EJB, spring & hibernate

I've been doing Java standa开发者_StackOverflow社区rd edition development for awhile, and the frameworks and solutions have been fairly obvious to me (Swing for GUI, etc). I've recently begun the task of building a server for my own needs and to host a web page (things the server will be doing in addition to hosting a web page would include personal SVN hosting and integrating more web functionality into existing and future applications). For coding for only a single computer (that is, distributed computing, etc. is not really a concern)- I'm not entirely certain between Spring, Hibernate and EJB and am not very knowledgeable as to the capabilities of each. Information would be appreciated. I know Spring is an alternative to EJB, and Hibernate is an object-relational mapping library, so does EJB combine the two?

EJB3 in summary consists of 3 bean types; Message Driven Beans, Stateless/Stateful Session Beans and Entity Beans or JPA (Java Persistance Architecture). Hibernate can be used as a JPA provider, but it doesn't have to be used that way.

Spring has functionality that is roughly similar to Message Driven Beans and Stateless/Stateful session beans but it does not have an equivalent to JPA. Instead it allows you to utilize JPA or hibernate directly but if you do combine Spring with JPA you'll need an EJB container.

Another difference is that EJB is provided by 'containers' whereas spring is a framework that can be deployed into a java se application or a java servlet container web application like jetty or tomcat. Its an important distinction to make. Tomcat is not an EJB container, only a servlet container, hence if you were to only use basic tomcat, you couldn't use EJBs but you could use spring by including the required spring jar files in your web application (WEB-INF/lib). In that case you wouldn't use JPA either but you could use hibernate.

Some java servers that ARE EJB containers include weblogic, websphere, jboss, geronimo, and glassfish. Tomcat can become an EJB container if you combine it with OpenEJB.

In an application i'm developing at the moment, I'm using tomcat + openejb so I have an EJB container so I can use JPA with OpenJPA as the persistance provider. I'm using Spring MVC to do the web application development and will most likely use spring security as well down the track. I probably will also use Stateless Session EJBs as well to encapsulate business functionality but i could just as easily use Spring service/dao beans instead of statless session ejbs as well.

Its pretty confusing sometimes to work out what parts of which framework or container you should use and really comes down to either preference or using functionality in one that doesn't exist in the other or ease of use. Another consideration is memory utilization. Some of the ejb containers consume large amounts of memory just starting up with no applications running. This is one reason I ended up using tomcat + openejb. Hope this helps.