https://github.com/mtumilowicz/jpa-criteria-api
SQL, JPQL, HQL & JPA Criteria API training
https://github.com/mtumilowicz/jpa-criteria-api
criteria-api hibernate hql jpa2 jpql static-metamodels
Last synced: 9 months ago
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SQL, JPQL, HQL & JPA Criteria API training
- Host: GitHub
- URL: https://github.com/mtumilowicz/jpa-criteria-api
- Owner: mtumilowicz
- Created: 2018-05-02T13:44:15.000Z (about 8 years ago)
- Default Branch: master
- Last Pushed: 2018-08-19T20:28:31.000Z (almost 8 years ago)
- Last Synced: 2025-09-20T10:44:17.741Z (10 months ago)
- Topics: criteria-api, hibernate, hql, jpa2, jpql, static-metamodels
- Language: Java
- Homepage:
- Size: 135 KB
- Stars: 3
- Watchers: 0
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
[](https://travis-ci.com/mtumilowicz/jpa-criteria-api)
# jpa-criteria-api
The main goal of this project is to explore basic query features of
`JPA 2.1` specification:
* **JPQL**
* **JPA Criteria API** (typesafe with auto-generated
static metamodels)
As a `JPA` provider we choose `Hibernate` to test some of `HQL`.
## project structure
## technologies used
* **Flyway** - constructs the database & provide datafeed in two migrations.
Ensures data coherence by checking if schema in database is up to date (
by validating additional database table concerning migrations:
`flyway_schema_history`).
_Reference_: https://flywaydb.org/documentation/
* **JPA 2.1**
_Reference_: [Pro JPA 2 2nd Edition](https://www.amazon.com/Pro-JPA-Experts-Voice-Java/dp/1430249269)
_Reference_: [JSR 338: JavaTM Persistence API, Version 2.1](http://download.oracle.com/otn-pub/jcp/persistence-2_1-fr-eval-spec/JavaPersistence.pdf)
* **Hibernate** - provider of `JPA 2.1` specification. We don't use
`EclipseLink` despite the fact that it is `reference implementation` of
`JPA 2.1` because apart from `JPQL` we want to explore `HQL` as a more
powerful query language.
_Reference_: [Java Persistence with Hibernate Second Edition](https://www.amazon.com/exec/obidos/ASIN/1617290459)
_Reference_: [Hibernate Interview Questions and Answers](https://www.journaldev.com/3633/hibernate-interview-questions-and-answers)
* **Jupiter & AssertJ** - to test result sets (`AssertJ` has very
convinient methods to comparing lists regardless order).
## project description
* The main idea is to explore `JPA Criteria API` by writing a querys in
`JPQL` or `HQL`, then to try re-write them in `JPA Criteria API` & check
result-sets identity.
* Comparing equality of result sets with `JUnit` & `hamcrest`:
```
import static org.hamcrest.Matchers.containsInAnyOrder;
...
Assert.assertThat(entityManager.createQuery(cc_query)
.getResultList(),
containsInAnyOrder(jpql_query.getResultList().toArray()));
```
but we decide to use `Jupiter` & `AssertJ` (more expressive):
```
import static org.assertj.core.api.Assertions.assertThat;
...
assertThat(entityManager.createQuery(cc_query).getResultList())
.containsExactlyInAnyOrderElementsOf(jpql_query.getResultList());
```
## project content
`src/main/java`: entities, utility classes & `META-INF` folder with
`persistence.xml`
`resources/db/migration`: `Flyway` migrations as `SQL` scripts
`test/java`: showcase of `JPQL`, `HQL` & `Criteria API` with tests
`target/generated-sources`: static metamodels of entities
## tests
* We have to classes with nearly the same content: `Tests` and
`TestsWithFullTypeSafe`. The only difference is that in the first class
we use strings to denote fields while in the letter we use static
metamodels.
* Example:
* From `Tests`:
```
orderBy(cb.asc(cc_query_root.get("title")));
```
* From `TestsWithFullTypeSafe`:
```
orderBy(cb.asc(cc_query_root.get(Book_.title)));
```
* All methods are quite simple & straightforward use of `Criteria API`.
The most interesting are:
* `getBookstoresWithMostExpensiveBook()` - we show how to use subqueries
* `getBookstoresThatHaveTitle()` - we show how to reference a `FROM`
expression of the parent query in the `FROM` clause of a subquery
* `getBookstoresThatHaveAtLeastOneBookWrittenBy()` - we show how to
reference a `JOIN` expression of the parent query in the `FROM` clause
of a subquery
* `countBooksByGenre()` - we show how to use `Tuple` with aliases
* `getBookstoresWithCountBooksAndPriceAverage()` - we show how to use
`multiselect` with dedicated class
## static metamodels
They are auto-generated by `maven-compiler-plugin`.
All you need to do is:
```
org.apache.maven.plugins
maven-compiler-plugin
1.8
1.8
org.hibernate.jpamodelgen.JPAMetaModelEntityProcessor
```
```
org.hibernate
hibernate-jpamodelgen
5.2.17.Final
provided
```
Mark `target/generated-sources` as a `Generated Sources Root`.
In `IntelliJ` just left-click on `target/generated-sources` ->
`Mark Directory As` -> `Generated Sources Root`.