在JAR文件内的Res-Folder中创建数据

Question

for a project of mine i found it necessary to safe a given int[] of colorvalues as a png-file. The png will represent a map of tiles, which are represented by the colorvalues. The generation of the BufferedImage and the process of saving works fine already.

public BufferedImage getTileImage() {
    BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_ARGB);
    for (int i = 0; i < height; i++) {
        for (int j = 0; j < width; j++) {
            image.setRGB(j, i, tiles[j+i*width].getType());
        }
    }
    return image;
}

public void safeMap(String mapname) {
    File file = new File("res/maps/"+mapname+".png");
    try {
        ImageIO.write(getTileImage(), "png",file );
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

The problem occurs, when i export it as an executeable JAR-File, since the ImageIO.write()-method doesnt seem to be able to work properly with relative pathes inside the JAR-File. (My guess would be that you can only read inside the structure, not write)

What would be a good solution for this problem? Is there a way to implement this, without using an external ressource-folder?

Answer 1

Dont save it to a JAR file. I also have a game that I need to create files that will go into the JAR file. I create those files by executing code in my IDE. Those files go into the resource directories that will eventually get put into my JAR. In my case the directories are in /src/. But they could easily have gone into src/main/resources if you are using Maven with standard dir layout.

If you are executing this outside of your IDE, not part of your development effort, then you can store it in a tempt folder or a folder off of user.home. To get a temp file that goes into the system's temp folder you can do something like this...

File colorsFile = File.createTempFile("color_generator", ".png"); 

Answer 2

If the image is an asset of the game (generated by you for all players), generate it in the resources folder of your project, and include it when generating your jar file.

If the image is generated dynamically (by a player), you can't put it in the jar, because you are not supposed to change a jar dynamically (and other players wouldn't see it, either) : you'll have to put it on the server / in your database and build a webservice to share it.