如何使用Spring处理表单错误（与类字段不匹配）

Question

I've been studying Spring for some weeks, so I don't know the "Logic" to use while handling certain issues.

I tell you immediately that my problem is not how to check if 2 form fields match! I'm just using mail and confirmMail to make an example.

I know how to handle form errors by using @Valid annotation on a Object, but what if the form contain a field that my class doesn't have?

Let's say there's a form to sign up: I have a class called User, with name, age and email fields. I have no problem handling errors with

<form:errors path="name" cssClass="error">
<form:errors path="age" cssClass="error">
<form:errors path="mail" cssClass="error">

Now let's say I want to add another field in my form, called for example confirmEmail, to check, server side, that the email is correct. How should I handle it? I can't create another field called confirmEmail in my class User, it doens't sound correct to me.

This is my Form

<form:form action="signUpSent" method="post" commandName="utente">

            <form:input path="nome"/>
            <form:errors path="nome" cssClass="DivErroriSpring"/>

            <form:input path="cognome"/>
            <form:errors path="cognome" cssClass="DivErroriSpring"/>

            <form:input path="email"/>
            <form:errors path="email" cssClass="DivErroriSpring"/>  

            <form:input path="confermaEmail"/>
            <form:errors path="confermaEmail" cssClass="DivErroriSpring"/>

            <input type="submit">

        </form:form>

this is my class User (Utente in italian)

public class Utente {

    @NotEmpty   
    @Size(min=3,max=20)
    private String nome;    

    @NotEmpty
    @NotNull
    @Size(min=3,max=20)
    private String cognome;     

    @NotEmpty
    @Email
    private String email;

    public String getNome() {
        return nome;
    }

    public void setNome(String nome) {
        this.nome = nome;
    }

    public String getCognome() {
        return cognome;
    }

    public void setCognome(String cognome) {
        this.cognome = cognome;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }       

}

As you can see, in my class User(Utente in italian) I don't have a field called confirmMail (confermaEmail in italian), because it wouldn't be correct to have it, would it?

To be more clear, the question is: how should I handle errors when form field doens't match a field of my class User?

Answer 1

I see 2 possible solutions (apart from adding the additional field to your User object).

The first involves treating your web layer as a different problem domain (bounded context) as your business domain. Generally there is a mismatch in what you want to show/use on screen as to what you actually need in the business part of your application.

@FieldMatch(first = "email", second = "confirmEmail", message = "The email fields must match")    
public class UserForm {
     private String email;
     private String confirmEmail;
     ...
}

In your controller you have the validation if it validates copy the needed fields to the User object (maybe using a mapper framework liker Dozer or MapStruct )

The second is adding a input field for the confirmation email, add that field as a @RequestParam to your method signature and do manual validation in your controller. You can simply add errors to the BindingResult .

public String register(@Valid @ModelAttribute User user, BindingResult result, @RequestParam("confirmEmail", required=false) String confirmEmail) {
     if (!StringUtils.equals(confirmEmail, user.getEmail()) {
         result.reject("email", "email.confirm.mustequal");
     }
    ....

}