update AccountService with getForUpdateById and save

src/main/kotlin/ltd/lulz/repository/AccountRepository.kt

@@ -2,8 +2,14 @@ package ltd.lulz.repository
 
 import java.util.UUID
 import ltd.lulz.model.AccountEntity
+import org.springframework.data.r2dbc.repository.Query
 import org.springframework.data.repository.reactive.ReactiveCrudRepository
 import org.springframework.stereotype.Repository
+import reactor.core.publisher.Mono
 
 @Repository
-interface AccountRepository : ReactiveCrudRepository<AccountEntity, UUID>
+interface AccountRepository : ReactiveCrudRepository<AccountEntity, UUID> {
+
+    @Query("SELECT * FROM accounts WHERE id = :id FOR UPDATE NOWAIT")
+    fun findByIdForUpdate(id: UUID): Mono<AccountEntity>
+}

src/main/kotlin/ltd/lulz/service/AccountService.kt

@@ -5,6 +5,7 @@ import java.util.UUID
 import ltd.lulz.model.AccountEntity
 import ltd.lulz.repository.AccountRepository
 import org.springframework.stereotype.Service
+import org.springframework.transaction.annotation.Transactional
 import reactor.core.publisher.Mono
 
 private val log = KotlinLogging.logger {}
@@ -20,4 +21,12 @@ class AccountService(
 
     fun getById(id: UUID): Mono<AccountEntity> = accountRepository.findById(id)
         .doOnNext { log.debug { "found account by id: ${it.id}" } }
+
+    @Transactional
+    fun getForUpdateById(id: UUID): Mono<AccountEntity> = accountRepository.findByIdForUpdate(id)
+        .doOnNext { log.trace { "account with id: ${it.id} locked for update" } }
+
+    @Transactional
+    fun save(entity: AccountEntity): Mono<AccountEntity> = accountRepository.save(entity)
+        .doOnNext { log.trace { "account with id: ${it.id} saved" } }
 }

src/test/kotlin/ltd/lulz/service/AccountServiceTest.kt

@@ -69,4 +69,42 @@ class AccountServiceTest {
 
         verify { repository.findById(any(UUID::class)) }
     }
+
+    @Test
+    fun `get for update by id`() {
+        // given
+        val capture = slot<UUID>()
+        every { repository.findByIdForUpdate(capture(capture)) }
+            .answers { Mono.just(AccountEntity(capture.captured, name, amount)) }
+
+        // when stepped
+        StepVerifier.create(service.getForUpdateById(uuid))
+            .assertNext { result ->
+                assertThat(result.id).isEqualTo(uuid)
+                assertThat(result.name).isEqualTo(name)
+                assertThat(result.amount).isEqualTo(amount)
+            }
+            .verifyComplete()
+
+        verify { repository.findByIdForUpdate(any(UUID::class)) }
+    }
+
+    @Test
+    fun `save change`() {
+        // given
+        val entity = AccountEntity(name = name, amount = amount)
+
+        val capture = slot<AccountEntity>()
+        every { repository.save(capture(capture)) }
+            .answers { Mono.just(capture.captured) }
+
+        // when stepped
+        StepVerifier.create(service.save(entity))
+            .assertNext { result ->
+                assertThat(result).isEqualTo(entity)
+            }
+            .verifyComplete()
+
+        verify { repository.save(any()) }
+    }
 }