Question

I am trying to add a text file to a zip archive through a Java program on Linux. The program spawns a process (using java.lang.Process) to execute the commandline “zip -j .zip .txt”, reads the output and error streams of the spawned process and waits for the process to complete using waitFor(). Though the program seems to run fine (spawned process exits with exit code 0, indicating that the zip commandline was executed successfully) and the output read from output and error streams do not indicate any errors, at the end of the program the zip archive doesn’t always contain the file supposed to have been added. This problem doesn’t happen consistently though (even with the same existing-archive and file-to-add) – once in a while (perhaps once in 4 attempts) the zip is found to have been updated correctly. Strangely, the problem doesn’t occur at all when the program is run through Eclipse debugger mode. Any pointers on why this problem occurs and how it can be addressed would be helpful. Thanks!

Below is the code snippet. The program calls addFileToZip(File, File, String):

public static void addFileToZip(final File zipFile, final File fileToBeAdded,
        final String fileNameToBeAddedAs) throws Exception {
    File tempDir = createTempDir();
    File fileToBeAddedAs = new File(tempDir, fileNameToBeAddedAs);
    try {
        FileUtils.copyFile(fileToBeAdded, fileToBeAddedAs);
        addFileToZip(zipFile, fileToBeAddedAs);
    } finally {
        deleteFile(fileToBeAddedAs);
        deleteFile(tempDir);
    }
}

public static void addFileToZip(final File zipFile, final File fileToBeAdded) throws Exception {
    final String[] command = {"zip", "-j", zipFile.getAbsolutePath(), fileToBeAdded.getAbsolutePath()};
    ProcessBuilder procBuilder = new ProcessBuilder(command);
    Process proc = procBuilder.start();
    int exitCode = proc.waitFor();
    /*
     * Code to read output/error streams of proc and log/print them
     */
    if (exitCode != 0) {
            throw new Exception("Unable to add file, error: " + errMsg);
    }
}

Answer 1

Make sure no other process has the zip file locked for write, or the file being added locked for read. If you’re generating the file to be added, make sure the stream is flushed and closed before spawning the zip utility.