Friday, March 18, 2011

As if Time isn't difficult enough! I say this is huge bug in java.sql.Timestamp

I found a bug in java.sql.Timestamp that was making my unit tests fail
once it a while when the planets aligned just the right way. I was
storing java.util.Date values to a Db using Hibernate and when they come
back out, they are represented as java.sql.Timestamp, which is a small
wrapper around java.util.Date.

In TimeStamp, they are storing the time in whole seconds and the
remaining nanos seperately. In the Timestamp.compareTo, they call the
super class first (but pass the time part only). So methods like
before() and after() are all in error when milliseconds count. Check out the following code:

* Copyright 2001-2009 The Apache Software Foundation.
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* See the License for the specific language governing permissions and
* limitations under the License.
package org.apache.juddi;

import java.sql.Timestamp;
import java.util.Date;

import junit.framework.Assert;

import org.junit.Test;

public class TimeStampDateTest {

public void testDates() {

java.util.Date startDate = new Date(1300286601055l);
java.util.Date modifiedDate = new Date(1300286601334l);
Timestamp timeStamp = new Timestamp(modifiedDate.getTime());

System.out.println(startDate.getTime() + " startDate " + startDate);
System.out.println(modifiedDate.getTime() + " modifiedDate " + modifiedDate);
System.out.println(timeStamp.getTime() + " modifiedDtDB " + timeStamp);

System.out.print("DT:" + startDate.getTime() + " is before " + modifiedDate.getTime() + ": ");
if (startDate.before(modifiedDate)) {
} else {
System.out.println("after ******* WRONG!!!!");

System.out.print("DB:" + startDate.getTime() + " is before " + timeStamp.getTime() + ": ");
if (startDate.before(timeStamp)) {
} else {
System.out.println("after ******* WRONG!!!!");
System.out.println("The reason is a bug in Timestamp, it stores the time (whole seconds) and the nanos seperately," +
"and when running a compareTo it only uses the nanos when the Time part is inconclusive, however" +
"it is not inconclusive because the compareTo from the super class (java.util.Date) DOES" +
"already take into account the millies!");


The second time the date comparison will fail and it will print out: 'after ******* WRONG!!!!'.

Yes Really!!

Then I was told to read the javadoc:

"Note: This type is a composite of a java.util.Date and a separate nanoseconds value. Only integral seconds are stored in the java.util.Date component. The fractional seconds - the nanos - are separate. The Timestamp.equals(Object) method never returns true when passed an object that isn't an instance of java.sql.Timestamp, because the nanos component of a date is unknown. As a result, the Timestamp.equals(Object) method is not symmetric with respect to the java.util.Date.equals(Object) method. Also, the hashcode method uses the underlying java.util.Date implementation and therefore does not include nanos in its computation.

Due to the differences between the Timestamp class and the java.util.Date class mentioned above, it is recommended that code not view Timestamp values generically as an instance of java.util.Date. The inheritance relationship between Timestamp and java.util.Date really denotes implementation inheritance, and not type inheritance.

Ahh that makes it all better! No no no, this is just crap and so easy to fix. Time skrewed up enough, please don't do this Snoracle!

There's a few of my life that I will never get back. The issue is that my unit test failed when the build machine was fast enough to make milli-seconds count when comparing dates!



Monday, February 14, 2011

IPhone 3Gs Battery Drain - part 2

OK so after removing all my apps, it was still draining the battery. Turns out the VPN I had installed was causing it. Not sure why it suddenly went sideways. It had been working just fine for about a year.

Now I'm busy putting all my apps back. It's kind off refreshing though to start with a clean phone :).


Sunday, February 13, 2011

IPhone 3Gs Battery Drain - part 1

I've had my iphone for a little over a year, and since last Friday it drains the battery in about 5 hours, this while the day before I could go for 48 hours between charges. I also noticed it being warmish. I figured it is an app that is stuck, however

- hard reset does not alleviate the issue, and
- doing a full restore does not help either.

I figured that before going over to see apple store I would restore it to having the default OS/firmware only. The idea being, that if it still drains in this configuration, then the phone is just defect. Well I did, and.. my phone is fine now! So while this is good news, this must mean that it is an app that is somehow causing the issues. How am I going to find which app is causing the issues?? I guess I have the following options:

1. Leave it the way it is and slow add apps back as I need them
2. Do a full restore and use bisection on app deletion/addition.
3. I guess i could try to figure out which apps I upgraded last week and delete those, hoping that it is one of these updates of last week.
4. There is no taskmon app right? Wouldn't it be great to simply see which process is eating my CPU cycles/battery..

Love to hear your ideas!