由于输入验证在软件开发中是必须的一件事情,特别是与用户交互的软件产品,验证用户的潜在输入错误是必不可少的一件事情,然而各种开源的验证框架也很多,为了一统标准,jsr303规范横空出世了,它定义了一些标准的验证约束,标准毕竟是标准,它不可能定义到所有的验证约束,它只是提供了一些基本的常用的约束,不过它提供了一个可拓展的自定义验证约束。下面就来说说怎么样自定义一个约束.
为了创建一个自定义约束,以下三个步骤是必须的。
Create a constraint annotation (首先定义一个约束注解)
Implement a validator(第二步是实现这个验证器)
Define a default error message(最后添加一条默认的错误消息即可)
假定有这么一个要求,要验证用户的两次输入密码必须是相同的,非常常见的一个要求。下面就基于这个要求来自定义一个约束。
- package org.leochen.samples;
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- import javax.validation.Constraint;
- import javax.validation.Payload;
- import java.lang.annotation.*;
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- @Target({ElementType.TYPE,ElementType.ANNOTATION_TYPE})
- @Retention(RetentionPolicy.RUNTIME)
- @Constraint(validatedBy = MatchesValidator.class)
- @Documented
- public @interface Matches {
- String message() default "{constraint.not.matches}";
- Class<?>[] groups() default {};
- Class<? extends Payload>[] payload() default {};
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- String field();
- String verifyField();
- }
从上到下来说吧,@Target表示注解可出现在哪些地方,比如可以出现在class上,field,method,又或者是在另外一个annotation上,这里限制只能出现在类和另外一个注解上,@Retention表示该注解的保存范围是哪里,RUNTIME表示在源码(source)、编译好的.class文件中保留信息,在执行的时候会把这一些信息加载到JVM中去的.@Constraint比较重要,表示哪个验证器提供验证。@interface表明这是一个注解,和class一样都是关键字,message(),groups()和payload()这三个方法是一个标准的约束所具备的,其中message()是必须的,{constraint.not.matches}表示该消息是要插值计算的,也就是说是要到资源文件中寻找这个key的,如果不加{}就表示是一个普通的消息,直接文本显示,如果消息中有需要用到{或}符号的,需要进行转义,用\{和\}来表示。groups()表示该约束属于哪个验证组,在验证某个bean部分属性是特别有用(也说不清了,具体可以查看Hibernate Validator的文档细看) default必须是一个类型为Class<?>[]的空数组,attribute payload that can be used by clients of the Bean Validation API to assign custom payload objects to a constraint. This attribute is not used by the API itself.下面连个字段是我们添加进去的,表示要验证字段的名称,比如password和confirmPassword.
下面就来实现这个约束。
- package org.leochen.samples;
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- import org.apache.commons.beanutils.BeanUtils;
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- import javax.validation.ConstraintValidator;
- import javax.validation.ConstraintValidatorContext;
- import java.lang.reflect.InvocationTargetException;
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- public class MatchesValidator implements ConstraintValidator<Matches,Object>{
- private String field;
- private String verifyField;
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- public void initialize(Matches matches) {
- this.field = matches.field();
- this.verifyField = matches.verifyField();
- }
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- public boolean isValid(Object value, ConstraintValidatorContext context) {
- try {
- String fieldValue= BeanUtils.getProperty(value,field);
- String verifyFieldValue = BeanUtils.getProperty(value,verifyField);
- boolean valid = (fieldValue == null) && (verifyFieldValue == null);
- if(valid){
- return true;
- }
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- boolean match = (fieldValue!=null) && fieldValue.equals(verifyFieldValue);
- if(!match){
- String messageTemplate = context.getDefaultConstraintMessageTemplate();
- context.disableDefaultConstraintViolation();
- context.buildConstraintViolationWithTemplate(messageTemplate)
- .addNode(verifyField)
- .addConstraintViolation();
- }
- return match;
- } catch (IllegalAccessException e) {
- e.printStackTrace();
- } catch (InvocationTargetException e) {
- e.printStackTrace();
- } catch (NoSuchMethodException e) {
- e.printStackTrace();
- }
- return true;
- }
- }
我们必须要实现ConstraintValidator这个接口,下面就来具体看看这个接口是怎么定义的吧:
- package javax.validation;
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- import java.lang.annotation.Annotation;
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- public interface ConstraintValidator<A extends Annotation, T> {
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- void initialize(A constraintAnnotation);
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- boolean isValid(T value, ConstraintValidatorContext context);
- }
A 表示边界范围为java.lang.annotation.Annotation即可,这个T参数必须满足下面两个限制条件:
- T must resolve to a non parameterized type (T 必须能被解析为非参数化的类型,通俗讲就是要能解析成具体类型,比如Object,Dog,Cat之类的,不能是一个占位符)
- or generic parameters of T must be unbounded wildcard types(或者也可以是一个无边界范围含有通配符的泛型类型)
我们在initialize (A constraintAnnotation)
方法中获取到要验证的两个字段的名称,在isValid方法中编写验证规则。
- String fieldValue= BeanUtils.getProperty(value,field);
- String verifyFieldValue = BeanUtils.getProperty(value,verifyField);
以上是我们把验证出错的消息放在哪个字段上显示,一般我们是在确认密码上显示密码不一致的消息。
好了这样我们的自定义约束就完成了,下面来使用并测试吧。
假如我们要验证这么一个formbean
- package org.leochen.samples;
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- @Matches(field = "password", verifyField = "confirmPassword",
- message = "{constraint.confirmNewPassword.not.match.newPassword}")
- public class TwoPasswords {
- private String password;
- private String confirmPassword;
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- public String getPassword() {
- return password;
- }
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- public void setPassword(String password) {
- this.password = password;
- }
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- public String getConfirmPassword() {
- return confirmPassword;
- }
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- public void setConfirmPassword(String confirmPassword) {
- this.confirmPassword = confirmPassword;
- }
- }
在路径下放入我们的资源文件:ValidationMessages.properties(名字必须叫这个,不然你就费好大一番劲,何苦呢是不是,基于约定来)
- javax.validation.constraints.AssertFalse.message = must be false
- javax.validation.constraints.AssertTrue.message = must be true
- javax.validation.constraints.DecimalMax.message = must be less than or equal to {value}
- javax.validation.constraints.DecimalMin.message = must be greater than or equal to {value}
- javax.validation.constraints.Digits.message = numeric value out of bounds (<{integer} digits>.<{fraction} digits> expected)
- javax.validation.constraints.Future.message = must be in the future
- javax.validation.constraints.Max.message = must be less than or equal to {value}
- javax.validation.constraints.Min.message = must be greater than or equal to {value}
- javax.validation.constraints.NotNull.message = may not be null
- javax.validation.constraints.Null.message = must be null
- javax.validation.constraints.Past.message = must be in the past
- javax.validation.constraints.Pattern.message = must match "{regexp}"
- javax.validation.constraints.Size.message = size must be between {min} and {max}
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- org.hibernate.validator.constraints.CreditCardNumber.message = invalid credit card number
- org.hibernate.validator.constraints.Email.message = not a well-formed email address
- org.hibernate.validator.constraints.Length.message = length must be between {min} and {max}
- org.hibernate.validator.constraints.NotBlank.message = may not be empty
- org.hibernate.validator.constraints.NotEmpty.message = may not be empty
- org.hibernate.validator.constraints.Range.message = must be between {min} and {max}
- org.hibernate.validator.constraints.SafeHtml.message = may have unsafe html content
- org.hibernate.validator.constraints.ScriptAssert.message = script expression "{script}" didn't evaluate to true
- org.hibernate.validator.constraints.URL.message = must be a valid URL
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- ## custom constraints
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- constraint.not.matches=two fields not matches
- constraint.confirmNewPassword.not.match.newPassword=two password not the same
单元测试如下:
- package org.leochen.samples;
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- import org.junit.BeforeClass;
- import org.junit.Test;
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- import javax.validation.ConstraintViolation;
- import javax.validation.Validation;
- import javax.validation.Validator;
- import javax.validation.ValidatorFactory;
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- import java.util.Set;
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- import static junit.framework.Assert.assertEquals;
- import static junit.framework.Assert.assertNotNull;
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- public class TwoPasswordsTest {
- private static Validator validator;
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- @BeforeClass
- public static void setUp() {
- ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
- validator = factory.getValidator();
- }
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- @Test
- public void testBuildDefaultValidatorFactory() {
- ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
- Validator validator = factory.getValidator();
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- assertNotNull(validator);
- }
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- @Test
- public void testPasswordEqualsConfirmPassword() {
- TwoPasswords bean = new TwoPasswords();
- bean.setPassword("110");
- bean.setConfirmPassword("110");
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- Set<ConstraintViolation<TwoPasswords>> constraintViolations = validator.validate(bean);
- for (ConstraintViolation<TwoPasswords> constraintViolation : constraintViolations) {
- System.out.println(constraintViolation.getMessage());
- }
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- assertEquals("newPassword and confirmNewPassword should be the same.", 0, constraintViolations.size());
- }
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- @Test
- public void testPasswordNotEqualsConfirmPassword() {
- TwoPasswords bean = new TwoPasswords();
- bean.setPassword("110");
- bean.setConfirmPassword("111");
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- Set<ConstraintViolation<TwoPasswords>> constraintViolations = validator.validate(bean);
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- assertEquals(1, constraintViolations.size());
- assertEquals("two password not the same", constraintViolations.iterator().next().getMessage());
- }
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- @Test
- public void testIfTwoPasswordWereNullShouldPast() {
- TwoPasswords bean = new TwoPasswords();
- bean.setPassword(null);
- bean.setConfirmPassword(null);
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- Set<ConstraintViolation<TwoPasswords>> constraintViolations = validator.validate(bean);
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- assertEquals(0, constraintViolations.size());
- }
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- @Test
- public void testIfOneIsNullAndOtherIsNotShouldNotPast() {
- TwoPasswords bean = new TwoPasswords();
- bean.setPassword(null);
- bean.setConfirmPassword("110");
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- Set<ConstraintViolation<TwoPasswords>> constraintViolations = validator.validate(bean);
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- assertEquals(1, constraintViolations.size());
- assertEquals("two password not the same", constraintViolations.iterator().next().getMessage());
- }
- }