java - Spring + Hibernate @autowired is null in ConstraintValidator

Question

I have search and found a lot of topic on this issue, but for whatever reason the solutions does not solve my problem.

I am running Spring boot 1.5.8 and Hibernate.

I have created a custom validation annotation to check if a email is unique compared to the database. The annotation is using a @autowired repository to query the database to check if the email already exist in the database. I keep getting an exception that the @autowired bean is null.

My theory is that the hibernate validator is being used instead of the UniqueEmailValidator class is therefore not wired properly. I am however clueless how to solve this issue.

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.FIELD)
@Constraint(validatedBy = UniqueEmailValidator.class)
public @interface UniqueEmail {

    String message() default "{generic.error}";

    Class<?>[] groups() default {};

    Class<? extends Payload>[] payload() default {};   
}

@Component
public class UniqueEmailValidator implements ConstraintValidator<UniqueEmail, String> {

    @Autowired
    private UserRepository us;

    @Override
    public void initialize(UniqueEmail constraint) {
    }

    @Override
    public boolean isValid(String val, ConstraintValidatorContext  context) {
        return !us.checkIfEmailExists(val);
    }
}

I am calling this annotation in my entities like this:

public class{
    @UniqueEmail 
    String email;
}

I am also calling @valid on the input of my rest methods.

@RestController
@RequestMapping(value = "/api", produces = MediaType.APPLICATION_JSON_VALUE)
public class UserController {

    @RolesAllowed(Role.SUPERADMIN)
    @RequestMapping(value = "/admin", method = RequestMethod.POST)
    public ResponseEntity<User> createAdmin(@RequestBody @Valid UserWrapper uw) {
    } 
}

Stacktrace:

2017-11-12 04:12:52.155 ERROR 2416848 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is javax.validation.ValidationException: HV000028: Unexpected exception during isValid call.] with root cause

java.lang.NullPointerException: null
    at dk.bagtag.validation.UniqueEmailValidator.isValid(UniqueEmailValidator.java:25) ~[classes/:na]
    at dk.bagtag.validation.UniqueEmailValidator.isValid(UniqueEmailValidator.java:1) ~[classes/:na]
    at org.hibernate.validator.internal.engine.constraintvalidation.ConstraintTree.validateSingleConstraint(ConstraintTree.java:448) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.validator.internal.engine.constraintvalidation.ConstraintTree.validateConstraints(ConstraintTree.java:127) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.validator.internal.engine.constraintvalidation.ConstraintTree.validateConstraints(ConstraintTree.java:87) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.validator.internal.metadata.core.MetaConstraint.validateConstraint(MetaConstraint.java:73) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateMetaConstraint(ValidatorImpl.java:620) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateConstraint(ValidatorImpl.java:583) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateConstraintsForSingleDefaultGroupElement(ValidatorImpl.java:527) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateConstraintsForDefaultGroup(ValidatorImpl.java:495) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateConstraintsForCurrentGroup(ValidatorImpl.java:460) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validateInContext(ValidatorImpl.java:410) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.validator.internal.engine.ValidatorImpl.validate(ValidatorImpl.java:207) ~[hibernate-validator-5.3.5.Final.jar:5.3.5.Final]
    at org.hibernate.cfg.beanvalidation.BeanValidationEventListener.validate(BeanValidationEventListener.java:114) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.cfg.beanvalidation.BeanValidationEventListener.onPreInsert(BeanValidationEventListener.java:78) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.action.internal.EntityIdentityInsertAction.preInsert(EntityIdentityInsertAction.java:197) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:75) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:619) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:273) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:254) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:299) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:317) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:272) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:178) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:109) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.jpa.event.internal.core.JpaPersistEventListener.saveWithGeneratedId(JpaPersistEventListener.java:67) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:189) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:132) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:58) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:775) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:748) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:753) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.jpa.spi.AbstractEntityManagerImpl.persist(AbstractEntityManagerImpl.java:1146) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_121]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_121]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
    at org.springframework.orm.jpa.ExtendedEntityManagerCreator$ExtendedEntityManagerInvocationHandler.invoke(ExtendedEntityManagerCreator.java:347) ~[spring-orm-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at com.sun.proxy.$Proxy99.persist(Unknown Source) ~[na:na]
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_121]
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_121]
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_121]
    at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_121]
    at org.springframework.orm.jpa.SharedEntityManagerCreator$SharedEntityManagerInvocationHandler.invoke(SharedEntityManagerCreator.java:298) ~[spring-orm-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at com.sun.proxy.$Proxy99.persist(Unknown Source) ~[na:na]
    at dk.bagtag.repository.UserRepository.save(UserRepository.java:22) ~[classes/:na]
    at dk.bagtag.repository.UserRepository$$FastClassBySpringCGLIB$$44d278e4.invoke(<generated>) ~[classes/:na]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) ~[spring-core-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738) ~[spring-aop-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:136) ~[spring-tx-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99) ~[spring-tx-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282) ~[spring-tx-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96) ~[spring-tx-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179) ~[spring-aop-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:673) ~[spring-aop-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at dk.bagtag.repository.UserRepository$$EnhancerBySpringCGLIB$$7b754dae.save(<generated>) ~[classes/:na]
    at dk.bagtag.service.UserService.createUser(UserService.java:86) ~[classes/:na]
    at dk.bagtag.service.UserService.createSuperAdminUser(UserService.java:49) ~[classes/:na]
    at dk.bagtag.service.UserService$$FastClassBySpringCGLIB$$dc11aefc.invoke(<generated>) ~[classes/:na]
    at org.springframework.cglib.proxy.MethodProxy.invoke(MethodProxy.java:204) ~[spring-core-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.aop.framework.CglibAopProxy$CglibMethodInvocation.invokeJoinpoint(CglibAopProxy.java:738) ~[spring-aop-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:157) ~[spring-aop-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.transaction.interceptor.TransactionInterceptor$1.proceedWithInvocation(TransactionInterceptor.java:99) ~[spring-tx-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:282) ~[spring-tx-4.3.12.RELEASE.jar:4.3.12.RELEASE]
    at org.springframework.transaction.interceptor.TransactionInte

Answer 1

Please see below answers, I could reproduce this in my environment as well.

The validator being called twice, once the request is posted, another one is after the validation is done and entity gets persisted to DB, for the second time the autowired bean becomes null and throws NPE.

From the below answers, set validator property in entity manager along with other properties

<bean
    id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="persistenceProvider">
      <bean class="org.hibernate.ejb.HibernatePersistence" />
    </property>
        <property name="jpaPropertyMap">
      <map>  
        <entry key="javax.persistence.validation.factory" value-ref="validator" />
      </map>
    </property>
</bean>

<bean id="validator" class="org.springframework.validation.beanvalidation.LocalValidatorFactoryBean" />

http://forum.spring.io/forum/spring-projects/web/84838-custom-jsr-303-validator-firing-twice

https://developer.jboss.org/thread/139770

How to inject spring bean into Validator(hibernate)

https://docs.jboss.org/hibernate/orm/3.6/reference/en-US/html/additionalmodules.html