snaker-core/src/main/java/org/snaker/engine/access/jdbc/JdbcHelper.java
public static <T> T requiredSingleResult(Collection<T> results) {
		int size = (results != null ? results.size() : 0);
		if (size == 0) {
			return null;
		}
		return results.iterator().next();
	}
public static <T> T requiredSingleResult(Collection<T> results) {
		int size = (results != null ? results.size() : 0);
		if (size == 0) {
			return null;
		}
		return results.iterator().next();
	}
根据返回的对象集合判断是否为单条记录，并返回
如果返回无记录，或者超过1条记录，则抛出异常
@param results
@return