How to load a serialized file back to an arrayList

问题

ive looked at a few problems on this matter already but couldnt resolve my issue.

As you can see below, i save all the objects in my Patient ArrayList(pList - which is private at the top of the class) into the "Patient.ser" file through serialization. As far as i can tell this is working with no problems. "patSizeAtSave" is a private variable which i am using to mark as a bound to work with when loading the file(see below)

the "patModel" is the DefaultListModel i use for the JLists in my GUI so i try to populate those lists with what has been added back to the Patient ArrayList(pList)

MY PROBLEM: When i hit the load button on the GUI it calls the loadPatientList() method below, but nothing is being put into my JLists so i can't tell if it works at all.

Any idea's on how to fix this?

private void savePatientList() throws FileNotFoundException {
    try
    {
    FileOutputStream fs = new FileOutputStream("Patient.ser");
    ObjectOutputStream os = new ObjectOutputStream(fs);
    for(Patient p: pList)
    {
        os.writeObject(p);
    }
    fs.close();
    os.close();
    patSizeAtSave = pList.size();
    JOptionPane.showMessageDialog(jTabPane, "Save Complete!", "Notification", JOptionPane.INFORMATION_MESSAGE);
    } 
    catch (IOException ex) {
        Logger.getLogger(MainFrame.class.getName()).log(Level.SEVERE, null, ex);
    } 

}
private void loadPatientList()
{
    FileInputStream fs;
    ObjectInputStream is;
    try
    {
    fs = new FileInputStream("Patient.ser");
    is = new ObjectInputStream(fs);

    for(int i = 0; i < patSizeAtSave; i++)
    {
        Patient p = (Patient) is.readObject();
        pList.add(p);
        patModel.addElement(p.getPNo() + ": " + p.getPName());
    }
    jListPatient.setModel(patModel);
    jListPatient2.setModel(patModel);
    fs.close();
    is.close();
    } 
    catch (FileNotFoundException ex) {
        Logger.getLogger(MainFrame.class.getName()).log(Level.SEVERE, null, ex);
    } catch (IOException | ClassNotFoundException ex) {
        Logger.getLogger(MainFrame.class.getName()).log(Level.SEVERE, null, ex);
    }
}

回答1:

Did you try to load you patients list in the same JVM (without exiting the JVM) after saving it ? Because if you exit your JVM before reloading you patients list, your patSizeAtSave will be reset to 0 (since it is not saved to any file/persitent storage) but only in memory. When you will call loadPatientList in a new JVM, your for loop will not load any patient since patSizeAtSave is 0.

You should rather save the whole list pList (assuming you use a Serializable implementation of List, sucha as ArrayList / LinkedList), like this :

FileOutputStream fs = new FileOutputStream("Patient.ser");
ObjectOutputStream os = new ObjectOutputStream(fs);
os.writeObject(pList);

And load it back with :

pList = (List<Patient>) is.readObject();
for(Patient p: pList)
{
    patModel.addElement(p.getPNo() + ": " + p.getPName());
}

This way, the list size will also be saved in you serialized file.

Regards

来源：https://stackoverflow.com/questions/15684586/how-to-load-a-serialized-file-back-to-an-arraylist

标签

java

arraylist

load

jlist

serializable