将mvc概念中的会话值从jsp传递给java中的servlet

Question

我正在使用 mvc 概念，因为我有一个带有一些私有字段和 setter 和 getter 方法的类，一个登录类一个操作类是 EmployeeBean，因为所有功能都在那里登录类在我到达另一个时正常工作EmployeeDetail.jsp 页面，然后当我通过普通 url 方式移动到 DailyWork.jsp 时 我可以检索会话变量，并且我保留了一个 empID 变量，即使我没有维护会话，它仍在打印，但是当我移动到 DailyWorkUpdate servlet 并尝试以给定方式接收会话变量时

 String z = emp.getName();

System.out.println("....name is " +z);
System.out.println("....n is " +n);
emp.setEmpId(emp.getEmpId());

n 是整数，表示它是 0，z 是字符串，表示 null 请帮我解决这个问题

这里是完整的代码...

   public class Employee {
   private int empId;
   private String Name;
   private String phone;
   private String email;
   private float salary;
   private String designation;
   private String password;
   private String access_type;
   private boolean valid;
   private String field1;
   private String field2;
   private String field3;
  public String getAccess_type() {
    return access_type;
  }
  public void setAccess_type(String access_type) {
    this.access_type = access_type;
  }
  public boolean isValid() {
    return valid;
  }

  public String getField1() {
    return field1;
  }
  public void setField1(String field1) {
    this.field1 = field1;
  }
  public String getField2() {
    return field2;
 }
 public void setField2(String field2) {
    this.field2 = field2;
 }
 public String getField3() {
    return field3;
 }
 public void setField3(String field3) {
    this.field3 = field3;
 }

  public void setValid(boolean valid) {
    this.valid = valid;
  }
  public int getEmpId() {
    return empId;
  }
  public void setEmpId(int empId) {
    this.empId = empId;
  }
  public String getName() {
    return Name;
  }
  public void setName(String Name) {
    this.Name = Name;
  }
  public String getPhone() {
    return phone;
  }
  public void setPhone(String phone) {
    this.phone = phone;
  }
  public String getEmail() {
    return email;
  }
  public void setEmail(String email) {
    this.email = email;
  }
  public float getSalary() {
    return salary;
  }
  public void setSalary(float salary) {
    this.salary = salary;
  }
  public String getDesignation() {
    return designation;
  }
  public void setDesignation(String designation) {
    this.designation = designation;
  }
  public String getPassword() {
    return password;
  }
  public void setPassword(String password) {
    this.password = password;
  }
  }

EmployeeBean 类

    public class EmployeeBean {
     public Employee login(int id, String password) {
        Connection con = null;
        Employee emp = null;
        Statement stmt = null;
        try {

            con = ConnectionManager.getConnection();
            stmt = con.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT * FROM emp WHERE empId 
         ='"+id+"' and password ='"+password+"'");
            boolean more = rs.next();
             if (!more) {

     System.out.println("Sorry, you are not a registered user! Please sign up first");
             emp.setValid(false);
            }
            else if(more)
            {
                emp = new Employee();
                emp.setEmpId(rs.getInt("empId"));
                emp.setName(rs.getString("empName"));
                emp.setPhone(rs.getString("phone"));
                emp.setEmail(rs.getString("email"));
                emp.setSalary(rs.getFloat("salary"));
                emp.setDesignation(rs.getString("desig"));
                emp.setPassword(rs.getString("password"));
                emp.setAccess_type(rs.getString("employee_type"));
                String Name = rs.getString("empId");

                System.out.println("id is :" +Name);

                emp.setValid(true);
            }
        } catch (SQLException  ex) {

        } finally {
            try {
                if (stmt != null) {
                    stmt.close();
                }
                if (con != null) {
                    con.close();
                }
            } catch (SQLException ex) {
            Logger.getLogger(EmployeeBean.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
        return emp;
    }

登录.Java

   @WebServlet(name = "Login", urlPatterns = {"/Login"})
    public class Login extends HttpServlet {
    protected void processRequest(HttpServletRequest request, 
    HttpServletResponse response)
            throws ServletException, IOException {
        HttpSession session = request.getSession(true);    
        Employee emp = new Employee();
        int id = Integer.parseInt(request.getParameter("empId"));
        String password = request.getParameter("password");
        EmployeeBean eb = new EmployeeBean();
       emp = eb.login(id,password);
       if(emp.isValid())
       {
           session.setAttribute("emp",emp);
           response.sendRedirect("EmployeeDetail.jsp"); 
           }


   }
        @Override
        protected void doGet(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            processRequest(request, response);
        }

           @Override
        protected void doPost(HttpServletRequest request, HttpServletResponse response)
                throws ServletException, IOException {
            processRequest(request, response);
        }

         @Override
        public String getServletInfo() {
            return "Short description";
        }
      }

EmployeeDetail.jsp

  <%@page import="com.info.EmployeeBean"%>
  <%@page import="com.info.Employee"%>
  <%@page import="java.util.List"%>

 <html>
 <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <link href="style.css" rel="stylesheet" type="text/css"/>
    <title>Employee Update Page</title>
  </head>
  <body>

 <ul>
  <li class='has-sub'>
        <a href="./DailyWork.jsp"><span>Update Your Work</span></a></li>
  <li class='has-sub'>
        <a href="./WorkDetail"><span>View Your Work Details</span></a></li>
  <li class='has-sub'>
    <a href="./ExcelFileGen.jsp"><span>Generetae Excel Sheet</span></a></li>
  </ul>


     <table align=center cellspacing=1 cellpadding=3>
   <p>Emp Id: ${info.empId}</p>
   <p> name is :${info.name}</p>
   <p>password is: ${info.password}</p>
    <p>designation: ${info.designation}</p>
 <p>email : ${info.email}</p>
 <p>salary: ${info.salary}</p>
 </table>
 </body>
 </html>

登录.jsp

    <%@page import="com.info.EmployeeBean"%>
   <%@page import="com.info.Employee"%>
   <%@page import="java.util.List"%>
<html>
   <form name="form" action="Login" method="post">

    <input type="text" name="empId" /><br>
   <input type="password" name ="password" /><br>
  <input type="submit" name="login" value="login" >
   </form>
   </html>

DailyWorkUpdate.jsp

   <%@page import="com.info.EmployeeBean"%>
   <%@page import="com.info.Employee"%>
    <%@page import="java.util.List"%>


  <html>
  <head>
 </head>

   <body>

  <%
  Employee emp = (Employee)session.getAttribute("emp");
  session.setAttribute("emp",emp);
  %>

      <ul>
     <li class='has-sub'>
         <a href="./DailyWork.jsp"><span>Update Your Work</span></a>
    </li>
     <li class='has-sub'>
         <a href="./WorkDetail"><span>View Your Work Details</span></a>
     </li>
     <li class='has-sub'>
         <a href="./ExcelFileGen.jsp"><span>Generetae Excel Sheet</span></a>
    </li>
     </ul>


     <table width="780" align=center cellspacing=0 border="4" cellpadding=0>
      <tr>
                    <td>
                        <fieldset id="fieldhead">
                            <legend>Update your DailyWork</legend>
                            <BR>
                            <table align=center cellspacing=1 cellpadding=3>
                        <form  name ="form" method= get action="DailyWorkUpdate">
                                <center>
                                    <tr>
                                    <Td>Support HRS</td>
                                    <TD><input name="field1"></td>
                                </tr>

                                <tr>
                                    <td> emp id</td>
                                    <td>${emp.empId}</td>
                                    </tr>
                                <tr>
                                    <Td>Leave  HRS</td>
                                    <TD><input name="field2" ></td>
                                </tr>

                                <tr>
                                    <Td>Project name</td>
                                    <TD><input name="field3"></td>
                                </tr>
            <tr><td><input type="submit"  value="DailyWorkUpdate" />
        &nbsp;&nbsp;<button type=reset accesskey="R"><u>R</u>efresh</button></td></tr>
                                </center>
                            </table>
                            <BR>
                        </fieldset>
                    </td>
                </tr>
            </table>
      </body>
     </html>






  @WebServlet(name = "DailyWorkUpdate", urlPatterns = {"/DailyWorkUpdate"})
  public class DailyWorkUpdate extends HttpServlet
  {

 protected void processRequest(HttpServletRequest request, 
 HttpServletResponse response)
        throws ServletException, IOException {
   HttpSession session = request.getSession(true);  

  Employee emp = (Employee)session.getAttribute("emp");
  session.setAttribute("emp",emp);
  java.sql.Date date = new java.sql.Date(new java.util.Date().getTime());

  emp = new Employee();
int n = emp.getEmpId();
String z = emp.getName();

   System.out.println("....name is " +z);// it is showing null
 System.out.println("....n is " +n);// it is showing 0 why i dont know how to get this 
 emp.setEmpId(emp.getEmpId());
 emp.setField1(request.getParameter("field1"));
 emp.setField2(request.getParameter("field2"));
  emp.setField3(request.getParameter("field3"));

  emp.setDate(date);
  EmployeeBean eb = new EmployeeBean();
 eb.addWorkDetail(emp);
 }


  @Override
  protected void doGet(HttpServletRequest request, HttpServletResponse response)
          throws ServletException, IOException {
      processRequest(request, response);
  }

     @Override
  protected void doPost(HttpServletRequest request, HttpServletResponse response)
          throws ServletException, IOException {
      processRequest(request, response);
  }

   @Override
  public String getServletInfo() {
      return "Short description";
  }
  }

Answer 1

看看你的代码：

 Employee emp = (Employee)session.getAttribute("emp");
  session.setAttribute("emp",emp);
  java.sql.Date date = new java.sql.Date(new java.util.Date().getTime());

  emp = new Employee();   // HERE you are reseting emp variable, so it no longer holds session data but new employee object with null name and 0 id, so just remove that line
int n = emp.getEmpId();
String z = emp.getName();

   System.out.println("....name is " +z);// it is showing null
 System.out.println("....n is " +n);// it is showing 0 why i dont know how to get this