public void (@Valid Person p) { ... }

对象上的@Valid注释表示验证框架处理带注释的对象.当在方法的参数上使用时,这被称为方法级验证.请注意,方法级别验证不是核心规范的一部分,实际上只有在将Bean Validation集成到容器类型框架(JSF,CDI,Java EE)中时才支持.当Bean Validation集成到这样的支持容器中时,会发生的是,当在bean上调用生命周期方法时,容器会检测方法参数上的JSR 303注释并触发关联bean的验证.

例如,如果您在JAX-RS资源类中具有以下方法定义：

@Path("/example")
public class MyExampleResourceImpl {

    @POST
    @Path("/")
    public Response postExample(@Valid final Example example) {
        // ....
    }
}

当调用postExample方法以响应JAX-RS容器处理的请求时,将验证示例bean.将此行为与运行独立Java SE应用程序时会发生的情况进行对比：

public class MyMainClass {
    public static void main(final String[] args) {
        final MyMainClass clazz = new MyMainClass();
        clazz.echo(new Example());
    }

    public Example echo(@Valid final Example example) {
        // ...
    }
}

在这种情况下,即使您包含了所有JSR 303运行时JAR,运行该程序也不会触发Example参数的验证.这是因为没有可用的容器实现方法级别验证. Bean Validation Specification在附录C中详细描述了所有这些.为了您的利益,我在下面引用了一些内容：

Proposal for method-level validation

This proposition has not been integrated into the core specification
and is not part of it. It remains here for archaeological purposes and
will be serIoUsly considered for a future revision of this
specification. This proposal is likely to be a bit out of sync with
the rest of the specification artifacts.

Note: Bean Validation providers are free to implement this proposal as
a specific extension. Such specific extension could for example be accessed
via the use of the Validator.unwrap method.

A popular demand was to provide a method and parameter level validation
mechanism reusing the constraint descriptions of the specification. This
set of APIs is meant to be used by interceptor frameworks such as:

• application frameworks like
  • JSR-299
• component frameworks like Enterprise Java Beans
• aspect based frameworks

These frameworks can call the validation APIs to validate either the parameter list or the returned value of a method when such method is called. More precisely,validation occurs around a method invocation. This extension of the Bean Validation API allows to reuse the core engine as well as the constraint definition and declaration for such method level validations.

@H_301_7@ @H_301_7@ 原文链接：https://www.f2er.com/java/126611.html