java – 将ServletOutputStream读取到String

我试图阅读FreemarkerView渲染的结果：

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

为了读取结果,我创建了mockResponse,它封装了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"));
    }
}

还有我的ServletOutputStream,它使用StringBuilder构建String：

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();
    }
}

有了这些,我可以使用方法ServletOutputStreamEx.toString轻松读取响应.

我的问题是write方法没有按正确的顺序调用,最后最终的String混合而且顺序不正确.这可能是由Freemarker中的并发引起的,但我不知道如何修复它.