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rsoika/GotenbergClient.java

Created September 14, 2021 14:43
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  1. rsoika created this gist Sep 14, 2021.
    95 changes: 95 additions & 0 deletions GotenbergClient.java
    View file
    Original file line number Diff line number Diff line change
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    package org.rsoika;

    import java.io.ByteArrayOutputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.OutputStream;
    import java.io.OutputStreamWriter;
    import java.io.PrintWriter;
    import java.net.HttpURLConnection;
    import java.net.URL;
    import java.nio.charset.StandardCharsets;

    /**
    * Gotenberg is a Docker-powered stateless API for converting HTML, Markdown and
    * Office documents to PDF.
    * <p>
    * This java client can be used to send a HTML file to the docker service to
    * receive a PDF file based on the Gotenberg API. This implementation uses pure
    * java based on JDK 1.8 and did not depend on any external library. You can use
    * this client on your own code base or as a scaffold for a custom
    * implementation.
    * <p>
    * The data is expected in UTF-8 encoding
    *
    * @author rsoika
    * @version 1.0
    * @see https://github.com/thecodingmachine/gotenberg/
    * @see https://www.codejava.net/java-se/networking/upload-files-by-sending-multipart-request-programmatically
    *
    */
    public class GotenbergClient {

    private static final String LINE_FEED = "\r\n";

    public static byte[] convertHTML(String gotenbertEndpoint, InputStream inputStream) throws IOException {
    byte[] pdfResult;
    String boundary;
    // creates a unique boundary based on time stamp
    boundary = "------------------------" + System.currentTimeMillis();
    if (!gotenbertEndpoint.endsWith("/")) {
    gotenbertEndpoint = gotenbertEndpoint + "/";
    }

    URL url = new URL(gotenbertEndpoint + "convert/html");
    HttpURLConnection httpConn = (HttpURLConnection) url.openConnection();
    httpConn.setUseCaches(false);
    httpConn.setDoOutput(true); // indicates POST method
    httpConn.setDoInput(true);
    httpConn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
    OutputStream outputStream = httpConn.getOutputStream();
    PrintWriter writer = new PrintWriter(new OutputStreamWriter(outputStream, StandardCharsets.UTF_8), true);

    // add html file...
    writer.append("--" + boundary).append(LINE_FEED);
    writer.append("Content-Disposition: form-data; name=\"fileUpload\"; filename=\"index.html\"").append(LINE_FEED);
    writer.append("Content-Type: text/html").append(LINE_FEED);
    writer.append("Content-Transfer-Encoding: binary").append(LINE_FEED);
    writer.append(LINE_FEED);
    writer.flush();

    byte[] buffer = new byte[4096];
    int bytesRead = -1;
    while ((bytesRead = inputStream.read(buffer)) != -1) {
    outputStream.write(buffer, 0, bytesRead);
    }
    outputStream.flush();
    inputStream.close();
    writer.append(LINE_FEED);
    writer.flush();
    writer.append("--" + boundary + "--").append(LINE_FEED);
    writer.close();

    // checks server's status code first
    int status = httpConn.getResponseCode();
    System.out.println("http con response code=" + status);
    if (status == HttpURLConnection.HTTP_OK) {
    InputStream in = null;
    ByteArrayOutputStream bout = new ByteArrayOutputStream();
    in = httpConn.getInputStream();
    byte[] block = new byte[1024];
    int length;
    while ((length = in.read(block)) != -1) {
    bout.write(block, 0, length);
    }
    in.close();
    pdfResult= bout.toByteArray();
    httpConn.disconnect();
    } else {
    throw new IOException("Server connection failed - status: " + status);
    }

    return pdfResult;
    }

    }