Sunday, March 26, 2006

Swapping Hell: Compiling JDK 1.5 on Freebsd 4.x

In the past few days I was playing with some AJAX + Java codes. As I plan to deploy it to my web site later, I thought it would be a good idea to upgrade the JDK (from 1.3.x to 1.5.x) on the web server. As expected, my antique web server (K6 400MHz with 192MB RAM) took forever to compile the FreeBSD port. After several hours of hard disk crunching, the build process stopped as there was not enough swap space... yuck! The swap partition on the machine is only 128MB. So I used vn to add another 500MB of temporary swap file.

And after 14 hours, 49 minutes and 45.95 seconds later, it finally completed the compilation :P

Sunday, March 12, 2006

Jetspeed 2.0 with Postgresql

Tonight during dinner, my friend mentioned to me that he recently deployed a project using Portlet technology. It reminded me that when I devloped a portal site back in 2002, there was no such standard. I wanted to give Portlet a try since the draft was finalized, but yeah, I was lazy :P. Tonight I finally downloaded Jetspeed 2.

Jetspeed 2 can work with many DBMSs, including my favourite: Postgresql. But after downloading the MultiDb version installer, I found that it won't install as the appropriate SQL scripts were not created. Instead of trying to build it from source (yes, I am very lazy recently and... what the hack, I was just trying to install it on a Windows machine... so I don't want to compile from source :P), I found that similar issue has been reported and you can download the script directly.

Just start the Jetspeed installer, and it will unpack itself to an "antinstall" directory under your temp directory (e.g. C:Documents and SettingsadministratorLocal SettingsTemp). Then, before you proceed with the installer, unpack the Postgresql script package into the database directory under antinstall. Then proceed as usual.

Thursday, March 2, 2006

Calling Javascript functions from a Java Applet

Many years ago, my colleagues encountered a problem that at that time there was no generic solution. The problem was to somehow let the Javascript on a web page to verify that an Applet is loaded correctly without using polling mehtods. Out of curiosity, I tried to find out if browsers today provide a general solution and will work with (at least) both IE and Netscape/Mozilla/Firefox.

It seems that there is a valid solution since IE 4 (and yes, I haven't looked at this problem for a very long time :P). There is a way for an Applet to invoke a Javascript function and will work with both IE and Netscape/Mozilla/Firefox.

First, the applet needs to import the
class "netscape.javascript.JSObject". Although the name says "netscape",
but IE's VM has no problem running the Applet.

(BTW, to compile the Applet, you will need to include plugin.jar in your classpath (e.g. C:Program
FilesJavajre1.5.0libplugin.jar). It is where the JSObject class is located.)

When defining the Applet in the HTML, you need to add the "MAYSCRIPT"
parameter to the <APPLET> tag. e.g.

<APPLET CODE="TestingApplet.class" WIDTH="100" HEIGHT="100" MAYSCRIPT>
<PARAM NAME="initFunction" VALUE="appletLoaded">

Here, I also pass a string "appletLoaded" as a parameter to the
Applet. In my testing HTML page, "appletLoaded" is in fact a
Javascript function name. Inside the Applet, when it is loaded, it
will call this function in its init() method.

I wrote a little testing program and put the HTML, Applet, and source code

On that page, the "Click Me" button was originally disabled. When the
applet loads, it will call a Javascript function. And that Javascript
function will in turn enable the button.

(Since I sign my own certificate, so when you visit my site using SSL,
you will see a warning message. That is normal. Just click OK)