how to transfer oversized string over message system

for text based message system, if there's a limit of x KB, you can still transfer (~5 * x) KB by

1. compressing the original payload
2. encoding compressed binary to text
3. sending it

receiver reverses the process to get original payload by

1. testing to make sure message is encoded
2. decoding it to compressed binary
3. uncompressing decoded binary

import org.apache.commons.codec.binary.Base64;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.util.zip.GZIPInputStream;
import java.util.zip.GZIPOutputStream;

String payload = """
        {
        }""";
System.out.printf("original size: %s bytes\n", payload.length());

ByteArrayOutputStream baos = new ByteArrayOutputStream();
GZIPOutputStream gos = new GZIPOutputStream(baos);
gos.write(payload.getBytes());
gos.close();
byte[] compressed = baos.toByteArray();
System.out.printf("compressed size: %s bytes\n", compressed.length);

String encoded = Base64.encodeBase64String(compressed);
System.out.printf("encoded size: %s bytes\n", encoded.length());

System.out.println("is message encoded? " + Base64.isBase64(encoded));
byte[] decoded = Base64.decodeBase64(encoded.getBytes());
System.out.printf("decoded size: %s bytes\n", decoded.length);

GZIPInputStream gis = new GZIPInputStream(new ByteArrayInputStream(decoded));
ByteArrayOutputStream output = new ByteArrayOutputStream();
byte[] buffer = new byte[4096];
int bytesRead;
while ((bytesRead = gis.read(buffer)) > 0) {
    output.write(buffer, 0, bytesRead);
}

gis.close();
String uncompressed = output.toString();
System.out.printf("uncompressed size: %s bytes\n", uncompressed.length());

original size: 9450 bytes

compressed size: 1235 bytes

encoded size: 1648 bytes

is message encoded? true

decoded size: 1235 bytes

uncompressed size: 9450 bytes