How Can I Append Files to Existing Zip Archives in Java Using TrueZip or Java 7\'s Zip File System?

Appending to Zip Files in Java: TrueZip and Java 7

In the context of extracting, modifying, and repackaging WAR files, it's common to consider enhancing efficiency by appending files directly to an existing WAR archive. While the Java documentation lacks explicit methods for this task, there are solutions available.

TrueZip Library

One option is to utilize the TrueZip library, as suggested in your updated inquiry. TrueZip provides specific functionality for manipulating and appending to Zip archives. Using TrueZip, one can selectively add, update, and delete files from a target Zip file.

Java 7's Zip File System

Additionally, Java 7 introduced the Zip File System, which allows for modifications to Zip archives without repackaging. With the Zip File System, you can directly write to or modify files within a Zip archive using standard Java I/O operations. For instance:

Map<String, String> env = new HashMap<>();
env.put("create", "true");
Path path = Paths.get("test.zip");
URI uri = URI.create("jar:" + path.toUri());
try (FileSystem fs = FileSystems.newFileSystem(uri, env)) {
    Path nf = fs.getPath("new.txt");
    try (Writer writer = Files.newBufferedWriter(nf, StandardCharsets.UTF_8, StandardOpenOption.CREATE)) {
        writer.write("hello");
    }
}

By using the Zip File System, you can interact with a Zip archive as if it were a regular file system, enabling efficient file additions and modifications.

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