Real-time detection of form data and prevention of repeated submissions using Java

Java implements real-time detection of form data and prevention of repeated submission

In Web development, real-time detection of form data and prevention of repeated submission is a common problem. When users fill in the form, we need to detect the data entered by the user in real time to provide immediate error prompts; repeated submissions may lead to data conflicts or unnecessary waste of resources, so corresponding measures need to be taken to prevent duplication. Submission processing. This article will introduce how to use Java to implement real-time detection of form data and prevent repeated submissions, and comes with code examples.

1. Real-time detection of form data

In the process of real-time detection of form data, we can implement real-time verification on the client side through JavaScript to optimize the user experience. The following is a simple example that uses JavaScript to detect in real time whether the format of the mobile phone number entered by the user is correct:

<script>
function checkPhoneNumber() {
    var phoneNumber = document.getElementById("phoneNumber").value;
    var phoneRegex = /^1[3-9]d{9}$/;
    
    if (!phoneRegex.test(phoneNumber)) {
        document.getElementById("phoneNumberError").innerHTML = "手机号码格式不正确";
    } else {
        document.getElementById("phoneNumberError").innerHTML = "";
    }
}
</script>

<form>
    <input type="text" id="phoneNumber" onkeyup="checkPhoneNumber()">
    <span id="phoneNumberError"></span>
    <button type="submit">提交</button>
</form>

Through the onkeyup event binding function checkPhoneNumber, when the user enters the mobile phone number, the format of the mobile phone number will be verified in real time. is correct, and the corresponding error message is displayed on the page.

Of course, the real-time verification on the client side is only to provide a better user experience and cannot replace the verification on the server side. The form data needs to be verified again on the server side to prevent malicious submission or bypassing client-side verification.

2. Prevent repeated submission of form data

In order to prevent repeated submission of form data, we can introduce the Token mechanism on the server side. Token is a randomly generated string that is submitted to the server as one of the form parameters each time the form is submitted. When the server processes the form request, it will check whether the Token is valid. If it is valid, it will process the request. If it is invalid, it will reject the request.

The following is a simple example to prevent repeated submissions:

@Controller
@RequestMapping("/form")
public class FormController {

    @Autowired
    private TokenService tokenService;

    @RequestMapping(method = RequestMethod.GET)
    public String showForm(Model model) {
        String token = tokenService.generateToken();
        model.addAttribute("token", token);
        return "form";
    }

    @RequestMapping(method = RequestMethod.POST)
    public String processForm(@RequestParam("token") String token) {
        if (!tokenService.isValidToken(token)) {
            return "error";
        }
        // 处理表单请求
        return "success";
    }
}

@Component
public class TokenService {
    private Set<String> tokens = new HashSet<>();

    public String generateToken() {
        String token = UUID.randomUUID().toString();
        tokens.add(token);
        return token;
    }

    public boolean isValidToken(String token) {
        return tokens.remove(token);
    }
}

In the FormController, we generate the Token through the showForm method and put the Token into the Model and pass it to the form page. When the form is submitted, the Token is passed to the server as a parameter, and the validity of the Token is verified in the processForm method. If the Token is invalid, the form request will be refused to be processed.

The TokenService class is used to generate and verify Token. We use a Set collection to store valid Tokens. When verifying the Token, it is removed from the set to ensure that each Token can only be used once.

By introducing the Token mechanism, we can effectively prevent repeated submission of form data and ensure the integrity and security of the system's data.

Summary:

In Web development, real-time detection of form data and prevention of repeated submissions are an important issue. Real-time verification of the client through JavaScript can provide a good user experience; by introducing the Token mechanism, repeated submission of form data can be effectively prevented. Through the introduction and examples of this article, I believe readers will have a deeper understanding of real-time detection of form data and prevention of repeated submissions in Java.

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