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.
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.
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))
}
If you use Spring Boot & Data Frameworks See more
You can easily write query using Entity associations.
If you want to return the DTO, use the DTO as the return type.
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))
}
Kotlin JDSL supports various expressions.
val max = max(column(Book::price))
val count = count(column(Book::price))
val greatest = greatest(column(Book::createdAt))
val case = case(
`when`(column(Book::name).like("A%")).then(liternal(1)),
`when`(column(Book::name).like("B%")).then(liternal(2)),
// ...
`else` = literal(999)
)
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))
}
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")),
)
val books = queryFactory.listQuery<Book> {
select(entity(Book::class))
from(entity(Book::class))
join(Book::author)
// ...
}
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
// ...
}
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))))
// ...
}
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)))
// ...
}
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();
}
}
If you have any questions, please make Issues. And PR is always welcome.
Are you ready to join us? - https://careers.linecorp.com/ko/jobs/862
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.
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.
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See LICENSE for more details.