Kotlin with JPA: default constructor hell

As of Kotlin 1.0.6, the kotlin-noarg compiler plugin generates synthetic default construtors for classes that have been annotated with selected annotations.

If you use gradle, applying the kotlin-jpa plugin is enough to generate default constructors for classes annotated with @Entity:

buildscript {
    dependencies {
        classpath "org.jetbrains.kotlin:kotlin-noarg:$kotlin_version"
    }
}

apply plugin: "kotlin-jpa"

For Maven:

<plugin>
    <artifactId>kotlin-maven-plugin</artifactId>
    <groupId>org.jetbrains.kotlin</groupId>
    <version>${kotlin.version}</version>

    <configuration>
        <compilerPlugins>
            <plugin>jpa</plugin>
        </compilerPlugins>
    </configuration>

    <dependencies>
        <dependency>
            <groupId>org.jetbrains.kotlin</groupId>
            <artifactId>kotlin-maven-noarg</artifactId>
            <version>${kotlin.version}</version>
        </dependency>
    </dependencies>
</plugin>

just provide default values for all arguments, Kotlin will make default constructor for you.

@Entity
data class Person(val name: String="", val age: Int=0)

see the NOTE box below the following section:

https://kotlinlang.org/docs/reference/classes.html#secondary-constructors

Adding the JPA plugin in gradle worked for me:

plugins {
   id("org.springframework.boot") version "2.3.4.RELEASE"
   id("io.spring.dependency-management") version "1.0.10.RELEASE"
   kotlin("jvm") version "1.3.72"
   kotlin("plugin.spring") version "1.3.72"
   kotlin("plugin.jpa") version "1.3.72"
}