Spring Boot单元测试中BCryptPasswordEncoder返回null问题解决

我在Spring Boot应用里用JUnit和Mockito做单元测试，测试用户注册方法时，创建User对象调用passwordEncoder.encode("password")得到的密码始终是null，导致断言失败。

原始代码 #

UserServiceImpl.java #

@Service
public class UserServiceImpl implements UserService {
    private final UserRepository userRepository;
    private final PasswordEncoder passwordEncoder;

    public UserServiceImpl(UserRepository userRepository, PasswordEncoder passwordEncoder) {
        this.userRepository = userRepository;
        this.passwordEncoder = passwordEncoder;
    }


    @Override
    public User register(User user) {


         Role role = roleService.findByName(ERole.ROLE_USER);

         Set<Role> roleSet = new HashSet<>();
         user.setFullName(user.getFullName());
         user.setEmailAddress(user.getEmailAddress());
         user.setPassword(passwordEncoder.encode(user.getPassword()));
         user.setConfirmPassword("");
         user.setEmailVerified(true);
         roleSet.add(role);
         user.setRoles(roleSet);

         if(userRepository.existsByEmailAddress(user.getEmailAddress())) {
             throw new EmailAlreadyExistsException("Account already exists with this email");
         }
        return userRepository.save(user);
    }
}

UserServiceImplTest.java #

@ExtendWith(MockitoExtension.class)
class UserServiceImplTest {

    @InjectMocks
    private UserServiceImpl userService;

    @Mock
    private UserRepository userRepository;

    @Mock
    public PasswordEncoder passwordEncoder;


   @BeforeEach
    void setUp() {
        userService = new UserServiceImpl(userRepository, passwordEncoder);
    }

  @Test
    void testIfUserCanRegisterSuccessfully() {

        User user = new User(1, "admin", "admin@gmail.com", passwordEncoder.encode("password"));

        when(userRepository.save(any())).thenReturn(user);
        User theUser = userService.register(user);


        System.out.println("theUser: " + theUser);

        assertNotNull(theUser);
        assertEquals(1, theUser.getId());
        assertEquals("admin@gmail.com", theUser.getEmailAddress());
        assertTrue(passwordEncoder.matches("password", theUser.getPassword()));
    }
}

SecurityConfig.java #

@Configuration
@EnableWebSecurity
@EnableGlobalMethodSecurity(prePostEnabled = true, securedEnabled = true, jsr250Enabled = true)
public class SecurityConfig extends WebSecurityConfigurerAdapter {


    @Value("${spring.security.ant.matchers}")
    private String[] securityAntMatchers;
    

    @Autowired
    private UserDetailsServiceImpl userDetailsService;

    @Autowired
    private JwtAuthenticationEntryPoint authenticationEntryPoint;

    @Bean
    public JwtAuthenticationTokenFilter jwtAuthenticationTokenFilter() {
        return new JwtAuthenticationTokenFilter();
    }

    @Bean
    public PasswordEncoder passwordEncoder() {
        return new BCryptPasswordEncoder();
    }

    @Bean
    @Override
    public AuthenticationManager authenticationManager() throws Exception {
        return super.authenticationManager();
    }


    @Override
    protected void configure(AuthenticationManagerBuilder auth) throws Exception {
        auth.userDetailsService(userDetailsService).passwordEncoder(passwordEncoder());
    }



    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .csrf().disable().formLogin().disable().httpBasic().disable();

        http
            .sessionManagement()
            .sessionCreationPolicy(SessionCreationPolicy.STATELESS)
            .and()
            .exceptionHandling().authenticationEntryPoint(authenticationEntryPoint)
            .and()
            .addFilterBefore(jwtAuthenticationTokenFilter(), UsernamePasswordAuthenticationFilter.class);

        http
            .authorizeRequests()
            .antMatchers(securityAntMatchers)
            .permitAll()
            .anyRequest()
            .authenticated();
    }
}

测试输出问题 #

测试时控制台输出的theUser信息如下，不确定怎么在测试中正确处理密码加密：

theUser: User{id=1, fullName='admin', emailAddress='admin@gmail.com', dateJoined=Tue Nov 15 00:06:01 CAT 2022, emailVerified=true, password='null'}

解决方案（修改后代码） #

通过在测试中实例化真实的BCryptPasswordEncoder替代Mockito模拟对象，解决密码为null的问题：

修改后的UserServiceImplTest.java关键代码 #

@BeforeEach
void setUp() {
    // 每次测试前实例化真实的密码编码器
    this.passwordEncoder = new BCryptPasswordEncoder();
    userService = new UserServiceImpl(userRepository, passwordEncoder);
}

@Test
void testIfUserCanRegisterSuccessfully() {
    User user = new User(1, "admin", "admin@gmail.com","password");

    when(userRepository.save(any())).thenReturn(user);
    User created = userService.register(user);

    assertEquals(created.getPassword(), user.getPassword());
    assertEquals(created.getEmailAddress(), user.getEmailAddress());
    verify(userRepository).save(any());
}

问题说明 #

原来的测试中用@Mock模拟了PasswordEncoder，但没有为encode方法设置返回值，所以调用passwordEncoder.encode("password")时默认返回null。除了使用真实编码器，也可以给模拟对象添加返回值设置：when(passwordEncoder.encode(anyString())).thenReturn("加密后的测试密码")，两种方式都能解决null问题。

内容的提问来源于stack exchange，提问作者ServletException