Add validator

build.gradle.kts

@@ -23,6 +23,7 @@ dependencies {
 	implementation("org.springframework.boot:spring-boot-starter-data-jpa")
 	implementation("org.springframework.boot:spring-boot-starter-thymeleaf")
 	implementation("org.springframework.boot:spring-boot-starter-web")
+	implementation("org.springframework.boot:spring-boot-starter-validation")
 	implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
 	implementation("org.jetbrains.kotlin:kotlin-reflect")
 	implementation("org.xerial:sqlite-jdbc")

src/main/kotlin/com/example/demo/controllers/UsersController.kt

@@ -2,7 +2,10 @@ package com.example.demo.controllers
 
 import com.example.demo.entities.User
 import com.example.demo.repositories.UserRepository
+import jakarta.validation.Valid
 import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.http.HttpStatus
+import org.springframework.http.ResponseEntity
 import org.springframework.web.bind.annotation.*
 
 @RestController
@@ -21,14 +24,15 @@ class UsersController {
     }
 
     @PostMapping("/users")
-    fun create(@RequestBody newUser: User): User {
-        return repo.save(newUser)
+    fun create(@Valid @RequestBody newUser: User): ResponseEntity<User> {
+        val user = repo.save(newUser)
+        return ResponseEntity(user, HttpStatus.CREATED)
     }
 
     @PatchMapping("/users/{id}")
-    fun update(@PathVariable id: Long, @RequestBody user: User): User {
+    fun update(@PathVariable id: Long, @Valid @RequestBody user: User): ResponseEntity<User> {
         user.id = id
-        return repo.save(user)
+        return ResponseEntity(repo.save(user), HttpStatus.OK)
     }
 
     @DeleteMapping("/users/{id}")

src/main/kotlin/com/example/demo/entities/User.kt

@@ -3,8 +3,16 @@ package com.example.demo.entities
 import jakarta.persistence.Entity
 import jakarta.persistence.GeneratedValue
 import jakarta.persistence.Id
+import jakarta.validation.constraints.Email
+import jakarta.validation.constraints.NotEmpty
 
 @Entity
-class User(
-        @Id @GeneratedValue var id: Long? = null,
-        var login: String)
+class User {
+    @Id
+    @GeneratedValue
+    var id: Long? = null;
+
+    @NotEmpty(message = "Login can't be empty")
+    @Email(message = "The email address is invalid.")
+    lateinit var login: String;
+}

src/main/kotlin/com/example/demo/exceptions/GlobalExceptionHandler.kt

@@ -0,0 +1,31 @@
+package com.example.demo.exceptions
+
+import org.springframework.http.HttpHeaders
+import org.springframework.http.HttpStatus
+import org.springframework.http.HttpStatusCode
+import org.springframework.http.ResponseEntity
+import org.springframework.validation.FieldError
+import org.springframework.web.bind.MethodArgumentNotValidException
+import org.springframework.web.bind.annotation.ControllerAdvice
+import org.springframework.web.context.request.WebRequest
+import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler
+import java.util.stream.Collectors
+
+
+@ControllerAdvice
+class GlobalExceptionHandler : ResponseEntityExceptionHandler() {
+
+    override fun handleMethodArgumentNotValid(ex: MethodArgumentNotValidException, headers: HttpHeaders, status: HttpStatusCode, request: WebRequest): ResponseEntity<Any>? {
+        val body: MutableMap<String, List<String?>> = HashMap()
+
+        val errors = ex.bindingResult
+                .fieldErrors
+                .stream()
+                .map { obj: FieldError -> obj.defaultMessage }
+                .collect(Collectors.toList())
+
+        body["errors"] = errors
+
+        return ResponseEntity(body, HttpStatus.BAD_REQUEST)
+    }
+}