Is it possible to load classes from a jar file

Using ClassLoader is it possible to load the classes from a jar file?

URL[] u = new URL[1] ;
u[0] = new URL( "file://" + jarLocation + jarFileName + "/" );
URLClassLoader jLoader = new URLClassLoader( u );
Object clsName = jLoader.loadClass( clsList.elementAt(i).toString() ).newInstance();
I get this error message.
java.lang.ClassNotFoundException: ExceptionTestCase
at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
at java.lang.ClassLoader.loadClass(ClassLoader.java:297)
at java.lang.ClassLoader.loadClass(ClassLoader.java:253)
// "file://" + fileLocation + fileName + "/" This works fine from a browser.
Is there anything I am missing? Thanks for the reply.

Similar Messages

Loading classes from another jar file

I've set up my jnpl file so that it references a core jar file (contains main() function). The jnlp also references another jar file (app.jar) which contains class files that I load and instantiate dynamically (using ClassLoader). The core.jar file contains a manifest that includes a reference to app.jar.
The app works fine when I use "java -jar core.jar" from the command line.
However, when I wrap the jars using jnlp, I always get a null pointer exception because it cannot find any class that is in the app.jar file. I've tried different strategies, such as trying to load a class file that sits on the server (in a jar file and not in a jar file), but that also fails if I use jnlp (However, it works if I use "java -jar core.jar")
Any ideas what is going on?

This is the "OckCore.jar" manifest before signing:
Manifest-Version: 1.0
Main-Class: com.Ock.OckCore.OckApp
Class-Path: . OckMaths.jar
Created-By: 1.4.0-beta3 (Sun Microsystems Inc.)
Name: com.Ock.OckCore.OckApp.class
Java-Bean: FalseThis is the manifest after signing:
Manifest-Version: 1.0
Main-Class: com.Ock.OckCore.OckApp
Created-By: 1.4.0-beta3 (Sun Microsystems Inc.)
Class-Path: http://hazel/Ock/. http://hazel/Ock/OckMaths.jar
Name: com/Ock/OckCore/OckApp.class
SHA1-Digest: KRZmOryizx9o2L61nN+DbUYCgwo=I have removed a load of irrelevant stuff from the "after" manifest to keep it readable.
note that :-
The OckApp.class loads normally from webstart and tries to load a class from OckMaths.jar.
I can prove that OckApp.class does load because it creates a log file when it does.
The OckApp.class tries to load a class from the OckMaths.jar. This fails if webstart is used but works if OckCore is launched using "java -jar OckCore.jar".
The jars do exist at the location specified by the manifest.
The application launches normally if I use "java -Jar OckCore.jar"
Here is the jnlp file
<?xml version='1.0' encoding='UTF-8'?>
<jnlp
     spec="1.0"
     codebase="http://hazel/Ock"
     href="OckMaths.jnlp">
     <information>
          <title>Ock Maths Demo</title>
          <vendor>Rodentware Inc</vendor>
          <description>Demo of a ported app running as a Java Webstart application</description>
          <description kind="short">An app running as a Java Webstart application"></description>
          <offline-allowed/>
     </information>
     <security>
          <all-permissions/>
     </security>
     <resources>
          <j2se version="1.3"/>
          <jar href="OckCore.jar"/>
          <jar href="OckMaths.jar"/>
     </resources>
     <application-desc main-class="com.Ock.OckCore.OckApp">
</jnlp> I have also signed the jars outside of a webdirectory. I get the following manifest file:
Manifest-Version: 1.0
Main-Class: com.Ock.OckCore.OckApp
Created-By: 1.4.0-beta3 (Sun Microsystems Inc.)
Class-Path: . OckMaths.jar
Name: com/Ock/OckCore/OckApp.class
SHA1-Digest: KRZmOryizx9o2L61nN+DbUYCgwo=
note that :-
The jars do exist at the location specified by the manifest.
The application launches normally if I use "java -Jar OckCore.jar".
The application doesn't launch from webstart.
I've found that cache, but the jar files have been renamed.
OckCore.jar is anOckCore.jar, etc... so I'm not sure if trying to write a cmdline will work anyway.

Issues with Loading Images from a Jar File

This code snippet basically loops through a jar of gifs and loads them into a hashmap to be used later. The images all load into the HashMap just fine, I tested and made sure their widths and heights were changing as well as the buffer size from gif to gif. The problem comes in when some of the images are loaded to be painted they are incomplete it looks as though part of the image came through but not all of it, while other images look just fine. The old way in which we loaded the graphics didn't involve getting them from a jar file. My question is, is this a common problem with loading images from a jar from an applet? For a while I had tried to approach the problem by getting the URL of the image in a jar and passing that into the toolkit and creating the image that way, I was unsuccessful in getting that to work.
//app is the Japplet
MediaTracker tracker = new MediaTracker(app);
//jf represents the jar file obj, enum for looping through jar entries
Enumeration e = jf.entries();
Toolkit toolkit = Toolkit.getDefaultToolkit();
//buffer for reading image stream
byte buffer [];
while(e.hasMoreElements())
fileName = e.nextElement().toString();
InputStream inputstream = jf.getInputStream(jf.getEntry(fileName));
buffer = new byte[inputstream.available()];
inputstream.read(buffer);
currentIm = toolkit.createImage(buffer);
tracker.addImage(currentIm, 0);
tracker.waitForAll();
images.put(fileName.substring(0, fileName.indexOf(".")), currentIm);
} //while
}//try
catch(Exception e)
e.printStackTrace();
}

compressed files are not the problem. It is just the problem of the read not returning all the bytes. Here is a working implementation:
InputStream is = jar.getInputStream(entry);
ByteArrayOutputStream os = new ByteArrayOutputStream(1024);
try{
byte[] buf = new byte[1024];
int read;
while((read = is.read(buf)) > 0) {
os.write(buf, 0, read);
catch(Exception e){
e.printStackTrace();
return null;
image = Toolkit.getDefaultToolkit().createImage(os.toByteArray());
This works but I think you end up opening the jar a second time and downloading it from the server again. Another way of getting the images is using the class loader:
InputStream is = MyApplet.class.getResourceAsStream(strImageName);
In this case, the image file needs to be at the same level than MyApplet.class but you don't get the benefit of enumerating of the images available in the jar.

How to combine the classes from 2 jar files into 1?

Hi there
I have got 2 jar files with the same name but the classes that they contain are different. So, I want to combine those 2 files into 1. Could anyone please tell me how to add the classes in a jar file to another jar file?
Thanks for your help!
From
Edmund

The jar utility allows you to extract files as well as put them into a jar. This is in the java docs.
You might have to hand modify the manifest file if it was hand modified in the first place. All you should have to do is copy the text from one file to another. The manifest will have the same name so you will have to extract to different dirs so it isn't overwritten.
Steps:
-Create dir1 and dir2
-Extract jar1 into dir1, Extract jar2 into dir2.
-Manually examine manifests and combine if needed.
-Copy files from one dir to another.
-Use jar tool to create new jar.

Loading images from a jar file

Hi,
My application displays images, until it's placed in a JAR file, then it can't display them even though the JAR file contains the images.
I saw this problem in a previous question which was solved using
URL url = MyClass.class.getResource("abc.gif");
Image img=Toolkit.getDefaultToolkit().getImage(url);
....which btw didn't work for me either......
This method should be made obsolete using ImageIcon, which I am using, but the images still won't appear...
Any suggestions?

It works fine that way (...getClass().getResource....) until I create the jar file, and then I get a null pointer exception when it tries to load the image.
When I use
javax.swing.ImageIcon icon = new javax.swing.ImageIcon(("/images/imageName.jpg"));
the application works but without the images.......

How To Load Sound From Inside jar File?

Hello There
i've made a jar file that contains Images&Pictures But I Can't Use Them
So I Used For Loading Images
URL url = this.getClass().getResource("image.jpg");
         setIconImage(new ImageIcon(url).getImage());and for loading sound when i use
URL url = this.getClass().getResource("Bond2.wav");
       AudioInputStream stream = AudioSystem.getAudioInputStream(new File(url));there's an error That The file Constructor doesn't take url
how can i fix it?

First_knight wrote:
and for loading sound when i use
URL url = this.getClass().getResource("Bond2.wav");
AudioInputStream stream = AudioSystem.getAudioInputStream(new File(url));there's an error That The file Constructor doesn't take url
how can i fix it?Remove the "new File()". There is a getAudioInputStream() method that takes a URL.
AudioInputStream in = AudioSystem.getAudioInputStream(url);

Is it possible to call a class in a jar file from JNI environment?

Hi
Is it possible to call a class in a jar file from JNI environment?
Thanks in advance.

Could you explain a bit more what you are trying to do? (In other words, your question is vague.)
o If your main program is written in C, you can use JNI to start a JVM, load classes from the jar of your choice, and call constructors and methods of the objects defined in the jar.
o If your main program is java, and has been laoded from a jar, a JNI routine can call back into java to use the constructors and methods of classes defined in the jar(s).

Can't load any classes from infobus.jar (WL 6.0 SP1)

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
load a class from infobus.jar, I get the following exception :
About to load class javax.infobus.InfoBusDataConsumer<<<<<<<<<<java.lang.ClassNotFoundException: InfoBusDataConsumer
at weblogic.utils.classloaders.GenericClassLoader.findClass(GenericClassLoader.java:178)
at weblogic.utils.classloaders.ChangeAwareClassLoader.findClass(ChangeAwareClassLoader.java:45)
at java.lang.ClassLoader.loadClass(ClassLoader.java:297)
at java.lang.ClassLoader.loadClass(ClassLoader.java:253)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:313)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:120)
at XDILoginForm.init(XDILoginForm.java:99)
at weblogic.servlet.internal.ServletStubImpl.createServlet(ServletStubImpl.java:638)
at weblogic.servlet.internal.ServletStubImpl.createInstances(ServletStubImpl.java:581)
at weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.java:526)
at weblogic.servlet.internal.WebAppServletContext.preloadServlet(WebAppServletContext.java:1078)
at weblogic.servlet.internal.WebAppServletContext.preloadServlets(WebAppServletContext.java:1022)
at weblogic.servlet.internal.HttpServer.loadWARContext(HttpServer.java:499)
at weblogic.servlet.internal.HttpServer.loadWebApp(HttpServer.java:421)
at weblogic.j2ee.WebAppComponent.deploy(WebAppComponent.java:74)
at weblogic.j2ee.Application.deploy(Application.java:175)
at weblogic.j2ee.J2EEService.deployApplication(J2EEService.java:173)
at weblogic.management.mbeans.custom.Application.setLocalDeployed(Application.java:217)
at weblogic.management.mbeans.custom.Application.setDeployed(Application.java:187)
at java.lang.reflect.Method.invoke(Native Method)
at weblogic.management.internal.DynamicMBeanImpl.invokeSetter(DynamicMBeanImpl.java:1136)
at weblogic.management.internal.DynamicMBeanImpl.setAttribute(DynamicMBeanImpl.java:773)
at weblogic.management.internal.DynamicMBeanImpl.setAttribute(DynamicMBeanImpl.java:750)
at weblogic.management.internal.ConfigurationMBeanImpl.setAttribute(ConfigurationMBeanImpl.java:256)
at com.sun.management.jmx.MBeanServerImpl.setAttribute(MBeanServerImpl.java:1356)
at com.sun.management.jmx.MBeanServerImpl.setAttribute(MBeanServerImpl.java:1331)
at weblogic.management.internal.ConfigurationMBeanImpl.updateConfigMBeans(ConfigurationMBeanImpl.java:318)
at weblogic.management.internal.ConfigurationMBeanImpl.setAttribute(ConfigurationMBeanImpl.java:259)
at com.sun.management.jmx.MBeanServerImpl.setAttribute(MBeanServerImpl.java:1356)
at com.sun.management.jmx.MBeanServerImpl.setAttribute(MBeanServerImpl.java:1331)
at weblogic.management.internal.MBeanProxy.setAttribute(MBeanProxy.java:291)
at weblogic.management.internal.MBeanProxy.invoke(MBeanProxy.java:173)
at $Proxy7.setDeployed(Unknown Source)
at weblogic.management.console.pages._panels._mbean._application._jspService(_application.java:303)
at weblogic.servlet.jsp.JspBase.service(JspBase.java:27)
at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:213)
at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:1265)
at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:1622)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:137)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:120)
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

BPC 7.5 : Is it possible to load data from ECC to BPC

Hi,
Is it possible to load data from ECC to BPC in BPC 7.5 Netweaver version.
Thanks
Prasad Bobburu

Option 1 -
ECC -> BW -> BPC NW (Standard, or recommended for NW)
Option 2
ECC -> BW -> Openhub / Flat file -> BPC MS
This is more common for SAP customers, who are using BW, but running MS version
Option 3
ECC -> ABAP Extractor Program (generated flat file) -> BPC
Again a more common for SAP customers using BPC MS
-Kiran Malineni

Is it possible to load data from attribute of I.O. to text of the same I.O.

Hi guys,
is it possible to load data from attribute of InfoObject to text of the same InfoObject.
I have this requierement: the text (description long) of InfoObject should be filled defends on the content of one attribute of this InfoObject.
Is it possible via Update Rule? (we are using BW3.5)
And how?
Thanks in adance!
Regards

HI,
1st) activate your object as data target and do the assignment in the transfer or update rules.
--- How can I active my InfoObject (Text if the InofoObject)as data target?
Right Click your info area and choose " Insert characteristics as a Datatarget" and give your info object Id.
2) create a generic datasource on the p-table of your object and assign that datasource as text datasource to your object.
--- How can I create a generic datasource on the p-table of your object ?
For Eg: your info object name is like this
ZIO_CID
For this P table will be like this
/BIC/PZIO_CID
In RSO2 tcode Generic datasources create datasource based on this table .
Hope it helps
Regards,
Arun.M.D

Loading Resources from a .JAR

I've read through this forum and searched java.sun.com and have found nothing to solve my problem, although I see many other people are having the same problem.
I wrote a small application that needs to load a text file and images. When I just compile everything and then run it, all is well, my text file is found and my images are displayed. Now the problem is when I package everything into a .JAR file, suddenly my magic stops. Here is the directory structure
- State.class
FiftyStatesGame.class
FlagPanel.class
StatsPanel.class
StatePanel.class
states.txt
/images
/flags
a bunch of .gif images (50 total)
/states
a bunch of .gif images (50 total)
I create my archive with the following command
jar cvf FiftyStates.jar *
and all seems well, I've even changed the extension to .zip to ensure that the images and text file is inside the jar
Now when I try to run the program using
java -cp FiftyStates.jar FiftyStatesGame
the program starts but I get a NullPointerException and my pictures don't load. :-(
I've read in the forum about using
URL imageURL = ClassLoader.getSystemResource(<path to image>);
Image logo = Toolkit.getDefaultToolkit().getImage(imageURL);
and I tried this and once again, it works when not in jar form, but as soon as the application is JARed, I encounter the same problems.
Can anyone give me the answer to this crazy problem?
and I guess I should go one step further and ask, if I want to give this program to a friend with the JRE installed on a windows machine, what command should I put in my batch file to run this program on his machine?
javaw -cp FiftyStates.jar FiftyStatesGame
Thanks for any help and advice

Hi,
Getting the image
=================
It seems to me you can't be too far away from resolving your problem.
I've never actually tried to get an image from a jar file, so I'm guessing that this may not work for you, but I have unzipped a zip file contained within an executable jar.
What I did was this:
    private ZipInputStream findInstallationFile() {
        ClassLoader classLoader;
        URL url;
        ZipInputStream zipInputStream = null;
        InputStream inputStream;
        classLoader = getClass().getClassLoader();
        url = classLoader.getResource(ZIP_RESOURCE_NAME);
        if (url != null) {
            try {
                inputStream = url.openStream();
                zipInputStream = new ZipInputStream(inputStream);
            } catch (IOException ioe) {
                ioe.printStackTrace();
        } else {
            System.err.println("Failed to find resource: " + ZIP_RESOURCE_NAME);
        return zipInputStream;
    }The good thing about this is that you can see whether or not the resource was found in the jar file. If the returned URL is null, then the resource isn't there.
Once you have the InputStream, you can just read the entire contents and do what you like with them.
Executable jars
===============
You can make it easier to run a jar file by including a manifest file. This is just a text file which should be in the META-INF directory in your jar file. The manifest file itself should be called Manifest.mf.
The contents of the Manifest should be:
Manifest-Version: 1.0
Main-Class: FiftyStatesGame
This assumes that your main class is FiftyStatesGame which is in the default package (tut, tut!).
Hope this helps!
Rhys

How to load all the classes in a JAR file at runtime?

Any clues o:
"How can I force JVM to load all the classes in a specified JAR at once?"
Thanx!
-Rajeev

Well I was thinking may be there exists an option with "java", when I
am starting an application from a jar file, I could force it to load all
the classes in the JAR. I don't want to do it programically. Is there such
an option available?? Or in other words can I ask JVM to not do the dynamic
loading for the JAR??
Thanx.
List all JarEntries and convert the paths to fully
qualified class files
e.g file in jar
[1] /com/mycompany/proj/X.class
should become
[2] com.mycompany.proj.X
then for each entry issue
Class.forName( [2] );

Exception while loading properties from an xml file

Hi all,
I've got a problem while loading properties from an XML file:
java.lang.ClassCastException: org.apache.xerces.dom.DeferredCommentImpl cannot be cast to org.w3c.dom.Element
ERROR - Cannot load properties from the specified file <./conf/login.prop> java.lang.ClassCastException: org.apache.xerces.dom.DeferredCommentImpl cannot be cast to org.w3c.dom.Element
     at java.util.XMLUtils.importProperties(XMLUtils.java:97)
     at java.util.XMLUtils.load(XMLUtils.java:69)
     at java.util.Properties.loadFromXML(Properties.java:852)
     at g2.utility.HRPMProperties.<init>(HRPMProperties.java:78)
     at g2.utility.HRPMProperties.getInstance(HRPMProperties.java:94)
     at g2.gui.workers.ApplicationSwingWorker.<init>(ApplicationSwingWorker.java:36)
     at g2.main.Main.main(Main.java:37)but this code worked before, and I've got the xerces and xercesImpl packages in the classpath, anyone can give me an hint on how to fix the problem?

Here there's the code that instantiates the HRPMProperties object loading the property file:
public class HRPMProperties extends Properties {
     * A reference to myself.
    protected static HRPMProperties mySelf = null;
     * The property file to which load the configuration.
    protected static String propertyFile = "./conf/login.prop";
      * A set of static strings used as keys in the properties file.
     public final static String DATABASE_URL = "database_url";
     public final static String DATABASE_USERNAME = "database_username";
     public final static String DATABASE_PASSWORD = "database_password";
     public final static String REAL_USERNAME = "real_username";
     public final static String REAL_PASSWORD = "real_password";
     public final static String PHANTOM_LOGIN = "login_thru_phantom_user";
     public final static String AUTOCONNECT = "autoconnect";
     public final static String TRANSLATION_FILE = "translation_file";
     * Builds up an empty properties map.
    protected HRPMProperties(){
     super();
     this.reload();
     * Builds up the property map from the specified input file. <B> The file must be in XML format</B>.
     * In case of exception and/or problems reading from the specified file, an empty property map is returned.
     * @param fileName the path and the name of the file with the XML representation of the properties.
    protected HRPMProperties(String fileName){
     super();
     try{
         this.loadFromXML(new FileInputStream(fileName));
     }catch(Exception e){
         Logger.error("Cannot load properties from the specified file <"+fileName+"> " + e);
         e.printStackTrace();
     * Provides an instance of the property class loaded from the default configuration file.
     * @return the property instance
    public static final HRPMProperties getInstance(){
     if( HRPMProperties.mySelf != null )
         return HRPMProperties.mySelf;
     else{
         HRPMProperties.mySelf = new HRPMProperties(HRPMProperties.propertyFile);
         return HRPMProperties.mySelf;
}The constructor is the one triggering the exception, so there's a problem loading the XML property file.

Loading data from a JavaScript file

I am writing a Java application that will run client-side, and will essentially allow the user to download, update, and then reupload a JavaScript file. The data I'm needing to parse / build to the JS file consists of staticlly-defined string arrays, and one associative array.
The file looks like this.
var array1 = new Array();
array1[0] = "String1";
array1[1] = "String 2";
array1[2] = "String 3";I'm wondering if there is a more simple/eleoquent way of loading arrays from a JavaScript file than simply reading them and writing parse code by hand to extract the data I want... I can write the parsing code without any problem, but, I'm wondering if there's something built-in that I just don't know about...
Thanks

You can use the ScriptEngine provided in Java 6. Takes a little hacking, but here's how you'd do it:
a simple javascript file:
//test.js
var myArray = [];
myArray[0] = 'Something';
myArray[1] = 'To';
myArray[2] = 'look';
myArray[3] = 'at';
//ScriptTest.java
import javax.script.*;
import sun.org.mozilla.javascript.internal.NativeArray;
import java.io.FileReader;
class ScriptTest {
public static void main(String[] argv) throws Exception {
    ScriptEngine js = new ScriptEngineManager().getEngineByName("javascript");
    FileReader script = new FileReader("test.js");
    js.eval(script);
    NativeArray array = (NativeArray)js.get("myArray");
    for(int i = 0; i < array.getLength(); i++)
      System.out.printf("Object: %s\n", array.get(i, array));
}Now, since NativeArray is an internal class, you'll need to add rt.jar to your bootclasspath:
javac -bootclasspath JAVA_HOME/lib/rt.jar ScriptTest.javaSee. Told you it was a hack. :-)

How to load data from a flat file which is there in the application server

HI All,
how to load data from a flat file which is there in the application server..

Hi,
Firstly you will need to place the file(s) in the AL11 path. Then in your infopackage in "Extraction" tab you need to select "Application Server" option. Then you need to specify the path as well as the exact file you want to load by using the browsing button.
If your file name keeps changing on a daily basis i.e. name_ddmmyyyy.csv, then in the Extraction tab you have the option to write an ABAP routine that generates the file name. Here you will need to append sy-datum to "name" and then append ".csv" to generate complete filename.
Please let me know if this is helpful or if you need any more inputs.
Thanks & Regards,
Nishant Tatkar.

Is it possible to load classes from a jar file

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