How to use io.netty.handler.codec.http

@Override
public int getRawStatusCode() throws IOException {
  return this.nettyResponse.getStatus().code();
}

@Override
public String getStatusText() throws IOException {
  return this.nettyResponse.getStatus().reasonPhrase();
}

  @Override
  public List<String> setValue(List<String> value) {
    List<String> previousValues = headers.getAll(this.key);
    headers.set(this.key, value);
    return previousValues;
  }
}

private static final FullHttpResponse http404() {
  FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.NOT_FOUND);
  HttpHeaders httpHeaders = response.headers();
  httpHeaders.set(HttpHeaders.Names.CONTENT_TYPE, "text/plain");
  httpHeaders.set(HttpHeaders.Names.CONTENT_LENGTH, response.content().readableBytes());
  return response;
}

 private void writeResponse(ChannelHandlerContext ctx, HttpRequest request, ByteBuf buf, CharSequence contentType, CharSequence contentLength) {
  // Build the response object.
  FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK, buf, false);
  HttpHeaders headers = response.headers();
  headers.set(CONTENT_TYPE_ENTITY, contentType);
  headers.set(SERVER_ENTITY, SERVER_NAME);
  headers.set(DATE_ENTITY, date);
  headers.set(CONTENT_LENGTH_ENTITY, contentLength);
  // Close the non-keep-alive connection after the write operation is done.
  ctx.write(response, ctx.voidPromise());
 }
});

@Override
public void addAll(String key, List<? extends String> values) {
  this.headers.add(key, values);
}

 @Override
 protected HttpMessage createMessage(String[] initialLine) {
  return new DefaultHttpRequest(
   HttpVersion.valueOf(initialLine[2]),
   HttpMethod.valueOf(initialLine[0]),
   initialLine[1],
   new VertxHttpHeaders());
 }
}

@Override
public boolean containsKey(Object key) {
  return (key instanceof String && this.headers.contains((String) key));
}

@Override
public List<String> getValue() {
  return headers.getAll(this.key);
}

@Override
public Set<String> keySet() {
  return this.headers.names();
}

@Override
public boolean isEmpty() {
  return this.headers.isEmpty();
}

@Override
public String rawMethod() {
 if (rawMethod == null) {
  rawMethod = request.method().toString();
 }
 return rawMethod;
}

@Override
public void clear() {
  this.headers.clear();
}

  @Override
  public int size() {
    return headers.size();
  }
};

private static final FullHttpResponse http404() {
  FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.NOT_FOUND);
  HttpHeaders httpHeaders = response.headers();
  httpHeaders.set(HttpHeaders.Names.CONTENT_TYPE, "text/plain");
  httpHeaders.set(HttpHeaders.Names.CONTENT_LENGTH, response.content().readableBytes());
  return response;
}

@Nullable
@Override
public List<String> put(String key, @Nullable List<String> value) {
  List<String> previousValues = this.headers.getAll(key);
  this.headers.set(key, value);
  return previousValues;
}

private static final FullHttpResponse http200(String result) {
  FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK,
      Unpooled.wrappedBuffer(result.getBytes()));
  HttpHeaders httpHeaders = response.headers();
  httpHeaders.set(HttpHeaders.Names.CONTENT_TYPE, "text/plain");
  httpHeaders.set(HttpHeaders.Names.CONTENT_LENGTH, response.content().readableBytes());
  return response;
}

private static final FullHttpResponse http200(String result) {
  FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.OK,
      Unpooled.wrappedBuffer(result.getBytes()));
  HttpHeaders httpHeaders = response.headers();
  httpHeaders.set(HttpHeaders.Names.CONTENT_TYPE, "text/plain");
  httpHeaders.set(HttpHeaders.Names.CONTENT_LENGTH, response.content().readableBytes());
  return response;
}

private static final FullHttpResponse http500(String errorMessage) {
  FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.INTERNAL_SERVER_ERROR
      , Unpooled.wrappedBuffer(errorMessage.getBytes()));
  HttpHeaders httpHeaders = response.headers();
  httpHeaders.set(HttpHeaders.Names.CONTENT_TYPE, "text/plain");
  httpHeaders.set(HttpHeaders.Names.CONTENT_LENGTH, response.content().readableBytes());
  return response;
}

private static final FullHttpResponse http500(String errorMessage) {
  FullHttpResponse response = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, HttpResponseStatus.INTERNAL_SERVER_ERROR
      , Unpooled.wrappedBuffer(errorMessage.getBytes()));
  HttpHeaders httpHeaders = response.headers();
  httpHeaders.set(HttpHeaders.Names.CONTENT_TYPE, "text/plain");
  httpHeaders.set(HttpHeaders.Names.CONTENT_LENGTH, response.content().readableBytes());
  return response;
}