My use case requires me to open a txt file, say abc.txt which is inside a zip archive which contains key-value pairs in the form
key1=value1
key2=value2
.. and so on where each key-value pair is in a new line. I have to change one value corresponding to a certain key and put the text file back in a new copy of the archive. How do I do this in java?
My attempt so far:
ZipFile zipFile = new ZipFile("test.zip");
final ZipOutputStream zos = new ZipOutputStream(new FileOutputStream("out.zip"));
for(Enumeration e = zipFile.entries(); e.hasMoreElements(); ) {
ZipEntry entryIn = (ZipEntry) e.nextElement();
if(!entryIn.getName().equalsIgnoreCase("abc.txt")){
zos.putNextEntry(entryIn);
InputStream is = zipFile.getInputStream(entryIn);
byte [] buf = new byte[1024];
int len;
while((len = (is.read(buf))) > 0) {
zos.write(buf, 0, len);
}
}
else{
// I'm not sure what to do here
// Tried a few things and the file gets corrupt
}
zos.closeEntry();
}
zos.close();
Java 7 introduced a much simpler way for doing zip archive manipulations - FileSystems API, which allows to access contents of a file as a file system.
Besides much more straightforward API, it is doing the modification in-place and doesn't require to rewrite other (irrelevant) files in a zip archive (as done in the accepted answer).
Here's sample code that solves OP's use case:
import java.io.*;
import java.nio.file.*;
public static void main(String[] args) throws IOException {
modifyTextFileInZip("test.zip");
}
static void modifyTextFileInZip(String zipPath) throws IOException {
Path zipFilePath = Paths.get(zipPath);
try (FileSystem fs = FileSystems.newFileSystem(zipFilePath, null)) {
Path source = fs.getPath("/abc.txt");
Path temp = fs.getPath("/___abc___.txt");
if (Files.exists(temp)) {
throw new IOException("temp file exists, generate another name");
}
Files.move(source, temp);
streamCopy(temp, source);
Files.delete(temp);
}
}
static void streamCopy(Path src, Path dst) throws IOException {
try (BufferedReader br = new BufferedReader(
new InputStreamReader(Files.newInputStream(src)));
BufferedWriter bw = new BufferedWriter(
new OutputStreamWriter(Files.newOutputStream(dst)))) {
String line;
while ((line = br.readLine()) != null) {
line = line.replace("key1=value1", "key1=value2");
bw.write(line);
bw.newLine();
}
}
}
For more zip archive manipulation examples, see demo/nio/zipfs/Demo.java
sample which you can download here (look for JDK 8 Demos and Samples).