Opening the file with a ZipOutputStream overwrites it. Is there a way to keep the file and just add new entries?

解决方案

The function renames the existing zip file to a temporary file and then adds all entries in the existing zip along with the new files, excluding the zip entries that have the same name as one of the new files.

public static void addFilesToExistingZip(File zipFile,

File[] files) throws IOException {

// get a temp file

File tempFile = File.createTempFile(zipFile.getName(), null);

// delete it, otherwise you cannot rename your existing zip to it.

tempFile.delete();

boolean renameOk=zipFile.renameTo(tempFile);

if (!renameOk)

{

throw new RuntimeException("could not rename the file "+zipFile.getAbsolutePath()+" to "+tempFile.getAbsolutePath());

}

byte[] buf = new byte[1024];

ZipInputStream zin = new ZipInputStream(new FileInputStream(tempFile));

ZipOutputStream out = new ZipOutputStream(new FileOutputStream(zipFile));

ZipEntry entry = zin.getNextEntry();

while (entry != null) {

String name = entry.getName();

boolean notInFiles = true;

for (File f : files) {

if (f.getName().equals(name)) {

notInFiles = false;

break;

}

}

if (notInFiles) {

// Add ZIP entry to output stream.

out.putNextEntry(new ZipEntry(name));

// Transfer bytes from the ZIP file to the output file

int len;

while ((len = zin.read(buf)) > 0) {

out.write(buf, 0, len);

}

}

entry = zin.getNextEntry();

}

// Close the streams

zin.close();

// Compress the files

for (int i = 0; i < files.length; i++) {

InputStream in = new FileInputStream(files[i]);

// Add ZIP entry to output stream.

out.putNextEntry(new ZipEntry(files[i].getName()));

// Transfer bytes from the file to the ZIP file

int len;

while ((len = in.read(buf)) > 0) {

out.write(buf, 0, len);

}

// Complete the entry

out.closeEntry();

in.close();

}

// Complete the ZIP file

out.close();

tempFile.delete();

}