Utility class to check if a file is an Illustrator file based on XMP metadata.

IllustratorDetector.java

import java.io.BufferedInputStream;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.regex.Matcher;
import java.util.regex.Pattern;


/**
 * This utility class checks if a file is an Illustrator file.
 * This is necessary because Illustrator files masquerade as PDF files and you have to check the XMP data to confirm
 * that it's actually an Illustrator file.
 *
 * @author Mark Woon
 */
public class IllustratorDetector {

  private static boolean isStringChar(char ch) {
    if (ch >= 'a' && ch <= 'z')
      return true;
    if (ch >= 'A' && ch <= 'Z')
      return true;
    if (ch >= '0' && ch <= '9')
      return true;
    switch (ch) {
      case '/':
      case '-':
      case '+':
      case ':':
      case ';':
      case '.':
      case ',':
      case '_':
      case '=':
      case '"':
      case '&':
      case '$':
      case '%':
      case '#':
      case '\'':
      case '(':
      case ')':
      case '[':
      case ']':
      case '<':
      case '>':
        return true;
    }
    return false;
  }


  /**
   * Extracts XMP metadata from binary file.
   */
  public static String extract(Path file) throws IOException {

    StringBuilder xmpBuilder = new StringBuilder();
    try (BufferedInputStream in = new BufferedInputStream(Files.newInputStream(file))) {
      StringBuilder sb = new StringBuilder();
      int i;
      char ch;
      while ((i = in.read()) != -1) {
        ch = (char)i;
        if (xmpBuilder.length() > 0 && ch == '\n' && sb.length() > 0) {
          xmpBuilder.append('\n');
        }
        if (isStringChar(ch) || (sb.length() > 0 && (ch == ' '))) {
          // if so, build up string
          sb.append(ch);
        } else {
          // if not, see if anything to output
          if (sb.length() == 0) {
            continue;
          }
          if (sb.length() >= 4) {
            if (xmpBuilder.length() > 0 || sb.toString().startsWith("<x:xmpmeta")) {
              xmpBuilder.append(sb);
            }
            if (sb.toString().startsWith("</x:xmpmeta")) {
              break;
            }
          }
          sb.setLength(0);
        }
      }

      return xmpBuilder.toString();
    }
  }

  private static final Pattern sf_dcFormatPattern = Pattern.compile("<dc:format>(.*?)</dc:format>", Pattern.CASE_INSENSITIVE);

  /**
   * Checks if file is an Illustrator file based on XMP metadata.
   */
  public static boolean isIllustratorFile(Path file) throws IOException {
    
    String xmp = extract(file);
    if (xmp.length() == 0) {
      return false;
    }

    Matcher m = sf_dcFormatPattern.matcher(xmp);
    if (m.find()) {
      return m.group(1).equalsIgnoreCase("application/vnd.adobe.illustrator");
    }
    return false;
  }
}