(Java) Retrieve Metadata from Gzip Data in Memory (BinData)

This example demonstrates how to use the GetGzipInfoBd method to retrieve metadata from Gzip data stored in memory within a BinData object.

The Gzip data is first loaded into the BinData instance. The GetGzipInfoBd method then extracts any available metadata from the Gzip header, including the embedded filename, comment, and optional extra data.

The metadata 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.

Note: This example requires Chilkat v11.5.0 or greater.

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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 from Gzip data
    // stored in a BinData object.

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

    // Load a Gzip file into BinData:
    success = bd.LoadFile("example.txt.gz");
    if (success == false) {
        System.out.println(bd.lastErrorText());
        return;
        }

    // Get the metadata information from the in-memory Gzip data:
    success = gzip.GetGzipInfoBd(bd,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);
        }
  }
}