Spring 驗(yàn)證(創(chuàng)建自定義JSR303的驗(yàn)證約束(Creating custom constraints) )

windli筆記 2012-10-07

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由于輸入驗(yàn)證在軟件開(kāi)發(fā)中是必須的一件事情，特別是與用戶交互的軟件產(chǎn)品，驗(yàn)證用戶的潛在輸入錯(cuò)誤是必不可少的一件事情，然而各種開(kāi)源的驗(yàn) 證框架也很多，為了一統(tǒng)標(biāo)準(zhǔn)，jsr303規(guī)范橫空出世了，它定義了一些標(biāo)準(zhǔn)的驗(yàn)證約束，標(biāo)準(zhǔn)畢竟是標(biāo)準(zhǔn)，它不可能定義到所有的驗(yàn)證約束，它只是提供了一些基本的常用的約束，不過(guò)它提供了一個(gè)可拓展的自定義驗(yàn)證約束。下面就來(lái)說(shuō)說(shuō)怎么樣自定義一個(gè)約束.

為了創(chuàng)建一個(gè)自定義約束，以下三個(gè)步驟是必須的。
Create a constraint annotation (首先定義一個(gè)約束注解)
Implement a validator(第二步是實(shí)現(xiàn)這個(gè)驗(yàn)證器)
Define a default error message(最后添加一條默認(rèn)的錯(cuò)誤消息即可)

假定有這么一個(gè)要求，要驗(yàn)證用戶的兩次輸入密碼必須是相同的，非常常見(jiàn)的一個(gè)要求。下面就基于這個(gè)要求來(lái)自定義一個(gè)約束。

Java代碼

package org.leochen.samples;
import javax.validation.Constraint;
import javax.validation.Payload;
import java.lang.annotation.*;
/**
* User: leochen
* Date: 11-12-8
* Time: 下午11:31
*/
@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 {};
String field();
String verifyField();
}

從上到下來(lái)說(shuō)吧，@Target表示注解可出現(xiàn)在哪些地方，比如可以出現(xiàn)在class上,field,method,又或者是在另外一個(gè) annotation上，這里限制只能出現(xiàn)在類(lèi)和另外一個(gè)注解上，@Retention表示該注解的保存范圍是哪里,RUNTIME表示在源碼 (source)、編譯好的.class文件中保留信息，在執(zhí)行的時(shí)候會(huì)把這一些信息加載到JVM中去的．@Constraint比較重要，表示哪個(gè)驗(yàn)證器提供驗(yàn)證。@interface表明這是一個(gè)注解,和class一樣都是關(guān)鍵字,message(),groups()和payload()這三個(gè)方法是一個(gè)標(biāo)準(zhǔn)的約束所具備的，其中message()是必須的，{constraint.not.matches}表示該消息是要插值計(jì)算的，也就是說(shuō)是要到資源文件中尋找這個(gè)key的，如果不加{}就表示是一個(gè)普通的消息，直接文本顯示,如果消息中有需要用到{或}符號(hào)的，需要進(jìn)行轉(zhuǎn)義,用\{和\}來(lái)表示。groups()表示該約束屬于哪個(gè)驗(yàn)證組,在驗(yàn)證某個(gè)bean部分屬性是特別有用(也說(shuō)不清了，具體可以查看Hibernate Validator的文檔細(xì)看) default必須是一個(gè)類(lèi)型為Class<?>[]的空數(shù)組,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.下面連個(gè)字段是我們添加進(jìn)去的，表示要驗(yàn)證字段的名稱，比如password和confirmPassword.

下面就來(lái)實(shí)現(xiàn)這個(gè)約束。

Java代碼

package org.leochen.samples;
import org.apache.commons.beanutils.BeanUtils;
import javax.validation.ConstraintValidator;
import javax.validation.ConstraintValidatorContext;
import java.lang.reflect.InvocationTargetException;
/**
* User: leochen
* Date: 11-12-8
* Time: 下午11:39
*/
public class MatchesValidator implements ConstraintValidator<Matches,Object>{
private String field;
private String verifyField;
public void initialize(Matches matches) {
this.field = matches.field();
this.verifyField = matches.verifyField();
}
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;
}
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;
}
}

我們必須要實(shí)現(xiàn)ConstraintValidator這個(gè)接口,下面就來(lái)具體看看這個(gè)接口是怎么定義的吧：

Java代碼

package javax.validation;
import java.lang.annotation.Annotation;
public interface ConstraintValidator<A extends Annotation, T> {
/**
* Initialize the validator in preparation for isValid calls.
* The constraint annotation for a given constraint declaration
* is passed.
* <p/>
* This method is guaranteed to be called before any use of this instance for
* validation.
*
* @param constraintAnnotation annotation instance for a given constraint declaration
*/
void initialize(A constraintAnnotation);
/**
* Implement the validation logic.
* The state of <code>value</code> must not be altered.
*
* This method can be accessed concurrently, thread-safety must be ensured
* by the implementation.
*
* @param value object to validate
* @param context context in which the constraint is evaluated
*
* @return false if <code>value</code> does not pass the constraint
*/
boolean isValid(T value, ConstraintValidatorContext context);
}

A 表示邊界范圍為java.lang.annotation.Annotation即可,這個(gè)T參數(shù)必須滿足下面兩個(gè)限制條件：

T must resolve to a non parameterized type (T 必須能被解析為非參數(shù)化的類(lèi)型,通俗講就是要能解析成具體類(lèi)型，比如Object,Dog,Cat之類(lèi)的，不能是一個(gè)占位符)
or generic parameters of T must be unbounded wildcard types(或者也可以是一個(gè)無(wú)邊界范圍含有通配符的泛型類(lèi)型)

我們?cè)?code>initialize (A constraintAnnotation) 方法中獲取到要驗(yàn)證的兩個(gè)字段的名稱，在isValid方法中編寫(xiě)驗(yàn)證規(guī)則。

Java代碼

String fieldValue= BeanUtils.getProperty(value,field);
String verifyFieldValue = BeanUtils.getProperty(value,verifyField);

以上是我們把驗(yàn)證出錯(cuò)的消息放在哪個(gè)字段上顯示，一般我們是在確認(rèn)密碼上顯示密碼不一致的消息。

好了這樣我們的自定義約束就完成了，下面來(lái)使用并測(cè)試吧。

假如我們要驗(yàn)證這么一個(gè)formbean

Java代碼

package org.leochen.samples;
/**
* User: leochen
* Date: 11-12-20
* Time: 下午4:04
*/
@Matches(field = "password", verifyField = "confirmPassword",
message = "{constraint.confirmNewPassword.not.match.newPassword}")
public class TwoPasswords {
private String password;
private String confirmPassword;
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getConfirmPassword() {
return confirmPassword;
}
public void setConfirmPassword(String confirmPassword) {
this.confirmPassword = confirmPassword;
}
}

在路徑下放入我們的資源文件：ValidationMessages.properties（名字必須叫這個(gè)，不然你就費(fèi)好大一番勁，何苦呢是不是，基于約定來(lái)）

Java代碼

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}
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
## custom constraints
constraint.not.matches=two fields not matches
constraint.confirmNewPassword.not.match.newPassword=two password not the same

單元測(cè)試如下：

Java代碼

package org.leochen.samples;
import org.junit.BeforeClass;
import org.junit.Test;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;
import java.util.Set;
import static junit.framework.Assert.assertEquals;
import static junit.framework.Assert.assertNotNull;
/**
* User: leochen
* Date: 11-12-20
* Time: 下午4:06
*/
public class TwoPasswordsTest {
private static Validator validator;
@BeforeClass
public static void setUp() {
ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
validator = factory.getValidator();
}
@Test
public void testBuildDefaultValidatorFactory() {
ValidatorFactory factory = Validation.buildDefaultValidatorFactory();
Validator validator = factory.getValidator();
assertNotNull(validator);
}
@Test
public void testPasswordEqualsConfirmPassword() {
TwoPasswords bean = new TwoPasswords();
bean.setPassword("110");
bean.setConfirmPassword("110");
Set<ConstraintViolation<TwoPasswords>> constraintViolations = validator.validate(bean);
for (ConstraintViolation<TwoPasswords> constraintViolation : constraintViolations) {
System.out.println(constraintViolation.getMessage());
}
assertEquals("newPassword and confirmNewPassword should be the same.", 0, constraintViolations.size());
}
@Test
public void testPasswordNotEqualsConfirmPassword() {
TwoPasswords bean = new TwoPasswords();
bean.setPassword("110");
bean.setConfirmPassword("111");
Set<ConstraintViolation<TwoPasswords>> constraintViolations = validator.validate(bean);
assertEquals(1, constraintViolations.size());
assertEquals("two password not the same", constraintViolations.iterator().next().getMessage());
}
@Test
public void testIfTwoPasswordWereNullShouldPast() {
TwoPasswords bean = new TwoPasswords();
bean.setPassword(null);
bean.setConfirmPassword(null);
Set<ConstraintViolation<TwoPasswords>> constraintViolations = validator.validate(bean);
assertEquals(0, constraintViolations.size());
}
@Test
public void testIfOneIsNullAndOtherIsNotShouldNotPast() {
TwoPasswords bean = new TwoPasswords();
bean.setPassword(null);
bean.setConfirmPassword("110");
Set<ConstraintViolation<TwoPasswords>> constraintViolations = validator.validate(bean);
assertEquals(1, constraintViolations.size());
assertEquals("two password not the same", constraintViolations.iterator().next().getMessage());
}
}

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