Hibernate and JPA

What Is ORM, and Why JPA Exists Object-relational mapping (ORM) bridges two different worlds: the object model of your Java code and the relational model of your database. Without ...

Configuring Hibernate and JPA Hibernate needs a database connection, a dialect, and rules for schema handling before it can persist anything. In a plain JPA environment you ...

Your First JPA Entity An entity is a class mapped to a table, and everything in JPA happens on entities. Writing one correctly requires three things: the mapping annotations, a ...

Mapping Fields and Column Types Every entity field maps to a schema, and getting the details right matters: the wrong column name, nullable rule, or length creates schema drift ...

Primary Keys and ID Generation The primary key identifies each row, and JPA crosses it with your Java identity. Choose the key strategy carefully: the most common approach uses a ...

Entity Relationships: OneToMany, ManyToOne, ManyToMany Relational databases connect tables with foreign keys, and JPA mirrors that with relationship annotations. The join is owned ...

JPQL and Native Queries You are not limited to derived method names. For complex reporting, JPQL expresses queries against entities with an SQL-like syntax, and native SQL handles ...

Spring Data JPA Repositories Spring Data JPA turns repository interfaces into working persistence layers. The framework generates implementations at runtime, so you never write ...

Derived Query Methods by Convention Spring Data can translate well-chosen method names into queries, letting you describe intent instead of writing SQL. The parser reads the ...

Caching and Performance Tips JPA makes development fast, but the generated SQL is only as good as your mapping and query strategy. Performance work usually means reducing the SQL ...