Matt RaibleMatt Raible is a Web Developer and Java Champion. Connect with him on LinkedIn.

The Angular Mini-Book The Angular Mini-Book is a guide to getting started with Angular. You'll learn how to develop a bare-bones application, test it, and deploy it. Then you'll move on to adding Bootstrap, Angular Material, continuous integration, and authentication.

Spring Boot is a popular framework for building REST APIs. You'll learn how to integrate Angular with Spring Boot and use security best practices like HTTPS and a content security policy.

For book updates, follow @angular_book on Twitter.

The JHipster Mini-Book The JHipster Mini-Book is a guide to getting started with hip technologies today: Angular, Bootstrap, and Spring Boot. All of these frameworks are wrapped up in an easy-to-use project called JHipster.

This book shows you how to build an app with JHipster, and guides you through the plethora of tools, techniques and options you can use. Furthermore, it explains the UI and API building blocks so you understand the underpinnings of your great application.

For book updates, follow @jhipster-book on Twitter.


Over 10 years ago, I wrote my first blog post. Since then, I've authored books, had kids, traveled the world, found Trish and blogged about it all.

I got the phone

a couple of days ago, and I love it! It's a GSM phone, and I don't know if they're all this way, but it sounds clearer than my home phone. It almost sounds like I'm in the same room as someone when I'm talking to them. This is a big plus for me as I've always been annoyed by the bad sound of my previous phones.

I can check my e-mail using the IMAP4 protocol, and I can also check my Yahoo! Mail anywhere I can get a signal. Very cool - helps to cure my e-mail addiction. I hooked it up to my Powerbook G4 via infrared with GSM Remote and was able to have all my contact's numbers in almost no time.

Posted in General at Aug 10 2002, 01:52:20 AM MDT Add a Comment

Explanation of Tomcat's Class Loader

from the Chief Developer of Tomcat and Struts:

> On Fri, 9 Aug 2002, Matt Raible wrote:
> Struts Dev Team - please verify my hypothesis below.
> I believe the Struts JARs and the DBCP JARs from common should be the 
> same.  After all, Struts does use the DBCP in it's distribution.  You 
> might want to upgrade to the latest build of Struts (which includes 
> DBCP and Logging, among others).  I know they're planning on releasing 
> 1.1 Beta 2 this weekend.

The story is somewhat convoluted (I *hate* class loaders :-), but it goes 
like this:

If you are going to use a JNDI datasource, then both your webapp AND 
Tomcat need to see the same copy of the JDBC driver and the dbcp classes
 (for 4.1.x) -- and the way to make that happen is to put the driver into 

Because commons-dbcp.jar is there, it's dependent jars (such as 
commons-collections.jar, jdbc2_0-stdext.jar, and (recently added) 
commons-lang.jar) need to be in common/lib as well.  Plus, of course, 
jndi.jar if you're on a 1.2 system.

Having any of these JARs duplicated inside the webapp causes a problem
 in 4.x based systems, because they try to use the local copy first -- and a
 copy if loaded from the webapp is *not* the same class 
as a copy of loaded from common/lib.  This is a place where 
Tomcat's modified class loader model causes grief (but only because you're 
trying to use the same classes that Tomcat internally is trying to use -- if you 
were using something like GenericDataSource with your own copy of the 
connection pool, it would not be a problem).

One workaround for this would be to try turning off the modified loader 
delegation model, by putting something like this in your server.xml file (or in
 a context configuration file on Tomcat 4.1.x.):

  <Context path="/myapp" ...>
    <Loader delegate="false"/>

This *should* let you have a copy of all the JAR files inside your webapp, 
as well as in common/lib, but not cause any conflicts.

Please let me know, one way or the other, if this works -- it's clearly a 
desireable goal that you can ship a WAR file with all the included commons 
JARs but not have problems like this.  I want to review how Tomcat's default 
configuration can make this easier.  And, from a Struts application perspective 
(not just for Roller), this is a pretty serious usability issue.

> HTH,
> Matt

Craig McClanahan

PS:  In Tomcat 4.1.x, the "deploy" command of the manager app lets you include 
a context configuration file in the WAR, at location "META-INF/context.xml".  So it 
might still be possible to configure a single WAR that works correctly in Tomcat 
4.1.x and still works in other servers (that would obviously ignore such a file).

Thanks for the clear and concise definition of how this all works Craig. So basically, in Tomcat 4.x, don't keep duplicates of your JARs in $CATALINA_HOME/common/lib AND in yourApp/WEB-INF/lib, OR turn off the modified loader delegation as specified above. Tomcat 4.1.x looks very cool, I'm just curious to know why they're on a Beta Release of 4.1.8, but still no official release?

Posted in Java at Aug 10 2002, 12:49:00 AM MDT Add a Comment