问题：
Java . lang . numberformatexception:null I
吉凯捷
在这里，我在执行诸如更新、删除和插入之类的操作时遇到了问题，但它返回了一些空值，请注意，如果错误的话，有些人可以查看代码：
错误：
HTTP Status 500 - null
type Exception report
message null
description The server encountered an internal error that prevented it from fulfilling this request.
exception
java.lang.NumberFormatException: null
java.lang.Integer.parseInt(Integer.java:454)
java.lang.Integer.parseInt(Integer.java:527)
Controller.ControllerTest.doGet(ControllerTest.java:48)
javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
javax.servlet.http.HttpServlet.service(HttpServlet.java:723)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.37 logs.
Apache Tomcat/6.0.37
用户.jsp：
<form method="POST" action='ControllerTest' name="frmAddUser">
<jsp:useBean id="users" class="java.util.ArrayList" scope="request" />
<% for(int i = 0; i < users.size(); i+=1)
{
UseBean user = (UseBean)users.get(i);
%>
id:<input type="text" name="ID" value="<%=user.getID() %>"><br/>
Name:<input type="text" name="Name" value="<%= user.getName() %>"><br/>
Password:<input type="text" name="password" value="<%= user.getPassword() %>"><br/>
phoneno:<input type="text" name="Phoneo" value="<%= user.getPhoneo() %>"><br/>
Emailid:<input type="text" name="Emailid" value="<%= user.getEmailID() %>"> <br/>
<%} %>
<input type="submit" value="Submit" />
</form>
listuser.jsp
<body>
<table border=1>
<thead>
<tr>
<th>Id</th>
<th>Name</th>
<th>password</th>
<th>phoneno</th>
<th>emailid</th>
<th colspan=2>Action</th>
</tr>
</thead>
<tbody>
<jsp:useBean id="users" class="java.util.ArrayList" scope="request" />
<% for(int i = 0; i < users.size(); i+=1)
{
UseBean user = (UseBean)users.get(i);
%>
<tr>
<td><%= user.getID() %></td>
<td><%= user.getName() %></td>
<td><%= user.getPassword() %></td>
<td><%= user.getEmailID() %></td>
<td><%= user.getPhoneo() %></td>
<td><a href="ControllerTest?action=edit&userId=<%= user.getID() %>" >Update</a></td>
<td><a href="ControllerTest?action=delete&userId=<%= user.getID() %>">Delete</a></td>
</tr>
<% } %>
</tbody>
</table>
<p>
<a href="ControllerTest?action=insert">Add User</a>
</p>
控制器测试. java:
package Controller;
import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import dao.UserDao;
import dbBean.UseBean;
public class ControllerTest extends HttpServlet
{
private static final long serialVersionUID = 1L;
private static String INSERT_OR_EDIT = "/user.jsp";
private static String LIST_USER = "/listUser.jsp";
private UserDao dao;
public ControllerTest()
{
super();
dao = new UserDao();
}
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException
{
String forward = "";
String action = request.getParameter("action");
if (action.equalsIgnoreCase("delete"))
{
try
{
int userId = Integer.parseInt(request.getParameter("userId"));
dao.deleteUser(userId);
forward = LIST_USER;
request.setAttribute("users", dao.getAllUsers());
}
catch (NumberFormatException ex)
{
System.out.println("Error occured with during conversion delete");
}
}
else if (action.equalsIgnoreCase("edit"))
{
forward = INSERT_OR_EDIT;
try
{
int userId = Integer.parseInt(request.getParameter("userId"));
UseBean bean = dao.getUserById(userId);
request.setAttribute("user", bean);
} catch (NumberFormatException ex)
{
System.out.println("Error occured with during conversion edit");
}
}
else if (action.equalsIgnoreCase("listUser"))
{
forward = LIST_USER;
request.setAttribute("users", dao.getAllUsers());
} else
{
forward = INSERT_OR_EDIT;
}
RequestDispatcher view = request.getRequestDispatcher(forward);
view.forward(request, response);
}
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException
{
try
{
UseBean bean = new UseBean();
bean.setName(request.getParameter("Name"));
bean.setPassword(request.getParameter("password"));
bean.setPhoneo(request.getParameter("Phoneo"));
bean.setEmailID(request.getParameter("Emailid"));
String userid = request.getParameter("ID");
if (userid == null || userid.isEmpty())
{
dao.addUser(bean);
} else
{
bean.setID(Integer.parseInt(userid));
dao.updateUser(bean);
}
RequestDispatcher view = request.getRequestDispatcher(LIST_USER);
request.setAttribute("users", dao.getAllUsers());
view.forward(request, response);
}
catch (Exception e)
{
e.printStackTrace();
System.out.println("erro occuring in update code");
}
}
}
共有3个答案
仲孙向明
您转发的页面可能有一些字符串到整数的转换，这可能会导致错误
何华灿
如果没有向Integer.parseInt()传递有效的数字，就会得到NumberFormatException
int userId = Integer.parseInt(request.getParameter("userid"));
尝试打印 request.getParameter（“userid”） 的值并检查。
满勇军
当试图将空字符串“”转换为整数时，您会得到NumberFormatException。。。
类似资料：