21.16.4 验证

Spring提供了一个验证器Validator接口,应用的任何一层都可以使用它来做验证。在Spring MVC中,你可以配置一个全局的Validator实例,用以处理所有注解了@Valid的元素或注解了@Validated的控制器方法参数、以及/或在控制器内的@InitBinder方法中用作局部的Validator。全局验证器与局部验证器实例可以结合起来使用,提供组合验证。

Spring还支持JSR-303/JSR-349的Bean验证。这是通过LocalValidatorFactoryBean类实现的,它为Spring的验证器接口org.springframework.validation.Validator到Bean验证的javax.validation.Validator接口做了适配。这个类可以插入到Spring MVC的上下文中,作为一个全局的验证器,如下所述。

如果在classpath下存在Bean验证器,诸如Hibernate Validator等,那么@EnableWebMvc<mvc:annotation-driven>默认会自动使用LocalValidatorFactoryBean为Spring MVC应用提供Bean验证的支持。

有时,能将LocalValidatorFactoryBean直接注入到控制器或另外一个类中会更方便。

Sometimes it's convenient to have a LocalValidatorFactoryBean injected into a controller or another class. The easiest way to do that is to declare your own @Bean and also mark it with @Primary in order to avoid a conflict with the one provided with the MVC Java config.

If you prefer to use the one from the MVC Java config, you'll need to override the mvcValidator method from WebMvcConfigurationSupport and declare the method to explicitly return LocalValidatorFactory rather than Validator. See Section 21.16.13, "Advanced Customizations with MVC Java Config" for information on how to switch to extend the provided configuration.

此外,你也可以配置你自己的全局Validator验证器实例:

@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {

    @Override
    public Validator getValidator(); {
        // return "global" validator
    }

}

XML中做法如下:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd">

    <mvc:annotation-driven validator="globalValidator"/>

</beans>

若要同时使用全局验证和局部验证,只需添加一个(或多个)局部验证器即可:

@Controller
public class MyController {

    @InitBinder
    protected void initBinder(WebDataBinder binder) {
        binder.addValidators(new FooValidator());
    }

}

做完这个最少的配置之后,任何时候只要方法中有参数注解了@Valid@Validated,配置的验证器就会自动对它们做验证。任何无法通过的验证都会被自动报告为错误并添加到BindingResult对象中去,你可以在方法参数中声明它并获取这些错误,同时这些错误也能在Spring MVC的HTML视图中被渲染。

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