Persistence confusion in EJB 3.0 .........

[sajhak]

hi ,

i m new to EJB development .. the question im going to ask might be a dumb one , if so pls excuse me ....

the question is ..
Does entity beans are a replacement for relational databases or it provides a layer on top of the database ??
what is actually doing by an Entity Bean ( or persistence object ) ?
does it saves the entity into a database table or does it keep the information about the entity in the application server's memory ?

because , i tried several examples from several tutorials , but i couldnt find any one of them "writes" the entity into a database ....

but i think a relational database must involve in this case , cos otherwise it will be impossible for entity be persistent ..

so , how we can define the database that we need to use ?? ( i need to use a MySQL datastore )

if i can get more help (regarding this prob) than this forum please give me the links of such resources ....

Thanks in advance
Saj

[jaikiran]

Entity Beans (now know as Entities in EJB3) are an Object representation of your relational data. To put it in simple words, an entity is mapped to a table in the database. The columns of the table are mapped through the member variables of the entity. Any operations on the table are performed through this entity in Java.

so , how we can define the database that we need to use ?? ( i need to use a MySQL datastore )

You can specify this through a configuration file (Ex: persistence.xml).

if i can get more help (regarding this prob) than this forum please give me the links of such resources ....

Read this http://java.sun.com/developer/technicalArticles/J2EE/jpa/

[sajhak]

thanks jaikiran ... i got it cleared