Servlet及JSP中的多線程同步問題

// instanceconcurrenttest.jsp<%@ page contentType="text/html;charset=GBK" %><%!     //定義實(shí)例變量     String username;     String password;    java.io.PrintWriter output;%><%     //從request中獲取參數(shù)    username = request.getParameter("username");    password = request.getParameter("password");    output = response.getWriter();    showUserInfo();  %> <%!     public void showUserInfo() {         //為了突出并發(fā)問題，在這兒首先執(zhí)行一個(gè)費(fèi)時(shí)操作         int i =0;         double sum = 0.0;         while (i++ < 200000000) {             sum += i;         }                  output.println(Thread.currentThread().getName() + "<br>");       output.println("username:" + username + "<br>");        output.println("password:" + password + "<br>");     } %>

// InstanceConcurrentTest.javaimport javax.servlet.*;import javax.servlet.http.*;import java.io.PrintWriter;public class InstanceConcurrentTest extends HttpServlet {       String username;       String password;       PrintWriter out;       public void doGet(HttpServletRequest request,        HttpServletResponse response)                 throws ServletException,java.io.IOException        {             //從request中獲取參數(shù)      username = request.getParameter("username");    password = request.getParameter("password");     System.out.println(Thread.currentThread().getName() +     "   set username:" + username);    out = response.getWriter();     showUserInfo();         }        public void showUserInfo() {             //為了突出并發(fā)問題，在這兒首先執(zhí)行一個(gè)費(fèi)時(shí)操作      int i =0;      double sum = 0.0;      while (i++ < 200000000) {       sum += i;      }      out.println("thread:" + Thread.currentThread().getName());    out.println("username:"+ username);     out.println("password:" + password);  }}

<%@ page contentType="text/html;charset=GBK" %><%     //使用局部變量    String username;    String password;    java.io.PrintWriter output;    //從request中獲取參數(shù)    username = request.getParameter("username");    password = request.getParameter("password");    output = response.getWriter();    showUserInfo(output, username, password);%><%!     public void showUserInfo(java.io.PrintWriter _output,     String _username, String _password) {    //為了突出并發(fā)問題，在這兒首先執(zhí)行一個(gè)費(fèi)時(shí)操作      int i =0;       double sum = 0.0;       while (i++ < 200000000) {         sum += i;        }          _output.println(Thread.currentThread().getName() + "<br>");      _output.println("username:" + _username + "<br>");      _output.println("password:" + _password + "<br>");      }%>