[JAVA] Self-made Validation with Spring

background

Make a note of the validation method other than annotating the Form (double check, etc.). This time we will use Spring Validator instead of Bean Validation.

Method

SessionForm

public class SessionForm {

    private CheckForm checkForm;
    //Variable for error output
    private String error1;

    private String error2;
    //Setter etc. omitted

CheckValidation

@Component
                             //Interface implementation
public class CheckValidation implements Validator {
    //Inject when using helper for Check
    @Autowired
    Helper helper;

    @Override
    public boolean supports(Class<?> clazz) {
        //Enter the Form you want to check(Session attributed class)
        //isAssignableFrom includes all inherited classes
        return SessionForm.class.isAssignableFrom(clazz);
    }

    @Override
    public void validate(Object target, Errors errors) {
        //Create the target class once
        SessionForm form = (SessionForm) target;
        //form.checkForm.~Nested elements can also be used by
        if (Conditional expression) {
                errors.rejectValue(
                       //Variable specified in the form
                       "error1",
                       //Null if the message is not defined in another file
                        null, 
                       "Message you want to output");
            }

        //Do another check
        if (Conditional expression) {
                errors.rejectValue(
                        "error2", 
                         null, 
                        "Message you want to output");
                }
}
          

Controller

@Controller
@SessionAttributes(names = "sessionForm")
public class ExampleController {
    //For key setting
    private static final String FORM_NAME = "sessionForm";

    //Inject your own validation class
    @Autowired
    CheckValidation checkValidation;

    //Added to WebDataBinder
    @InitBinder("sessionForm")
    public void initBinder(WebDataBinder binder) {
        binder.addValidators(checkValidation);
    }
    
    //The mode attached to the method adds a place to the model before calling
    @ModelAttribute(value = "sessionForm")
    public SessionForm sessionForm() {
        return new SessionForm();
    }

//a
@RequestMapping(path="The path you put in the redirect", method=RequestMethod.GET)
    public String putInformation(@ModelAttribute(FORM_NAME) SessionForm session, BindingResult result,ModelMap model) {

        String key = BindingResult.MODEL_KEY_PREFIX + FORM_NAME;
        //If there is an error in the model when redirecting
        if(model.containsKey("errors")) {
            //Error storage in map format in the form set in Key
            model.addAttribute(key, model.get("errors"));
            model.addAttribute("sessionForm" , session);
            return "JSP etc. you want to transition";
        }
        //Others omitted
}

//b
@RequestMapping(path="Input confirmation screen, etc.", method=RequestMethod.POST)
    public String confirmInfomation(@Validated SessionForm session, BindingResult result, Model model, RedirectAttributes ra)throws Exception {

            if(result.hasErrors()) {
            ra.addFlashAttribute("errors", result);
            //Redirect to input screen
            return "redirect:/{To the path of the controller you want to call}";
        }
        //Others omitted
}

JSP

<form:errors path="error1" />
<form:errors path="error2" />

Note

-First, create variables for errors on the full form. -Information is stored in the variable in the validator class. -By adding a validator to WebDataBinder with the controller, the validator added after calling Bean Validation is called and the self-made check is performed. Don't forget Autowired. -If there is an error in BindingResult, redirect while retaining that information (check the part before transitioning to the input confirmation screen, etc.). The method flow is in the order of a → b → a. -Branch depending on the presence or absence of an error in the redirect destination method, and if there is, store the error information in the model and share it with the JSP. -Use errors of form tag in JSP, match the path and the variable of the session form, and output the error message.

Summary

This time, I created it through trial and error, so I think there is a better way, but I made a note because it worked. I was able to compare it with the information (date, etc.) brought from the DB in the validator class, so I thought that the validator had a high degree of freedom. If you want to implement a validator other than Spring, I thought you should write a condition using a filter or something.