How to use Spring Data JPA in a simple Servlet?

Question

I'm very new to Spring, but I am working on a project which is using Spring Data JPA to generate repositories for JPA entities.

I'm currently adding a simple module to be able to show some data on a webpage. I have added a Servlet, but I am having trouble accessing the repositories from there.

I have added a ContextLoaderListener in web.xml, I'm referencing the jpa:repositories and persistence.xml in the applicationContext.xml, but I'm currently stuck with this exception:

No unique bean of type [javax.persistence.EntityManagerFactory] is defined: expected single bean but found 0.

But when I add an EntityManagerFactory in persistence.xml I get the following cryptic message:

java.lang.IllegalAccessError: tried to access field org.hibernate.engine.spi.CascadeStyle.STYLES from class org.hibernate.engine.spi.EJB3CascadeStyle

My question is: is what I am trying to do even possible? And if so, how? Or should I just bite the bullet and use Spring MVC or something else entirely?

Note: this is just for a one-page web site and I'm trying to keep it as simple as possible.

Answer 1

In order to use Spring Data JPA you need to configure the underlying JPA implementation as you would typically do in Spring, see for example, infrastructure.xml and META-INF/persistence.xml in spring-data-jpa-showcase (since Spring 3.1 you can get rid of persistence.xml if you use packagesToScan property of LocalContainerEntityManagerFactoryBean ).

Your second problem with IllegalAccessError looks like a classloading problem caused by presence of different versions of Hibernate jars in classpath.