'Getting a nullpointerexception for my EntityManager
Working with Wildfly 10 on the following: a JSON webservice accessing a postgresql db using hibernate through a DAO object.
More specifically, my POJO User.java:
@Entity (name="User")
@Table(name = "users")
public class User {
@Id @GeneratedValue
@Column(name="id")
private int id;
@Column(name="username")
private String userName;
@Column(name="password")
private String password;
@Column(name="email")
private String emailAddress;
public User(String userName, String password, String emailAddress) {
super();
this.userName = userName;
this.password = password;
this.emailAddress = emailAddress;
}
public User() {
super();
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
My UserDao:
@Stateless
public class UserDao {
@PersistenceContext (unitName="librarysoftjpa")
private EntityManager entityManager;
public List<User> getAllUsers(){
List<User> allUsers=null;
CriteriaBuilder criteriaBuilder = this.entityManager.getCriteriaBuilder();
CriteriaQuery<User> criteria = criteriaBuilder.createQuery(User.class);
criteria.from(User.class);
TypedQuery<User>query = entityManager.createQuery(criteria);
allUsers = query.getResultList();
return allUsers;
}
}
My webservice:
@RequestScoped
@Path("/users")
@Produces("application/json")
@Consumes("application/json")
public class UserWebService {
private UserDao userDao;
public UserWebService(){
this.userDao=new UserDao();
}
@GET
@Path("/all")
public List<User> getAllUsers(){
List<User>users=this.userDao.getAllUsers();
return users;
}
}
My persistence.xml:
<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="librarysoftjpa" transaction-type="JTA">
<jta-data-source>java:/PostGreLibrarySoftDS</jta-data-source>
<class>org.declercq.librarysoftbackend.models.Permission</class>
<class>org.declercq.librarysoftbackend.models.Role</class>
<class>org.declercq.librarysoftbackend.models.User</class>
<properties>
<!-- Properties for Hibernate -->
<property name="hibernate.hbm2ddl.auto" value="update" />
<property name="hibernate.show_sql" value="true" />
<property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect"/>
<property name="hibernate.format_sql" value="true"/>
</properties>
</persistence-unit>
</persistence>
So I'm using container managed persistence, managed by Wildfly 10. However, when accessing the webservice, I get a nullpointer exception for my entitymanager:
10:17:10,095 INFO [org.wildfly.extension.undertow] (ServerService Thread Pool -- 62) WFLYUT0021: Registered web context: /librarysoftbackend
10:17:10,174 INFO [org.jboss.as.server] (ServerService Thread Pool -- 34) WFLYSRV0010: Deployed "librarysoftbackend.war" (runtime-name : "librarysoftbackend.war")
10:17:10,341 INFO [org.jboss.as] (Controller Boot Thread) WFLYSRV0060: Http management interface listening on http://127.0.0.1:9990/management
10:17:10,342 INFO [org.jboss.as] (Controller Boot Thread) WFLYSRV0051: Admin console listening on http://127.0.0.1:9990
10:17:10,343 INFO [org.jboss.as] (Controller Boot Thread) WFLYSRV0025: WildFly Full 10.1.0.Final (WildFly Core 2.2.0.Final) started in 14178ms - Started 422 of 670 services (404 services are lazy, passive or on-demand)
10:17:18,898 ERROR [io.undertow.request] (default task-3) UT005023: Exception handling request to /librarysoftbackend/rest/users/all: org.jboss.resteasy.spi.UnhandledException: java.lang.NullPointerException
at org.jboss.resteasy.core.ExceptionHandler.handleApplicationException(ExceptionHandler.java:77)
at org.jboss.resteasy.core.ExceptionHandler.handleException(ExceptionHandler.java:220)
at org.jboss.resteasy.core.SynchronousDispatcher.writeException(SynchronousDispatcher.java:175)
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:418)
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:209)
at org.jboss.resteasy.plugins.server.servlet.ServletContainerDispatcher.service(ServletContainerDispatcher.java:221)
at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:56)
at org.jboss.resteasy.plugins.server.servlet.HttpServletDispatcher.service(HttpServletDispatcher.java:51)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at io.undertow.servlet.handlers.ServletHandler.handleRequest(ServletHandler.java:85)
at io.undertow.servlet.handlers.security.ServletSecurityRoleHandler.handleRequest(ServletSecurityRoleHandler.java:62)
at io.undertow.servlet.handlers.ServletDispatchingHandler.handleRequest(ServletDispatchingHandler.java:36)
at org.wildfly.extension.undertow.security.SecurityContextAssociationHandler.handleRequest(SecurityContextAssociationHandler.java:78)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.security.SSLInformationAssociationHandler.handleRequest(SSLInformationAssociationHandler.java:131)
at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:57)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:60)
at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:77)
at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
at io.undertow.security.handlers.AbstractSecurityContextAssociationHandler.handleRequest(AbstractSecurityContextAssociationHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:292)
at io.undertow.servlet.handlers.ServletInitialHandler.access$100(ServletInitialHandler.java:81)
at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:138)
at io.undertow.servlet.handlers.ServletInitialHandler$2.call(ServletInitialHandler.java:135)
at io.undertow.servlet.core.ServletRequestContextThreadSetupAction$1.call(ServletRequestContextThreadSetupAction.java:48)
at io.undertow.servlet.core.ContextClassLoaderSetupAction$1.call(ContextClassLoaderSetupAction.java:43)
at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
at io.undertow.servlet.api.LegacyThreadSetupActionWrapper$1.call(LegacyThreadSetupActionWrapper.java:44)
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:272)
at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:81)
at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:104)
at io.undertow.server.Connectors.executeRootHandler(Connectors.java:202)
at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:805)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at org.declercq.librarysoftbackend.dao.UserDao.getAllUsers(UserDao.java:64)
at org.declercq.librarysoftbackend.rest.UserWebService.getAllUsers(UserWebService.java:69)
at org.declercq.librarysoftbackend.rest.UserWebService$Proxy$_$$_WeldClientProxy.getAllUsers(Unknown Source)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.jboss.resteasy.core.MethodInjectorImpl.invoke(MethodInjectorImpl.java:139)
at org.jboss.resteasy.core.ResourceMethodInvoker.invokeOnTarget(ResourceMethodInvoker.java:295)
at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:249)
at org.jboss.resteasy.core.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:236)
at org.jboss.resteasy.core.SynchronousDispatcher.invoke(SynchronousDispatcher.java:402)
... 43 more
More specifically:
Caused by: java.lang.NullPointerException
at org.declercq.librarysoftbackend.dao.UserDao.getAllUsers(UserDao.java:64)
Which points to:
CriteriaBuilder criteriaBuilder = this.entityManager.getCriteriaBuilder();
in UserDao.java.
Any idea what I'm doing wrong here?
UPDATE: the topic linked here as possible duplicate has absolutely zero procent to do with this. My issue is with container managed persistence context and injecting an entitymanager in my application, not with not knowing how to initialize an object.
UPDATE2: I changed my code a bit and consider my UserDao as a Bean by adding the annotation @Stateless after reading this post from Adam Bien: http://www.adam-bien.com/roller/abien/entry/ejb_3_persistence_jpa_for. Basically states that DAO's are no longer needed for JPA, EJB's are better. However, still nullpointerexception on same location. (tried @Stateful too, same result).
UPDATE3: Configuration of my datasource in standalone.xml of Wildfly:
<datasources>
<datasource jndi-name="java:/PostGreLibrarySoftDS" pool-name="PostgrePool">
<connection-url>jdbc:postgresql://127.0.0.1:5432/librarysoft</connection-url>
<driver>postgres</driver>
<security>
<user-name>test</user-name>
<password>test</password>
</security>
</datasource>
<drivers>
<driver name="postgres" module="org.postgres">
<driver-class>org.postgresql.Driver</driver-class>
</driver>
</drivers>
Solved. The solution was to add @Stateless notation to my UserDao class, making it a bean. Next, in UserWebService, add the attribute:
@EJB
private UserDao userDao;
Injecting the bean here with @EJB was the solution.
Solution 1:[1]
Your UserDao is not managed by any framework. Please note that in the example you provided there's @Stateful on the Movies object. That tells you container that it should inject dependencies: PersistenceManager in your case.
Solution 2:[2]
In your UserWebService resource, you are instantiating your UserDao as follows:
public UserWebService(){
this.userDao=new UserDao();
}
Your UserDao is a @Stateless EJB (with a local no-interface view).
Therefore, let the EJB container inject the UserDao EJB as follows:
@EJB
private UserDao userDao;
You can now delete the UserWebService constructor.
I hope this helps.
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
| Solution | Source |
|---|---|
| Solution 1 | Alexey Soshin |
| Solution 2 | Buhake Sindi |