Java, Save & open files with objectStream

Hello,

I'm trying to save and open files by using the ObjectOutputStream and ObjectInputStream classes. I ensured that the object I'm writing is defined only by primitive types and implements Serializable.

When saving objects:
Layer 1
Layer 2
Layer 3
Layer 4

It will open:
Layer 1
Layer 3
It skips always a full object, I'm obviously missing something...

public static void saveImage() {
        ArrayList<Layer> layers = (ArrayList<Layer>) DrawingPanel.getInstance().getLayers();
        ObjectOutputStream outputStream = null;
        int option = fileChooser.showOpenDialog(Main.getInstance());
        if (option == JFileChooser.APPROVE_OPTION) {
            File file = fileChooser.getSelectedFile();
            try {
                outputStream = new ObjectOutputStream(new FileOutputStream(file));
                for (Layer layer : layers) {
                    outputStream.writeObject(layer);
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                // close outputStream, left it out here
            }
        }
    }

    public static void openImage() {
        List<Layer> layers = new ArrayList<Layer>();
        ObjectInputStream inputStream = null;
        int option = fileChooser.showOpenDialog(Main.getInstance());
        if (option == JFileChooser.APPROVE_OPTION) {
            File file = fileChooser.getSelectedFile();
            try {
                inputStream = new ObjectInputStream(new FileInputStream(file));
                while (inputStream.readObject() != null) {
                    Layer layer = (Layer) inputStream.readObject();
                    layers.add(layer);
                }
            } catch (EOFException e) {
                e.printStackTrace();
            } finally {
                // close inputStream, left it out here
            }
        }
        DrawingPanel.getInstance().setLayers(layers);
    }

Code (markup):

Tia

 

Can you post the entire java class?

Two things I would check. First check if its actually writing all the layers after the save function.

I will also step into the open function to check if it does read in all the layer objects.

 

Yeh can you post a bit more?

 

This put me to thinking in a new direction. The thing is that when invoking the readObject() method, the object is read and the ObjectInputStream moves along to the next object. So what happens is that by checking

inputStream.readObject() != null

Code (markup):

you already passed/skipped an object ! Here's a simple solution using a boolean to check if the EOFException occured (the end of file is reached then):

    public static void openImage() {
        boolean isEnded = false;
        List<Layer> layers = new ArrayList<Layer>();
        ObjectInputStream inputStream = null;
        int option = fileChooser.showOpenDialog(Main.getInstance());
        if (option == JFileChooser.APPROVE_OPTION) {
            File file = fileChooser.getSelectedFile();
            try {
                inputStream = new ObjectInputStream(new FileInputStream(file));
                while (!isEnded) {
                    Layer layer = (Layer) inputStream.readObject();
                    layers.add(layer);
                }
            } catch (EOFException e) {
                isEnded = true;
            } catch (IOException e) {
                e.printStackTrace();
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            } finally {
                try {
                    inputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        DrawingPanel.getInstance().setLayers(layers);
    }

Code (markup):

Thanks!

ps: Those two methods are all what takes to save & load objects into a file, that's all code to it...

 

Actually, to improve the code, try to handle downcasting better..

            try {
                inputStream = new ObjectInputStream(new FileInputStream(file));
                while (!isEnded) {
                    Object object = inputStream.readObject();
                    if (object instanceof Layer) {
                        Layer layer = (Layer) object;
                        layers.add(layer);
                    }
                }
            }

Code (markup):

 

The function inputStream.readObject(); is used as a condition in the while loop.