EJB #PersistenceContext EntityManager Throws NullPointerException - nullpointerexception

Question

I'm having a problem with injecting EntityManager by using #PersistenceContext. I try to inject EntityManager in EJB class with #PersistenceContext and I always get NullPointerException.
Here is EJB class:
#Stateless
public class BookEJB {
public BookEJB(){
}
#PersistenceContext(unitName = "BookWebStorePU")
private EntityManager em;
public Book createBook(Book book) throws Exception {
System.out.println("EM: " + em);
em.persist(book);
return book;
}
public Book findBookByIsbn10(String isbn10){
Book book = new Book();
em.find(Book.class, isbn10);
return book;
}
//Other methods here
}
Here's Persistence.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1" xmlns="http://xmlns.jcp.org/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence
http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
<persistence-unit name="BookWebStorePU" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<exclude-unlisted-classes>false</exclude-unlisted-classes>
<validation-mode>NONE</validation-mode>
<properties>
<property name="javax.persistence.schema-generation.database.action" value="create"/>
<property name="javax.persistence.jdbc.driver" value="org.apache.derby.jdbc.EmbeddedDriver"/>
<property name="javax.persistence.jdbc.url" value="jdbc:derby://localhost:1527/BookWebStoreDB"/>
<property name="javax.persistence.jdbc.user" value="bookwebstoreadmin"/>
<property name="javax.persistence.jdbc.password" value="password"/>
<!-- Let EclipseLink create database schemas automatically -->
<property name="eclipselink.ddl-generation" value="drop-and-create-tables"/>
<property name="eclipselink.ddl-generation.output-mode" value="database"/>
</properties>
Here's my test file:
public class BookDaoTests {
private BookEJB bookDao;
private Book newBook;
#Before
public void init() {
newBook = new Book();
newBook.setName("Flying Cow");
newBook.setDescription("Super cool story about flying cow");
newBook.setAuthor("Me");
newBook.setIsbn10("0123456789");
newBook.setIllustrations(true);
newBook.setPublishYear(2013);
newBook.setNumberOfPages(1567);
newBook.setQuantity(58);
bookDao = new BookEJB();
}
#Test
public void createBook() throws Exception{
bookDao.createBook(newBook);
Assert.assertEquals("Book was created!", bookDao.findBookByIsbn10("0123456789"), newBook);
}
}
So when I run that test file I get following error:
Testcase: createBook(com.mysite.bookstore.tests.BookDaoTests): Caused an ERROR
null
java.lang.NullPointerException
at com.mysite.bookwebstore.beans.BookEJB.createBook(BookEJB.java:27)
at com.mysite.bookstore.tests.BookDaoTests.createBook(BookDaoTests.java:46)
EM: null
I use following technologies:
Glassfish 4
JavaEE 7
JSF
EclipseLink 2.1
Java DB
I hope we can find some solution for this problem. I have been tackling now 3 days of this problem and searched and tested solutions from Google and from Stackoverflow but none of the solutions helped/worked. To make sure that the EntityManager was really null, I debugged test file and saw that indeed it gives null. So how can I solve this problem?

Answer 1

The EntityManager instance, is injected when the EJB is deployed in the Container.
If you take a look at the lifecycle of enterprise bean, you will see clearly when dependency injection occurs.
When the Container sees the #Persistencecontext annotation it will inject a container-managed EntityManager.
The problem is that the code executed in this test is not managed by the Container, therefore, no one inject the necessary dependencies.
bookDao = new BookEJB();
When you run the test, the BookEJB class is just a simple POJO, the #Stateless and #PersistenceContext annotations are simply ignored.
You have several alternatives in order to test your EJB, take a look at this link.