英文:
How to check if input is numeral when using Thymeleaf and Java Spring?
问题
我有一个货币转换器，如果我在输入框中输入一个字符串，那么在任何检查之前，我会得到一个错误，因为输入值与控制器中声明的内容不匹配。我的控制器：
@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>
我可以看出问题是在变量声明中引起的错误。
那么我的问题是，在输入进入控制器之前如何对其进行检查？
（注意：这里只是提供了代码和内容的中文翻译部分，其他内容已被略去。）
英文:
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?
答案1
得分: 1
这不仅仅是在提交请求之前验证输入字段的类型，或者添加 Spring 的验证器就足够了。
英文:
It is not enough to verify the type of the input field before submitting the request, or add spring's verifier
答案2
得分: 1
一个更简单的方法是将String作为方法参数。
例如：
@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 {
// 在这里添加你的代码
} catch (...) {...}
} catch (NumberFormatException e) {
// 当输入为字符串时处理错误
}
}
英文:
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
}
答案3
得分: 1
你的输入元素需要是文本类型吗？你需要处理多少位小数？例如，<input type="number" step="0.01"> 可以让你输入带有两位小数的数值。数字输入类型文档。
英文:
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
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