Unit testing EJB3

One thing I like EJB3 is the use of annotations. So, if you want to unit test your EJB you can use the annotations and reflective programming to mock the dependencies and inject them.



Here is the source of this method.

The injector code:

import java.lang.annotation.Annotation;

import java.lang.reflect.Field;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

 

import javax.annotation.Resource;

import javax.ejb.EJB;

import javax.persistence.PersistenceContext;

 

public class EJBTestInjector {

 

  private static final List<Class<? extends Annotation>> EJB_ANNOTATIONS;

  static {

    EJB_ANNOTATIONS = new ArrayList<Class<? extends Annotation>>();

    EJB_ANNOTATIONS.add(EJB.class);

    EJB_ANNOTATIONS.add(PersistenceContext.class);

    EJB_ANNOTATIONS.add(Resource.class);

  }

 

  final Map<Class<?>, Object> mappings = new HashMap<Class<?>, Object>();

 

  public void inject(final Object bean) throws Exception {

    for (final Field field : getEJBAnnotatedFields(bean)) {

       injectField(field, bean);

    }

  }

 

  public void assign(final Class<?> type, final Object instance) {

    mappings.put(type, instance);

  }

 

  private void injectField(final Field field, final Object bean)  throws Exception {

    final Object instanceToInject = mappings.get(field.getType());

    if (!field.isAccessible()) {

      field.setAccessible(true);

    }

    field.set(bean, instanceToInject);

  }

 

  private List<Field> getEJBAnnotatedFields(final Object bean) {

    final Class<? extends Object> beanClass = bean.getClass();

    final List<Field> annotatedFields = new ArrayList<Field>();

    for (final Field field : beanClass.getDeclaredFields()) {

      if (hasEJBAnnotation(field)) {

        annotatedFields.add(field);

      }

    }

    return annotatedFields;

  }

 

  private static boolean hasEJBAnnotation(final Field field) {

    for (final Class<? extends Annotation> annotation : EJB_ANNOTATIONS) {

      if (field.isAnnotationPresent(annotation)) {

        return true;

      }

    }

    return false;

  }

}

 

The example:

 final EJBTestInjector injector = new EJBTestInjector();

  injector.assign(EntityManager.class, entityManagerMock);

  injector.assign(SessionTokenManager.class, sessionTokenManagerMock);

  injector.inject(<your EJBean>);

 

That is all. Now you can unit test your ejb as well as other POJO.