TempFileOutputStream.java

package ilarkesto.io;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;

/**
 * This FileOutputStream writes all data to a temporary file. Olny on call on the close()-method the original
 * file will be deleted and replaced by the temporary file. This ensures a more secure way of writing files.
 * When the VM crashes, the original file will not be damaged.
 * 
 * @author wko
 */
public class TempFileOutputStream extends OutputStream {

	@Override
	public void write(int b) throws IOException {
		out.write(b);
	}

	@Override
	public void flush() throws IOException {
		super.flush();
		out.flush();
	}

	@Override
	public void close() throws IOException {
		super.close();
		out.close();
		if (file.exists()) IO.delete(file);
		IO.move(tempFile, file);
	}

	@Override
	protected void finalize() throws Throwable {
		try {
			out.close();
			IO.delete(tempFile);
		} catch (Throwable t) {}
	}

	// --- dependencies ---

	private File file;
	private File tempFile;
	private OutputStream out;

	public TempFileOutputStream(File file) throws IOException {
		this.file = file;

		if (file.exists() && !file.canWrite()) throw new IOException(file + " is not writable");

		tempFile = new File(file.getPath() + ".~tmp");
		out = new BufferedOutputStream(new FileOutputStream(tempFile));
	}

	public TempFileOutputStream(String filePath) throws IOException {
		this(new File(filePath));
	}

}