Question

我创建了一个JSP Mysql和Bootstrap Crud应用程序。当我点击Update按钮时，将调用validation（）来更新所有字段，成功更新后，它将重定向到另一个JSP页面，其中所有细节都将插入到phpMyAdmin数据库中。

但我收到Stacktrace:] with root cause错误。另外java.lang.NumberFormatException: null例外。我希望你能帮助我。

以下是代码：

的index.jsp

 <%@page import="java.sql.ResultSet"%>
<%@page import="java.sql.PreparedStatement"%>
<%@page import="java.sql.Connection"%>
<%@page import="com.dbconnectionutil.org.DbConnection"%>
<%@page import="java.net.ConnectException"%>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html lang="en">
    <head>
        <title>Bootstrap Example</title>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <link rel="stylesheet" href="bootstrap/css/bootstrap.css">
        <script src="js/jquery.js"></script>
        <script src="bootstrap/js/bootstrap.js"></script>
    </head>
    <body>
    <%
    Connection conn=null;

    PreparedStatement ps = null;

    ResultSet rs = null;

    String query = "SELECT * FROM newtable";

    try{

    conn = DbConnection.getConnection();

    ps = conn.prepareStatement(query);

    rs = ps.executeQuery();


    %>
    <div class="container bg-info" style="padding-top:20px; padding-bottom:20px;">
    <h1>Jsp Mysql And Bootstrap Crud App</h1>

    <hr>

    <div class="row">
        <div class="col-sm-4">
            <form role="form" action="addRecord.jsp" method="post">
                <div class="form-group">
                <label>First Name</label>
                <input type ="text" class="form-control" name="fname">
                </div>

                <div class="form-group">
                <label>Last Name</label>
                <input type ="text" class="form-control" name="lname">
                </div>

                <div class="form-group">
                <label>Email</label>
                <input type ="email" class="form-control" name="email">
                </div>
                <button class="btn btn-info btn-block" type="submit">Add Record</button>
            </form>
        </div>

        <div class="col-sm-8">
            <table class="table">
                <thead>
                    <tr>
                        <th>First Name</th>
                        <th>Last Name</th>
                        <th>Email</th>
                        <th>Crud Actions</th>
                    </tr>
                </thead>
                <tbody>
                <%
                    while(rs.next()){
                %>
                    <tr>
                        <td><%=rs.getString("fname") %></td>
                        <td><%=rs.getString("lname") %></td>
                        <td><%=rs.getString("emailid") %></td>
                        <td>
                        <a href="editform.jsp?uid<%=rs.getInt("uid") %>" class="btn btn-success" role="button">Uptade</a>
                        <a href="#" class="btn btn-danger" role="button">Delete</a>
                        </td>
                    </tr>
                <%
                }//while
                }//try
                catch(Exception ex){
                    ex.printStackTrace();   
                }
                %>
                </tbody>
            </table>
        </div>
    </div>
    </div>
    </body>

</html>

editform.jsp

 <%@page import="com.dbconnectionutil.org.DbConnection"%>
<%@page import="java.sql.ResultSet"%>
<%@page import="java.sql.PreparedStatement"%>
<%@page import="java.sql.Connection"%>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html lang="en">
<head>
    <title>Bootstrap Example</title>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scaled=1">
    <link rel="stylesheet" href="bootstrap/css/bootstrap.css">
    <script src="js/jquery.js"></script>
</head>
<body>

<%
String uid = request.getParameter("uid");

int id = Integer.parseInt(uid);

Connection conn = null;

PreparedStatement ps = null;

ResultSet rs = null;

try{
    conn = DbConnection.getConnection();

    String query = "SELECT * FROM newtable WHERE uid='"+id+"'";

    ps = conn.prepareStatement(query);

    rs = ps.executeQuery();

%>
    <div class="container bg-info" style="padding-top:20px; padding-bottom:20px;">
    <h1>Update Form</h1>
    <hr>
    <form action="" role="form">

    <%
        while(rs.next()){
    %>
    <input type="hidden" name="id" value="<%=rs.getInt("uid") %>">
        <div class="form-group">
        <label>First Name</label>
        <input type="text" name="fname" value="<%=rs.getString("fname") %>" class="form-control">
        </div>

        <div class="form-group">
        <label>Last Name</label>
        <input type="text" name="lname" value="<%=rs.getString("lname") %>" class="form-control">
        </div>


        <div class="form-group">
        <label>Email address</label>
        <input type="email" name="email" value="<%=rs.getString("emailid") %>" class="form-control">
        </div>

        <%
        }//while
    }//try

    catch(Exception ex){
        ex.printStackTrace();
    }
        %>
        <button type="submit" class="btn btn-success btn-block">Update</button>
    </form>
    </div>
</body>
</html>

Answer 1

=内的元素的href属性中缺少关键字index.jsp。这就是为什么你得到NumberFormatException。

替换<a href="editform.jsp?uid<%=rs.getInt("uid") %>" >

带

<a href="editform.jsp?uid=<%=rs.getInt("uid") %>" >
                         ^

当你尝试进行转换过程时，有必要捕获异常：

try{
  int id = Integer.parseInt(uid);
}catch(NumberFormatException e){id = 0; } //maybe default value

重要提示：请记住@Jens对评论提出的建议。

Stacktrace：]有根本原因

1 个答案: