Tuesday, August 25, 2009

Curious Concept's Excellent JSON Pretty Formatter and Validator

I just wrote a bit of code using Groovy HTTPBuilder to fetch and parse some JSON content to help answer someone's question on StackOverflow.  When trying to pull some interesting data out of the JSON to display, I realized that it would be much easier for me to understand the structure of the JSON if it were pretty-printed (or pretty-formatted).  When I googled for "JSON pretty format", I found a helpful blog entry pointing me to Curious Concept's JSON Formatter (& Validator).  It's a simple online tool that allows you to paste in either a URL pointing to JSON content or the content itself and display it in either compressed or readable form.  It might not have been very hard to code, but it's extremely useful.  Thanks Curious Concept!

Update: I'm trying out the JSONView Firefox plug-in.  So far it seems to work pretty well.  Even so, I expect I'll continue to use Curious Concept's tool for a while, since I spend a fair amount of time in Chrome.

Friday, August 21, 2009

Merger Madness & One Sample App To Rule Them All

VMware --- SpringSource --- /---G2One
Terracotta --- Ehcache
Oracle --- Sun

With all the mergers and acquisitions happening in the Java world, I thought I'd suggest a sample app someone could build to bring them all together.

Here it is: a Grails app using an Oracle DB with distributed caching provided by Terracotta and Ehcache, all running in a VMware cloud, with deployment and management handled by CloudFoundry.  I think that covers all the bases.  I have no idea what it will do yet, but let me know if I've missed anything. :)

Note: I actually have a lot of respect for all the technologies and people involved, I'm just feeling a bit overwhelmed with all of the recent consolidation!

Wednesday, August 19, 2009

Interruptible JDBC Statements

I work for a client on a product that makes direct queries against databases via JDBC. A while ago, I added some code so that a user could stop the execution of a series of queries by clicking on a cancel button. Behind the scenes, it interrupts the thread executing the queries. Since that thread checks whether it's been interrupted by calling Thread.currentThread().isInterrupted() before starting to execute each query, no new queries will start once the cancel button was pushed. However, any query that's already started will run to completion before the code discovers that a request to cancel had been made. Recently, my client decided that we should make cancellation more granular and add the ability to stop a query in mid-stream. Looking at the JDBC docs, there's nothing to indicate that any of the relevant methods respond to interrupts (none throw InterruptedExceptions or claim to wrap them in a SQLException), so I had to come up with another way. I settled on an approach where I submit the query as a Callable to an ExecutorService and then block, waiting for the result via Future.get(). If the thread is interrupted while we're waiting, get() throws an InterruptedException, which gives us the chance to call Statement.cancel(). It's pretty simple and works nicely. :)
Here's the code in a somewhat abridged/condensed form (I create the ExecutorService elsewhere using Executors.newCachedThreadPool()):
final String sql = "...<some SQL>...";
final Statement statement = conn.createStatement();
Future<ResultSet> queryFuture =
 execService.submit(new Callable<ResultSet>() {
   public ResultSet call() throws Exception {
     return statement.getResultSet();

ResultSet rs;
try {
 rs = queryFuture.get();
} catch (InterruptedException e) {
 logger.info("Query interrupted - calling Statement.cancel()");
 throw e;
} catch (ExecutionException e) {
 //code to handle or rethrow the exception
By the way, if any of the java.util.concurrent classes above are unfamiliar to you, I highly recommend Java Concurrency in Practice by Brian Goetz (et al.). It's an excellent book.

Tuesday, August 18, 2009

Terracotta Acquires Ehcache

Exciting news!  This morning I received a note from Greg Luck via the Ehcache Open Discussion mailing list announcing that the Ehcache project was joining forces with Terracotta and that Greg would be joining the team at Terracotta, Inc.  Since there's been a Terracotta Integration Module for Ehcache for a while, I don't foresee any instant improvements with regard to integration between the two technologies, but I was quite excited to see the following in Greg's blog post announcing the news:

I am full-time on Ehcache. I have not had the time I would have liked to devote to Ehcache (I have been doing a miserly 10-15 hours per week for the past 6 years) but now I do. Look out!

Given what he's done so far with limited time, I'm looking forward to seeing what Greg can do when Ehcache becomes his full-time job!

For more information, see Terracotta's announcement, CTO of Terracotta Ari Zilka's blog post, or Alex Miller's blog post.

p.s. I submitted a patch that Greg ended up incorporating into Ehcache 1.6, so I feel a tiny bit of ownership toward the project – similar to the way I feel toward Tomcat.

Update: Terracotta and Ehcache are holding a webcast on August 20th at 4PM ET to further discuss the acquisition.  Also, I just submitted my second patch to Ehcache. :)