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jOOQ and Kotlin
Applies to ✅ Open Source Edition ✅ Express Edition ✅ Professional Edition ✅ Enterprise Edition
As any other library, jOOQ can be easily used in Kotlin, taking advantage of the many Kotlin language features such as for example:
- Optional ";" at the end of a Kotlin statement
- Type inference for local variables
A short example jOOQ application in Kotlin might look like this:
package org.jooq.example.kotlin
import java.util.Properties
import org.jooq.*
import org.jooq.impl.DSL
import org.jooq.impl.DSL.*
import org.jooq.example.db.h2.Tables.*
fun main(args: Array<String>) {
val properties = Properties();
properties.load(Properties::class.java.getResourceAsStream("/config.properties"));
DSL.using(
properties.getProperty("db.url"),
properties.getProperty("db.username"),
properties.getProperty("db.password")
).use { ctx ->
val a = AUTHOR
val b = BOOK
ctx.select(a.FIRST_NAME, a.LAST_NAME, b.TITLE)
.from(a)
.join(b).on(a.ID.eq(b.AUTHOR_ID))
.orderBy(1, 2, 3)
.forEach {
println("${it[b.TITLE]} by ${it[a.FIRST_NAME]} ${it[a.LAST_NAME]}")
}
}
}
Note that Kotlin supports some means of operator overloading. For instance, a + b in Kotlin maps to a formal a.plus(b) method invocation, and jOOQ provides the required synonyms in its API to help you write such expressions.
One particularly nice language feature is the fact that [square brackets] allow for accessing any object's contents via get() and set() methods. Instead of using the above value1(), value2(), and value3() methods, we could also iterate as such:
ctx.select(AUTHOR.FIRST_NAME, AUTHOR.LAST_NAME, BOOK.TITLE)
.from(AUTHOR)
.join(BOOK).on(AUTHOR.ID.eq(BOOK.AUTHOR_ID))
.orderBy(1, 2, 3)
.forEach {
println("${it[BOOK.TITLE]} by ${it[AUTHOR.FIRST_NAME]} ${it[AUTHOR.LAST_NAME]}")
// Notice: ^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^
}
A caveat of Kotlin operator overloading is the fact that operators such as == or >= map to a.equals(b), a.compareTo(b) == 0, a.compareTo(b) >= 0 respectively. This behaviour does not make sense in a fluent API such as jOOQ.
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