migrate to Kotlin

Author: Romanow

.github/workflows/build.yaml

@@ -5,13 +5,16 @@ jobs:
     name: Build
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
-      - uses: actions/setup-java@v3
+      - uses: actions/setup-java@v4
         with:
           distribution: "corretto"
           java-version: "21"
           cache: "gradle"
 
+      - name: Validate styles
+        uses: pre-commit/action@v3.0.0
+
       - name: Build project
         run: ./gradlew clean build

README.md

@@ -6,6 +6,12 @@
 
 ## Аннотация
 
+Наверняка вы много раз сталкивались с тем, что при работе Hibernate вам приходилось писать много кода по перекладыванию
+из `@Entity` в DTO и обратно. Это громоздкий некрасивый boilerplate код, к тому же подверженный ошибкам. И вот, казалось
+бы появился спаситель – MapStruct! С помощью codegen он забирает на себя всю рутинную работу по перекладке, а вы лишь
+вызываете готовый метод. Но так ли все просто и радужно? В докладе поговорим про сложные случаи, когда нам надо
+создавать и обновлять сущности, имеющие связи на другие объекты.
+
 ## План
 
 1. Что за настройка `spring.jpa.open-in-view=false` и почему появилась проблема?

_config.yml

@@ -0,0 +1,16 @@
+title: JPA example
+description: JPA and MapStruct usage example
+author:
+  name: Romanow Alexey
+  email: romanowalex@mail.ru
+
+show_downloads: false
+remote_theme: jekyll/minima
+header_pages: ['']
+
+minima:
+  skin: classic
+  social_links:
+    - { platform: linkedin, user_url: "https://www.linkedin.com/company/it-enduro" }
+    - { platform: telegram, user_url: "https://t.me/romanowalex" }
+    - { platform: youtube, user_url: "https://www.youtube.com/@it_enduro" }

build.gradle

@@ -1,24 +1,34 @@
 plugins {
-    id "java"
     id "idea"
+    id "org.jetbrains.kotlin.jvm" version "1.9.25"
+    id "org.jetbrains.kotlin.plugin.jpa" version "1.9.25"
+    id "org.jetbrains.kotlin.plugin.spring" version "1.9.25"
+    id "org.jetbrains.kotlin.kapt" version "1.9.25"
+    id "org.jlleitschuh.gradle.ktlint" version "12.1.2"
     id "org.springframework.boot" version "3.5.7"
     id "com.gorylenko.gradle-git-properties" version "2.4.2"
     id "com.adarshr.test-logger" version "4.0.0"
     id "io.spring.dependency-management" version "1.1.7"
 }
 
+ext {
+    springBootVersion = "3.5.7"
+    mapstructVersion = "1.6.3"
+    jetbrainsAnnotationsVersion = "22.0.0"
+    postgresContainerVersion = "1.21.3"
+}
+
 idea {
     module {
         downloadJavadoc = true
         downloadSources = true
     }
 }
 
-ext {
-    springBootVersion = "3.5.7"
-    mapstructVersion = "1.6.3"
-    jetbrainsAnnotationsVersion = "22.0.0"
-    postgresContainerVersion = "1.21.3"
+[compileKotlin, compileTestKotlin]*.kotlinOptions*.jvmTarget = "21"
+
+ktlint {
+    version.set("1.1.1")
 }
 
 repositories {
@@ -40,13 +50,12 @@ dependencies {
     implementation "org.postgresql:postgresql"
     implementation "org.flywaydb:flyway-database-postgresql"
 
-    implementation "org.jetbrains:annotations:$jetbrainsAnnotationsVersion"
-    implementation "org.mapstruct:mapstruct:$mapstructVersion"
     implementation "org.apache.commons:commons-lang3"
-
-    compileOnly "org.projectlombok:lombok"
-    annotationProcessor "org.projectlombok:lombok"
-    annotationProcessor "org.mapstruct:mapstruct-processor:$mapstructVersion"
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk8"
+    implementation "org.jetbrains.kotlin:kotlin-reflect"
+    implementation "com.fasterxml.jackson.module:jackson-module-kotlin"
+    implementation "org.mapstruct:mapstruct:$mapstructVersion"
+    kapt "org.mapstruct:mapstruct-processor:$mapstructVersion"
 
     testImplementation "org.springframework.boot:spring-boot-starter-test"
     testImplementation "org.springframework.boot:spring-boot-testcontainers"

src/main/java/ru/romanow/jpa/JpaExampleApplication.kt

@@ -1,11 +1,11 @@
-package ru.romanow.jpa;
+package ru.romanow.jpa
 
-import org.springframework.boot.SpringApplication;
-import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication
+import org.springframework.boot.runApplication
 
 @SpringBootApplication
-public class JpaExampleApplication {
-    public static void main(String[] args) {
-        SpringApplication.run(JpaExampleApplication.class, args);
-    }
+class JpaExampleApplication
+
+fun main(args: Array<String>) {
+    runApplication<JpaExampleApplication>(*args)
 }

src/main/java/ru/romanow/jpa/domain/Address.kt

@@ -1,57 +1,49 @@
-package ru.romanow.jpa.domain;
+package ru.romanow.jpa.domain
 
-import lombok.Data;
-import lombok.experimental.Accessors;
-import org.apache.commons.lang3.builder.ToStringBuilder;
+import jakarta.persistence.*
 
-import jakarta.persistence.*;
-import java.util.List;
-import java.util.Objects;
-import java.util.StringJoiner;
-
-@Data
-@Accessors(chain = true)
 @Entity
 @Table(name = "address")
-public class Address {
-
+data class Address(
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)
-    private Integer id;
+    val id: Int? = null,
 
     @Column(name = "city", nullable = false)
-    private String city;
+    var city: String? = null,
 
     @Column(name = "country", nullable = false)
-    private String country;
+    var country: String? = null,
 
     @Column(name = "street")
-    private String street;
+    var street: String? = null,
 
     @Column(name = "address", nullable = false)
-    private String address;
-
-    @Override
-    public boolean equals(Object o) {
-        if (this == o) return true;
-        if (o == null || getClass() != o.getClass()) return false;
-        Address other = (Address) o;
-        return Objects.equals(city, other.city) && Objects.equals(country, other.country) && Objects.equals(street, other.street) && Objects.equals(address, other.address);
+    var address: String? = null,
+) {
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other !is Address) return false
+
+        if (id != other.id) return false
+        if (city != other.city) return false
+        if (country != other.country) return false
+        if (street != other.street) return false
+        if (address != other.address) return false
+
+        return true
     }
 
-    @Override
-    public int hashCode() {
-        return Objects.hash(city, country, street, address);
+    override fun hashCode(): Int {
+        var result = id ?: 0
+        result = 31 * result + (city?.hashCode() ?: 0)
+        result = 31 * result + (country?.hashCode() ?: 0)
+        result = 31 * result + (street?.hashCode() ?: 0)
+        result = 31 * result + (address?.hashCode() ?: 0)
+        return result
     }
 
-    @Override
-    public String toString() {
-        return new ToStringBuilder(this)
-                .append("id", id)
-                .append("city", city)
-                .append("country", country)
-                .append("street", street)
-                .append("address", address)
-                .toString();
+    override fun toString(): String {
+        return "Address(id=$id, city=$city, country=$country, street=$street, address=$address)"
     }
 }

src/main/java/ru/romanow/jpa/domain/Authority.kt

@@ -1,50 +1,42 @@
-package ru.romanow.jpa.domain;
+package ru.romanow.jpa.domain
 
-import lombok.Data;
-import lombok.experimental.Accessors;
-import org.apache.commons.lang3.builder.ToStringBuilder;
+import jakarta.persistence.*
 
-import jakarta.persistence.*;
-import java.util.Objects;
-
-@Data
-@Accessors(chain = true)
 @Entity
 @Table(name = "authority")
-public class Authority {
-
+data class Authority(
     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)
-    private Integer id;
+    val id: Int? = null,
 
     @Column(name = "name", length = 80, nullable = false)
-    private String name;
+    var name: String? = null,
 
     @Column(name = "priority", nullable = false)
-    private Integer priority;
+    var priority: Int? = null,
 
     @ManyToOne(fetch = FetchType.LAZY)
-    private Person person;
-
-    @Override
-    public boolean equals(Object o) {
-        if (this == o) return true;
-        if (o == null || getClass() != o.getClass()) return false;
-        Authority grant = (Authority) o;
-        return Objects.equals(id, grant.id) && Objects.equals(name, grant.name) && Objects.equals(priority, grant.priority);
+    val person: Person? = null,
+) {
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other !is Authority) return false
+
+        if (id != other.id) return false
+        if (name != other.name) return false
+        if (priority != other.priority) return false
+
+        return true
     }
 
-    @Override
-    public int hashCode() {
-        return Objects.hash(id, name, priority);
+    override fun hashCode(): Int {
+        var result = id ?: 0
+        result = 31 * result + (name?.hashCode() ?: 0)
+        result = 31 * result + (priority ?: 0)
+        return result
     }
 
-    @Override
-    public String toString() {
-        return new ToStringBuilder(this)
-                .append("id", id)
-                .append("name", name)
-                .append("priority", priority)
-                .toString();
+    override fun toString(): String {
+        return "Authority(id=$id, name=$name, priority=$priority)"
     }
 }