Hibernate Interview Questions

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Difference between save and persist in Hibernate

Following are the concurrency strategies that can be implemented by the developer:

• Transactional: This strategy is used mostly to read data where the prevention of stale data is critical in concurrent transactions, in the unique case of an update.
• Read- Only: This strategy is compatible with the data that can’t be modified. We can use it for reference data only.
• Read-Write: It is similar to transactional strategy. where we read mostly data and prevention of stale data is critical.
• Non-strict-Read-Write: This strategy assures no guarantee of consistency between the database and cache. We can use this strategy only if the data can be modified and a small likelihood of stale data is not the critical concern.

• It is used to define specific mappings from Java classes to database tables.
• It is used to define the mapping of unique ID attribute in class to the primary key of the database table.
• It is used to generate the primary key values automatically.
• It is used to map a Java class property to a column in the database table.
• It is used to map a java.util.set, java.util.Sortedset property in hibernate.
• It is used to map a java.util.List property in hibernate.
• It is used to map a java.util.Collection property in hibernate.
• It is used to map a java.util.Map property in hibernate.

• Hibernates allows us to focus on business logic, eliminating all the boiler-plate code that comes with JDBC and handles the resources.
• Code implementation becomes independent as Hibernate framework provides the support for XML and also to the JPA annotations.
• HQL is powerful Query Language which is similar to SQL, and HQL understands the concepts of polymorphism, inheritance, and association, which makes it fully object-oriented.
• Better performance can be achieved by Hibernate cache.
• It supports Lazy initialization with the use of proxy objects and when required performs actual database queries.
• We can execute native SQL queries using hibernate for vendor specific feature.

On the whole, hibernate makes it a better choice in the current market for ORM tool, as it contains all the features that you will require in an ORM tool.

• It allows business code access the objects rather than Database tables.
• It hides the details of SQL queries from OO logic.
• It is based on JDBC “under hood”.
• Dealing with database implementation is not required.
• Entities are based on business concepts rather than database structures.
• It generates the automatic key and Transaction management.
• Application development is faster.

• Session: It is used to get a physical network with a database.
• Transaction: It represents the unit of work with a database.
• Query: It uses SQL and HQL string to retrieve the data from the database and create objects.
• Criteria: It is used create and execute object-oriented queries and retrieve the objects.
• Configuration: It represents the properties of files required by Hibernate
• Session Factory: It configures hibernate for the application using the provided configuration file and instantiates the session object.

• HSQL Database Engine
• DB2/NT
• Oracle
• Microsoft SQL Server Database
• Sybase SQL Server
• Informix Dynamic Server
• MySQL
• PostgreSQL
• FrontBase