Slick2D automatically load images?

Newbie & Debugging Questions
#1

So, while I was working on a game I was making, I made myself a little Art class. Here it is:

package com.kirc.drilldescent;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FilenameFilter;
import java.net.URI;
import java.net.URISyntaxException;
import java.util.HashMap;
import java.util.Map;

import org.newdawn.slick.AngelCodeFont;
import org.newdawn.slick.Image;
import org.newdawn.slick.SlickException;
import org.newdawn.slick.util.ResourceLoader;

public class Art
{
	
//	public static Image dirtTile;
	private static Map<String,Image> loadedImages;
	private static AngelCodeFont font;
	/**
	 * Loads all .png images located in the /res folder.
	 * @throws SlickException
	 */
	public static void init() throws SlickException {
		
//		dirtTile = new Image("res/dirtTile.png");
		loadedImages = new HashMap<>();
		try
		{
			URI uri = new URI(ResourceLoader.getResource("res").toString());
			File[] files = new File(uri).listFiles(new FilenameFilter(){

				@Override
				public boolean accept(File dir, String name)
				{
					if(name.endsWith(".png"))
						return true;
					return false;
				}
				
			});
			
			for(File f:files)
			{
				FileInputStream fis = new FileInputStream(f);
				Image image = new Image(fis, "res/"+f.getName(), false);
				loadedImages.put(f.getName(), image);
			}
		} catch (URISyntaxException | FileNotFoundException e)
		{
			System.err.println("UNABLE TO LOAD IMAGES FROM RES FOLDER!");
			e.printStackTrace();
		}
		
		font = new AngelCodeFont("res/bitmapfont.fnt",Art.get("bitmapfont.png"));

	}
	/**
	 * 
	 * @param filename The filename of the image in the /res folder
	 * @return The loaded image of that filename
	 */
	public static Image get(String filename)
	{
		return loadedImages.get(filename);
	}
	
	public static AngelCodeFont getFont()
	{
		return font;
	}
}

Unfortunately, while this will automatically load all images in my res/ directory (and let me load them once and only once), it won’t work if I decide to pack everything into a .jar. I was wondering if anyone used a nicer pattern to keep all their game art organized and easy to access in their code. I took the lazy way because I didn’t want to add a line for every single one of my images. (Also, if you know how to adapt this to a .jar that’d be nice to share.)

#2

You can iterate over the entries in a jar/zip file with

import java.io.FileInputStream;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;

    ZipInputStream zis = new ZipInputStream(new FileInputStream(pathToZip));
    for (ZipEntry ze; (ze = zis.getNextEntry()) != null;) {
      System.out.println(ze.getName());
    }

That way you can enumerate all paths that start with “res/”, ending with “.png” and load them using ClassLoader.getResourceAsStream(path).

#3

Okay, but how do I get “pathToZip” to point to itself without having to keep the .jar strictly named? (If you use the .jar’s name then you can’t rename it or it won’t work).

#4

You could search it in the classpath.

#5

Well, got an answer from StackExchange. Figured i’d post the working code here for future reference:

package com.kirc.drilldescent.res;

import java.io.File;
import java.io.FileInputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.net.JarURLConnection;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.jar.JarInputStream;

import org.newdawn.slick.AngelCodeFont;
import org.newdawn.slick.Image;
import org.newdawn.slick.SlickException;
import org.newdawn.slick.util.ResourceLoader;

public class Art
{
	
	private static Map<String,Image> loadedImages;
	private static AngelCodeFont font;
	/**
	 * Loads all .png images located in source folders.
	 * @throws SlickException
	 */
	public static void init() throws SlickException {
		
		loadedImages = new HashMap<>();
		try
		{
			URL url = Art.class.getResource("../res");
			//use filesystem loading
			if(url != null)
			{
				File resDir = new File(new URI(url.toString()));
				File[] files = resDir.listFiles(new FilenameFilter(){
					@Override
					public boolean accept(File dir, String name)
					{
						if(name.endsWith(".png"))
							return true;
						return false;
					}
					
				});
				
	
				for(File f:files)
				{
					FileInputStream fis = new FileInputStream(f);
					Image image = new Image(fis, f.getName(), false);
					loadedImages.put(f.getName(), image);
				}
			}
			//use jar loading
			else
			{
				
				URLConnection uc = ClassLoader.getSystemResource("com/kirc/drilldescent/res").openConnection();
				if(uc instanceof JarURLConnection)
				{
					JarURLConnection juc = (JarURLConnection) uc;
					JarFile jarFile = juc.getJarFile();
					Enumeration<JarEntry> jarFileEntries = jarFile.entries();
					while (jarFileEntries.hasMoreElements()) {
						JarEntry jarEntry = jarFileEntries.nextElement();
						String jarEntryName = jarEntry.getName();
						if(jarEntryName.startsWith("com/kirc/drilldescent/res") && jarEntryName.endsWith(".png"))
						{
							Image image = new Image(jarEntryName);
							loadedImages.put(jarEntryName.replace("com/kirc/drilldescent/res/",""),image);
						}
						
					}
				}
				
			}
		} catch (URISyntaxException | IOException e)
		{
			e.printStackTrace();
		}
		
		font = new AngelCodeFont("com/kirc/drilldescent/res/bitmapfont.fnt",Art.get("bitmapfont.png"));

	}
	/**
	 * 
	 * @param filename The filename of the image in the /res folder
	 * @return The loaded image of that filename
	 */
	public static Image get(String filename)
	{
		return loadedImages.get(filename);
	}
	
	public static AngelCodeFont getFont()
	{
		return font;
	}
}

EDIT: Well, it works before I try to package the natives with jarsplice. After that, ClassLoader.getSystemResource fails to return anything. What does jarsplice do to prevent this from working? (I haven’t actually got a clear idea what getSystemResource does either)