Querydsl

Querydsl - Typesafe queries for Java

Easy and safe to use, the right tool for agile domain development.

Description

Querydsl (spell: query diesel) is a framework which enables the construction of statically typed SQL-like queries. Instead of writing queries as inline strings or externalizing them into XML files they can be constructed via a fluentDSL/API like Querydsl.

The benefits of using a fluent API in comparison to simple strings are

code completion in IDE
almost none syntactically invalid queries allowed
domain types and properties can be referenced safely
adopts better to refactoring changes in domain types

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Get started

See our module specific integration guides

and for more documentation see Documentation

Supported backends

JPAQL/HQL via the querydsl-hql module

JDOQL via the querydsl-jdoql module (experimental)

RDF via RDFBean, our Object/RDF persistence framework

Java Collections via the querydsl-collections module (experimental)

SQL/JDBC via the querydsl-sql module (experimental)

In a nutshell

Name	Querydsl
Most Recent Version	0.4.6
Javadocs	v 0.4.6
State	Stable
License	LGPL v2.1
Version Control	on Mysema Source
Maven repo	on Mysema Source
Issue Management	on Launchpad
Commercial Support	contact us

Popular pages (last 7 days):

Querydsl	126
JDOQL Guide	35
Similar frameworks	21
HQL and JPAQL Guide	17
Collections Guide	13
Documentation	10
Querydsl expressions	9
Querydsl Collections - Performance	5
Developer's Guide	5
SQL Guide	4
Alias usage	4
Querydsl - new frontpage	3
Getting started	2
TreeNavigation	2
Features	1

Examples

The syntax of Querydsl is similar to SQL, but the order of elements is different. Instead of the basic SELECT FROM WHERE pattern, FROM WHERE LIST is used.

Example 1

Get the cats where the name's first character is between A and B :

HQLQuery q = new HQLQueryImpl(session);
QCat cat = new QCat("cat"); // query type
List<Cat> cats = q.from(cat).where(cat.name.between("A", "B")).list(cat);

The related HQL query would be

select cat from Cat cat where cat.name between A and B

As you can see the Querydsl syntax resembles the underlying HQL query very much.

Example 2

Get the cats with kittens :

HQLQuery q = new HQLQueryImpl(session);
QCat cat = new QCat("cat");  // query type
List<Cat> cats = q.from(cat).where(cat.kittens.size().gt(0)).list(cat);

Example 3

Get the mother, mate and offspring and list them as Family instances :

HQLQuery q = new HQLQueryImpl(session);
QCat mother= new QCat("mother"); // query type
QCat mate= new QCat("mate");
QCat offspr= new QCat("offspr");
List<Family> families = q.from(mother).innerJoin(mother.mate, mate).leftJoin(mother.kittens, offspr)
  .list(new QFamily(mother, mate, offspr));

Alternatively you may also write this shorter as

HQLQuery q = new HQLQueryImpl(session);
QCat mother= new QCat("mother"); // query type
QCat offspr= new QCat("offspr");
List<Family> families = q.from(mother).leftJoin(mother.kittens, offspr)
  .list(new QFamily(mother, mother.mate;, offspr));