UnzipHelper

UnzipHelper extracts ZIP archives with path-traversal, symbolic-link, entry-count, size, and compression-ratio protection. It is intentionally separate from ZipHelper.

import com.ajaxjs.util.io.UnzipHelper;

new UnzipHelper("C:/downloads/archive.zip").extract();

Without a target directory, archive.zip is extracted into a sibling archive directory. Supply a target when the destination is explicit:

new UnzipHelper("C:/downloads/archive.zip", "C:/work/extracted").extract();

Limits and legacy filenames

Default limits allow 10,000 entries, 1 GB per entry, 10 GB in total, and a 100:1 compression ratio. Trusted archives with different operational requirements can use custom limits:

UnzipHelper.ExtractionLimits limits =
        new UnzipHelper.ExtractionLimits(2_000, 100L * 1024 * 1024, 500L * 1024 * 1024, 50.0);
new UnzipHelper("archive.zip", "output", limits).extract();

ZIP filenames normally use UTF-8. For a legacy GBK archive, configure the charset before extracting:

UnzipHelper helper = new UnzipHelper("legacy.zip");
helper.setCharset(java.nio.charset.Charset.forName("GBK"));
helper.extract();

Entries are written to temporary files and moved only after each entry succeeds. Extraction can still leave files from entries completed before a later archive error; callers needing all-or-nothing behaviour should extract to a fresh temporary directory first.