There's been a ZipFile class in Java sinds a long time. But nowadays sinds JDK7 there's also a ZipFileSystem which is a bit easier to work with in some cases and can do more things.
Below are two examples, one using ZipFile and one using ZipFileSystem.
Using ZipFile
Unzipping works as follows:
@Test
public void testOldZip() throws URISyntaxException, IOException {
URL resource = UnzipperTest.class.getResource("/test.zip");
assert resource != null;
Path path = Path.of(resource.toURI());
try (var zipFile = new ZipFile(path.toFile())) {
Enumeration<? extends ZipEntry> entries = zipFile.entries();
while (entries.hasMoreElements()) {
ZipEntry nextElement = entries.nextElement();
if (nextElement.isDirectory()) {
log.add("File " + nextElement.getName() + " from zipfile is a directory - skipped");
}
else if (nextElement.getName().contains("__MACOSX")) {
log.add("File " + nextElement.getName() + " from zipfile is a MACOS file/dir - skipped");
}
else {
log.add("File " + nextElement.getName() + " retrieved from zip.");
var filename = nextElement.getName();
InputStream inputStream = zipFile.getInputStream(nextElement);
result.add(new FileContents(filename, inputStream.readAllBytes()));
}
}
}
assertThat(result).hasSize(6);
assertThat(result.stream().map(x -> x.filename).collect(Collectors.toList())).isEqualTo(
List.of("test/test1.txt",
"test/test/ziptest.zip",
"test/test/ziptest/zippem2.txt",
"test/test/ziptest/zippem.txt",
"test/test2/test2.txt",
"test/test2/text3.xml"));
assertThat(log).hasSize(11)
.isEqualTo(List.of("File test/ from zipfile is a directory - skipped",
"File test/test1.txt retrieved from zip.",
"File test/test/ from zipfile is a directory - skipped",
"File test/test/ziptest.zip retrieved from zip.",
"File test/test/ziptest/ from zipfile is a directory - skipped",
"File test/test/ziptest/zippem2.txt retrieved from zip.",
"File test/test/ziptest/zippem.txt retrieved from zip.",
"File test/test2/ from zipfile is a directory - skipped",
"File test/test2/test2.txt retrieved from zip.",
"File test/test2/test3/ from zipfile is a directory - skipped",
"File test/test2/text3.xml retrieved from zip."));
}
Using ZipFileSystem
Apparently it is also possible to mount a zip file as a FileSystem (sinds JDK 7).
It's a bit easier to work with, and has less problems with leaking resources/streams, and allows easy editing and removing items from the zip.
On the other hand, some FileSystem operations are not available in a ZipFileSystem, and then you get a UnsupportedOperationException.
private static class ZipVisitor
extends SimpleFileVisitor<Path> {
private final List<FileContents> result;
private final List<String> log;
private ZipVisitor(List<FileContents> result, List<String> log) {
this.result = result;
this.log = log;
}
@Override
public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
if (file.toString().contains("__MACOSX")) {
log.add("File " + file + " from zipfile is a MACOS file/dir - skipped");
return FileVisitResult.CONTINUE;
}
if (Objects.equals(file.toString(), ".DS_Store")) {
log.add("File " + file + " from zipfile is a .DS_Store file/dir - skipped");
return FileVisitResult.CONTINUE;
}
log.add("File " + file + " retrieved from zip.");
String filename = file.toString();
// file.toFile() -> unsupported operation.
result.add(new FileContents(filename, Files.readAllBytes(file)));
return FileVisitResult.CONTINUE;
}
}
@Test
public void testNewZip() throws URISyntaxException, IOException {
URL resource = UnzipperTest.class.getResource("/test.zip");
assert resource != null;
var path = Path.of(resource.toURI());
try (FileSystem filesystem = FileSystems.newFileSystem(path, Collections.emptyMap())) {
var rootDirectories = filesystem.getRootDirectories();
rootDirectories.forEach(root ->
//walk the zip file tree
{
try {
Files.walkFileTree(root, new ZipVisitor(result, log));
}
catch (IOException e) {
throw new RuntimeException(e);
}
}
);
}
assertThat(result).hasSize(6);
assertThat(result.stream().map(x -> x.filename).collect(Collectors.toList())).isEqualTo(
List.of("/test/test2/text3.xml",
"/test/test2/test2.txt",
"/test/test/ziptest/zippem.txt",
"/test/test/ziptest/zippem2.txt",
"/test/test/ziptest.zip",
"/test/test1.txt"));
assertThat(log).hasSize(6)
.isEqualTo(List.of("File /test/test2/text3.xml retrieved from zip.",
"File /test/test2/test2.txt retrieved from zip.",
"File /test/test/ziptest/zippem.txt retrieved from zip.",
"File /test/test/ziptest/zippem2.txt retrieved from zip.",
"File /test/test/ziptest.zip retrieved from zip.",
"File /test/test1.txt retrieved from zip."));
}
References
- fahd.blog - Java 7: Working with Zip Files
- https://fahdshariff.blogspot.com/2011/08/java-7-working-with-zip-files.html
- Oracle Java Documentation - Zip File System Provider
- https://docs.oracle.com/javase/8/docs/technotes/guides/io/fsp/zipfilesystemprovider.html
