Using JPA + H2 with Spring Boot + Kotlin - Error booting - spring

Question

I have a very simple sample Spring Boot + Kotlin project.
I added all the basic dependencies:
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-thymeleaf</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-stdlib-jdk8</artifactId>
<version>${kotlin.version}</version>
</dependency>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-reflect</artifactId>
</dependency>
<dependency>
<groupId>org.jetbrains.kotlin</groupId>
<artifactId>kotlin-test</artifactId>
<version>${kotlin.version}</version>
<scope>test</scope>
</dependency>
I have annotated two model classes with JPA annotations:
#Entity
class Author(
#Id #GeneratedValue(strategy = GenerationType.AUTO) val id: Long,
val firstName: String,
val lastName: String,
#ManyToMany(mappedBy = "authors") val books: Set<Book> = emptySet()
)
and
#Entity
class Book(
#Id #GeneratedValue(strategy = GenerationType.AUTO)
val id: Long,
#ManyToMany #JoinTable(
name = "author_book",
joinColumns = [JoinColumn(name = "book_id")],
inverseJoinColumns = [(JoinColumn(name = "author_id"))])
val author: Set<Author> = emptySet(),
val title: String,
val label: String,
val publisher: String
)
I have a basic Main:
#SpringBootApplication
open class Spring5webappApplication {
companion object {
#JvmStatic
fun main(args: Array<String>) {
SpringApplication.run(Spring5webappApplication::class.java, *args)
}
}
}
But when I boot, I get a bit error stack.
Could you give me some clue on this? I googled the errors but the answers are too unrelated. Thanks.

Answer 1

You have a typo in your code.
The attribute in book is called author instead of authors.
So this is the correct code.
val authors: Set<Author> = emptySet(),
Always look at the last exception in the stacktrace
Caused by: org.hibernate.AnnotationException:
mappedBy reference an unknown target entity property:
guru.springframework.spring5webapp.model.Book.authors in guru.springframework.spring5webapp.model.Author.books