El implementation is not found for hibernate-validator in osgi-container

Question

I try to run Hibernate validator in osgi container.

<dependency>
    <groupId>javax.el</groupId>
    <artifactId>javax.el-api</artifactId>
    <version>2.2.4</version>
</dependency>
<dependency>
    <groupId>org.glassfish.web</groupId>
    <artifactId>javax.el</artifactId>
    <version>2.2.4</version>
</dependency>

<dependency>
    <groupId>org.apache.servicemix.bundles</groupId>
    <artifactId>org.apache.servicemix.bundles.hibernate-validator</artifactId>
    <version>5.0.2.Final_1</version>
</dependency>

<dependency>
    <groupId>joda-time</groupId>
    <artifactId>joda-time</artifactId>
    <version>2.7</version>
</dependency>

<dependency>
    <groupId>org.jsoup</groupId>
    <artifactId>jsoup</artifactId>
    <version>1.8.1</version>
</dependency>


public class HibernateValidationProviderResolver implements ValidationProviderResolver {
    @Override
    public List<ValidationProvider<?>> getValidationProviders() {
        List<ValidationProvider<?>> list = new ArrayList<>(1);
        list.add(new HibernateValidator());
        return list;
    }
}


Configuration<?> configuration = Validation.byDefaultProvider().providerResolver(
    new HibernateValidationProviderResolver()
).configure();

ValidatorFactory validatorFactory = configuration.buildValidatorFactory();
Validator validator = validatorFactory.getValidator();
Set<ConstraintViolation<Group>> constraintViolations = validator.validate(group);


public class Group {
    @NotNull
    @Size(min=2)
    private String title;
}

Try to run, equinox console is okay:

10      RESOLVED    org.glassfish.web.javax.el_2.2.4
39      RESOLVED    org.apache.servicemix.bundles.hibernate-validator_5.0.2.Final_1
47      RESOLVED    javax.validation.api_1.1.0.Final
49      RESOLVED    javax.el-api_2.2.4

If I pass Group class instance with title = null, then validation is okay and constraintViolations contains one violation "not null". If I pass Group class instance with title = "A" (one character against minimal length = 2), then it throws an exception

Caused by: javax.el.ELException: Provider com.sun.el.ExpressionFactoryImpl not found
Caused by: java.lang.ClassNotFoundException: com.sun.el.ExpressionFactoryImpl

It 100% caused by osgi, but how I should setup hibernate-validator in osgi? All articles what I can found describes creating of HibernateValidationProviderResolver and that's all.

UPDATE 1

Maven: javax.el:javax.el-api:2.2.4

Export-Package: javax.el;version="2.2.4"
Import-Package: javax.el;version="2.2.4"

Maven: org.glassfish.web:javax.el:2.2.4 MANIFEST.MF

Export-Package: com.sun.el;uses:="javax.el";version="2.2.4"
Private-Package: com.sun.el.lang;version="2.2.4",com.sun.el.parser;version="2.2.4",com.sun.el.util;version="2.2.4"
Import-Package: com.sun.el;version="2.2.4",javax.el;version="2.2"

Maven: org.apache.servicemix.bundles:org.apache.servicemix.bundles.hibernate-validator:5.0.2.Final_1

Implementation-Version: 5.0.2.Final
Import-Package: javax.el,javax.persistence;resolution:=optional, ...

Export-Package: org.hibernate.validator.internal.engine.messageinterpola
tion.el;uses:="javax.el,javax.validation,org.hibernate.validator.intern
al.engine.messageinterpolation";version="5.0.2.Final",org.hibernate.val
idator.internal.engine.messageinterpolation;uses:="javax.validation.met
adata,org.hibernate.validator.internal.engine.messageinterpolation.el,j
avax.el,javax.validation,org.hibernate.validator.internal.util.logging"
;version="5.0.2.Final", ...

Any version for import in hibernate bundle, 2.2.4 in export of el-api and el-impl and el-impl imports el-api as 2.2, not a 2.2.4. All bundles are resolved.

Update 2

Decision 1

my implementation of @hwellmann's idea. @hwellmann, is it correct?

public void createGroup(Group group) {
    ClassLoader prevClassLoader = Thread.currentThread().getContextClassLoader();

    try {
        ClassLoader[] classLoaders = new ClassLoader[] {
            prevClassLoader,
            ExpressionFactoryImpl.class.getClassLoader()
        };

        // build composite classloader

        Thread.currentThread().setContextClassLoader(compositeClassLoader);

        Set<ConstraintViolation<Group>> constraintViolations = validator.validate(group);

    } finally {
        Thread.currentThread().setContextClassLoader(prevClassLoader);
    }
}

It works but looks strange. And change TCCL on each validation processing looks as some overhead.

Decision 2

The error has gone when I add my own message attribute to each validation annotation, for example for Group:

public class Group {
    @NotNull
    @Size(min=2, message="field.too_short")
    private String title;
}

It seems in this case hibernate interpolator is not started so ExpressionFactoryImpl is not retrieved from TCCL (previously we read min=2 value, now we don't). If it is okay for us, this decision is simplest. I will investigate this area futhermore and share my observations there.

Answer 1

The full stack trace might give some more insight than just the exception messages.

My guess is that you're seeing the results of a failed service lookup via META-INF/service/javax.el.ExpressionFactory. The bundle that's doing the lookup apparently can't see com.sun.el.

Importing this package into your application bundle and setting the thread context classloader to your bundle classloader might help.