Archive for the ‘Software Development’ Category

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Online Vs Offline Applications: Everything old is new again

Released March 28th, 2007

Everyone has probably noticed this already but the old is new again cycle for “online” desktop apps has been shortening at a rapid pace. Everywhere you turn you see people talking about offline and online apps and what should be online vs offline. If you take your time machine back you would see something like the following timeline:

  • 1970s 3270
  • 1980s X terminal
  • 1990s Java applets
  • 2000 Flash
  • 2005 Ajax

Up until about 2000 it was taking 10 years to cycle from “we want everything on our desktop” to “we want everything on the server”. Now the cycle seems to have sped up to every year and then to constant. A couple recent examples of new faces on this old idea are Adobe’s Apollo and Joyent’s Slingshot.

Fundamentally not much has changed from the 1970s. The goal is to centralize computing resources into one place (in the simple view of things) and make issues like software deployment easier.The main difference now is that the industry has come to the point where there isn’t any turning back and everyone has bought on to the need and usefulness of online apps. The main sticking point seems to be finding a way to resolve issues that come up from users being disconnected from time to time. I’ll bet that one won’t be fully resolved until you have connectivity anywhere and everywhere you go.

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Hibernate and your Getters and Setters

Released March 11th, 2007

When you’re using Hibernate and are mapping to properties, keep your getters and setters as simple and self-contained as possible. The receiver being initialized may not have any other properties set, and the value being passed may not be fully initialized yet, either.

If you don’t respect these two possibilities, then you will get bit in the butt alot, when you least expect it. To be fair, these situations can happen whether you’re using Hibernate or not, but when we first started using the framework we made lots of assumptions.

Here is a completely ridiculous example that violates the above restrictions:
(more…)

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Using the Hibernate API to Inspect Mapped Classes

Released August 2nd, 2006

For my current project we needed to audit the property setters Hibernate was using on our objects to make sure that any logic in them was not overly state dependent. More about this issue in Hibernate is available here. We have fairly rich object models, and a lot of methods, including setters, are never used by Hibernate. We wanted a report of the setters actually used by Hibernate to limit the amount of code we had to examine.

The Hibernate API allows you a lot of access to its configuration object model, and this is ideal for finding out how Hibernate is interacting with your code. I wrote a small class to do this inspection. The method below is run after a Hibernate Configuration object named creatively as “configuration” has been built with mapping files:

public Map findSetters() throws MappingException
{
  Map classToSetters = new HashMap();
  Iterator classMappingIterator =   configuration.getClassMappings();

  while(classMappingIterator.hasNext())
  {
    PersistentClass persistentClass = (PersistentClass)classMappingIterator.next();
    Class mappedClass = persistentClass.getMappedClass();
    Iterator propertyIt = persistentClass.getPropertyIterator();
    List classSetters = new LinkedList();

    classToSetters.put(mappedClass, classSetters);

    while(propertyIt.hasNext())
    {
      Property property = (Property)propertyIt.next();
      Setter setter = property.getSetter(mappedClass);

      classSetters.add(setter.getMethodName());
    }
  }
  return classToSetters;
}

I have uploaded a Java project that contains the full HibernateInspector class, as well as some sample classes and mappings. Un-tar it, and run

ant -Dhibernate.home="path to hibernate 3"

to build and run the example.

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Slides for “You’ll Be Seeing Ruby”

Released May 17th, 2006

The slides for the presentation are finally available, along with a zipfile, on the Presentation: You’ll Be Seeing Ruby page.

It’s been a month now since our last performance, but it all comes back every time I look at the slides.

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Thread pooling with Java concurrency utilities new (java 1.5) and old (util.concurrent)

Released April 24th, 2006

Threading in java is fairly easy and now with java 1.5 some of the stuff that was harder has become even easier. A few years ago someone pointed me to a site that had some concurrency utils that where the precursor to what are now the concurrent utils in java 1.5. They are very close in functionality and if you can’t use java 1.5 the older version of the utils will work with older versions of java and give you a lot of the same functionality.

I’m going to give a quick thread pooling example using both the new and old concurrency utils. I picked the thread pooling out of both since that seems to be what I end up using the most out of all the new utilities. I may revisit this again at some point to go over the periodic executors or some of the other things I have used but just not as much.

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Using strptime to parse ISO 8601 formated timestamps

Released April 15th, 2006

A lot of dates that come back from XML based web services are in the ISO 8601 form. I found out recently that it isn’t straight forward to parse such a date using C functions and have the time come out in the correct timezone. It isn’t rocket science but it is a lot more convoluted than higher level languages like Java.

First of lets see an example of the ISO 8601 format:

2006-02-03T16:45:09.000Z

That breaks down into:

<date>T<time><timezone>

Where a timezone of Z is equal to UTC. I was only interested in parsing timestamps in UTC so the following only applies to that timezone.

If you want to know any more about the format check out this page.

The strptime function is a flexible way to turn a string into a struct tm given a specified format. It is like a sscanf for dates. For more information on it check here. I’m not exactly sure of the portability of this function but it seems to be fairly old now so it is probably reasonably portable.

The format used to parse the a ISO 8601 timestamp is: %FT%T%z

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Howto base64 encode with C/C++ and OpenSSL

Released April 11th, 2006

I’ve been doing a little C programming lately and I have found that if you have a up to date distribution of linux there are a lot of libraries out there that make doing things you do in other languages like java easier.

As I have time I’m going to post some examples of what I have found. The first here is how to base64 encode a chunk of memory using OpenSLL.

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Using axis with https and a self signed certificate

Released April 8th, 2006

While developing a webservice based application we ran across some issues using a self signed certificate. After running our wsdl2java ant task we got the following error using Java 1.4:

sun.security.validator.ValidatorException: No trusted certificate found

Using Java 1.5 the error looks like this:

sun.security.validator.ValidatorException: PKIX path building failed:
sun.security.provider.certpath.SunCertPathBuilderException:
unable to find valid certification path to requested targ

Fair enough. Java is telling us we need to import our self signed certificate into java:

/usr/local/java5/bin/keytool -import -alias mycert \\
  -file server.crt -keystore /usr/local/java5/jre/lib/security/cacerts
Enter keystore password:  changeit
... CERTIFICATE DUMP ...
Trust this certificate? [no]:  yes
Certificate was added to keystore

Running our ant task again:

java.io.IOException: HTTPS hostname wrong:  should be <localhost>
  at sun.net.www.protocol.https.HttpsClient.checkURLSpoofing(HttpsClient.java:490)
  at sun.net.www.protocol.https.HttpsClient.afterConnect(HttpsClient.java:415)
...LONG STACK TRACE TRUNCATED....
</localhost>

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Seeing Ruby

Released April 5th, 2006

This past Friday I participated in my first presentation, Seeing Ruby: An Introduction to the Ruby Programming Language at the iTRC in Louisville, Kentucky. Chuck Fouts, Steven Yelton, and I did our level best to introduce our audience to one of our favorite development tools. Our audience was fantastic, and had lots of questions. Everyone stayed a good 15 minutes after the official end to finish Steven’s awesome Rails demo.

Honestly, Ruby sells itself though. People tend to sit up and notice blocks and open classes.

We’ll be posting the presentation slides very soon to the permanent page. And as we take the show to other venues we’ll be tweaking and refining the content. Initial feedback is to beef up the handout with a cheatsheet of language features; our whirlwind tour of the language goes by quickly and some sort of reference will help keep everything together.

Our audience expressed great interest in Ruby on Rails and AJAX, even a few requests for some Seeing More Ruby classes. We’re debating on whether “You’ll Be Seeing AJAX” or “You’ll Be Seeing Rails” next. :) Let us know which you’d rather see.

Incidentally, we’re also taking this presentation to a company for a private show, and we’d be willing to come talk with you and your colleagues as well. Just contact us!

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JDBC + Batch updates + Non-Standard == Oracle

Released February 11th, 2006

I recently ran into an issue where doing a large number of inserts and updates in an Oracle 8i database was taking forever. I was already using a prepared statement and commiting only after a certain number of rows. After some digging I found out that there is a special Oracle way of doing batch updates that made things a good bit faster. They do support the normal addBatch batch updates but it isn’t as fast as using their special way.

Here is an example of how to do things their way:

public static void doBatchInsert(List aLargeList, Connection connection) throws SQLException
{
  // You have to turn auto commit off, if you are doing a large set of inserts and updates you are probably doing this already.
  connection.setAutoCommit(false);

  PreparedStatement preparedStatement = connection.prepareStatement("insert into a_table(a_col) values (?)");
  // This is the magic. Set the number of statements to allow in one batch
  ((OraclePreparedStatement)ps).setExecuteBatch (10);

  int count = 0;
  for(Iterator i=aLargeList.iterator(); i.hasNext(); count++)
  {
    YourData yourData = (YourData)i.next();

    preparedStatement.setInt(1, yourData.getAnInt());
    preparedStatement.executeUpdate();

    if(count % 10 == 0)
    {
      // Send all currently queued statements
      ((OraclePreparedStatement)preparedStatement).sendBatch();
      connection.commit();
    }
  }

  ((OraclePreparedStatement)preparedStatement).sendBatch();
  connection.commit();
  preapredStatement.close();
}

For more information see the following link:
http://www.oracle.com/technology/products/oracle9i/daily/jun07.html

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