insert时没有生成id

    @Test
    public void insert(){
        User user = new User();
        user.setName("tom");
        user.setManagerId(1088248166370832385L);
        user.setCreateTime(new Date());
        int insert = userMapper.insert(user);
        System.out.println("insert = " + insert);
    }

org.springframework.dao.DataIntegrityViolationException: 

### Error updating database.  Cause: java.sql.SQLException: Field 'id' doesn't have a default value

### The error may exist in com/exam/demo/mapper/UserMapper.java (best guess)

### The error may involve com.exam.demo.mapper.UserMapper.insert-Inline

### The error occurred while setting parameters

### SQL: INSERT INTO user  ( name,   manager_id, create_time )  VALUES  ( ?,   ?, ? )

### Cause: java.sql.SQLException: Field 'id' doesn't have a default value

; Field 'id' doesn't have a default value; nested exception is java.sql.SQLException: Field 'id' doesn't have a default value