数据验证框架 Apache BVal 简介（更新）

Apache BVal （源码）是实体数据验证 Java Bean Validation 的参考实现。Apache BVal 提供了 JSR 303 规范中所有内置 constraint 的实现，用于对 Bean 中的字段的值进行约束定义、描述和验证。若单单说 JSR 规范大渣可能还不清楚，但做过 POJO 的 Hibernate Validator 注解的朋友就知道是啥，——那为什么不使用主流的 Hibernate Validator 呢？因为这货净是个压缩包都已经 13mb 了（尽管可以有文档、源码其他在内），BVal 才只有 400 多 kb，而我只需要服务端验证而已，——天真的孩纸伤不起啊。俺的 ORM 也是 Mybatis 的，务求尽可能地轻量级。

Spring MVC 3.x 虽然自带了验证器 Validatior，可以在控制器中对表单提交的数据进行验证，但这个验证器是极其弱，因为你需要完全手工编码 if (null) else warn("不能空数据")，——太变态了（入下面的例子）——我们需要框架来减轻费时耗力的劳动，于是这类验证框架出现了。

    import org.springframework.validation.Errors;      import org.springframework.validation.ValidationUtils;      import org.springframework.validation.Validator;             public class UserValidator implements Validator {                 public boolean supports(Class<?> clazz) {             // TODO Auto-generated method stub             return User.class.equals(clazz);          }                 public void validate(Object obj, Errors errors) {             // TODO Auto-generated method stub             ValidationUtils.rejectIfEmpty(errors, "username", null, "Username is empty.");             User user = (User) obj;             if (null == user.getPassword() || "".equals(user.getPassword()))                 errors.rejectValue("password", null, "Password is empty.");          }             }  

而我们理想的是这样的，在 POJO 身上声明验证条件的注解（Fields or Method 均可）：

import javax.validation.constraints.Min;  import javax.validation.constraints.NotNull;     public class User {  
    @NotNull(message="用户名不能为空")  
    private String username;        private String password;      private int age;         public String getUsername() {         return username;      }      public void setUsername(String username) {         this.username = username;      }      @NotNull(message="密码不能为null")      public String getPassword() {         return password;      }      public void setPassword(String password) {         this.password = password;      }         @Min(value=10, message="年龄的最小值为10")      public int getAge() {         return age;      }      public void setAge(int age) {         this.age = age;      }  }  

好了，现在准备一下 BVal jar 包：

加入测试用例：

import static org.junit.Assert.assertNotNull;import java.util.Set;import javax.validation.ConstraintViolation;import javax.validation.Validation;import javax.validation.Validator;import javax.validation.ValidatorFactory;import org.apache.bval.jsr.ApacheValidationProvider;import org.junit.Test;import com.ajaxjs.business.model.News;public class TestValidation {@Testpublic void testValid() {News news = new News();ValidatorFactory avf = Validation.byProvider(ApacheValidationProvider.class).configure().buildValidatorFactory();Validator validator = avf.getValidator();//news.setName("dsdsa");Set<ConstraintViolation<News>> constraintViolations = validator.validate(news);for (ConstraintViolation<News> constraintViolation : constraintViolations) {System.out.println(constraintViolation.getMessage());}assertNotNull(constraintViolations);}}

注解说明

@Vaild 是用于嵌套另外一个 pojo 的，如：

@NotNull@Validprivate Person driver;

那么，

Car car = new Car(null, "", 1);Person driver = new Person();car.setDriver(driver);

AnnotationSupported data typesUseHibernate metadata impact@AssertFalseBoolean, booleanChecks that the annotated element is falseNone@AssertTrueBoolean, booleanChecks that the annotated element is trueNone@DecimalMax(value=, inclusive=)BigDecimal, BigInteger, CharSequence, byte, short, int, long and the respective wrappers of the primitive types; Additionally supported by HV: any sub-type of NumberChecks whether the annotated value is less than the specified maximum, when inclusive=false. Otherwise whether the value is less than or equal to the specified maximum. The parameter value is the string representation of the max value according to the BigDecimal string representation.None@DecimalMin(value=, inclusive=)BigDecimal, BigInteger, CharSequence, byte, short, int, long and the respective wrappers of the primitive types; Additionally supported by HV: any sub-type of NumberChecks whether the annotated value is larger than the specified minimum, when inclusive=false. Otherwise whether the value is larger than or equal to the specified minimum. The parameter value is the string representation of the min value according to the BigDecimal string representation.None@Digits(integer=, fraction=)BigDecimal, BigInteger, CharSequence, byte, short, int, long and the respective wrappers of the primitive types; Additionally supported by HV: any sub-type of NumberChecks whether the annoted value is a number having up to integer digits and fraction fractional digitsDefines column precision and [e-mail], supported by HV, if the Joda Time date/time API is on the class path: any implementations of ReadablePartial and ReadableInstantChecks whether the annotated date is in the futureNone@Max(value=)BigDecimal, BigInteger, byte, short, int, long and the respective wrappers of the primitive types; Additionally supported by HV: any sub-type of CharSequence (the numeric value represented by the character sequence is evaluated), any sub-type of NumberChecks whether the annotated value is less than or equal to the specified maximumAdds a check constraint on the column@Min(value=)BigDecimal, BigInteger, byte, short, int, long and the respective wrappers of the primitive types; Additionally supported by HV: any sub-type of CharSequence (the numeric value represented by the char sequence is evaluated), any sub-type of NumberChecks whether the annotated value is higher than or equal to the specified minimumAdds a check constraint on the column@NotNullAny typeChecks that the annotated value is not null.Column(s) are not nullable@NullAny typeChecks that the annotated value is [e-mail], java.util.Calendar; Additionally date/time API is on the class path: any implementations of ReadablePartial and ReadableInstantChecks whether the annotated date is in the pastNone@Pattern(regex=, flag=)CharSequenceChecks if the annotated string matches the regular expression regex considering the given flag matchNone@Size(min=, max=)CharSequence, Collection, Map and arraysChecks if the annotated element's size is between min and max (inclusive)Column length will be set to max@ValidAny non-primitive typePerforms validation recursively on the associated object. If the object is a collection or an array, the elements are validated recursively. If the object is a map, the value elements are validated recursively.

翻译是：

Constraint详细信息@Null被注释的元素必须为 null@NotNull被注释的元素必须不为 null@AssertTrue被注释的元素必须为 true@AssertFalse被注释的元素必须为 false@Min(value)被注释的元素必须是一个数字，其值必须大于等于指定的最小值@Max(value)被注释的元素必须是一个数字，其值必须小于等于指定的最大值@DecimalMin(value)被注释的元素必须是一个数字，其值必须大于等于指定的最小值@DecimalMax(value)被注释的元素必须是一个数字，其值必须小于等于指定的最大值@Size(max, min)被注释的元素的大小必须在指定的范围内@Digits (integer, fraction)被注释的元素必须是一个数字，其值必须在可接受的范围内@Past被注释的元素必须是一个过去的日期@Future被注释的元素必须是一个将来的日期@Pattern(value)被注释的元素必须符合指定的正则表达式

Apache BVal 提供额外的注解，在 org.apache.bval.constraints.* 下。

注入到 Spring

如果用 Apache BVal 结合 Spring 是怎么做的呢？首先在 MVC 的 xml 配置文件中加入以下：

<mvc:annotation-driven validator="validator"/><!-- 数据验证 Validator bean --><bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean">    <property name="providerClass" value="org.apache.bval.jsr.ApacheValidationProvider" /></bean><!-- // -->

这是一种全局的配置方式，我们注入 Bval 的验证器，另外，还要让 MVC 打开注解驱动。加上了 <mvn:annotation-driven/> 之后 Spring 会自动检测 classpath 下的 JSR-303 提供者并自动启用对 JSR-303 的支持。然后就可以在 POJO 中添加注解，而且要在控制器中声明 bean 的验证，如下例的 @Valid T news，否则 Bval 不会起作用。

/** * 新建  * @return */@RequestMapping(method = RequestMethod.POST)public String create(@Valid T news,  BindingResult result,Model model) {System.out.println("新建");if (result.hasErrors()) {LOGGER.info("create error!");}else{LOGGER.info("create ok!");}news.setService(getService());try {getService().create(news);model.addAttribute("newlyId", news.getId());} catch (ServiceException e) {model.addAttribute("errMsg", e.toString());}return "common/entity/json_cud";}

一定要注意的是，控制器方法的参数顺序。Binding Result 必须在 Bean 后面。这是 Spring MVC 的约定。MVC 对控制器其他参数的顺序没什么规定，唯独这个 BindingResult 作了如此规定。目的是为了可以允许有多个 bean，于是也就有多个 BindingResult。

怎么处理错误就不详细说了，不同场景下要求不同。

自定义验证

可否自定义验证条件？我还没试，应该可以参考 Hibernate Validator 的做法。下面这篇文章说得很详细。

《Springmvc validator 验证的使用》

JSR 303 - Bean Validation 介绍及最佳实践

lk

调用 Apache BVal

07-18 补充如下：

可否脱离 Spring 运行？本身 BVal 就是一个独立的框架，因此答案不仅是可以的，而且非常简单。下面使用工厂和单例两种模式，返回一个校验器。

import javax.validation.Validation;import javax.validation.Validator;import javax.validation.ValidatorFactory;import org.apache.bval.jsr.ApacheValidationProvider;public enum MyValidatorFactory {SINGLE_INSTANCE {// BVal 与 JSR 接口结合，返回 ValidatorFactory 工厂ValidatorFactory avf = Validation.byProvider(ApacheValidationProvider.class).configure().buildValidatorFactory();@Overridepublic Validator getValidator() {return avf.getValidator();}};/** * 返回一个校验器 * @return 校验器 */public abstract Validator getValidator();}

这里一点技巧就是通过 Java 枚举来实现单例。

好了，拿一个 Bean 来测试下，分别有通过和报错两种情况的测试。

import java.util.Set;import static org.junit.Assert.*;import org.junit.*;import javax.validation.ConstraintViolation;import javax.validation.Validator;import com.ajaxjs.framework.model.MyValidatorFactory;import com.ajaxjs.framework.model.News;public class TestValid {@Testpublic void testQuery()  {Validator v = MyValidatorFactory.SINGLE_INSTANCE.getValidator();News news = new News();news.setName("标题");Set<ConstraintViolation<News>> result = v.validate(news);assertTrue("应该通过校验", result.isEmpty());News news2 = new News();result = v.validate(news2);assertTrue("应该不通过校验", !result.isEmpty());System.out.println(result.size());for(ConstraintViolation<News> r : result) {System.out.println(r.getMessage());// 什么错？System.out.println(r.getPropertyPath());// 哪个字段错？}}}

主要通过返回 ConstraintViolation 的 isEmpty() 方法来判断是否有错误。