晚上好,我想知道如何清除写入PrintWriter的数据,即打印后是否可以从PrintWriter中删除数据?
在此 servlet 中,我将一些文本打印到响应中,并在 # 表示的行处,我想删除所有以前打印的数据并打印新内容:
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:我尝试了 out.flush() 但旧的打印文本仍然存在
创建一个内存中的PrintWriter
用一个StringWriter
。您可以从以下位置获取底层缓冲区StringWriter
并在需要时清除它。
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());
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