如何解决Mock ResultSet.getUninterruptibly时出现的NPE问题

问题根源 #

你测试代码里只mock了session.executeAsync(any(BoundStatement.class))，但实际业务代码中传入executeAsync的是BatchStatement对象，导致mock方法未匹配，返回null，调用getUninterruptibly时触发空指针异常。

修复方案 #

1. 调整mock的参数匹配器
   将针对BoundStatement的mock改为匹配BatchStatement，或者更通用的Statement（因为两者都继承自Cassandra的Statement接口），确保mock能命中实际调用：

   // 替换原来的BoundStatement匹配
   Mockito.when(session.executeAsync(any(BatchStatement.class))).thenReturn(resultSetFuture);
   // 或者用更通用的Statement匹配，兼容更多场景
   // Mockito.when(session.executeAsync(any(Statement.class))).thenReturn(resultSetFuture);
   

2. 确保所有依赖实例已正确初始化
   检查cassandraSuppSession、session、resultSetFuture、resultSet这些mock对象是否已经通过@Mock注解或Mockito.mock()方法创建实例，避免这些对象本身为null。比如测试类顶部应该有：

   @Mock
   private CassandraSuppSession cassandraSuppSession;
   @Mock
   private Session session;
   @Mock
   private ResultSetFuture resultSetFuture;
   @Mock
   private ResultSet resultSet;
   // 其他需要的mock对象同理
   

修改后的测试代码片段 #

调整mock部分后的测试方法：

void saveObject() throws ParseException, TimeoutException, ExecutionException, InterruptedException {
    Object rec16 = getRec16_3();
    Mockito.when(cassandraSession.getOrCreateStatement(any(String.class)))
        .thenReturn(preparedStatement);
    Mockito.when(preparedStatement.bind()).thenReturn(boundStatement);
    Mockito.when(boundStatement.setString(anyInt(), any(String.class))).thenReturn(boundStatement);
    Mockito.when(boundStatement.setTimestamp(anyInt(), any(Date.class))).thenReturn(boundStatement);
    Mockito.when(boundStatement.setLong(anyInt(), anyLong())).thenReturn(boundStatement);
    Mockito.when(boundStatement.setDouble(anyInt(), any(Double.class))).thenReturn(boundStatement);
    Mockito.when(boundStatement.setInt(anyInt(), anyInt())).thenReturn(boundStatement);
    Mockito.when(cassandraSuppSession.getCassandraSession()).thenReturn(session);
    // 关键修改：匹配BatchStatement
    Mockito.when(session.executeAsync(any(BatchStatement.class))).thenReturn(resultSetFuture);
    Mockito.when(resultSetFuture.getUninterruptibly(anyLong(), any(TimeUnit.class))).thenReturn(resultSet);
    objectDao.saveObject(rec16);
}

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