从 ZipInputStream 复制条目

Question

I am able to iterate over ZipEntry s of a ZipInputStream like this:

ByteArrayInputStream schema = new ByteArrayInputStream(schemaData);
ZipInputStream zis = new ZipInputStream(schema);
ZipEntry entry;
while((entry = zis.getNextEntry()) != null) {
     String entryName = entry.getName();
     // filter based on entry name
     // how to copy this entry?
}

How can I copy certain entries of this Zip file?

Answer 1

Yes it is certainly possible. When you call ZipInputStream.getNextEntry() it positions the stream at the start of the next entry of data, in this case you want the data when it's a sub zip file. The stream wont go past the end of that data so don't worry about reading into the next entry, the entries of a ZipInputStream can essentially be treated like an individual stream of their own.

public static void main(String[] args) throws IOException {
    // ** specify an output directory to copy files to
    final File outDir = new File("path\\to\\...\\OutDir");

    // ** read the zip input stream and do for each entry...
    final String pathToZip = "path\\to\\...\\ZipTest.zip";
    try (InputStream is = new FileInputStream(pathToZip);
            ZipInputStream zis = new ZipInputStream(is);) {

        forEachZipEntry(zis, (zipEntry, subZipStream) -> {
            // ** specify how to consume each zip entry and stream...
            // ** apply filters here, based on the zip entry
            if (zipEntry.getName().equals("normalZippedDir.zip")) {
                // ** copy the zip stream to the file
                File outFile = new File(outDir, zipEntry.getName());
                try (FileOutputStream fis = new FileOutputStream(outFile);) {
                    // apache IOUtils or whatever copy method you want
                    IOUtils.copy(subZipStream, fis);
                } catch (IOException e) { e.printStackTrace(); }
            }
        });
    }
}

/**
 * Iterates through all {@linkplain ZipEntry}s of the given {@linkplain ZipInputStream} and
 * passes the current zip entry and stream to the provided {@linkplain BiConsumer}, but does
 * <b>not</b> recursively parse entries of nested zip files.
 */
public static void forEachZipEntry(ZipInputStream zis, BiConsumer<ZipEntry, ZipInputStream> consumer)
        throws IOException {
    Objects.requireNonNull(zis);
    Objects.requireNonNull(consumer);
    ZipEntry entry;
    while ((entry = zis.getNextEntry()) != null) {
        consumer.accept(entry, zis);
    }
}

/**
 * Recursively iterates through <b>all</b> {@linkplain ZipEntry}s <i>(including entries of nested zip
 * files)</i> of the given {@linkplain ZipInputStream} passing the current zip entry and stream to
 * the provided {@linkplain BiConsumer}.
 */
public static void forEachZipEntryRecursive(ZipInputStream zis,
        BiConsumer<ZipEntry, ZipInputStream> consumer) throws IOException {
    Objects.requireNonNull(zis);
    Objects.requireNonNull(consumer);
    ZipEntry entry;
    while ((entry = zis.getNextEntry()) != null) {
        consumer.accept(entry, zis);
        @SuppressWarnings("resource") // ** caller shall close `zis`
        ZipInputStream subZis = new ZipInputStream(zis);
        forEachZipEntryRecursive(subZis, consumer);
    }
}