java.lang.NumberFormatException: For input string: "id"

Question

I am using SPRING MVC to develop a project to display a list of users in a JSP file. My Controller file has:

Map<String, Object> model = new HashMap<String, Object>();
model.put("user", userService.getUser()); //userService.getUser() returns a List

The JSP file has:

<c:if test="${!empty user}">  
  <table>
    <tr>  
      <td>User Id</td>  
      <td>First Name</td>  
      <td>Last Name</td>  
      <td>Gender</td>  
      <td>City</td>  
   </tr>  
   <c:forEach items="${user}" var="user">
   <tr>  
     <td><c:out value="${user.id}"/></td>  
     <td><c:out value="${user.firstName}"/></td>  
     <td><c:out value="${user.lastName}"/></td>  
     <td><c:out value="${user.gender}"/></td>  
     <td><c:out value="${user.city}"/></td>  
   </tr>  
   </c:forEach>  
  </table>  
</c:if>

When displaying the above JSP file, java.lang.NumberFormatException: For input string: "id" is shown. Can anybody please help to find out the solution?

Thank you very much.

items="${user}" var="user" which user is what.. Replacing by var="u" and using u in the foreach might help — user180100
– user180100, Commented Feb 23, 2014 at 10:13
I know this answer comes pretty late but I believe that your user variable within the foreach is actually a collection. Check that out. — kazbeel
– kazbeel, Commented Jul 24, 2014 at 16:54

helderdarocha · Accepted Answer · 2014-02-23 10:16:02Z

1

NumberFormatException happens during an failed attempt to convert a string to a number. Check if any of your input data that should be a number is actually receiving something different (ex: an empty string, which can't be converted to a number, is a possible cause).

answered Feb 23, 2014 at 10:16

helderdarocha

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Comments

Damian S. · Accepted Answer · 2014-02-23 11:06:05Z

0

First good rule: variables containing lists you schould naming plural for example, list of users put name "users":

<c:forEach items="${users}" var="user">

Now you know what variable contain, "users" have list of users but "user" is one item of users list.

Second rule: if you want check, whether a variable is a number, do not catch exceptions, it's slow. Better and faster is regex:

if (anyString.matches("\\d+")){
    isANumber();
}
else{
    notNumber();
}

answered Feb 23, 2014 at 11:06

Damian S.

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Comments

Somaiah Kumbera · Accepted Answer · 2014-02-24 12:46:22Z

0

In addition to heldrarocha and Damien's answers, I think your problem is that you are not checking ID before adding it into the User object.

Ensure that the id variable in User is an integer (or long or whatever). This way if you fill it from the DB, your rowmapper will add numeric values.

If it HAS to be a String, ensure that whatever goes in is numeric.

An easy way to check if a String is numeric is to user Apache Commons StringUtils isNumeric method:

http://commons.apache.org/proper/commons-lang/javadocs/api-2.6/org/apache/commons/lang/StringUtils.html#isNumeric(java.lang.String)

answered Feb 24, 2014 at 12:46

Somaiah Kumbera

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Jaswinder Singh · Accepted Answer · 2021-03-11 17:21:53Z

0

I'm not sure your problem is, but I remember to put below code at the beginning of the jsp page

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"pageEncoding="ISO-8859-1"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

edited Mar 11, 2021 at 17:21

Jaswinder Singh

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answered Mar 11, 2021 at 9:11

Ángel del Peso Barroso

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1 Comment

Jordan Over a year ago

Hi there! it'd be great if you could format your code using the code tags for better readability! thanks.

Sathwik Pinninti · Accepted Answer · 2022-06-21 18:47:55Z

0

Since you made sure that userService.getUser() returns a list that can be iterated over using forEach in jsp, the only change i would think of is

model.put("users", userService.getUser())

and in jsp file as follows:

<c:forEach items="${users}" var="user">

It may eliminate ambiguity and may actually solve your problem.

I came accross same problem today and later realised that I was iterating over the object itself when I intend to iterate over a list of such objects.

edited Jun 21, 2022 at 18:47

answered Jun 21, 2022 at 18:47

Sathwik Pinninti

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