Develop Reference

Deploying images used in Java Application with the built jar file

After using images for example on a Button, when I build the application creating the .jar file and execute only the file, the images are not there but would only show if I copy the images folder in the same directory as the jar file. Why is that and how can I resolve this if possible?
I am currently using the following code to set the icon/image:
JButton btn = new JButton("Text", "img/icon.png");

The fact that you can use the images when they are stored outside the jar, suggests that you are doing something of the kind:
File image = new File("directory/image.jpg");
InputStream is = new FileInputStream(image);
This reads a file from a directory on the file system, not from the classpath. Now, if you have packaged your image in a "directory" inside your Jar, you must load the image from the classpath.
InputStream is = getClass().getResourceAsStream("/directory/image.jpg");
(note the slash in the path)
Or
InputStream is = getClass().getClassLoader().getResourceAsStream("directory/image.jpg");
(note the absence of the slash in the path)
Your example, as it is now, should not compile. (The second argument of your JButton construtor is an Icon, not a String, java 8). So when you were getting the image from the file system, you were probably doing something else.
With your example, you need to read an image from the inputstream and convert it to an Icon:
try (InputStream is = getClass.getClassLoader().getResourcesAsStream("directory/image.jpg")) {
BufferedImage image = ImageIO.read(is);
return new JButton("Text", new ImageIcon(image));
} catch (IOException exc) {
throw new RuntimeException(exc);
}
That should use the image that is located in "directory" inside your jar. Of course, you need to include the image within your jar, or you will get a NullPointerException on the inputstream is.

I think you need to understand the
ClassLoader:
A typical strategy is to transform the name into a file name and then
read a "class file" of that name from a file system.
So with this you will be able to lead Resources of your project with getResource
public URL getResource(String name)
Finds the resource with the given name. A resource is some data
(images, audio, text, etc) that can be accessed by class code in a way
that is independent of the location of the code.

java.lang.NullPointerException when using getClass().getResource() to load an image [duplicate]

I am trying to load an image to use as an icon in my application. The appropriate method according to this tutorial is:
protected ImageIcon createImageIcon(String path, String description)
{
java.net.URL imgURL = getClass().getResource(path);
if (imgURL != null) {
return new ImageIcon(imgURL, description);
} else {
System.err.println("Couldn't find file: " + path);
return null;
}
}
So, I placed the location of the file, and passed it as a parameter to this function. This didn't work, i.e. imgURL was null. When I tried creating the ImageIcon by passing in the path explicitly:
ImageIcon icon = new ImageIcon(path,"My Icon Image");
It worked great! So the application can pick up the image from an explicitly defined path, but didn't pick up the image using getResources(). In both cases, the value of the path variable is the same. Why wouldn't it work? How are resources found by the class loader?
Thanks.

getClass().getResource(path) loads resources from the classpath, not from a filesystem path.

You can request a path in this format:
/package/path/to/the/resource.ext
Even the bytes for creating the classes in memory are found this way:
my.Class -> /my/Class.class
and getResource will give you a URL which can be used to retrieve an InputStream.
But... I'd recommend using directly getClass().getResourceAsStream(...) with the same argument, because it returns directly the InputStream and don't have to worry about creating a (probably complex) URL object that has to know how to create the InputStream.
In short: try using getResourceAsStream and some constructor of ImageIcon that uses an InputStream as an argument.
Classloaders
Be careful if your app has many classloaders. If you have a simple standalone application (no servers or complex things) you shouldn't worry. I don't think it's the case provided ImageIcon was capable of finding it.
Edit: classpath
getResource is—as mattb says—for loading resources from the classpath (from your .jar or classpath directory). If you are bundling an app it's nice to have altogether, so you could include the icon file inside the jar of your app and obtain it this way.

As a noobie I was confused by this until I realized that the so called "path" is the path relative to the MyClass.class file in the file system and not the MyClass.java file. My IDE copies the resources (like xx.jpg, xx.xml) to a directory local to the MyClass.class. For example, inside a pkg directory called "target/classes/pkg. The class-file location may be different for different IDE's and depending on how the build is structured for your application. You should first explore the file system and find the location of the MyClass.class file and the copied location of the associated resource you are seeking to extract. Then determine the path relative to the MyClass.class file and write that as a string value with "dots" and "slashes".
For example, here is how I make an app1.fxml file available to my javafx application where the relevant "MyClass.class" is implicitly "Main.class". The Main.java file is where this line of resource-calling code is contained. In my specific case the resources are copied to a location at the same level as the enclosing package folder. That is: /target/classes/pkg/Main.class and /target/classes/app1.fxml. So paraphrasing...the relative reference "../app1.fxml" is "start from Main.class, go up one directory level, now you can see the resource".
FXMLLoader loader = new FXMLLoader();
loader.setLocation(getClass().getResource("../app1.fxml"));
Note that in this relative-path string "../app1.fxml", the first two dots reference the directory enclosing Main.class and the single "." indicates a file extension to follow. After these details become second nature, you will forget why it was confusing.

getResource by example:
package szb.testGetResource;
public class TestGetResource {
private void testIt() {
System.out.println("test1: "+TestGetResource.class.getResource("test.css"));
System.out.println("test2: "+getClass().getResource("test.css"));
}
public static void main(String[] args) {
new TestGetResource().testIt();
}
}
output:
test1: file:/home/szb/projects/test/bin/szb/testGetResource/test.css
test2: file:/home/szb/projects/test/bin/szb/testGetResource/test.css

getResourceAsStream() look inside of your resource folder. So the fil shold be placed inside of the defined resource-folder
i.e if the file reside in /src/main/resources/properties --> then the path should be /properties/yourFilename.
getClass.getResourceAsStream(/properties/yourFilename)

Invalid file reference, where am i going wrong?

Whenever i try to draw an image with paintComponent and ImageIcon i get a NullPointerException from an unknown source, then pointing to my image getter and the thread start.
Image getter
ImageIcon image = new ImageIcon(this.getClass().getResource("C:/Users/Rhys/Desktop/workspace/Mindcracker RPG/Res/Background.jpg"));
Thanks for any answers

Use the JavaDoc:
this.getClass().getResource() only for acquiring resources on the ClassPath where / represents the default package.
You are supplying a fully qualified path which won't work.
What you need to do is use this constructor:
public ImageIcon(String filename)
Creates an ImageIcon from the specified file.
The specified String can be a file name or a file path. When
specifying a path, use the Internet-standard forward-slash ("/") as a
separator. (The string is converted to an URL, so the forward-slash
works on all systems.)
For example, specify:
new ImageIcon("C:/Users/Rhys/Desktop/workspace/Mindcracker RPG/Res/Background.jpg");
note that there is a space in the path there and this path eventually gets converted into a file::// URL so you might want to take that into consideration

Load Java Image inside package from a class in a different package

I have a Java project called MyProject. I have a few different packages (keeping names simple for the purpose of this question), as follows:
src/PackageA
src/PackageA/PackageAa
src/PackageA/PackageAa/PackageAaa
src/PackageB
src/PackageB/PackageBa
src/PackageB/PackageBa/PackageBaa
I have a class
src/PackageA/PackageAa/PackageAaa/MyJavaFile.java
And I have an image
src/PackageB/PackageBa/PackageBaa/MyImage.png
Inside of MyJavaFile.java, I would like to declare an Image oject of MyImage.png
Image img = new Image(....what goes here?...)
How can I do this?

You could either call Class.getResource and specify a path starting with /, or ClassLoader.getResource and not bother with the /:
URL resource = MyJavaFile.class
.getResource("/PackageB/PackageBa/PackageBaa/MyImage.png");
or:
URL resource = MyJavaFile.class.getClassLoader()
.getResource("PackageB/PackageBa/PackageBaa/MyImage.png");
Basically Class.getResource will allow you to specify a resource relative to the class, but I don't think it allows you to use ".." etc for directory navigation.
Of course, if you know of a class in the right package, you can just use:
URL resource = SomeClassInPackageBaa.class.getResource("MyImage.png");
(I'm assuming you can pass a URL to the Image constructor in question. There's also getResourceAsStream on both Class and ClassLoader.)

you can use relative path since the the relative path is project folder.
ImageIcon img = new ImageIcon("src/PackageB/PackageBa/PackageBaa/MyImage.png");

/folderB/folderBa/folderBaa/MyImage.png
The image can stored into a project folder location .eg: /images/MyImage.png
Then try:
Image img = new Image(/images/MyImage.png);
Using a file path is not possible when running a program that's in a jar file, especially if the program is being loaded as an applet or WebStart application then you can use ClassLoader to get image.
use the following code to load the images:
ClassLoader cldr = this.getClass().getClassLoader();
java.net.URL imageURL = cldr.getResource("/PackageB/PackageBa/PackageBaa/MyImage.png");
ImageIcon aceOfDiamonds = new ImageIcon(imageURL);

This IS the best way to handle all images and icons in a JAR App.
Once you've zipped up all of your images and icons into its own JAR file - Configure your build path by adding the images JAR file into your libraries tab so that its now included in your classpath.
Then simply use the following 3x lines of code at the start of your constuctor to access any image you need for anything including a SystemTray image which doesn't accept the simple ImageIcon's as its main icon (weird I know). The 3x lines are:
URL iconUrl = this.getClass().getResource("/image-iconb.png");
Toolkit tk = this.getToolkit();
imageIcon = tk.getImage(iconUrl);
(imageIcon is just a constructor declared Image variable)
Now you can set a window icon as simply as:
setIconImage(imageIcon );
and at the same time use the same variable when setting the System TrayIcon by declaring:
trayIcon = new TrayIcon(imageIcon, "SystemTray Demo", popupMenu);
The above allows you to declare Images or ImageIcons easily and centrally without running the risk of not keeping image resources in the right place. It keeps it nice and tidy, with the JAR containing all your images automatically compiled at run time and distribution of your program.
As a bonus, once the JAR is registered in your classpath - you can keep adding any other images into the same JAR at any time without any fuss too - Everything just works and the added images are instantly available to your app.
Much better in my view.

Use the getResource method to read resources inside the src root. For example, the following code retrieves images from a folder src/images.
// Get current classloader
ClassLoader cl = this.getClass().getClassLoader();
// Create icons
Icon saveIcon = new ImageIcon(cl.getResource("images/save.gif"));
Icon cutIcon = new ImageIcon(cl.getResource("images/cut.gif"));
The example assumes that the following entries exist in the application's JAR file:
images/save.gif
images/cut.gif

Image img = new Image("./src/PackageB/PackageBa/PackageBaa/MyImage.png");
This shall go the path of the image is first inside src (source) then package so the program would access the image this way.

Create a java file inside a package

Currently, my plugin creates a java file in my project(IProject). But I want that java file within a specified Package. How to do it.
IFile sampleFile = parentFolder.getFile("Sample.java");
if(!sampleFile.exists()) FileInputStream fileStream = new FileInputStream("C:\Users\Uma\Desktop\treasureHunt\Application.java"); sampleFile.create(fileStream, false, null);
This is my current piece of code.
How can I create the sampleFile within a package. For example: in package com.mdh.se as com.mdh.se.Sample.java

If you have a "package" (e.g. "com.mdh.se") then you'll have a corresponding subdirectory (for example, "c:\users\uma\desktop\treasurehunt\com\mdh\se"). Simply write your file there.

I think, that the only thing you need to do is to create folders representing your package structure. So your path should look like C:\Users\Uma\Desktop\treasureHunt\com\mdh\se\Sample.java for your example.

You can get a special file inside the package by calling
java.net.URL imgURL = ResourceManager.class.getResource( "ResourceManager.class" );
From these URL you can extract the directory, the file is placed.
A new file you can create with
new File(directory,filename);