title: WebAPI POST in Java with file in body
body: <p>I have a problem calling a webAPI in Java. Basically, I have to upload a file (xml or pdf) but I cannot get it work. I tried in Postman and it works, I had to put in the body the filename and the content of the file<a href="https://i.stack.imgur.com/79UpO.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/79UpO.jpg" alt="enter image description here" /></a></p>
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  <p><a href="https://i.stack.imgur.com/7JozR.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/7JozR.jpg" alt="enter image description here" /></a></p>
  <p>If I declare the filedata as file (see pic. 3) it works. I tried to do it in Java but I cannot find a way to do it. I tried many snippets from the web buut at best when I run them I get error 500.</p>
  <p>The code I got so far is</p>
  <pre><code>package api_post;
  
  import java.io.BufferedReader;
  import java.io.File;
  import java.io.FileInputStream;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.OutputStream;
  import java.io.OutputStreamWriter;
  import java.io.PrintWriter;
  import java.net.HttpURLConnection;
  import java.net.URL;
  import java.net.URLConnection;
  import java.util.ArrayList;
  import java.util.List;
  
  public class API_POST {
  
  /**
   * @param args the command line arguments
   */
  public static void main(String[] args) throws IOException {
    String charset = &quot;UTF-8&quot;;
      File uploadFile1 = new File(&quot;[fileWithPath]&quot;);
      String requestURL = &quot;&quot;;
      requestURL = &quot;[URL]&quot;;
      
      try {
          MultipartUtility multipart = new MultipartUtility(requestURL, charset);
           
           
          multipart.addFormField(&quot;username&quot;, &quot;[user]&quot;);
          multipart.addFormField(&quot;password&quot;, &quot;[pwd]&quot;);
          multipart.addFormField(&quot;owner&quot;, &quot;[owner]&quot;);
          multipart.addFormField(&quot;destination&quot;, &quot;[destination]&quot;);
           
          multipart.addFilePart(&quot;fileData&quot;, uploadFile1);
  
          List&lt;String&gt; response = multipart.finish();
           
          System.out.println(&quot;SERVER REPLIED:&quot;);
           
          for (String line : response) {
              System.out.println(line);
          }
      } catch (IOException ex) {
          System.err.println(ex);
      }
  }
  
  public static class MultipartUtility {
  private final String boundary;
  private static final String LINE_FEED = &quot;\r\n&quot;;
  private HttpURLConnection httpConn;
  private String charset;
  private OutputStream outputStream;
  private PrintWriter writer;
  
  public MultipartUtility(String requestURL, String charset) throws IOException {
      this.charset = charset;
       
      // creates a unique boundary based on time stamp
      boundary = &quot;===&quot; + System.currentTimeMillis() + &quot;===&quot;;
       
      URL url = new URL(requestURL);
      httpConn = (HttpURLConnection) url.openConnection();
      httpConn.setUseCaches(false);
      httpConn.setDoOutput(true); // indicates POST method
      httpConn.setDoInput(true);
      httpConn.setRequestProperty(&quot;Content-Type&quot;,
              &quot;multipart/form-data; boundary=&quot; + boundary);
  
      outputStream = httpConn.getOutputStream();
      writer = new PrintWriter(new OutputStreamWriter(outputStream, charset),
              true);
  }
  
  /**
   * Adds a form field to the request
   * @param name field name
   * @param value field value
   */
  public void addFormField(String name, String value) {
      writer.append(&quot;--&quot; + boundary).append(LINE_FEED);
      writer.append(&quot;Content-Disposition: form-data; name=\&quot;&quot; + name + &quot;\&quot;&quot;)
              .append(LINE_FEED);
      writer.append(&quot;Content-Type: text/plain; charset=&quot; + charset).append(
              LINE_FEED);
      writer.append(LINE_FEED);
      writer.append(value).append(LINE_FEED);
      writer.flush();
  }
  
  /**
   * Adds a upload file section to the request
   * @param fieldName name attribute in &lt;input type=&quot;file&quot; name=&quot;...&quot; /&gt;
   * @param uploadFile a File to be uploaded
   * @throws IOException
   */
  public void addFilePart(String fieldName, File uploadFile) throws IOException {
      String fileName = uploadFile.getName();
      writer.append(&quot;--&quot; + boundary).append(LINE_FEED);
      writer.append(
              &quot;Content-Disposition: form-data; name=\&quot;&quot; + fieldName
                      + &quot;\&quot;; filename=\&quot;&quot; + fileName + &quot;\&quot;&quot;)
              .append(LINE_FEED);
      writer.append(
              &quot;Content-Type: &quot;
                      + URLConnection.guessContentTypeFromName(fileName))
              .append(LINE_FEED);
      writer.append(&quot;Content-Transfer-Encoding: binary&quot;).append(LINE_FEED);
      writer.append(LINE_FEED);
      writer.flush();
  
      FileInputStream inputStream = new FileInputStream(uploadFile);
      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();    
  }
  
  /**
   * Adds a header field to the request.
   * @param name - name of the header field
   * @param value - value of the header field
   */
  public void addHeaderField(String name, String value) {
      writer.append(name + &quot;: &quot; + value).append(LINE_FEED);
      writer.flush();
  }
   
  /**
   * Completes the request and receives response from the server.
   * @return a list of Strings as response in case the server returned
   * status OK, otherwise an exception is thrown.
   * @throws IOException
   */
  public List&lt;String&gt; finish() throws IOException {
      List&lt;String&gt; response = new ArrayList&lt;String&gt;();
  
      writer.append(LINE_FEED).flush();
      writer.append(&quot;--&quot; + boundary + &quot;--&quot;).append(LINE_FEED);
      writer.close();
  
      // checks server's status code first
      int status = httpConn.getResponseCode();
      if (status == HttpURLConnection.HTTP_OK) {
          System.out.println(&quot;Entrato&quot;);
          BufferedReader reader = new BufferedReader(new InputStreamReader(
                  httpConn.getInputStream()));
          String line = null;
          while ((line = reader.readLine()) != null) {
              response.add(line);
          }
          reader.close();
          httpConn.disconnect();
      } else {
          throw new IOException(&quot;Server returned non-OK status: &quot; + status);
      }
  
      return response;
  }}}
  </code></pre>
  <p>Can anybody help me please?</p>