如何在Play Framework 2.0中创建自定义验证器？ [英] How to create a custom validator in Play Framework 2.0?

问题描述

Play 1.0附带一个基于 http://oval.sourceforge.net/ 的全功能验证框架。

Play 1.0 comes with a full featured validation framework base on http://oval.sourceforge.net/.

随着2.0的发布，我的自定义验证器不再起作用了。

With the release of 2.0, my custom validators do not work anymore.

如何创建自定义使用Play Framework 2.0的验证器？

How does one create custom validator using Play Framework 2.0 ?

推荐答案

在Play 2.0中，验证框架超出了数据的实际验证范围。 ：

In Play 2.0, the validation framework extends beyond the actual validation of the data as it reaches to:

• 注释 - 使用'@'符号轻松声明验证限制


• 验证者 - 哪个实际上实现验证后面的逻辑


• 消息 - 显示参数化错误消息（符合i18）


• 最后，HTML帮助器 - 粘合所有以前的一起

• Annotations - to easily declare validation contraints using the '@' sign
• Validators - which actually implements to logic behind the validation
• Messages - to display parametrized error messages (i18 compliant)
• Finally, HTML helpers - that glue all the previous together

HTML助手是Play 2.0的新功能。在1.x中，Play已经非常擅长强制执行一个定义良好的验证框架。它功能强大且易于使用。然而，我们仍然需要将HTML表单和验证框架连接在一起。这对初学者来说可能有点混乱。

The HTML Helpers are something new to Play 2.0. In 1.x, Play was already pretty good at enforcing a well defined validation framework. It was powerful and easy to use. Yet we still had to wire the HTML form and the validation framework together. This could be a little confusing to the beginner.

使用Play 2.0，现在可以自动完成。

With Play 2.0, this is now done automatically.

但是让我们专注于答案并提供一些指导：我们将创建一个 AllUpperCase 验证器，在以下情况下生成错误：

But let's focus on the answer and provide some guidance: We will create an AllUpperCase validator, that generates an error either when:

• 输入不是字符串


• 输入为空


• 其中一个字符是小写的。

package myvalidators;

import javax.validation.*;

public class AllUpperCaseValidator 
        extends play.data.validation.Constraints.Validator<Object> 
        implements ConstraintValidator<AllUpperCase, Object> {

    /* Default error message */
    final static public String message = "error.alluppercase";

    /**
     * Validator init
     * Can be used to initialize the validation based on parameters
     * passed to the annotation.
     */
    public void initialize(AllUpperCase constraintAnnotation) {}

    /**
     * The validation itself
     */
    public boolean isValid(Object object) {
        if(object == null)
            return false;

        if(!(object instanceof String))
            return false;

        String s = object.toString();  
        for(char c : s.toCharArray()) {
            if(Character.isLetter(c) && Character.isLowerCase(c))
                return false;
        }

        return true;
    }

    /**
     * Constructs a validator instance.
     */
    public static play.data.validation.Constraints.Validator<Object> alluppercase() {
        return new AllUpperCaseValidator();
    }
}

您可能会注意到的第一件事是导入：播放2.0确实符合JSR 303 - Bean Validation Framework。在此上下文中，验证器需要实现 ConstraintValidator 。在我们的例子中，将注释转换为类 AllUpperCase （我们将在一分钟内介绍）和T作为通用对象。

The first thing you may notice is the import: Play 2.0 indeed complies with JSR 303 - Bean Validation Framework. In this context, the validator needs to implement ConstraintValidator. Which in our case translates into the annotation as class AllUpperCase (which we will introduce in a minute) and T as a generic Object.

验证器是直接的：

我们定义了方法 public boolean isValid（Object object ）返回一个布尔值，如果为true则验证通过。还有一个消息ID和一个实例化验证器的方法。

The validator is straighforward:
We defined the method public boolean isValid(Object object) that returns a boolean, if true the validation passed. There is also an message id and a method that instanciates the validator.

下面的类定义一个名为 @AllUpperCase 的注释，它不带任何参数，但强制执行先前定义的验证。提供与注释框架相关的详细信息超出了本文的范围。

The class below defines an annotation named @AllUpperCase which takes no parameters but enforces the validation defined previously. Providing details related to the annotation framework is outside the scope of this post.

package myvalidators;

import java.lang.annotation.*;
import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;

import javax.validation.*;

@Target({FIELD})
@Retention(RUNTIME)
@Constraint(validatedBy = AllUpperCaseValidator.class)
@play.data.Form.Display(name="constraint.alluppercase")
public @interface AllUpperCase {
    String message() default AllUpperCaseValidator.message;
    Class<?>[] groups() default {};
    Class<? extends Payload>[] payload() default {};
}

注意anotation如何粘合到拼图的其他部分。

Note how the anotation glues to the other pieces of the puzzle.

• @Constraint ，一个JSR 303注释，链接到验证器


• @ play.data.Form.Display ，将注释链接到play html帮助器。请注意，名称很重要：我们正在定义名为 alluppercase 的约束。 Play使用此信息调用方法 public static play.data.validation.Constraints.Validator< Object>验证器上的alluppercase（）。


• 最后请注意，默认消息是在anotation界面中设置的。

• @Constraint, a JSR 303 annotation, links to the validator
• @play.data.Form.Display, links the annotation to the play html helpers. Note that the name is important: we are defining a constraint named alluppercase. Play uses this information to call the method public static play.data.validation.Constraints.Validator<Object> alluppercase() on the Validator.
• Finally note that the default message is set within the anotation interface.

我们现在有自定义验证器和注释

We now have our custom validator and annotation

import myvalidators.*;
public static class MyData {
    @AllUpperCase
    public String name;
}

描述用法超出了本文的范围，请查找工作样本在此网址

Describing the usage is outside the scope of this post, please find a working sample at this URL

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