Kotlin JDSL
Kotlin JDSL is DSL for JPA Criteria API without generated metamodel and reflection. It helps you write a JPA query like writing an SQL statement.
Background
There are several libraries in the easy way to use JPA. However, those libraries have to use APT. If you use APT, there is a problem that you have to compile again when the name or type of entity field is changed. So, in order not to use APT, we created this library using the KProperty created by the kotlin compiler.
Quick start
Hibernate
Add Hibernate Kotlin JDSL and Hibernate to dependencies
dependencies {
implementation("com.linecorp.kotlin-jdsl:hibernate-kotlin-jdsl:x.y.z")
implementation("org.hibernate:hibernate-core:x.y.z")
}
Create QueryFactory using EntityManager
val queryFactory: QueryFactory = QueryFactoryImpl(
criteriaQueryCreator = CriteriaQueryCreatorImpl(entityManager),
subqueryCreator = SubqueryCreatorImpl()
)
Query using it
queryFactory.listQuery<Entity> {
select(entity(Book::class))
from(entity(Book::class))
where(column(Book::id).equal(1000))
}
Spring Data
If you use Spring Boot & Data Frameworks See more
Usage
You can easily write query using Entity associations.
If you want to return the DTO, use the DTO as the return type.
Query
QueryFactory allows you to create JPA queries using DSL just like SQL queries.
val books: List<Book> = queryFactory.listQuery {
select(entity(Book::class))
from(entity(Book::class))
where(column(Book::author).equal("Shakespeare"))
}
If you want to select the DTO, select columns in the order of constructor parameters.
val books: List<Row> = queryFactory.listQuery {
select(column(Book::author), count(column(Book::id)))
from(entity(Book::class))
groupBy(column(Book::author))
}
Expression
Kotlin JDSL supports various expressions.
Aggregation
val max = max(column(Book::price))
val count = count(column(Book::price))
val greatest = greatest(column(Book::createdAt))
Case When
val case = case(
`when`(column(Book::name).like("A%")).then(liternal(1)),
`when`(column(Book::name).like("B%")).then(liternal(2)),
// ...
`else` = literal(999)
)
Subquery
val authorIds = queryFactory.subquery<Long> {
select(column(Book::authorId))
from(entity(Book::class))
// ...
}
val authors: List<Author> = queryFactory.listQuery {
// ...
where(column(Author::id).`in`(authorIds))
}
Predicate
Kotlin JDSL supports various predicates.
val condition = and(
column(Book::author).equal("Shakespeare"),
column(Book::price).lessThanOrEqualTo(100.toBigDecimal()),
column(Book::status).`in`(SALE, OUT_OF_STOCK),
column(Book::createdAt).between(Time.of("2001-01-01"), Time.of("2010-12-31")),
)
Join
val books = queryFactory.listQuery<Book> {
select(entity(Book::class))
from(entity(Book::class))
join(Book::author)
// ...
}
Fetch
val books = queryFactory.listQuery<Book> {
select(entity(Book::class))
from(entity(Book::class))
fetch(Book::author)
// ...
}
If join and fetch are used together for the same entity, only fetch is applied.
val books = queryFactory.listQuery<Book> {
select(entity(Book::class))
from(entity(Book::class))
join(Book::author) // Join is ignored
fetch(Book::author) // Only fetch is applied
// ...
}
Cross Join
val books = queryFactory.listQuery<Book> {
select(entity(Book::class))
from(entity(Book::class))
join(entity(Author::class) on(column(Book::authorId).equal(column(Author::id))))
// ...
}
Alias
There may be models with the two associations of same type. In this case, separate the Entity using alias.
val orders = queryFactory.listQuery<Order> {
select(entity(Order::class))
from(entity(Order::class))
join(entity(Order::class), entity(Address::class, alias = "shippingAddress", on(Order::shippingAddress)))
join(entity(Order::class), entity(Address::class, alias = "receiverAddress", on(Order::receiverAddress)))
// ...
}
How it works
Kotlin's property reference provides KProperty interface. KProperty is created in java file at kotlin compile time. Since KProperty has the name of property, we can use it to write the expression of the Critical API.
If you type the JPA query as below,
queryFactory.listQuery<Book> {
select(entity(Book::class))
from(entity(Book::class))
where(column(Book::name).equal("Hamlet").and(column(Book::author).equal("Shakespeare")))
}
Kotlin compiler creates PropertyReference.
final class ClassKt$books$1 extends PropertyReference1Impl {
public static final KProperty1 INSTANCE = new ClassKt$books$1();
books$1() {
super(Book.class, "name", "getName()Ljava/lang/String;", 0);
}
@Nullable
public Object get(@Nullable Object receiver) {
return ((Book) receiver).getName();
}
}
final class ClassKt$books$2 extends PropertyReference1Impl {
public static final KProperty1 INSTANCE = new ClassKt$books$2();
ClassKt$books$2() {
super(Book.class, "author", "getAuthor()Ljava/lang/String;", 0);
}
@Nullable
public Object get(@Nullable Object receiver) {
return ((Book) receiver).getAuthor();
}
}
Support
If you have any questions, please make Issues. And PR is always welcome.
We Are Hiring
Are you ready to join us? - https://careers.linecorp.com/ko/jobs/862
How to contribute
See CONTRIBUTING. If you believe you have discovered a vulnerability or have an issue related to security, please contact the maintainer directly or send us an email before sending a pull request.
License
Copyright 2021 LINE Corporation
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
See LICENSE for more details.
[그림 1 : 목표 코드]
[그림 2: 해결 방법 1 - let 구문 안에 where 절 삽입]
[그림 3 : 해결 방법 2 - PredicateSpec.empty 사용]
[그림 4 : where interface 리팩토링]
[그림 5 : QueryDslImpl 리팩토링]
또한 그림4와 그림 5의 코드를 통해 and()구문을 사용하지 않아도 되니, 좀 더 간결한 코드를 작성할 수 있지 않을까 합니다.
Currently kotlin-jdsl does not support the CriteriaBuilder.exists method. An implementation of this method is required.
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