How to use javax.sip.header

/** decrement MaxForwards field one by one.
 */
public void decrementMaxForwards() throws TooManyHopsException {
  if (maxForwards > 0)
    maxForwards--;
  else throw new TooManyHopsException ("has already reached 0!");
}

/**
 * Creates a default content list.
 */
public MultipartMimeContentImpl(ContentTypeHeader contentTypeHeader) {
 this.multipartMimeContentTypeHeader = contentTypeHeader;
 this.boundary = contentTypeHeader.getParameter(BOUNDARY);
}

/**
 * Check if the via header is external
 * @param viaHeader the via header to check 
 * @return true if the via header is external, false otherwise
 */
public final boolean isViaHeaderExternal(ViaHeader viaHeader) {
  if (viaHeader != null) {			
    return isExternal(viaHeader.getHost(), viaHeader.getPort(), viaHeader.getTransport());
  }
  return true;
}

protected void setLocalParty(SIPMessage sipMessage) {
  if (!isServer()) {
    this.localParty = sipMessage.getFrom().getAddress();
  } else {
    this.localParty = sipMessage.getTo().getAddress();
  }
}

@Override
public CallIdHeader getCallId(
    MobicentsExtendedListeningPoint extendedListeningPoint, String callId) throws ParseException {
  String callIdString = callId;
  if(callIdString == null) {
    callIdString = extendedListeningPoint.getSipProvider().getNewCallId().getCallId();
  }
  if(callIdMaxLength > 0 && callIdString.length() > callIdMaxLength) {
    callIdString = callIdString.substring(0, callIdMaxLength);
  }
  return SipFactoryImpl.headerFactory.createCallIdHeader(callIdString);
}

  public boolean equals(Object other) {
    if (other instanceof ContentLengthHeader) {
      final ContentLengthHeader o = (ContentLengthHeader) other;
      return this.getContentLength() == o.getContentLength();
    }
    return false;
  }
}

public void setExpires(int seconds) {
  try {
    ExpiresHeader expiresHeader = 
      SipFactoryImpl.headerFactory.createExpiresHeader(seconds);			
    expiresHeader.setExpires(seconds);
    this.message.setExpires(expiresHeader);
  } catch (Exception e) {
    throw new IllegalArgumentException("Error setting expiration header!", e);
  }
}

private static int generateNcFromMessage(Message message) {
  int nc = 1;
  CSeqHeader cseq = (CSeqHeader) message.getHeader(CSeqHeader.NAME);
  if (cseq != null) {
    nc = (int) (cseq.getSeqNumber() % Integer.MAX_VALUE);
  }
  return nc;
}

  private static URI getURI(HeaderAddress header) {
    if (header == null) {
      return null;
    }
    Address address = header.getAddress();
    if (address == null) {
      return null;
    }
    return address.getURI();
  }
}

private void createEventHeader() throws ParseException {
  eventHeader = getHeaderFactory().createEventHeader(getEventHeaderName());
  eventHeader.setEventId(getEventId());        
}

public static String findRouteOrRequestUriTransport(Request request) {
  RouteHeader route = (RouteHeader) request.getHeader(RouteHeader.NAME);
  if(route != null) {
    URI uri = route.getAddress().getURI();
    return findURITransport(uri, request.getContentLength().getContentLength());
  }
  URI ruri = request.getRequestURI();
  return findURITransport(ruri, request.getContentLength().getContentLength());
}
// https://github.com/Mobicents/sip-servlets/issues/62

public String getCharacterEncoding() {
  if (this.message.getContentEncoding() != null) {
    return this.message.getContentEncoding().getEncoding();
  } else {
    ContentTypeHeader cth = (ContentTypeHeader)
      this.message.getHeader(ContentTypeHeader.NAME);
    if(cth == null) return null;
    return cth.getParameter("charset");
  }
}

  public boolean equals(Object other) {
    if (this==other) return true;
    if (other instanceof MaxForwardsHeader) {
      final MaxForwardsHeader o = (MaxForwardsHeader) other;
      return this.getMaxForwards() == o.getMaxForwards();
    }
    return false;
  }
}

/**
 * Removes all via headers from <tt>request</tt> and replaces them with a new one, equal to
 * the one that was top most.
 *
 * @param request the Request whose branchID we'd like to remove.
 *
 */
private void removeBranchID(Request request) {
  ViaHeader viaHeader = (ViaHeader) request.getHeader(ViaHeader.NAME);
  viaHeader.removeParameter("branch");
}

@Override
public Object clone() {
  ParameterableHeaderImpl cloned = new ParameterableHeaderImpl();
  cloned.parameters = cloneParameters(super.parameters);
  cloned.value = this.value;
  cloned.header = (Parameters)((Header)super.header).clone();
  return cloned;
}

public int getExpires() {
  if (this.message.getExpires() != null)
    return this.message.getExpires().getExpires();
  else
    return -1;
}

public Locale getContentLanguage() {
  if (this.message.getContentLanguage() != null)
    return this.message.getContentLanguage().getContentLanguage();
  else
    return null;
}

/**
 * Set the content length header.
 *
 * @param contentLength -- content length header.
 */
public void setContentLength(ContentLengthHeader contentLength) {
  try {
    this.contentLengthHeader.setContentLength(contentLength.getContentLength());
  } catch (InvalidArgumentException ex) {
  }
}

public int getMaxForwards() {
  return ((MaxForwardsHeader) ((Request) message)
      .getHeader(MaxForwardsHeader.NAME)).getMaxForwards();
}

public int getContentLength() {
  if (this.message.getContentLength() != null) {
    return this.message.getContentLength().getContentLength();
  } else {
    return 0;
  }
}