Hibernate Interview Questions

Q.What is the difference between hibernate and jdbc ?

1) Hibernate is data base independent, In case of JDBC query must be data base specific.
2) As Hibernate is set of Objects , SQL Language learning is not required. TABLE can be treated as Java Object
3) Don?t need Query tuning in case of Hibernate. If you use Criteria Quires in Hibernate then hibernate automatically tuned your query and return best result with performance. In case of JDBC you need to tune your queries.
4) You will get benefit of Cache. Hibernate support two level of cache. First level and 2nd level. So you can store your data into Cache for better performance. In case of JDBC you need to implement your java cache .
5) Hibernate supports Query cache and It will provide the statistics about your query and database status. JDBC Not provides any statistics.
6) Development fast in case of Hibernate because you don?t need to write queries
7) No need to create any connection pool in case of Hibernate. You can use c3p0. In case of JDBC you need to write your own connection pool
8) In the xml file you can see all the relations between tables in case of Hibernate. Easy readability.
9) You can load your objects on start up using lazy=false in case of Hibernate. JDBC Don?t have such support. <> 10 ) Hibernate Supports automatic versioning of rows but JDBC does not.

Q. What are the core components in Hibernate ?

SessionFactory (org.hibernate.SessionFactory)

A threadsafe (immutable) cache of compiled mappings for a single database. A factory for Session and a client of ConnectionProvider. Might hold an optional (second-level) cache of data that is reusable between transactions, at a process- or cluster-level.

Session (org.hibernate.Session)

A single-threaded, short-lived object representing a conversation between the application and the persistent store. Wraps a JDBC connection. Factory for Transaction. Holds a mandatory (first-level) cache of persistent objects, used when navigating the object graph or looking up objects by identifier.

Persistent objects and collections

Short-lived, single threaded objects containing persistent state and business function. These might be ordinary JavaBeans/POJOs, the only special thing about them is that they are currently associated with (exactly one) Session. As soon as the Session is closed, they will be detached and free to use in any application layer (e.g. directly as data transfer objects to and from presentation).

Transient and detached objects and collections

Instances of persistent classes that are not currently associated with a Session. They may have been instantiated by the application and not (yet) persisted or they may have been instantiated by a closed Session.

Transaction (org.hibernate.Transaction)

(Optional) A single-threaded, short-lived object used by the application to specify atomic units of work. Abstracts application from underlying JDBC, JTA or CORBA transaction. A Session might span several Transactions in some cases. However, transaction demarcation, either using the underlying API or Transaction, is never optional!

Architecture

Hibernate 3.0.2 9

ConnectionProvider (org.hibernate.connection.ConnectionProvider)

(Optional) A factory for (and pool of) JDBC connections. Abstracts application from underlying Datasource or DriverManager. Not exposed to application, but can be extended/implemented by the developer.

TransactionFactory (org.hibernate.TransactionFactory)

(Optional) A factory for Transaction instances. Not exposed to the application, but can be extended/ implemented by the developer.

Extension Interfaces

Hibernate offers many optional extension interfaces you can implement to customize the behavior of your persistence layer. See the API documentation for details.

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