public static Escaper xmlAttributeEscaper() {
    return XML_ATTRIBUTE_ESCAPER;
  }

  private static final Escaper XML_ESCAPER;
  private static final Escaper XML_CONTENT_ESCAPER;
  private static final Escaper XML_ATTRIBUTE_ESCAPER;

  static {
    Escapers.Builder builder = Escapers.builder();
    // The char values \uFFFE and \uFFFF are explicitly not allowed in XML

    Escaper escaper = Escapers.builder().setSafeRange('a', 'z').build();
    assertThat(escaper.escape("The Quick Brown Fox")).isEqualTo("The Quick Brown Fox");
  }

  public void testBuilderInitialStateNoneUnsafe() {
    // No characters are unsafe by default (safeMin == 0, safeMax == 0xFFFF).
    Escaper escaper = Escapers.builder().setUnsafeReplacement("X").build();
    assertThat(escaper.escape("\0\uFFFF")).isEqualTo("\0\uFFFF");

    }
  }

  public void testFalsePositivesForNextEscapedIndex() {
    UnicodeEscaper e =
        new UnicodeEscaper() {
          // Canonical escaper method that only escapes lower case ASCII letters.
          @Override
          protected char @Nullable [] escape(int cp) {
            return ('a' <= cp && cp <= 'z') ? new char[] {Character.toUpperCase((char) cp)} : null;
          }

    }
  }

  public void testFalsePositivesForNextEscapedIndex() {
    UnicodeEscaper e =
        new UnicodeEscaper() {
          // Canonical escaper method that only escapes lower case ASCII letters.
          @Override
          protected char @Nullable [] escape(int cp) {
            return ('a' <= cp && cp <= 'z') ? new char[] {Character.toUpperCase((char) cp)} : null;
          }

    assertUnicodeEscaping(e, "%F4%8F%BF%BF", '\uDBFF', '\uDFFF');

    // simple string tests
    assertEquals("", e.escape(""));
    assertEquals("safestring", e.escape("safestring"));
    assertEquals("embedded%00null", e.escape("embedded\0null"));
    assertEquals("max%EF%BF%BFchar", e.escape("max\uffffchar"));
  }

  /** Tests the various ways that the space character can be handled */
  public void testPlusForSpace() {

    assertUnicodeEscaping(e, "%F4%8F%BF%BF", '\uDBFF', '\uDFFF');

    // simple string tests
    assertEquals("", e.escape(""));
    assertEquals("safestring", e.escape("safestring"));
    assertEquals("embedded%00null", e.escape("embedded\0null"));
    assertEquals("max%EF%BF%BFchar", e.escape("max\uffffchar"));
  }

  /** Tests the various ways that the space character can be handled */
  public void testPlusForSpace() {

    }

    /**
     * Escapes specific characters in a query string.
     * Replaces each specified character with its escaped version (prefixed with backslash).
     *
     * @param q the query string to escape
     * @param values the characters to escape
     * @return the escaped query string
     */
    protected String escape(final String q, final String... values) {
        String value = q;

 *
 */
public class JsonUtil {

    /**
     * Defualt constructor.
     */
    protected JsonUtil() {
    }

    /**
     * Escapes a value as Json string.
     *
     * @param value input
     * @return escaped string.
     */
    public static String escape(final String value) {
        if (value == null) {
            return null;
        }

        char c;
        final int len = value.length();

            return escape(s) + ".*";
        }
        final StringBuilder buf = new StringBuilder(100);
        return appendFileterPath(buf, escape(s));
    }

    /**
     * Escapes special regex characters in a string to create a literal pattern.

    }

    /**
     * Escapes a callback name.
     * @param callbackName The callback name.
     * @return The escaped callback name.
     */
    protected String escapeCallbackName(final String callbackName) {
        return "/**/" + callbackName.replaceAll("[^0-9a-zA-Z_\\$\\.]", StringUtil.EMPTY);
    }

    /**
     * Escapes a JSON object.
     * @param obj The object to escape.