Program: 93487
Project: 93487
Buggy source:
/** 
 * @param exchange
 * @param context
 * @throws Exception
 */
@Override public void handleRequest(HttpServerExchange exchange,RequestContext context) throws Exception {
  DBObject content=context.getContent();
  if (content == null) {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_NOT_ACCEPTABLE,"String_Node_Str");
    return;
  }
  if (content instanceof BasicDBList) {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_NOT_ACCEPTABLE,"String_Node_Str");
    return;
  }
  Object id=context.getDocumentId();
  if (content.get("String_Node_Str") == null) {
    content.put("String_Node_Str",id);
  }
 else   if (!content.get("String_Node_Str").equals(id)) {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_NOT_ACCEPTABLE,"String_Node_Str");
    return;
  }
  ObjectId requestEtag=RequestHelper.getWriteEtag(exchange);
  OperationResult result=documentDAO.upsertDocument(context.getDBName(),context.getCollectionName(),context.getDocumentId(),content,requestEtag,true);
  if (result.getEtag() != null) {
    exchange.getResponseHeaders().put(Headers.ETAG,result.getEtag().toString());
  }
 else {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_CONFLICT,"String_Node_Str" + Headers.IF_MATCH + "String_Node_Str");
    return;
  }
  if (context.getWarnings() != null && !context.getWarnings().isEmpty()) {
    sendWarnings(result.getHttpCode(),exchange,context);
  }
 else {
    exchange.setResponseCode(result.getHttpCode());
  }
  exchange.endExchange();
}

Fixed version (ground truth):
/** 
 * @param exchange
 * @param context
 * @throws Exception
 */
@Override public void handleRequest(HttpServerExchange exchange,RequestContext context) throws Exception {
  DBObject content=context.getContent();
  if (content == null) {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_NOT_ACCEPTABLE,"String_Node_Str");
    return;
  }
  if (content instanceof BasicDBList) {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_NOT_ACCEPTABLE,"String_Node_Str");
    return;
  }
  Object id=context.getDocumentId();
  if (content.get("String_Node_Str") == null) {
    content.put("String_Node_Str",id);
  }
 else   if (!content.get("String_Node_Str").equals(id)) {
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_NOT_ACCEPTABLE,"String_Node_Str");
    return;
  }
  ObjectId requestEtag=RequestHelper.getWriteEtag(exchange);
  OperationResult result=documentDAO.upsertDocument(context.getDBName(),context.getCollectionName(),context.getDocumentId(),content,requestEtag,true);
  if (result.getEtag() != null) {
    exchange.getResponseHeaders().put(Headers.ETAG,result.getEtag().toString());
  }
 else {
    ResponseHelper.injectEtagHeader(exchange,this.documentDAO.getDocumentEtag(context.getDBName(),context.getCollectionName(),context.getDocumentId()));
    ResponseHelper.endExchangeWithMessage(exchange,HttpStatus.SC_CONFLICT,"String_Node_Str" + Headers.IF_MATCH + "String_Node_Str");
    return;
  }
  if (context.getWarnings() != null && !context.getWarnings().isEmpty()) {
    sendWarnings(result.getHttpCode(),exchange,context);
  }
 else {
    exchange.setResponseCode(result.getHttpCode());
  }
  exchange.endExchange();
}