Why is my attempt to append text to a file not responding?

Question

I'm simply trying to add a new line of text to my *.txt file, but nothing happens at all. The file is packed with a .war, so I use a ClassLoader to access the file. Also, both my eclipse IDE, and the contents of the file, use UTF-8 encoding.

I've used these for inspiration:

How to add a new line of text to an existing file in Java?

Java BufferedWriter object with utf-8

Now my code is mainly based on the last post, and looks like this:

public class test {


    public static void main(String[] args){

        URL url = Thread.currentThread().getContextClassLoader().getResource("MilestoneExport.txt");

        File file = new File(url.getFile());

        System.out.println(file.canRead()); //true
        System.out.println(file.canWrite()); //true


        try {
            BufferedWriter out = new BufferedWriter
                (new OutputStreamWriter(new FileOutputStream(file),"UTF-8"));
            out.append("new line");
            out.append("new line 2");
            out.append("new line 3");
            out.close();
        } catch (IOException e) {
            e.printStackTrace();
        }   
    }
}

I've confirmed that the file is in fact found, and it reads fine. I've been able to output the entire content of it to the console through the use of a BufferedReader. The path of the file is also correct, but absolutely no text is added to the file. I've made sure that I have refreshed and updated every time I've run the program.

Also, I've tried to create a simple empty file called foo.txt, which is located in the same directory as test.java. I added the following code to the main method, as provided by the BufferedWriter API, at http://docs.oracle.com/javase/7/docs/api/java/io/BufferedWriter.html

PrintWriter out2 = new PrintWriter(
    new BufferedWriter(new FileWriter("foo.txt")));
out2.println("new Line");
out2.close();

What am i missing here? Why are there no error messages, and no responses or feedbacks whatsoever?

EVERYTHING BELOW IS ONLY ADDITIONAL INFO ABOUT WHAT I'VE TRIED. NO FEEDBACK IN ANY CASES:

• Not this one: Why is BufferedWriter not writing to file?
• Not this one: why is bufferedwriter not writing in the file?
• Not this one: Unable to write to file using BufferedWriter
• Yet another "remember to close/flush": Java : Problems accessing and writing to file
• Defining the BufferedWriter outside the try block makes no difference, but I tried it anyway, due to How to write detail into file using BufferedWriter and FileWriter in Java?

Also, this code, from this answer, does nothing as well...

try {
        BufferedWriter output = new BufferedWriter(new FileWriter(new File("house.txt")));

        output.write("text");
        output.close();
    } 
    catch (IOException e) {
        e.printStackTrace();
    } 

last but not least, I suspected that it might have something to do with the packaging of my Web-App, and differences between the source and target-folders. So I copied the code to a brand new clean project, but it still does nothing at all...

EDIT:

this code:

System.out.println(file.exists());
System.out.println(file.getAbsolutePath());
System.out.println(file.getCanonicalPath());
System.out.println(file.getName());
System.out.println(file.isDirectory());
System.out.println(file.isFile());
System.out.println(file.setLastModified(new   GregorianCalendar().getTimeInMillis()));

gives these outputs:

• true
• D:\Data\myworkspace\MyProject\target\classes\MilestoneExport.txt
• D:\Data\myworkspace\MyProject\target\classes\MilestoneExport.txt
• MilestoneExport.txt
• false
• true
• true

Am I completely misunderstanding the use of java's File-objects, and it's uses with FileWriters? The file is clearly 100% confirmed the correct file.

Answer 1

You should use the other constructor of FileOutputStream in order to open the file in append mode :

FileOutputStream(File file, boolean append)

I.e,

new FileOutputStream(file, true)

Answer 2

Since I can't comment, you might not be saving the file back into the archive it came from (I'm not sure if java supports writing to the internal structures of archives by editing the files that are included, however you might want to try to store the file externally to the archive to see if that is the place the issue comes from).

The cause of what you posted in the comments is that your IDE won't extract the resource file from a compiled program, if you want to sync the internal data you might be able to setup a client-server connection using sockets and creating a program that writes the data to the local file from data packets send to your web-app, otherwise retrieving the edited file from where you are hosting might be less complicated (or if you are deploying from the same PC you might be able to get away with a symbolic or hard link)

Answer 3

I've tried this code that is very similar to yours and it's working nicely, so i think the problem is the way you are picking the path of the file.

public static void main(String[] args){

    File file = new File("./localtest.txt");

    System.out.println(file.canRead()); //true
    System.out.println(file.canWrite()); //true


    try {
        BufferedWriter out = new BufferedWriter
            (new OutputStreamWriter(new FileOutputStream(file),"UTF-8"));
        out.append("new line");
        out.append("new line 2");
        out.append("new line 3");
        out.close();
    } catch (IOException e) {
        e.printStackTrace();
    }   
}

Answer 4

this works

 PrintWriter pw= new PrintWriter(
    new BufferedWriter(new FileWriter("C:\\foo.txt")));
    pw.println("line 1");
    pw.close();