I am trying to develop a simple Spring web application using Jersey (JAX-RS), deployed in a Tomcat container. The entities are managed using JPA with EclipseLink provider and stored in a MySQL database. I don't use EJB.
I'm trying to inject the EntityManager via Spring, however when I want to get (or persist) an entity from the DB, I get a NullPointerException showing that EntityManager is null.
I have spent lots of hours trying to find the solution and tried every code I've found in tutorials and threads, but got the same result.
I have included all the required dependecies in the project. If I manually create an EntityManagerFactory and then an EntityManager in getPerson, it works, but I don't think that should be the proper way. Also, when I start the service, I can see in the console output logs that Spring root WebApplicationContext is initialized, bean definitions are loaded and JPA container EntityManagerFactory for persistence unit 'defaultPU' is built.
I am clearly missing something, could you please help me how can I make this work? Why is EntityManager null and how should I inject it in order to be able to use it in the PersonController?
Person.java:
package TestSpringApp;
import javax.persistence.Entity;
import javax.persistence.Id;
@Entity
public class Person {
@Id
private int id;
private String name;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
PersonController.java:
package TestSpringApp;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.ws.rs.GET;
import javax.ws.rs.Path;
@Component
@Path("/person")
public class PersonController {
@PersistenceContext
EntityManager entityManager;
@GET
@Transactional
public String getPerson() {
Person p = entityManager.find(Person.class, 0);
return p.getName();
}
public void setEntityManager(EntityManager em) {
this.entityManager = em;
}
public EntityManager getEntityManager() {
return this.entityManager;
}
}
beans.xml:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:tx="http://www.springframework.org/schema/tx"
xsi:schemaLocation=
"http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-2.5.xsd">
<context:component-scan base-package="TestSpringApp"/>
<tx:annotation-driven />
<context:annotation-config/>
<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
<property name="jpaVendorAdapter" ref="jpaAdapter" />
<property name="persistenceUnitName" value="defaultPU"/>
</bean>
<bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
<property name="entityManagerFactory" ref="entityManagerFactory" />
</bean>
<bean id="jpaAdapter" class="org.springframework.orm.jpa.vendor.EclipseLinkJpaVendorAdapter">
<property name="database" value="MYSQL" />
<property name="showSql" value="true" />
</bean>
</beans>
persistence.xml:
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"
version="1.0">
<persistence-unit name="defaultPU" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<class>TestSpringApp.Person</class>
<properties>
<property name="javax.persistence.jdbc.url" value="jdbc:mysql://localhost:3306/test"/>
<property name="javax.persistence.jdbc.driver" value="com.mysql.jdbc.Driver"/>
<property name="javax.persistence.jdbc.user" value="root"/>
<property name="javax.persistence.jdbc.password" value="root"/>
<property name="eclipselink.ddl-generation" value="create-tables" />
<property name="eclipselink.ddl-generation.output-mode" value="database" />
<property name="eclipselink.weaving" value="false"/>
</properties>
</persistence-unit>
</persistence>
web.xml:
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://java.sun.com/xml/ns/javaee"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
id="WebApp_ID" version="3.0">
<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:beans.xml</param-value>
</context-param>
<listener>
<listener-class>
org.springframework.web.context.ContextLoaderListener
</listener-class>
</listener>
<display-name>testspring</display-name>
<servlet>
<servlet-name>/</servlet-name>
<servlet-class>org.glassfish.jersey.servlet.ServletContainer</servlet-class>
<init-param>
<param-name>jersey.config.server.provider.packages</param-name>
<param-value>TestSpringApp</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>/</servlet-name>
<url-pattern>/rest/*</url-pattern>
</servlet-mapping>
</web-app>
EDIT:
Until now, I have thought that context:component-scan or context:annotation-config in beans.xml was taking care of making Spring aware of PersonController, however now I checked it and I found out that setEntityManager is only called if I place @PersistenceContext on setEntityManager instead of on EntityManager itself and annotate the PersonController class with @Component. This way I can see that setEntityManager is called on Spring bean initialization, and its value is "Shared EntityManager proxy for target factory [org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean@15bd577]".
My problem still occurs, because when I do a http://localhost:8080/rest/person request, entityManager is still null in line entityManager.find(Person.class, 0).
After reading through Jersey docs, I have found this chapter on Spring DI support in Jersey.
Adding jersey-spring3 and spring-bridge dependecies to the project solved the problem.