Part 2, Chapter 12

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Table of content

This chapter explains JPA inheritance from a data access performance point of view.

12. Inheritance
12.1 Single table 
12.2 Join table 
12.3 Table-per-class 
12.4 Mapped superclass 

Chapter summary

Inheritance is undoubtedly the most obvious impedance mismatch between an object-oriented domain model and a relational database schema. This chapter explains the benefits of entity inheritance and its inherent trade-offs.

As a rule of thumb, inheritance should be used with care.

Most often, when polymorphic queries and associations are needed, the choice is between single table and joined table, each one having pluses and minuses. Table-per-class can generate statements that are way too complex, and if entity polymorphism is not needed, the @MappedSuperclass might be a better alternative anyway.