I'm trying to load an image that I have stored in my /src/main/resources folder. When I do, however, I keep running into a NullPointerException that stems from the resource not being found.
Here is the code snippet:
try {
String path = this.getClass().getClassLoader().getResource("bern.png").toString();
} catch (IOException ex) {
System.out.println(path);
}
Here is an image of my project file tree:
And here is an image of my target build file tree:
Here is the NullPointerException stacktrace:
https://pastebin.com/KqJVxWEL
I have tried using pretty well every possible path for the image file that I can think of. (/src/main/resources/bern.png, src/main/resources/bern.png, /bern.png, etc.).
I have also tried using getClass().getClassLoader().getResource() instead of getClass().getResource(). From what I understand, the only difference between the Class and ClassLoader version of getResource() is that the Class version is not inherently absolute relative to the root, whereas the ClassLoader version is.
When I run getClass().getResource("").toPath(), I get the path that leads to the classes directory. This aligns with what I've read about the getResource() method working with the target build file tree. However, I don't see the resources folder showing up anywhere in the target build; I think that's the core of my problem. I'm just not sure how to fix it.
I know this question has been asked numerous times before, but the answers to the other version of this question haven't helped me out much.
I'm using NetBeans 11, and this project is running on the Maven build system. I haven't done much work with Maven in the past, so forgive me if this problem is extremely easy to fix.
Anyone know how I'm approaching this wrong?
EDIT: The problem is not anything with my project structure or code as shown by the code compiling correctly when run using mvn via the command line. As a result, it's an issue with NetBeans specifically and the way that it is viewing the resources folder.
Read the resource contents as a Stream (instead of the URL or file path)
public static void main(String[] args) throws IOException {
InputStream in = Application.class.getClassLoader().getResourceAsStream("bern.png");
BufferedImage testImage = ImageIO.read(in);
ImageIcon icon = new ImageIcon(testImage);
}
Related
I am creating an eclipse workspace starting by a java project (not written by me).
I am facing problems with the following method:
public static URL getURL(String fileName) {
URLClassLoader urlLoader = (URLClassLoader) getInstance().getClass()
.getClassLoader();
URL fileLocation = urlLoader.findResource(fileName);
return fileLocation;
since the findResource doesn't find the JPG resource (filename = "icons/INIT.JPG").
Looking on urlLoader.getUrl, I noticed the class aims only to jar files. Adding the folder icon to the Project->Libraries under eclipse I managed to let findResources look into the icon folder: nevertheless, the image is not a jar file and so it isn't considered.
Honestly, I don't get the point of using this process to load an image, but I cannot change the code and I was hoping in a solution within Eclipse project setup.
Thanks in advance
Based on the answers to my questions in the original comment, there are some facts:
You cannot change the code, and it looks like it's retrieving the AppClassLoader.
Even if you cast it into URLClassLoader, it's still an instance of an AppClassLoader, so it will look for the contents of the classpath and all JAR/ZIP files in JAVA_HOME\lib\ext.
You said that the project is guaranteed to work without to move the file anywhere, so there's only one option: add the file that you want to retrieve with the ClassLoader to the classpath.
Right click on the project, select Build Path and choose Configure Build Path.
Click on Source > Add Folder... and add the folder where the resources that you want to take are.
PD: If you add the folder as Class Folder in the Libraries tab, the JPG image won't be recognised by the AppClassLoader.
I have spent all last night (until 3am) and this morning researching, testing, refactoring, and attempting to debug this issue. I have a simple Java game in Netbeans and while it runs perfectly perfect within the IDE in either run or debug mode, once exported into a jar file it refuses to load any resources corrrectly. There are many similar questions to this such as this one regarding loading an ImageIcon and despite great effort none of these solutions work for my project. I am not using ImageIcons, only simple BufferedImages and wav sound files. I recently refactored to combine my BufferedImageLoader and Sound classes into one Resource class, which I then moved into the same package as all my resources even though it worked perfectly well in a separate code package before in the IDE, although it works in its new location as well, strictly within the IDE.
I'm rather irritated and flustered from this issue. The truly infuriating thing is that this project used to work with resources after being exported into a jar, and now it seems to have stopped working with no changes. The only real programmatic difference between back when it worked and now is that I didn't have or use sound files back then, but this error isn't related to the sound files, as it catches an exception (and generates an error dialog) just from first trying to load the art assets.
I've tried every possible solution I've found in my research to no avail. Hopefully a fresh set of eyes can reveal the error of my ways.
The offending line of code is
return ImageIO.read(Resource.class.getResource("/res/" + imageFileName));
whereas imageFileName is the parameter with values passed from method calls such as
blockSheet = Resource.loadImage("art_assets/platform.png");
The location of the Resource class seemed to have no bearing on this working within Netbeans. My res folder is inside src, next to the com class package beginning.
It throws an IllegalArgumentException: input == null! exception. After some testing it seems that Resource.class.getResource("/res/" + imageFileName) returns a null value, which makes no sense at all. Again, this works perfectly perfect within the IDE. I can change the jar file into a zip and look inside to see that all the resources are exactly where they should be with the correct names and the correct extensions.
Here is a zip file of my entire project. Any help is immensely appreciated. Thank you.
EDIT:
Some of the things I've already tried:
getResourceAsStream() instead of getResource()
classLoader() between Resource.class and getResource()
this.getClass() instead of Resource.class from a non-static context
I think this should help:
How to get the path of a running JAR file?
CodeSource codeSource = YourMainClass.class.getProtectionDomain().getCodeSource();
File jarFile = new File(codeSource.getLocation().toURI().getPath());
String jarDir = jarFile.getParentFile().getPath();
provided by Benny Neugebauer in the post.
I am developing a Java application which displays a big amount of images. The problem is I can't figure out how to make Java find these images.
I have followed several tutorials and answers here at Stackoverflow, but I still haven't managed to find a solution that works regardless of OS (Linux or Windows) and running method (embedded on eclipse or exported jar file). This might be due to the fact that I am still a newbie, though.
I have created a class, which I call myIcon and through this class I mean to access all of these images. In the following code, I want to pass the string "resources/icon/image.gif" to the function getIconPath. The output should be a ImageIcon of this image, since this file exists. Despite that, if I pass to this function the path to an image that doesn't exist, null should be returned. In this case, my application will display a default image (a red x).
public class MyIcon {
// some other functions and properties
private static final ImageIcon getIconPath(String path) {
File f = new File(path);
if (f.exists()) {
return new ImageIcon(path, "");
} else {
return null;
}
}
}
The resources folder is a sibling to the src folder in my directory structure. That is, both resources and src are subfolders of the root directory.
When I run the code above, no image is ever found. The default image is thus always displayed and getIconPath returns null.
I am also aware of the getResource method of ClassLoader, but I still don't really understand how these things should be used.
While running in eclipse, you should print out f.getAbsolutePath(). It probably doesn't point to your file. More generally, you want to access the file as a resource. See:
https://docs.oracle.com/javase/tutorial/deployment/webstart/retrievingResources.html
There are two parts to this - making sure that when you build a jar, the images are part of it, and accessing a resource within the jar.
For the first part, I am guessing that whatever you're using to build a jar, it will put your images into the META-INF folder, which should work without too much issue (if its not there, or in with the Java class/source in the generated jar, that might cause the lookup to fail)
There is another Stack Overflow Post for the second part. The key is to make sure the images you want to load are on the classpath.
Hope this helps!
If resources is in classpath, you can find for the image at classpath, using getResource(String name) or getResourceAsStream(String name).
However, in a simple Java Project, even adding resources to build path, like this:
it will just put the folder content, in other words, just icon/..., to bin folder, something like this:
So, since resources isn't in classpath, just icon, to retrieve the images, you'll need to inform as path only /icon/image.gif, like this:
URL url = YourClass.class.getResource("/icon/image.gif");
ImageIcon icon = new ImageIcon(url);
I'm having this problem where none of the resources load when I run a JAR of the program. I've changed code and checked that it is indeed both the code that loads images and the code that loads sounds do not work. It works perfectly fine when I run it in eclipse. I checked with 7-Zip and the sounds and images files aren't in a res folder anymore. I tried changing the path files and the location of the resources in my program before I exported it, but that didn't work. I also have the res folder as a source folder in the build path. I'm exporting the JAR with eclipse, and then adding my libraries into it with JarSplicer. Here are the codes that load images and sound resources:
-Load Sound-
public static WaveData LoadSound(String path){
WaveData sound = null;
try {
sound = WaveData.create(new BufferedInputStream(new FileInputStream(path)));
} catch (Exception e) {
e.printStackTrace();
}
return sound;
}
-Load Images-
public static Texture LoadTexture(String path, String fileType){
Texture tex = null;
InputStream in = ResourceLoader.getResourceAsStream(path);
try{
tex = TextureLoader.getTexture(fileType,in);
}catch(IOException e){
e.printStackTrace();
}
return tex;
}
Here's my error in the command prompt:
Here are the files in the jar every time I exported it (regardless of whether the resources were in res or not):
I'm stumped here. If someone knows how to fix this, then please help me out.
I found the answer to my problem.
ResourseLoader.getResourceStreamAs() does not work inside of JAR files, so you need to do getClass().getResourceStreamAs(), or [ClassName].class.getResourceStreamAs(), if it's static.
Also, I had to change the location of the files from res/[resource file]/[resource] to /[resource file]/[resource] because when you export, it takes out all of the files in res. Also, you have to make sure that you have that / at the beginning of the path there in order to designate it to search in the source folder, or else it will search in the folder of the class that called getResourceStreamAs(). And also, new FileInputStream() doesn't work in JAR files, so you have to use [ClassName].class.getResourceStreamAs() instead. Oh, and on top of that, I had a few files that somehow got the extension part its name in all capitals for no reason. So that gave me some confusion. I basically just had to do a bunch of fiddling with code, but I got it working!
One more thing: make sure you add your resources folder to the sources tab in the build path, or else eclipse won't export it. And if you want your libraries to be exported in your JAR, then you'll have to add them manually by making a fat jar with JarSplicer.
Turns out that paths to resources are case sensitive and do not work in jar files if there is a single misstyped letter in the path.
First of all, I am aware of Stack Overflow (and any competent forum-like website) policy of "search first, ask last", and, doing my homework, I searched various sources to find a solution to my issue. That said, I, failing to find any suitable answers, was left no choice but to ask this problem personally.
I have somewhat moderate programming skills, especially regarding the Java language. I am working on this 2D game with the default Java SE JDK. More specifically JDK 7u4. In this project, we have a class that manages most I/O operations. One of its methods returns the path to a file:
public static URL load(String resource) {
return ZM.class.getResource(resource);
}
Now, this method works fine when running the project on Netbeans (version 7.1). However, when building and cleaning the project, the resulting .jar file does not seem to agree with its creator. When running the .jar on command line, the JVM caught a NullPointerException. It seemed that the file was not being able to be read inside the .jar. Following my programmers instinct, I started debugging the project. My first attempt was to check whether the load method was the faulty member. I ran some tests and obtained a couple of interesting results:
When running the application on Netbeans and with "ZM.class" as the methods argument, it returned:
/D:/Projects/GeometryZombiesMayhem/build/classes/geometryzombiesmayhem/ZM.class
But when running it from the .jar file, it returned:
file:/D:/Projects/GeometryZombiesMayhem/dist/GeometryZombiesMayhem.jar!/geometryzombiesmayhem/ZM.class
Naturally, I tried removing the initial file: string from it. No effect. Then I tried taking the exclamation mark from [...].jar![...]. Again, nothing. I tried removing all the possible permutations from the path. No luck.
Testing the method against the very own .jar file worked okay. Now, when I try to access the inside of the file, it doesn't let me. On earlier versions of this project it worked just fine. I am not really sure of what is going on. Any help is welcome.
Thank you in advance,
Renato
When loading resources from a jar file, I've always used a classLoader. Everything seems to work the same whether you run from within the IDE, launch the executable jar file or run the program from a web site using JNLP.
Try loading the resource this way instead:
try {
ClassLoader cl = ZM.getClass().getClassLoader();
ImageIcon img = new ImageIcon(cl.getResource("images/programIcon.jpg"));
// do stuff with img.
}
catch(Exception failed) {
System.out.println(failed);
}
One more suggestion - you should create a separate folder for resources. In my example above, images is a folder inside of my src folder. This way it will automatically become part of the jar when I build it, but I am keeping resources separate from source code.
I suppose your problem is in loading an image from your jar file.
Here is how i do it
URL imageurl = Myclassanme.class.getResource("/test/Ergophobia.jpg");
Image myPicture = Toolkit.getDefaultToolkit().getImage(imageurl);
JLabel piclabel = new JLabel(new ImageIcon( myPicture ));
piclabel.setBounds(0,0,myPicture.getWidth(null),myPicture.getHeight(null));
This way I can get the Ergophobia.jpg file inside 'test' package.