EntityManager is null in EJB - jpa

Question

My client runs on Tomcat and Server is on Wildfly 11.
The EJB is:
package dao;
import java.util.List;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
import model.User;
#Stateless
public class UserDaoImpl implements UserDao {
#PersistenceContext(unitName = "nju")
protected EntityManager em;
#Override
public String login(String userName, String password) {
try {
Query query = em.createQuery("from User u where u.userName='" + userName + "'");
#SuppressWarnings("unchecked")
List<User> list = query.getResultList();
em.clear();
if (list.isEmpty()) {
return "failure";
} else if (list.get(0).getPassword().equals(password)) {
return "success";
}
} catch (Exception e) {
e.printStackTrace();
return "failure";
}
return "failure";
}
}
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="nju">
<description>This unit manages users.</description>
<jta-data-source>java:/MySqlDS</jta-data-source>
<properties>
<property name="showSql" value="true" />
<property name="hibernate.dialect" value="org.hibernate.dialect.MySQL5InnoDBDialect" />
</properties>
</persistence-unit>
When I run server, the output contains
18:53:38,997 INFO [org.jboss.as.clustering.infinispan] (ServerService Thread Pool -- 62) WFLYCLINF0002: Started client-mappings cache from ejb container
18:53:39,005 INFO [org.jboss.as.jpa] (ServerService Thread Pool -- 62) WFLYJPA0010: Starting Persistence Unit (phase 2 of 2) Service 'J2EEServer.war#nju'
So the location of persistence.xml is not wrong.
However, when I run client and call the function in EJB. There is NullPointerException which indicates that the entitymanager is not injected.
In client I use a factory to get EJB. The method is
private static Object getEJB(String JNDIPath) {
Hashtable<String, String> jndiProperties = new Hashtable<>();
jndiProperties.put(Context.URL_PKG_PREFIXES, "org.jboss.ejb.client.naming");
try {
Context context = new InitialContext(jndiProperties);
return context.lookup(JNDIPath);
} catch (NamingException e) {
e.printStackTrace();
}
return null;
}
The exception only shows on wildfly and when it occurs, the tomcat message is
org.jboss.ejb.client.EJBClient <clinit>
INFO: JBoss EJB Client version 2.1.4.Final
org.xnio.Xnio <clinit>
INFO: XNIO version 3.4.0.Final
org.xnio.nio.NioXnio <clinit>
INFO: XNIO NIO Implementation Version 3.4.0.Final
org.jboss.remoting3.EndpointImpl <clinit>
INFO: JBoss Remoting version 4.0.21.Final
org.jboss.ejb.client.remoting.VersionReceiver handleMessage
INFO: EJBCLIENT000017: Received server version 3 and marshalling strategies [river]
org.jboss.ejb.client.remoting.RemotingConnectionEJBReceiver associate
INFO: EJBCLIENT000013: Successful version handshake completed for receiver context EJBReceiverContext{clientContext=org.jboss.ejb.client.EJBClientContext#51e6ae57, receiver=Remoting connection EJB receiver [connection=org.jboss.ejb.client.remoting.ConnectionPool$PooledConnection#5281b661,channel=jboss.ejb,nodename=microwin10-115]} on channel Channel ID 8d8bb52c (outbound) of Remoting connection 3607d423 to localhost/127.0.0.1:8080 of endpoint "client-endpoint" <41cb456e>
org.jboss.ejb.client.remoting.ChannelAssociation$ResponseReceiver handleEnd
INFO: EJBCLIENT000016: Channel Channel ID 8d8bb52c (outbound) of Remoting connection 3607d423 to localhost/127.0.0.1:8080 of endpoint "client-endpoint" <41cb456e> can no longer process messages
How can I solve this problem?

Answer 1

I finally find the solution!!
In my project, my previous Service code is
#Stateless
public class UserServiceImpl implements UserService {
private UserDao userdao=Factory.getUserDao();
#Override
public String login(String userName, String password) {
return userdao.login(userName, password);
}
#Override
public String register(User user) {
return userdao.register(user);
}
}
And in the Factory, I get the object by using new UserDaoImpl(). That's the question!
The EntityManager will not be injected if the object is used like this way.
So I delete the Factory and change the code in Service
#Stateless
public class UserServiceImpl implements UserService {
/**
* Will be injected
*/
#EJB
private UserDao userdao;
#Override
public String login(String userName, String password) {
return userdao.login(userName, password);
}
#Override
public String register(User user) {
return userdao.register(user);
}
}
That works perfectly.