写入后如何清除PrintWriter的内容

本文介绍了写入后如何清除PrintWriter的内容的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

晚上好，我想知道如何清除写入到PrintWriter中的数据，即，打印后是否可以从PrintWriter中删除数据?

Good evening, i want to know how to clear the data written to a PrintWriter, i.e. is it possible to remove the data from a PrintWriter after printing?

在此servlet中，我在响应中打印一些文本，并在#表示的行上删除所有先前打印的数据并打印新内容:

here in this servlet i print some text to the response and at the line denoted by # i want to remove all the previously printed data and print new stuff:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { PrintWriter out = response.getWriter(); String uName = request.getParameter("uName"); String uPassword = request.getParameter("uPassword"); if (uName .equals("Islam")) { out.println("Valid-Name"); if (uPassword !=null) { if (uPassword .equals("Islam")) { // # clear the writer from any printed data here out.println("Valid-password"); } else { out.println(""); out.println("InValid-password"); } } } else { out.println("InValid-Name"); } }

注意:我尝试过out.flush()，但旧的打印文本仍然保留

Note: i tried out.flush() but the old printed text remains

推荐答案

使用 StringWriter 创建内存中的 PrintWriter .您可以从 StringWriter 获取基础缓冲区，并在需要时清除它.

Create an in-memory PrintWriter using a StringWriter. You can get the underlying buffer from the StringWriter and clear it if you need to.

StringWriter sr = new StringWriter(); PrintWriter w = new PrintWriter(sr); w.print("Some stuff"); // Flush writer to ensure that it's not buffering anything w.flush(); // clear stringwriter sr.getBuffer().setLength(0); w.print("New stuff"); // write to Servlet out w.flush(); response.getWriter().print(sr.toString());