CODEWITHSUNDEEP
javaspringthymeleaf
TomasB
TomasB

Reputation: 47

How to check if input is numeral when using Thymeleaf and Java Spring?

I have a Currency converter and if I enter a string into the input field I get an error before any of my checks can be used as the input value doesn't match what is declared in the controller. My Controller:

@RequestMapping(value = "/index", method = RequestMethod.POST)
    public String convertCurrency(@RequestParam String toCurrency, Double amount, Model model,
            RedirectAttributes redirectAttributes) {
        
        if (!(amount == null)&&(amount== (double)amount)) {
            if (amount > 0) {
                try {
                    ConvertionCurrency currency = currencyService.getCurrencyRate(toCurrency);
                    Double conRate = currency.getConvertionRateToEUR();

                    Double result = amount * conRate;
                    System.out.println(result);
                    redirectAttributes.addFlashAttribute("result", result);
                    redirectAttributes.addFlashAttribute("successClass", "alert-success");
                } catch (Exception e) {
                    redirectAttributes.addFlashAttribute("message", "A positive number is needed");
                    redirectAttributes.addFlashAttribute("alertClass", "alert-danger");
                }

Double amount is the attribute in question.

In the HTML page the input is nothing special:

                        <div class="float-right">
                            <input type="text" class="form-control" placeholder="Amount"
                                id="amount" name="amount">
                        </div>

I can see that the problem is that the error is caused in the declaration of the variables.

So my question is how do I check the input before it goes to the Controller?

Upvotes: 0

Views: 1054

Answers (3)

JustAnotherDeveloper
JustAnotherDeveloper

Reputation: 2266

Does your input element need to be of type text, and how many decimal places do you have to work with? <input type="number" step="0.01"> would allow you to enter numeric values with two decimals, for example. Input type number documentation

Upvotes: 1

Achmad Afriza
Achmad Afriza

Reputation: 125

A simpler way of doing that is to take a String as the method arguments.

e.g.

@RequestMapping(value = "/index", method = RequestMethod.POST)
    public String convertCurrency(@RequestParam String toCurrency, String amount, Model model,
            RedirectAttributes redirectAttributes) {
    try {
        Double foo = Double.valueOf(amount);
        try {
            // Your code here
        } catch (...) {...}
    } catch (NumberFormatException e) {
        // Handle your error when the input is a String
    }

Upvotes: 1

jml940616
jml940616

Reputation: 11

It is not enough to verify the type of the input field before submitting the request, or add spring's verifier

Upvotes: 1

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