Java

Retrieve Metadata from a Gzip File

See more Gzip Examples

This example demonstrates how to use the GetGzipInfo method to retrieve metadata embedded within a Gzip file.

The method reads the Gzip header and extracts any available metadata, including the embedded filename, comment, and optional extra data. The extracted information is returned in a JsonObject.

Because these fields are optional, the example checks for the existence of each JSON member using HasMember before retrieving its value. This avoids attempting to access values that may not be present.

Java

import com.chilkatsoft.*;

public class ChilkatExample {

  static {
    try {
        System.loadLibrary("chilkat");
    } catch (UnsatisfiedLinkError e) {
      System.err.println("Native code library failed to load.\n" + e);
      System.exit(1);
    }
  }

  public static void main(String argv[])
  {
    boolean success = false;

    //  This example demonstrates how to retrieve metadata embedded in a Gzip file.

    CkGzip gzip = new CkGzip();
    CkJsonObject json = new CkJsonObject();

    //  The Gzip file to examine:
    String gzPath = "example.txt.gz";

    //  Get the metadata information:
    success = gzip.GetGzipInfo(gzPath,json);
    if (success == false) {
        System.out.println(gzip.lastErrorText());
        return;
        }

    //  Output the JSON containing metadata:
    System.out.println("Gzip metadata JSON:");
    System.out.println(json.emit());

    //  Access individual fields only if they exist:

    if (json.HasMember("filename") == true) {
        String filename = json.stringOf("filename");
        System.out.println("Filename: " + filename);
        }

    if (json.HasMember("comment") == true) {
        String comment = json.stringOf("comment");
        System.out.println("Comment: " + comment);
        }

    if (json.HasMember("extraData") == true) {
        String extraData = json.stringOf("extraData");
        System.out.println("ExtraData (Base64): " + extraData);
        }
  }
}