Adding a text watermark in Java with Java.net

In this guide, we'll show you how to add text watermarks to your PDFs using Java and the Java.net library.

When generating PDFs, you might want to add text watermarks to your documents for protection or branding purposes.

import java.net.*;
import java.io.*;

// You can get an API key at https://pdfshift.io
String apiKey = "sk_xxxxxxxxxxxx";

URL url = new URL("https://api.pdfshift.io/v3/convert/pdf");
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("POST");
connection.setRequestProperty("X-API-Key", apiKey);
connection.setRequestProperty("Content-Type", "application/json");
connection.setDoOutput(true);

String payload = "{\n" +
    "  \"source\": \"https://www.example.com\",\n" +
    "  \"watermark\": {\n" +
    "    \"text\": \"CONFIDENTIAL\",\n" +
    "    \"opacity\": 0.3,\n" +
    "    \"size\": \"20px\",\n" +
    "    \"color\": \"#000000\"\n" +
    "  }\n" +
    "}";

try (OutputStream os = connection.getOutputStream()) {
    byte[] input = payload.getBytes("utf-8");
    os.write(input, 0, input.length);
}

int responseCode = connection.getResponseCode();

// Handle errors:
if (responseCode >= 400) {
    throw new RuntimeException("Request failed with status code " + responseCode);
}

InputStream inputStream = connection.getInputStream();
FileOutputStream outputStream = new FileOutputStream("result.pdf");
byte[] buffer = new byte[1024];
int bytesRead;
while ((bytesRead = inputStream.read(buffer)) != -1) {
    outputStream.write(buffer, 0, bytesRead);
}
outputStream.close();
inputStream.close();

System.out.println("The PDF document was generated and saved to result.pdf");

This allows you to add textual protection to your documents with customizable text.

For further details on the watermark property and its usage, please refer to our dedicated documentation.

We hope this guide was helpful. If you have any questions or noticed any issues on the code above,
feel free to drop us a line.