Mocking Spring 的 jdbc KeyHolder 使用 Mockito

Question

我需要你的帮助来解决一个问题。我在我的DAO类中有这样一个方法，它保存Role:

@Repository(value="jdbcRoleDAO")
@Transactional(propagation=Propagation.SUPPORTS, readOnly=true, rollbackFor=Exception.class)
public class JdbcRoleDAO implements RoleDAO {
    @Autowired
    private JdbcTemplate jdbcTemplate;
    @Autowired
    private DBLogger<Role> dbLogger;
    /**
     * @throws DublicateEntryException if object with specified unique for application field already 
     *              exists in DB.
     */
    @CacheEvict(value = "roles", allEntries = true)
    @Transactional(propagation=Propagation.REQUIRED, readOnly=false, rollbackFor=Exception.class)
    @Override
    public Role save(final Role role) {
        if (this.getRoleByName(role.getName()) != null) {
            throw new DublicateEntryException("Record with specified role name already exists in application.");
        }
        KeyHolder keyHolder = new GeneratedKeyHolder();
        jdbcTemplate.update(new PreparedStatementCreator() {
            @Override
            public PreparedStatement createPreparedStatement(Connection connection)
                    throws SQLException {
                PreparedStatement ps = connection.prepareStatement(SQL_INSERT_ROLE, new String[]{"ID"});
                ps.setString(1, role.getName());
                ps.setString(2, role.getDesription());
                ps.setObject(3, (role.getParentRole()!=null)?role.getParentRole().getId():null);
                ps.setString(4, role.getPrivilege().toString());
                return ps;
            }
        }, keyHolder);
        Long key = (Long) keyHolder.getKey();
        if (key != null) {
            role.setId(key);
        } else {
            role.setId(-1);
        }
        // Add information about operation to log table
        dbLogger.logBasicOperation(role, OperationName.CREATE);
        return role;
    }
...
}

我想用Mockito为这个方法编写单元测试。目前看来：

@RunWith(MockitoJUnitRunner.class)
public class JdbcRoleDAOTest {
    private static final long TEST_ROLE_ID = 1L;
    private static final int TEST_ROLE_VERSION = 7;
    @Mock
    private DBLogger<Role> dbLogger;
    @Mock
    private JdbcTemplate jdbcTemplate;
    @InjectMocks
    private JdbcRoleDAO roleDAO;
    /**
     * test role that is used in all methods.
     */
    private Role role;
    @Before
    public void setUp(){
        // Create a test role object
        role = new Role();
        role.setId(TEST_ROLE_ID);
        role.setName("TEST");
        role.setDesription("Test role");
        role.setPrivilege(Privilege.DEFAULT);
        role.setVersion(TEST_ROLE_VERSION);
        // Return correct version of the object
        Mockito.when(jdbcTemplate.queryForInt(JdbcRoleDAO.SQL_GET_VERSION, TEST_ROLE_ID))
            .thenReturn(TEST_ROLE_VERSION);
    }
    @Test
    public void testSave() {
        Assert.assertNotNull(role);
        roleDAO.save(role);
        InOrder inOrder = Mockito.inOrder(jdbcTemplate, dbLogger);
        // Verify execution of the conditions.
        inOrder.verify(jdbcTemplate, Mockito.times(1)).update(Mockito.any(PreparedStatementCreator.class), 
                Mockito.any(KeyHolder.class));
        inOrder.verify(dbLogger, Mockito.times(1)).logBasicOperation(role, OperationName.CREATE);
        /* 
         * Expected -1 because I can't mock KeyHolder and should be returned -1 value (because 
         * KeyHolder will return null instead of key)
         */ 
        Assert.assertEquals("Generated id is wrong!", -1, role.getId());
    }
…
}

问题是，我想以某种方式嘲笑KeyHolder，但我不知道该怎么做更好。正如您所看到的，现在KeyHolder实例是在save方法中创建的，这是一个主要的困难。我曾想过使用Spring将KeyHolder与范围"prototype"一起注入，但据我所知，当很少有用户同时尝试保存新角色时，这可能会导致问题。我还试着做这样的事情：

Mockito.when(jdbcTemplate.update(Mockito.any(PreparedStatementCreator.class), 
                Mockito.any(KeyHolder.class)))
                .thenAnswer(new Answer<Void>() {
                    @Override
                    public Void answer(InvocationOnMock invocation)
                            throws Throwable {
                        Object[] arguments = invocation.getArguments();
                        for (int i=0; i<arguments.length; i++) {
                            if (arguments[i] instanceof KeyHolder) {
                                KeyHolder keyHolder = (KeyHolder) arguments[i];
                                KeyHolder spyKeyHolder = Mockito.spy(keyHolder);
                                Mockito.when(spyKeyHolder.getKey()).thenReturn(TEST_GENERATED_ID);
                                Mockito.doReturn(TEST_GENERATED_ID).when(spyKeyHolder).getKey();
                            }
                        }
                        return null;
                    }
                });

但这行不通。也许有人可以给我一个建议，如何可能嘲笑（或监视）KeyHolder不将其从保存方法中移出？Mockito中是否有一些功能可以实现这一点？或者这是不可能的？

提前感谢

Answer 1

您可以创建以下接口：

public interface KeyHolderFactory {
     KeyHolder newKeyHolder();
}

然后在JdbcRoleDAO中添加一个KeyHolderFactory字段，在生产中通过依赖项注入填充，并在测试时手动使用mock填充。生产实现很简单，您可以使用它的单个实例（singleton）：

public class GeneratedKeyHolderFactory implements KeyHolderFactory {
     public KeyHolder newKeyHolder() {
         return new GeneratedKeyHolder();
     }
}

在方法内部，您将拥有

...
KeyHolder keyHolder = factory.newKeyHolder();
...

Answer 2

如果您可以切换到PowerMock，您也可以模拟构造函数，然后您可以模拟GeneratedKeyHolder构造函数以返回模拟KeyHolder