Java IO Can't Read Input File Under Java Applet

Question

Java throws an exception when reading image file:

javax.imageio.IIOException: Can't read input file!
at javax.imageio.ImageIO.read(ImageIO.java:1275)
at UI.readMatrix(UI.java:27)
at MazeViewControl.init(MazeViewControl.java:45)
at sun.applet.AppletPanel.run(AppletPanel.java:424)
at java.lang.Thread.run(Thread.java:680)

The image IO works fine while running as Java application:

public class MazeViewControl extends JApplet {
UI ui;
MazeView view;
Maze maze;
int theme;
int option;
String filename="src/maze0.bmp";

public  void init() {
    ui=new UI();
    maze=new Maze();
        try {
            ui.readMatrix("src/maze0.bmp", maze, 1, 0, 0,0,319,239);
        } catch (IOException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

public class UI {
    public UI(){
        return;
    }
/**
   * read and construct the map from a txt file
   * @param filename
   * @throws IOException 
   */
    public void readMatrix(String filename, Maze m, int theme, int option, int sx, int sy, int ex, int ey) throws IOException{
        /* pre-read the file*/

        //Create file for the source
        File input = new File(filename);
        int rows=0;
        int columns=0;
        //Read the file to a BufferedImage
        // Surround this with try/catch or have your method
        // throw an exception
        System.out.println(filename);
        BufferedImage image = ImageIO.read(input);

Giuseppe Scrivano · Accepted Answer · 2012-09-27 19:26:05Z

3

that is how it is supposed to work. An applet can't access local files. You might need a signed applet with granted access to the file system.

answered Sep 27, 2012 at 19:26

Giuseppe Scrivano

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2 Comments

flint_stone Over a year ago

Thanks! Would file chooser be able to build the connection by the way?

Giuseppe Scrivano Over a year ago

coderanch.com/how-to/java/…

john_science · Accepted Answer · 2012-09-27 19:41:41Z

0

This is expected.

If a Java applet had free access to all local files, imagine how easy it would be to attack someone's local machine. You can use java.io.File to read a file when you are writing a Java application. But if you are writing a Java applet, you have to package the input file as part of your jar and access the file as a "resource":

In order to solve this problem, you will need to use the following method:

YourClass.class.getClassLoader().getResourceAsStream("yourfile.txt")

or

InputStream inputStream = classLoader.getResourceAsStream("yourfile.txt")

It is very easy to do and a quick explanation and usage of this can be found here.

edited Sep 27, 2012 at 19:41

answered Sep 27, 2012 at 19:35

john_science

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