Java 服务器页面。如何将参数从一个 JSP 页面发送到另一个页面

Question

所以 m 有两个 JSP 页面 一个是由注册表单组成的 register.jsp。当用户单击 register.jsp 页面上的提交按钮时，我正在调用第二个 JSP 页面。第二个 JSP 页面用于将数据添加到数据库中。 我想做的是从第二页开始，我想返回上一页并在注册成功与否时显示一条消息。 其他一切工作正常。正在将数据添加到数据库中。 这是我的注册表单，我在点击提交按钮时调用另一个 jsp 页面。

<head>
</head>
<%!
String val;
%>
<article class="registrationform">
    <%
//Here m trying to access the attribute val which is set in the 2nd jsp page and whose value is true or false depending on data is added successfully or not.
    val=(String)request.getSession().getAttribute("val");
    if(val.equals("true"))
    {
    %>
    <h2 color="blue">Registration Successfull </h2>
    <%
    }else if(val.equals("false"))
    {
    %>
        <h2 color="red">Registration Failed. Please Try Again</h2>
    <%
    } else{

    }
    %>
    <h2>Registration form</h2>

    <form class="registration form-horizontal" name="regform" method="post" action="http://localhost:8080/mysrc/vt/components/jsp/RegisterDataBase.jsp">

      <fieldset id="personalinfo">
        <legend>Personal Info</legend>

                <section class="row">
                    <label class="col col-lg-4 control-label" for="myfirstname">First Name</label>
                    <div class="controls">
                        <input class="col col-lg-8" type="text" name="myfirstname" id="myfirstname">
                    </div><!-- controls -->
                </section><!-- row -->
<section class="row">
                    <label class="col col-lg-4 control-label" for="mylastname">Last Name</label>
                    <div class="controls">
                        <input class="col col-lg-8" type="text" name="mylastname" id="mylastname" >
                    </div><!-- controls -->
                </section><!-- row -->


                <section class="row">
                    <label class="col col-lg-4 control-label" for="myemail">Email</label>
                    <div class="controls">
                        <input class="col col-lg-8" type="email" name="myemail" id="myemail" required autocomplete="off" />
                    </div><!-- controls -->
                </section><!-- row -->

                <section class="row">
                    <label class="col col-lg-4 control-label" for="mypassword">Password</label>
                    <div class="controls">
                        <input class="col col-lg-8" type="password" name="mypassword" id="mypassword" required autocomplete="off" />
                    </div><!-- controls -->
                </section><!-- row -->

      </fieldset><!-- personal info -->

      <fieldset id="otherinfo">
            <legend>Other Info</legend>

                <section class="row">
                  <label class="col col-lg-4 control-label" for="dateofbirth">D.O.B</label>
                    <div class="controls">
                        <input class="col col-lg-8" type="date" name="dateofbirth" id="dateofbirth" />
                    </div><!-- controls -->
                </section><!-- row -->

                                <section class="row">
            <label class="col col-lg-4 control-label">Gender</label>
                    <div class="controls col col-lg-8">
                        <label class="radio">
                            <input type="radio" name="gender" value="male" /> Male
                        </label>
                        <label class="radio">
                            <input type="radio" name="gender" value="female" /> Female
                        </label>
                    </div><!-- controls -->
                </section><!-- row -->


                <section class="row">
                    <label class="col col-lg-4 control-label" for="collegename">College</label>
                    <div class="controls">
                        <input class="col col-lg-8" type="text" name="college" id="collegename" />
                    </div><!-- controls -->
                </section><!-- row -->
                <section class="row">
                    <label class="col col-lg-4 control-label" for="myaddress">Address</label>

                    <div >
                        <textarea class="col col-lg-8" type="text" name="address" id="myaddress" rows="3"></textarea>
                    </div><!-- controls -->
                </section><!-- row -->
    </fieldset>
      <button class="btn" type="submit" >Submit</button>

    </form>

</article>

这是第二个具有数据库连接的 JSP 页面，其中数据被添加到数据库中。现在我想再次重定向回上一页并显示一个弹窗说明注册成功是数据添加成功否则失败。

<%@ page language="java" %>

<%@ page import="java.sql.*" %>
<%!     
    String myfirstname, mylastname, myemail, mypassword, dateofbirth, gender,college, address;  
    Connection con;
    PreparedStatement pst;
%>

<% 
myfirstname=request.getParameter("myfirstname");
mylastname=request.getParameter("mylastname");
myemail=request.getParameter("myemail");
mypassword=request.getParameter("mypassword");
dateofbirth=request.getParameter("dateofbirth");
gender=request.getParameter("gender");
college=request.getParameter("college");
address=request.getParameter("address");

        try{
                    Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                    con=DriverManager.getConnection("jdbc:odbc:vtdsn");
                    pst=con.prepareStatement("insert into studentdetail values(?,?,?,?,?,?,?,?)");
                    }
                    catch(Exception e)
                    {
                        e.printStackTrace();
                    }

        try{
                     pst.setString(1,myfirstname);
                     pst.setString(2,mylastname);
                     pst.setString(3,myemail);
                     pst.setString(4,mypassword);
                     pst.setString(5,dateofbirth);
                     pst.setString(6,gender);
                     pst.setString(7,college);
                     pst.setString(8,address);
                     int i=pst.executeUpdate();
                     if(i>=1)
                     {

//this is what i tried to set an attribute as true is data is added successfully which is being accesses at the previous page but m getting errors.

                     //request.getSession().setAttribute("val", "true");

                     response.sendRedirect("http://localhost:8080/mysrc/vt/register.jsp");
                     }
                     else
                     {
                     response.sendRedirect("http://localhost:8080/mysrc/vt/error.html");
                     }
                    }
                    catch(Exception e){
                                        e.printStackTrace();
                                        }

%>

Answer 1

从一个jsp向另一个jsp发送参数有三种方式： 1.在会话中存储参数然后重定向，就像你做的那样。 2.在url中设置参数然后重定向。 3.将参数存储在request中，并将request转发给下一个jsp。

据我所知，你的方法应该没问题，那么你得到了什么具体的错误？

此外， val=(String)request.getSession().getAttribute("val"); 此 val 可能为空 所以 if(val.equals("true")) 可以抛出 NullPointer 异常 尝试 if("true".equals(val)) 代替