do is to export all the classes I need to a directory or jar-file and then add this to the classpath. Then my app recognizes the classes. But this is too cumbersome.
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Regards,
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Loading a class from specified classpath

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