Question

我有一个employeeDB类，我在其中设置了与db的连接，我可以从db中读取数据。在这个类中，我有一个名为getAllEmaployee的函数，用于检索数据，它看起来像这样：

public class EmployeeDB {

    private Connection connection;

    public EmployeeDB() {
        connection = DBUtil.getConnection();
    }

    public HashMap<String, List<String>> getAllEmployee() throws FileNotFoundException, UnsupportedEncodingException {

        HashMap<String, List<String>> total = new HashMap<>();

        try {

            Statement statementE = connection.createStatement();
            PreparedStatement pStatement = connection.prepareStatement("select month from paycheck where id=?");

            ResultSet rse = statementE.executeQuery("select id from employee");


            while (rse.next()) {    
                List<String> months = new ArrayList<>();

                pStatement.setString(1, rse.getString("id"));
                ResultSet rs = pStatement.executeQuery();


                while (rs.next()) {
                    months.add(rs.getString("month"));
                }

                total.put(rse.getString("id"), months);
            }

        } catch (SQLException e) {

            e.printStackTrace();

        }
        return total;
    }
}

现在，我从我的servlet调用这个方法＆＃34; EmployeeInfo＆＃34;并返回具有我需要的所有数据对的hashmap（我已经打印过，看到我有正确的数据）。

现在我希望从servlet将此hashmap设置为会话的属性，然后转到我的jsp文件并使用此hashmap数据填充表。这是我的servlet：

public class EmployeeInfo extends HttpServlet {

    private final EmployeeDB edb;

    public EmployeeInfo() {
        super();
        edb = new EmployeeDB();
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String forward = "";
        Employee e = new Employee();
        Employee retEmp = new Employee();
        HashMap<String, List<String>> total = new HashMap<>();
        e.setId(request.getParameter("ID"));

        try {
            retEmp = edb.getEmpInfo(e.getId());

            if (e.getId().equals("")) {
                total=edb.getAllEmployee();
                request.getSession().setAttribute("EmployeeHashMap", total);
                forward = "AllEmployee.jsp?";
            }            
            else if (retEmp.getId() == null) {
                forward = "errorID.jsp?";
            } else {

                request.getSession().setAttribute("newEmployee", retEmp);
                forward = "WelcomeUser.jsp";
            }
            RequestDispatcher view = request.getRequestDispatcher(forward);
            view.forward(request, response);

        } catch (SQLException ex) {
            Logger.getLogger(EmployeeInfo.class.getName()).log(Level.SEVERE, null, ex);
        }

    }

}

现在在AllEmployee.jsp我希望填充表格，它看起来像这样：

<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>
    </head>
    <body>
        <table id="ptable" border="1">

            <tr>
                <td style="text-align: center;">ID</td>
                <td style="text-align: center;">Month</td>
            </tr>
            <c:forEach var="entry" items="${EmployeeHashMap}" >
                <!-- entry.key is employee.key -->
                <!-- entry.value is employee.skills -->
                <c:forEach var="skillId" items="${entry.value}" >
                    <tr>
                        <td>${entry.key}</td>
                        <td>${skillId}</td>
                    </tr>
                </c:forEach>
            </c:forEach>
        </table>
    </body>
</html>Type a message

我不知道为什么它不工作，我可以看到一张空桌子...... 请尽量帮我解决这个问题。感谢!!!

无法使用servlet和jsp使用java hashmap填充html表

0 个答案: