Hello,
I’m building a web application with Vaadin 7, Spring 4 and Hibernate 4. I’m using JPAContainer add-on for persistence and I’m getting a NullPointerException when calling addEntity on my container. The same container is set as a data source for a table and it works perfectly fine - the table is displayed properly with no exceptions.
SEVERE: Servlet.service() for servlet [VaadinServlet]
in context with path
[/erasmus-plus-system] threw exception [com.vaadin.server.ServiceException: java.lang.NullPointerException]
with root cause
java.lang.NullPointerException
at sun.reflect.GeneratedMethodAccessor22.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:483)
at com.vaadin.addon.jpacontainer.metadata.ClassMetadata.getPropertyValueFromField(ClassMetadata.java:201)
at com.vaadin.addon.jpacontainer.metadata.ClassMetadata.getPropertyValue(ClassMetadata.java:165)
at com.vaadin.addon.jpacontainer.metadata.ClassMetadata.getPropertyValue(ClassMetadata.java:343)
at com.vaadin.addon.jpacontainer.JPAContainer.addEntity(JPAContainer.java:1115)
at pl.edu.pw.mini.erasmus.ui.ErasmusPlusApplication.init(ErasmusPlusApplication.java:97)
at com.vaadin.ui.UI.doInit(UI.java:639)
at com.vaadin.server.communication.UIInitHandler.getBrowserDetailsUI(UIInitHandler.java:222)
at com.vaadin.server.communication.UIInitHandler.synchronizedHandleRequest(UIInitHandler.java:74)
at com.vaadin.server.SynchronizedRequestHandler.handleRequest(SynchronizedRequestHandler.java:41)
at com.vaadin.server.VaadinService.handleRequest(VaadinService.java:1402)
at com.vaadin.server.VaadinServlet.service(VaadinServlet.java:305)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:51)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:953)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1041)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:603)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:312)
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)
The container:
public class UserJPAContainer extends JPAContainer<User> {
private static final long serialVersionUID = 1L;
@PersistenceContext
private EntityManager entityManager;
private JPAEntityProvider<User> jpaEntityProvider;
public UserJPAContainer() {
super(User.class);
jpaEntityProvider = new JPAEntityProvider<User>(User.class);
setEntityProvider(jpaEntityProvider);
}
@PostConstruct
public void init() {
jpaEntityProvider.setEntityManager(entityManager);
}
}My entity provider:
[code]
@Transactional(propagation = Propagation.REQUIRED)
public class JPAEntityProvider extends CachingMutableLocalEntityProvider {
private static Logger LOG = LoggerFactory.getLogger(JPAEntityProvider.class);
public JPAEntityProvider(Class<T> entityclass) {
super(entityclass);
setTransactionsHandledByProvider(false);
}
@Override
public T updateEntity(T entity) {
LOG.info("Updating entity started");
long t = System.currentTimeMillis();
T updated = super.updateEntity(entity);
LOG.info("Updated: " + updated.toString());
t = System.currentTimeMillis() - t;
LOG.info("Updating entity took: " + t + "ms");
return updated;
}
@Override
public T addEntity(T entity) {
LOG.info("Adding entity started");
long t = System.currentTimeMillis();
T added = null;
try {
added = super.addEntity(entity);
LOG.info("Added: " + added.toString());
} catch (Throwable e) {
LOG.error(e.getMessage());
}
t = System.currentTimeMillis() - t;
LOG.info("Adding entity took: " + t + "ms");
return added;
}
@Override
public void removeEntity(Object entityId) {
super.removeEntity(entityId);
}
@Override
public void updateEntityProperty(Object entityId, String propertyName,
Object propertyValue) throws IllegalArgumentException {
LOG.info("Updating entity's property started");
long t = System.currentTimeMillis();
super.updateEntityProperty(entityId, propertyName, propertyValue);
t = System.currentTimeMillis() - t;
LOG.info("Updating entity's property took: " + t + "ms");
}
// @PostConstruct
public void init(EntityManager em) {
setEntityManager(em);
/*
* The entity manager is transaction scoped, which means that the
* entities will be automatically detached when the transaction is
* closed. Therefore, we do not need to explicitly detach them.
*/
setEntitiesDetached(false);
}
}
[/code]Relevant part of my applicationContext.xml:
<context:annotation-config />
<context:spring-configured />
<context:component-scan base-package="my.package" />
<bean id="propertyConfigurer"
class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"
p:location="classpath:META-INF/persistence/jdbc.properties" />
<bean id="entityManagerFactory"
class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="persistenceXmlLocation" value="classpath:META-INF/persistence/spring-persistence.xml" />
<property name="persistenceUnitName" value="persistenceUnit" />
<property name="packagesToScan" value="my.package.*" />
<property name="dataSource" ref="dataSource" />
<property name="jpaVendorAdapter" ref="jpaVendorAdapter" />
<property name="jpaDialect" ref="jpaDialect" />
</bean>
<bean id="jpaVendorAdapter"
class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter">
<property name="showSql" value="false" />
<property name="generateDdl" value="true" />
<property name="database" value="MYSQL" />
<property name="databasePlatform" value="org.hibernate.dialect.MySQL5Dialect"/>
</bean>
<bean id="jpaDialect" class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
<property name="dataSource" ref="dataSource" />
<property name="jpaDialect" ref="jpaDialect" />
</bean>
<tx:annotation-driven />
<bean id="dataSource"
class="org.springframework.jdbc.datasource.DriverManagerDataSource">
<property name="driverClassName" value="${jdbc.driverClassName}" />
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</bean>
<bean id="userJPAContainer" class="pl.edu.pw.mini.erasmus.container.UserJPAContainer" scope="prototype"/>Application code:
[code]
private JPAContainer getContainer() {
if (container == null) {
container = (UserJPAContainer) applicationContext.getBean(“userJPAContainer”);
}
return container;
}
// Create table
Table table = new Table(“Users”);
table.setContainerDataSource(getContainer());
content.addComponent(table); // THIS WORKS FINE
// Add a new user
User user = new User();
user.setEmail(“email@example.com”);
user.setLogin(“login”);
getContainer().addEntity(user); // THIS LINE RAISES THE EXCEPTION
[/code]The stack trace doesn’t seem helpful to me - I have no idea what the problem is. Maybe some of you had similar problems using Spring, Hibernate and JPAContainer and will be able to help? 
Thank you in advance!