hi Julian, Thank you for your replay . It’s very helpful to me. I want to learn more about the conversion relationship between SQL's time type and Java's time type and SQL’s time type with timezone . Can you give me some suggestions or links ?
Thanks Jiayichao > 在 2018年12月29日，上午8:14，Julian Hyde <[email protected]> 写道： > > The root of the problem is that SQL’s TIMESTAMP type has no time zone (not > even UTC) whereas Java’s Timestamp represents an instant in time, internally > represented as an offset from the UTC epoch. Therefore translation between > java.sql.Timestamp and SQL TIMESTAMP always needs a time zone. > >> On Dec 27, 2018, at 7:53 PM, jia yichao <[email protected]> wrote: >> >> Hi community >> >> >> Recently I have encountered a problem with time conversion. I want to know >> why the following methods need to add or subtract time zone offsets. Is this >> designed to meet some specifications? These methods are located in >> SqlFunctions.java. >> >> /** Converts the Java type used for UDF parameters of SQL TIMESTAMP type >> * ({@link java.sql.Timestamp}) to internal representation (long). >> * >> * <p>Converse of {@link #internalToTimestamp(long)}. */ >> public static long toLong(Timestamp v) { >> return toLong(v, LOCAL_TZ); >> } >> >> // mainly intended for java.sql.Timestamp but works for other dates also >> public static long toLong(java.util.Date v, TimeZone timeZone) { >> final long time = v.getTime(); >> return time + timeZone.getOffset(time); >> } >> >> /** Converts the internal representation of a SQL TIMESTAMP (long) to the >> Java >> * type used for UDF parameters ({@link java.sql.Timestamp}). */ >> public static java.sql.Timestamp internalToTimestamp(long v) { >> return new java.sql.Timestamp(v - LOCAL_TZ.getOffset(v)); >> } >> >> thanks >> Jiayichao > >
