1. What is ORM ?
ORM stands for object/relational mapping. ORM is the automated persistence of objects in a Java application to the tables in a relational database.
2.What does ORM consists of ?
An ORM solution consists of the followig four pieces:
API for performing basic CRUD operations
API to express queries refering to classes
Facilities to specify metadata
Optimization facilities : dirty checking,lazy associations fetching
3.What are the ORM levels ?
The ORM levels are:
Pure relational (stored procedure.)
Light objects mapping (JDBC)
Medium object mapping
Full object Mapping (composition,inheritance, polymorphism, persistence by reachability)
4. Why do you need ORM tools like hibernate?
The main advantage of ORM like hibernate is that it shields developers from messy SQL. Apart from this, ORM provides following benefits:
- Improved productivity
- High-level object-oriented API
- Less Java code to write
- No SQL to write
- Improved performance
- Sophisticated caching
- Lazy loading
- Eager loading
- Improved maintainability
- A lot less code to write
- Improved portability
- ORM framework generates database-specific SQL for you
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