我创建status.jsp用于在数据库中插入文件的状态数据。状态有两个选项（IN或OUT）。提交它会转到inserted.jsp，表示已插入数据，并为status.jsp提供goback链接以插入更多或注销。
我希望用户无法注销，除非他选择了IN（做完后）。
例如，用户在提交后输入某个文件编号的状态会导致inserted.jsp页面返回status.jsp页面并尝试注销，但他/她在进入状态IN之前无法进行操作对于他输入的相同文件号。我该怎么做？
如果某人可以提供某个类似示例的链接，或者解释类似内容的网站也会有帮助
status.jsp（仅限正文）
<body style="background-color:lightsteelblue;">
<%
String userName = null;
String sessionID = null;
Cookie[] cookies = request.getCookies();
if (cookies != null) {
for (Cookie cookie : cookies) {
if (cookie.getName().equals("user")) {
userName = cookie.getValue();
}
}
}
%>
<header>
<h3>File Tracking System</h3>
<div><span style="float:right">Hi <%=userName%></span></div>
<br>
</header>
<a href="create1.jsp"><font color="black">back</font></a>
<form action=" LogoutServlet" method="post">
<input type="submit" value="Logout" >
</form>
<nav>
<h3>Change Status</h3>
<form action="statusServlet" method="post">
<table>
<tbody>
<tr>
<td>
File Number :<select name="files">
<%
try {
String sql = "select * from files";
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/login",
"root", "root");
Statement st = con.createStatement();
ResultSet rs = st.executeQuery(sql);
while (rs.next()) {
%>
<option value="<%=rs.getString("fileno")%>"><%=rs.getString("fileno")%></option>
<%}
rs.close();
st.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
%>
</select></td>
</tr>
<tr>
<td>
File Department :<select name="departments">
<%
try {
String sql = "select * from department";
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/login",
"root", "root");
Statement st = con.createStatement();
ResultSet rs = st.executeQuery(sql);
while (rs.next()) {
%>
<option value="<%=rs.getString("departmentname")%>"><%=rs.getString("departmentname")%></option>
<%}
rs.close();
st.close();
con.close();
} catch (Exception e) {
e.printStackTrace();
}
%>
</select></td>
</tr>
<tr>
<td>
File Status:
<br>
<select name="input">
<option>IN</option>
<option>OUT</option>
</select></td>
</tr>
<tr>
<td>
<input type="submit" value="submit" name="submit" />
</td>
</tr>
</tbody>
</table>
</form>
</nav>
<section><img src="css/NSIC-logo1.png" width="537" height="267" alt="NSIC-logo1"/>
</section>
<footer>
Copyright 2016 NSIC. All right reserved.
</footer>
</body>
statusServlet.java（仅在数据库中插入值）
public class statusServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
Cookie[] cookies = request.getCookies();
if (cookies != null) {
for (Cookie cookie : cookies) {
if (cookie.getName().equals("JSESSIONID")) {
System.out.println("JSESSIONID=" + cookie.getValue());
break;
}
}
}
HttpSession session = request.getSession(false);
System.out.println("User=" + session.getAttribute("user"));
if (session != null && session.getAttribute("user") != null) {
String user = (String) session.getAttribute("user");
boolean status = false;
try {
String fname = request.getParameter("files");
String departments = request.getParameter("departments");
String input = request.getParameter("input");
int i;
if (input.equals("IN")) {
i = 1;
} else {
i = 0;
}
Connection con = ConnectionProvider.getCon();
String sql = "insert into status(fname,fstatus,department) values (?,?,?) ";
PreparedStatement pstmt = con.prepareStatement(sql);
pstmt.setString(1, fname);
pstmt.setInt(2, i);
pstmt.setString(3, departments);
int rs = pstmt.executeUpdate();
if (rs > 0) {
if (input.equals("IN")) {
String sql1 = "update files set location='" + departments + "' where fileno='" + fname + "'";
PreparedStatement st = con.prepareStatement(sql1);
int rs1 = st.executeUpdate();
}
status = true;
}
} catch (Exception e) {
}
if (status) {
response.sendRedirect("inserted.jsp");
PrintWriter out = response.getWriter();
out.println("Values have been inserted," + user);
//out.flush();
} else {
PrintWriter out = response.getWriter();
out.println("failed");
response.sendRedirect("notinserted.jsp");
}
} else {
RequestDispatcher rd = getServletContext().getRequestDispatcher("/index.html");
PrintWriter out = response.getWriter();
out.println("<font color=red>Either user name or password is wrong.</font>");
rd.include(request, response);
}
}
}
inserted.jsp（仅限正文）
<body style="background-color:lightsteelblue;">
<header>Data inserted!!</header>
<a href="fileStatus.jsp"><font color="black"> goback</font></a>
<form action=" LogoutServlet" method="post">
<input type="submit" value="Logout" >
</form>
<footer>
Copyright 2008 NSIC. All right reserved.
</footer>
</body>
答案 0 :(得分：0)
使用HttpSession记住以前的选择
// add following lines in 'doPost' method after session initialization in statusServlet
String input = request.getParameter("input"); // you have wrote this one already
if(input != null && (input.equals("IN") || input.equals("OUT"))){
session.setAttribute("last-value", input);
}
和...
//wrap logout form in status.jsp like following:
<%
String lastValue = session.getAttribute("last-value");
if(lastValue != null && lastValue.equals("IN")){
%>
<form action=" LogoutServlet" method="post">
<input type="submit" value="Logout" >
</form>
<%
}
%>
注意：我没有测试过这个，我只是在Notepad ++中编写代码
如果您需要更多帮助，请发表评论