Java EJB / Hibernate性能，首次调用较慢

Question

I have an Java application which is using an EJB client to make a calls to the server. Server side EJB's create again calls to the DB. Hibernate is used, but second level cache is disabled. When performance testing DB calls using EJB client, usually the first calls take much longer than the next ones, even though calls are made using different parameters. What things can explain or have effect on the performance in this scenario?

Answer 1

EJB's on the top uses Java's RMI calls. Whenever your client calls the EJB components running in an EJB container, then in the meanwhile some expensive operations are performed.

Lets say, you have a remote interface called HelloRemote and a service bean called HelloBean which implements the HelloRemote interface .

1) First your client needs to look-up for the service object which is registered with the JNDI Registry as :

HelloRemote service=(HelloRemote)context.lookup("HelloBean/remote");  
// JBoss specific

Here,

i) Your client makes a call to LDAP Server which contains the JNDI Registry and looks for the remote bean registered with the given name.

ii) If the any bean registry with the given name is found then the container first serializes the registered bean object and sends it to the client where it is again deserialized which is also known as marshaling and unmarshaling .

The above step in itself is somewhat costly and that is why it is recommended that if your application architecture is going to use the same JVM for both the client application and the session beans, then use the local interface ( which can be a no-interface option starting from EJB 3.1) instead of using the remote interface.

iii) With the Business interface stub in hand, you now invoke the business operations on that stub interface. This stub performs the required serialization and delegates the call to the container.

The container now performs the deserialization and invokes the corresponding methods on Business interface object. The same process occurs when the result of this invocation is being returned to the cilent.

As you can see there is a lot of Serialization and De-Serialization happening when a client communicates with the EJB component. Enabling Second Level cache does improves the performance in Hibernate, but In view the communication b/w an EJB Client and an EJB service object is more expensive wrto time.

NOTE : I was looking for someone to respond to this post, as i was also eager to know the reasons, however not finding any responses, I had this post with the whatever understanding i have on these topics