Is there any good generic JPA DAO implemenation?

问题:

According this article, generic JPA DAO(Data Access Object) is a pretty nice pattern.

Is there any good implementation?

回答1:

You could take a look into the Spring Data JPA.

A few new concepts were introduced into Spring Data JPA, for instance the Query creation based on the method name, so you can declare a method like findById(String id) and the "generic" implementation will interpret the method's name and execute something like select Entity from Entity where id = 'given string'

Methods like findByNameAndLastName(String name, String lastName) or even findByNameOrInternalId(String name, int internalId) are supported too.

回答2:

Just wanted to mention a couple more generic dao implementations for JPA:

• Generic DAO toolkit - http://code.google.com/p/generic-dao/
• Related Question in SO - Single DAO & generic CRUD methods (JPA/Hibernate + Spring)
• A good blog article on JPA DAO - http://blog.xebia.com/2009/03/09/jpa-implementation-patterns-data-access-objects/

回答3:

Querydsl supports JPA and has an extensive support for building complex predicates for queries.

It doesn't support updates and inserts but you can use Spring Data for that, as Querydsl also integrates with Spring repositories.