Spring Web, Kotlin, Gradle, IntelliJ -> MongoRepository “Unresolved reference: save” problem

Question

I have a problem when I try to use a MongoRepository. This is my Document class:

package model

import org.springframework.data.annotation.Id
import org.springframework.data.mongodb.core.mapping.Document

@Document
class Product (@Id val name: String, var desc: String, var price: Double) {

    var pictureCategory: String? = null

}

This is the repository:

package model.repositories

import model.Product
import org.springframework.data.mongodb.repository.MongoRepository
import org.springframework.stereotype.Repository

@Repository
interface ProductRepository : MongoRepository <Product, String>

and this is the file where I have the compile error:

package controllers

import model.Product
import model.repositories.ProductRepository
import org.springframework.stereotype.Controller
import org.springframework.web.bind.annotation.PostMapping
import org.springframework.web.bind.annotation.RequestBody
import org.springframework.web.bind.annotation.RequestMapping

@Controller
@RequestMapping("/product")
class ProductController {

    @PostMapping("")
    fun addProduct(@RequestBody newProduct: Product){
        ProductRepository.save()  //Unresolved reference: save <----------------------
    }
}

I tried to performe and invalidate/restart but nothing is changed.

This is my build.gradle.kts file:

import org.jetbrains.kotlin.gradle.tasks.KotlinCompile

plugins {
    id("org.springframework.boot") version "2.4.3"
    id("io.spring.dependency-management") version "1.0.11.RELEASE"
    kotlin("jvm") version "1.4.30"
    kotlin("plugin.spring") version "1.4.30"
    kotlin("plugin.jpa") version "1.4.30"
}

group = "com.example"
version = "1.0.0"
java.sourceCompatibility = JavaVersion.VERSION_11

repositories {
    mavenCentral()
}

dependencies {
    implementation("org.springframework.boot:spring-boot-starter-data-mongodb")
    implementation("org.springframework.boot:spring-boot-starter-web")
    implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
    implementation("org.jetbrains.kotlin:kotlin-reflect")
    implementation("org.jetbrains.kotlin:kotlin-stdlib-jdk8")
    testImplementation("org.springframework.boot:spring-boot-starter-test")
}

tasks.withType<KotlinCompile> {
    kotlinOptions {
        freeCompilerArgs = listOf("-Xjsr305=strict")
        jvmTarget = "11"
    }
}

tasks.withType<Test> {
    useJUnitPlatform()
}

Maybe some dependencies that I have to add?

Answer 1

You are supposed to inject your repository in the REST controller, not using the static "save" method.

See: https://spring.io/guides/tutorials/rest/ for example.