Reading ServletOutputStream for string

Question

I am trying to read the FreemarkerView rendering result:

View view = viewResolver.resolveViewName(viewName, locale);
view.render(model, request, mockResponse);

To read the result, I created mockResponseone that encapsulates the HttpServletResponse:

public class HttpServletResponseEx extends HttpServletResponseWrapper {

    ServletOutputStream outputStream;

    public HttpServletResponseEx(HttpServletResponse response) throws IOException {
        super(response);
        outputStream = new ServletOutputStreamEx();
    }

    @Override
    public ServletOutputStream getOutputStream() {
        return outputStream;
    }

    @Override
    public PrintWriter getWriter() throws IOException {
        return new PrintWriter(new OutputStreamWriter(outputStream, "UTF-8"));
    }
}

And also my ServletOutputStream, which builds a String using StringBuilder:

public class ServletOutputStreamEx extends ServletOutputStream {

    StringBuilder stringBuilder;

    public ServletOutputStreamEx() {
        this.stringBuilder = new StringBuilder();
    }

    @Override
    public void write(int b) throws IOException {
    } 

    @Override
    public void write(byte b[], int off, int len) throws IOException {
        stringBuilder.append(new String(b, "UTF-8"));
    }

    @Override
    public String toString() {
        return stringBuilder.toString();
    }
}

With these, I can easily read the answer using the method ServletOutputStreamEx.toString.

My problem is that the write method is not called in the correct order, and in the end the final line is mixed, not in the correct order . This is probably caused by concurrency in Freemarker, but I have no idea how to fix it.

Answer 1

: write(int b) , . - , . String(b, off, len, "UTF-8").