工作中使用到了oracle12的版本，使用hibernate5儲存時發現生成的結果除了1正常其餘的都從-49開始往上加，

資料庫自身查詢是沒有問題的。

跟蹤hibernate5的原始碼發現@SequenceGenerator還需要配置一個allocationSize=1才能正常

如

@SequenceGenerator(name="UMS_USER_SEQ", sequenceName="UMS_USER_SEQ",allocationSize = 1)

相關原始碼在org.hibernate.id.enhanced.PooledOptimizer#generate

generationState.value = callback.getNextValue();
			// unfortunately not really safe to normalize this
			// to 1 as an initial value like we do the others
			// because we would not be able to control this if
			// we are using a sequence...
			if ( generationState.value.lt( 1 ) ) {
				log.pooledOptimizerReportedInitialValue( generationState.value );
			}
			// the call to obtain next-value just gave us the initialValue
			if ( ( initialValue == -1
					&& generationState.value.lt( incrementSize ) )
					|| generationState.value.eq( initialValue ) ) {
				generationState.hiValue = callback.getNextValue();
			}
			else {
				generationState.hiValue = generationState.value;
				generationState.value = generationState.hiValue.copy().subtract( incrementSize - 1 );
			}