Java Web应用开发实用教程 龚永罡 限制表单重复提交新.ppt

public synchronized void reset(HttpServletRequest request)...{ HttpSession session=request.getSession(false); if(session==null)...{ return; } session.removeAttribute(FORM_TOKEN_KEY); } /**//* * 产生表单标识号并将之保存在当前用户得session中 */ public synchronized void saveToken(HttpServletRequest request)...{ HttpSession session=request.getSession(); try ...{ byte id[]=session.getId().getBytes(); long current=System.currentTimeMillis(); if(current==privious)...{ current++; } privious=current; byte now[]=String.valueOf(current).getBytes(); MessageDigest md=MessageDigest.getInstance(MD5); md.update(id); md.update(now); String token=toHex(md.digest()); session.setAttribute(FORM_TOKEN_KEY, token); } catch (NoSuchAlgorithmException e) ...{ } } /**//* * 将一个字节数转换成十六进制得字符串 * */ public String toHex(byte buffer[])...{ StringBuffer sb=new StringBuffer(buffer.length*2); for (int i = 0; i buffer.length; i++) ...{ sb.append(Character.forDigit((buffer[i]0x60)4, 16)); sb.append(Character.forDigit(buffer[i]0x0f, 16)); } return sb.toString(); } } import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class FormDoubleServlet extends HttpServlet ...{ protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException ...{ response.setContentType(text/html;charset=gb2312); PrintWriter out=response.getWriter(); TokenProcessor tokemProcessor=TokenProcessor.getInstance(); if(!tokemProcessor.isTokenValid(request))...{ out.println(重复提交);