玩！ - 独特的模型领域 [英] Play! - unique model field

问题描述

如何让我的模型类字段独一无二？例如。如果已经登录，我想为用户显示正确的消息。我必须编写自己的验证检查并使用它，或者可以使用JPA @UniqueConstraint ？

How can I make my model class fields unique? Eg. if login is already taken, I'd like to display proper message for the user. I have to write my own validation check and use it, or JPA @UniqueConstraint can be used?

推荐答案

我这样做了：

@Entity
public class User extends Model {

    @Basic(optional=false) @Column(unique=true) public String name;

    public User(String name) {
        this.name = name;
        create();
    }

    /** used in registration to find name clash */
    public static User findByName(String name) {
        return find("name", name).first();
    }

}

然后在你做的控制器中类似于：

and then in the controller you do something like:

public static void register(@Required String name) {
    if(User.findByName(name)!=null) {
        Validation.addError("name", "this name is not available");
    }
    if (validation.hasErrors()) {
        validation.keep();
        params.flash();
        flash.error("Please correct the form data.");
        signup(); // whatever your GET action was
    }

    User user = new User(name);
    login(); // whatever your success action is
}

你可以在没有User.findByName的情况下做到这一点（）检查，你会得到一个ConstrainViolationException但当然不是非常用户友好。您也可以尝试/捕获该异常。我更喜欢这两种方式，用户友好且在数据库中保持一致。

you could do it without the User.findByName() check and you would get a ConstrainViolationException but which is of course not very user friendly. You could also just try/catch that exception. I prefer it both ways, being user friendly and consistent in the database.

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