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Kotlin ResultQuery Collectors
Applies to ✅ Open Source Edition ✅ Express Edition ✅ Professional Edition ✅ Enterprise Edition
jOOQ's runtime API implements a few useful Collectors that can be used to fetch data into a map, for example:
public class Records {
// [...]
public static final <K, V, R extends Record2<K, V>> Collector<R, ?, Map<K, V>> intoMap() {
return intoMap(Record2::value1, Record2::value2);
}
// [...]
}
These can be used with the collect() method as follows:
val map: Map<Int, String> =
create.select(LANGUAGE.ID, LANGUAGE.CD)
.from(LANGUAGE)
.collect(intoMap())
The Collector leverages the query's type safety, such that it works only for queries projecting exactly 2 columns. Using the kotlin extensions module, a few useful extension functions are made available as follows:
package org.jooq.kotlin inline fun <reified E> ResultQuery<Record1<E>>.fetchArray(): Array<E> = collect(Records.intoArray(E::class.java)) fun <K, V, R : Record2<K, V>> ResultQuery<R>.fetchGroups(): Map<K, List<V>> = collect(Records.intoGroups()) fun <E, R : Record1<E>> ResultQuery<R>.fetchList(): List<E> = collect(Records.intoList()) fun <K, V> ResultQuery<Record2<K, V>>.fetchMap(): Map<K, V> = collect(Records.intoMap()) fun <E, R : Record1<E>> ResultQuery<R>.fetchSet(): Set<E> = collect(Records.intoSet())
This allows for the leaner version below:
val map: Map<Int, String> =
create.select(LANGUAGE.ID, LANGUAGE.CD)
.from(LANGUAGE)
.fetchMap()
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