Spring数据JPA与JDBC的关系

Question

I understand that SimpleJpaRepository, the basic implementation of Spring Data JPA, uses JPA (provided by Java) internally.

So does JPA use plain JDBC (provided by Java) internally? Or does JPA use Spring JDBC internally?

Also, does Spring JDBC (JdbcTemplate) use plain JDBC internally? Is it just that we made plain JDBC easy to use?

I expect that the JPA used inside the SimpleJpaRepository will use plain JDBC. Because Jpa itself is provided by Java. And I expect Spring JDBC (JdbcTemplate) use plain JDBC.

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Answer 1

The answer depends a little on the type of database you connect to. I am assuming you are interested in relational databases such as MySQL, Oracle, etc.

First some concepts

JDBC is the low level standard for connecting to a DB directly and running SQL against it, and each database provider (MySQL, Oracle, etc) implements the specifics in order to make that connection possible.

The issue with it is that you may end up with a lot of code trying to map ResulSets, parameters, and so on depending on your needs.

JPA, JDBC Template (or any other ORM for that matter) are higher level standards that helps to "hide" some of the code you would have to write using JDBC alone, allowing the developers to focus on more important things. So, in a (little) naïve answer you could say JPA will use JDBC under the hood in order to connect to a DB.

However, this is not 100% of the time, as there are data stores like MongoDB, Neo4J, and others that do not follow JDBC standard for connection, but you may find ORM implementations for them, which will most likely not use JDBC.