CODEWITHSUNDEEP
java
hkguile
hkguile

Reputation: 4369

check the input null

i've found this line of code got error if the input not an number

int sum = Integer.parseInt(request.getParameter("sum"));

the error message is

type Exception report

message

descriptionThe server encountered an internal error () that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: java.lang.NumberFormatException: For input string: "a"
root cause

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

how to handle the input if the input is a string or null?

thanks

Upvotes: 1

Views: 4948

Answers (8)

parkovski
parkovski

Reputation: 1523

Try:

int sum = 0;
try {
    sum = Integer.parseInt(request.getParameter("sum"));
}
catch (NumberFormatException e) {
    // sum = 0. If you needed to do anything else for invalid input
    // put it here.
}

Upvotes: 2

BillRobertson42
BillRobertson42

Reputation: 12883

I see the org.apache.jasper.JasperException Which means this is in a JSP? If you're adding code like that to a JSP, you might want to reconsider what you're doing. Ideally, you should handle things like input validation in a controller of some sort, and then pass off results to a template of JSP for rendering.

There are many frameworks out there to help with this sort of thing, and in general they're worth using because your web application will benefit from all of the work that the framework authors have already done in the realm of security etc...

Pretty much any of the half a dozen code answers already posted will work for you though if you just want to hack it out.

Upvotes: 1

Bohemian
Bohemian

Reputation: 425368

Here's a different approach that doesn't involve throwing and catching exceptions:

String input = request.getParameter("sum");
// Validate the input using regex
if (input == null || !input.matches("^-?\\d{1,8}$")) {
    // handle bad input, eg throw exception or whatever you like
}
int sum = Integer.parseInt(input);

Note that this regex doesn't allow numbers too large, and allows negative numbers

Upvotes: 1

Amritpal Singh
Amritpal Singh

Reputation: 1785

Check for null before Using Intefer.parseInt and also you can check whether input contains other than numeric value

Upvotes: 1

LeleDumbo
LeleDumbo

Reputation: 9340

  1. Check manually (loop over the characters)
  2. Catch the exception

Try this:

try {
  sum = Integer.parseInt(request.getParameter("sum"));
} catch (NumberFormatException e) {
  ... // handle if the string isn't a number
} catch (NullPointerException e) {
  ... // handle if it's null
}

Upvotes: 1

anubhava
anubhava

Reputation: 786091

You should first make sure request parameter is not null and contains numbers only using:

if (request.getParameter("sum") != null &&
    request.getParameter("sum").matches("^\\d+$"))
    int sum = Integer.parseInt(request.getParameter("sum"));

Upvotes: 3

everconfusedGuy
everconfusedGuy

Reputation: 2797

It really depends on what should be done if sum is not a number.

try{
 int sum = Integer.parseInt(request.getParameter("sum"));
 }
 catch(Exception e)
 {
  //how do you want to handle it? like ask the user to re-enter the values
 }

Upvotes: 1

Petar Ivanov
Petar Ivanov

Reputation: 93090

Just catch the exception and handle it accordingly:

int sum;
try {
    sum = Integer.parseInt(request.getParameter("sum"));
}
catch {
    //do something if invalid sum
}

Upvotes: 1

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