BAEL-8113: How to fix JPA NoResultException: No entity found for query (#18981)

* BAEL-8113: How to fix JPA NoResultException: No entity found for query

* BAEL-8113: How to fix JPA NoResultException: No entity found for query

* BAEL-8113: fix indentation

Author: achraftt

persistence-modules/spring-boot-persistence-5/src/main/java/com/baeldung/exception/UserNotFoundException.java

@@ -0,0 +1,12 @@
+package com.baeldung.exception;
+
+public class UserNotFoundException extends RuntimeException {
+
+    public UserNotFoundException(String message) {
+        super(message);
+    }
+
+    public UserNotFoundException(String message, Throwable cause) {
+        super(message, cause);
+    }
+}

persistence-modules/spring-boot-persistence-5/src/main/java/com/baeldung/exception/entity/User.java

@@ -0,0 +1,36 @@
+package com.baeldung.exception.entity;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+
+@Entity
+public class User {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    private String username;
+    private String email;
+
+    public User() {}
+
+    public User(String username, String email) {
+        this.username = username;
+        this.email = email;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public String getUsername() {
+        return username;
+    }
+
+    public String getEmail() {
+        return email;
+    }
+}

persistence-modules/spring-boot-persistence-5/src/main/java/com/baeldung/exception/repository/UserRepository.java

@@ -0,0 +1,13 @@
+package com.baeldung.exception.repository;
+
+import com.baeldung.exception.entity.User;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+import java.util.Optional;
+
+public interface UserRepository extends JpaRepository<User, Long> {
+
+    Optional<User> findByUsername(String username);
+
+    Optional<User> findByEmail(String email);
+}

persistence-modules/spring-boot-persistence-5/src/main/java/com/baeldung/exception/service/UserService.java

@@ -0,0 +1,45 @@
+package com.baeldung.exception.service;
+
+import com.baeldung.exception.UserNotFoundException;
+import com.baeldung.exception.entity.User;
+import com.baeldung.exception.repository.UserRepository;
+import org.springframework.stereotype.Service;
+
+import java.util.List;
+import java.util.Optional;
+
+@Service
+public class UserService {
+
+    private final UserRepository userRepository;
+
+    public UserService(UserRepository userRepository) {
+        this.userRepository = userRepository;
+    }
+
+    // Optional-based API
+    public Optional<User> findUserByUsername(String username) {
+        return userRepository.findByUsername(username);
+    }
+
+    public Optional<User> findUserByEmail(String email) {
+        return userRepository.findByEmail(email);
+    }
+
+    // Business-level exception handling
+    public User findUserByUsernameOrThrow(String username) {
+        return userRepository.findByUsername(username)
+          .orElseThrow(() ->
+            new UserNotFoundException("User not found: " + username));
+    }
+
+    public User findUserByEmailOrThrow(String email) {
+        return userRepository.findByEmail(email)
+          .orElseThrow(() ->
+            new UserNotFoundException("User not found: " + email));
+    }
+
+    public List<User> getAllUsers() {
+        return userRepository.findAll();
+    }
+}

persistence-modules/spring-boot-persistence-5/src/test/java/com/baeldung/exception/UserServiceUnitTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.exception;
+
+import com.baeldung.exception.entity.User;
+import com.baeldung.exception.repository.UserRepository;
+import com.baeldung.exception.service.UserService;
+import org.junit.jupiter.api.Test;
+
+import java.util.Optional;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+class UserServiceUnitTest {
+
+    private final UserRepository userRepository = mock(UserRepository.class);
+    private final UserService userService = new UserService(userRepository);
+
+    @Test
+    void givenExistingUsername_whenFindUserByUsernameOrThrow_thenReturnUser() {
+        User user = new User("john", "[email protected]");
+        when(userRepository.findByUsername("john"))
+          .thenReturn(Optional.of(user));
+
+        User result = userService.findUserByUsernameOrThrow("john");
+
+        assertEquals("john", result.getUsername());
+    }
+
+    @Test
+    void givenUnknownUsername_whenFindUserByUsernameOrThrow_thenThrowUserNotFoundException() {
+        when(userRepository.findByUsername("ghost"))
+          .thenReturn(Optional.empty());
+
+        assertThrows(
+          UserNotFoundException.class,
+          () -> userService.findUserByUsernameOrThrow("ghost")
+        );
+    }
+
+    @Test
+    void givenExistingEmail_whenFindUserByEmailOrThrow_thenReturnUser() {
+        User user = new User("anna", "[email protected]");
+        when(userRepository.findByEmail("[email protected]"))
+          .thenReturn(Optional.of(user));
+
+        User result = userService.findUserByEmailOrThrow("[email protected]");
+
+        assertEquals("[email protected]", result.getEmail());
+    }
+
+    @Test
+    void givenUnknownEmail_whenFindUserByEmailOrThrow_thenThrowUserNotFoundException() {
+        when(userRepository.findByEmail("[email protected]"))
+          .thenReturn(Optional.empty());
+
+        assertThrows(
+          UserNotFoundException.class,
+          () -> userService.findUserByEmailOrThrow("[email protected]")
+        );
+    }
+}