Spring验证，如何让PropertyEditor生成特定的错误信息 [英] Spring validation, how to have PropertyEditor generate specific error message

问题描述

我使用 Spring 进行表单输入和验证.表单控制器的命令包含正在编辑的模型.模型的某些属性是自定义类型.例如，Person 的社会安全号码是自定义的 SSN 类型.

I'm using Spring for form input and validation. The form controller's command contains the model that's being edited. Some of the model's attributes are a custom type. For example, Person's social security number is a custom SSN type.

public class Person {
    public String getName() {...}
    public void setName(String name) {...}
    public SSN getSocialSecurtyNumber() {...}
    public void setSocialSecurtyNumber(SSN ssn) {...}
}

并将 Person 包装在 Spring 表单编辑命令中:

and wrapping Person in a Spring form edit command:

public class EditPersonCommand {
    public Person getPerson() {...}
    public void setPerson(Person person) {...}
}

由于 Spring 不知道如何将文本转换为 SSN，因此我使用表单控制器的绑定器注册了一个客户编辑器:

Since Spring doesn't know how to convert text to a SSN, I register a customer editor with the form controller's binder:

public class EditPersonController extends SimpleFormController {
    protected void initBinder(HttpServletRequest req, ServletRequestDataBinder binder) {
        super.initBinder(req, binder);
        binder.registerCustomEditor(SSN.class, "person.ssn", new SsnEditor());
    }
}

而 SsnEditor 只是一个自定义的 java.beans.PropertyEditor，可以将文本转换为 SSN 对象:

and SsnEditor is just a custom java.beans.PropertyEditor that can convert text to a SSN object:

public class SsnEditor extends PropertyEditorSupport {
    public String getAsText() {...} // converts SSN to text
    public void setAsText(String str) {
        // converts text to SSN
        // throws IllegalArgumentException for invalid text
    }
}

如果 setAsText 遇到无效且无法转换为 SSN 的文本，则它会抛出 IllegalArgumentException(根据 PropertyEditor setAsText 的规范).我遇到的问题是文本到对象的转换(通过 PropertyEditor.setAsText())发生在之前我的 Spring 验证器被调用.当setAsText 抛出IllegalArgumentException 时，Spring 只会显示errors.properties 中定义的一般错误消息.我想要的是一个特定的错误消息，它取决于输入的 SSN 无效的确切原因.PropertyEditor.setAsText() 将确定原因.我尝试在 IllegalArgumentException 的文本中嵌入错误原因文本，但 Spring 只是将其视为一般错误.

If setAsText encounters text that is invalid and can't be converted to a SSN, then it throws IllegalArgumentException (per PropertyEditor setAsText's specification). The issue I'm having is that the text to object conversion (via PropertyEditor.setAsText()) takes place before my Spring validator is called. When setAsText throws IllegalArgumentException, Spring simply displays the generic error message defined in errors.properties. What I want is a specific error message that depends on the exact reason why the entered SSN is invalid. PropertyEditor.setAsText() would determine the reason. I've tried embedded the error reason text in IllegalArgumentException's text, but Spring just treats it as a generic error.

有没有办法解决这个问题?重复一遍，我想要的是由 PropertyEditor 生成的特定错误消息，以显示 Spring 表单上的错误消息.我能想到的唯一替代方法是将 SSN 作为文本存储在命令中并在验证器中执行验证.文本到 SSN 对象的转换将在表单的 onSubmit 中进行.这不太理想，因为我的表单(和模型)有很多属性，而且我不想创建和维护一个命令，该命令将每个模型属性都作为文本字段.

Is there a solution to this? To repeat, what I want is the specific error message generated by the PropertyEditor to surface to the error message on the Spring form. The only alternative I can think of is to store the SSN as text in the command and perform validation in the validator. The text to SSN object conversion would take place in the form's onSubmit. This is less desirable as my form (and model) has many properties and I don't want to have to create and maintain a command that has each and every model attribute as a text field.

以上只是一个例子，我的实际代码不是Person/SSN，所以不需要回复为什么不将SSN存储为文本..."

The above is just an example, my actual code isn't Person/SSN, so there's no need to reply with "why not store SSN as text..."

推荐答案

您正尝试在活页夹中进行验证.这不是活页夹的目的.活页夹应该将请求参数绑定到您的支持对象，仅此而已.属性编辑器可将字符串转换为对象，反之亦然 - 它并非旨在执行任何其他操作.

You're trying to do validation in a binder. That's not the binder's purpose. A binder is supposed to bind request parameters to your backing object, nothing more. A property editor converts Strings to objects and vice versa - it is not designed to do anything else.

换句话说，您需要考虑关注点分离 - 您试图将功能硬塞到一个对象中，而该对象除了将字符串转换为对象外，别无他法，反之亦然.

In other words, you need to consider separation of concerns - you're trying to shoehorn functionality into an object that was never meant to do anything more than convert a string into an object and vice versa.

您可能会考虑将您的 SSN 对象分解为多个易于绑定的可验证字段(字符串对象、日期等基本对象等).这样可以在绑定后使用validator来验证SSN是否正确，也可以直接设置错误.使用属性编辑器，您抛出一个 IllegalArgumentException，Spring 将其转换为类型不匹配错误，因为它就是这样 - 字符串与预期的类型不匹配.这就是全部.另一方面，验证器可以做到这一点.您可以使用 spring 绑定标记绑定到嵌套字段，只要填充了 SSN 实例 - 它必须首先使用 new() 进行初始化.例如:

You might consider breaking up your SSN object into multiple, validateable fields that are easily bound (String objects, basic objects like Dates, etc). This way you can use a validator after binding to verify that the SSN is correct, or you can set an error directly. With a property editor, you throw an IllegalArgumentException, Spring converts it to a type mismatch error because that's what it is - the string doesn't match the type that is expected. That's all that it is. A validator, on the other hand, can do this. You can use the spring bind tag to bind to nested fields, as long as the SSN instance is populated - it must be initialized with new() first. For instance:

<spring:bind path="ssn.firstNestedField">...</spring:bind>

如果你真的想坚持这条路，但是，让你的属性编辑器保留一个错误列表 - 如果它抛出一个 IllegalArgumentException，将它添加到列表中，然后抛出 IllegalArgumentException(如果需要，捕获并重新抛出).因为您可以在与绑定相同的线程中构建您的属性编辑器，如果您简单地覆盖属性编辑器的默认行为，它将是线程安全的 - 您需要找到它用于进行绑定的钩子，并覆盖它 - 执行相同的属性编辑器您现在正在注册(除了使用相同的方法，以便您可以保留对编辑器的引用)然后在绑定结束时，如果您提供公共访问器，您可以通过从编辑器中检索列表来注册错误.检索到列表后，您可以对其进行处理并相应地添加您的错误.

If you truly want to persist on this path, however, have your property editor keep a list of errors - if it is to throw an IllegalArgumentException, add it to the list and then throw the IllegalArgumentException (catch and rethrow if needed). Because you can construct your property editor in the same thread as the binding, it will be threadsafe if you simply override the property editor default behavior - you need to find the hook it uses to do binding, and override it - do the same property editor registration you're doing now (except in the same method, so that you can keep the reference to your editor) and then at the end of the binding, you can register errors by retrieving the list from your editor if you provide a public accessor. Once the list is retrieved you can process it and add your errors accordingly.

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