Loading Images

I'm struggling and need a little help please. My application which I'm running from the Eclipe IDE loads images for icons for buttons using code like this which works fine.

result = new ImageIcon(Common.image_path+filename);

However I ultimately want to package my application into a JAR file and I've tried to replace this code with many variants of this :-

ClassLoader cldr = this.getClass().getClassLoader();
java.net.URL imageURL = cldr.getResource("\\Java\\eclipse\\workspace\\b4images"+filename);
result = new ImageIcon(imageURL);

I'm not sure if this would work if the application would run as a .JAR file, but imageURL is always null when I run it as a regular java program.

Is there a way to code it so that it works in either mode. Also I'm unsure about how the path should look. The images are held in a subdirectory called "Images" which is a subdirectory off my main project workspace. However the classloaded is part of a class in a java package, does the path have to be relative to the workspace or the class or neither ?

Thanks

Dave

Assuming that your images are located in the 'b4images' sub-folder of your bin Eclipse project folder, you could do:

ClassLoader cldr = this.getClass().getClassLoader();
java.net.URL imageURL = cldr.getResource("/b4images/" + filename);
result = new ImageIcon(imageURL);

Then when it comes to packaging in a jar file, simply put all the images under a sub-folder named 'b4images'.

Remember, either it's under your bin Eclipse project folder, or within your jar file, you should have the same folder structure.

Regards

OK I think I see the problem. My images directory is not a subdirectory of the bin directory. I will have to reorganise my directory structure.

Many thanks

Dave

I hope I'm not beating a dead horse, but it's necessary to use URLs, not Files, to identify resources like images so that your program works whether it is zipped in a jar or not. Avoid constructor ImageIcon(String filename), since it assumes the parameter is a file system path. If the image is in the same folder as file X.class (whether that folder is in the file system or a "folder" in a jar file), the following will work:

URL url = X.class.getResource("sample.jpeg");
Icon icon = new ImageIcon(url);

But it's better to separate resources from code, so suppose we have the organization:

C:\blahblah\SampleProject\com\acme\widget\X.class
C:\blahblah\SampleProject\images\sample.jpeg

class X is in package com.acme.widget. When we zip this up in a jar, there should be paths within the jar:

/com/acme/widget/X.class
/images/sample.jar

In either case the code that works will be:

URL url = X.class.getResource("/images/sample.jpeg"); //note initial slash
Icon icon = new ImageIcon(url);

(You can always use forward slashes in URLs.) If you run this on unzipped code the URL expands to

file:/C:/blahblah/SampleProject/images/sample.jpeg

If you run this on the jar file mentioned, the URL might expand to

jar:file:/C:/elsewhere/app.jar!/images/sample.jpeg

So when the code is in a jar, "/images/sample.jpeg" denotes a "path" in the jar file and when the code isn't zipped, "/images/sample.jpeg" extends the folder that contains the start of the package hierarchy. That sounds more complicated than it really is. Once you've set things up (and I prefer using Ant), it's a snap.

OK this is my abbreviated directory structure which is all of my Eclipse Project workspace c:\java\eclipse\workspace\b4

C:.
+---audio
+---bin
| \---com
| \---commander4j
| +---app
| +---bar
| +---db
| +---sys
| +---util
| \---xtest
+---help
+---images
+---jars
| +---browserlauncher
| +---commons-collections-3.1
| +---commons-digester-1.7
| +---commons-logging-1.0.4
| +---dom4j-1.6.1
| +---itext-1.3
| +---jasperreports-1.0.3
| +---javahelp
| +---JBarcode
| +---logging-log4j-1.2.9
| +---mysql-connector-java-3.1.10
| +---oracle
| +---poi-bin-2.5.1-final-20040804
| \---swt-jasperviewer
+---logs
+---reports
+---src
| \---com
| \---commander4j
| +---app
| +---bar
| +---db
| +---sys
| +---util
| \---xtest
\---xml

The entry point for my application is com.commander4j.sys.Start

and the batch file that runs my application resides in the directory c:\java\eclipse\workspace\b4

%JAVA_HOME%\bin\javaw.exe -Dlog4j.configuration=file:xml\log4j.xml -classpath .\bin;.\jars\blah blah blah...... com.commander4j.sys.Start

So relative to the starting point I have currently referenced my gif files by using a path "./Images/mypic.gif"

Using your syntax then I should be using a url instead of a path and change it to "/Images/mypic.gif"

What is it that determines the root for the URL then ? If my batch file that started the app was it a different directory with a different default directory would with make a difference ?

Thanks muchly,

Dave