@Override
	public ExpertEntity getExpertById(Long id) {
		ExpertEntity Expert = ExpertMapper.getObjectById(id);
		if (Expert.getFilepath().length()>1) {
			...
		}
		return Expert;
	}

物件的Stirng的length大於1就進行操作，很理想對不對，然而報空指標錯誤

解決方案：

@Override
	public ExpertEntity getExpertById(Long id) {
		ExpertEntity Expert = ExpertMapper.getObjectById(id);
		if (Expert.getFilepath()!=null && Expert.getFilepath().length()>1) {
			...
		}
		return Expert;
	}