Monday, August 24, 2009

Hyperlink in JavaFX

It's a long time being blogging. Actually not done anything new from long time :). Here is one simple concept which some guys asked me. We have provided hyperlink API in JavaFX 1.2 but some of us struggled to open a URL using hyperlink API.

Hmm, 2 ways to do it actually.

No1 : Use the Desktop API of JDK6. It's simple to use. One example is here.

So, very basic code will go like this :


package sample2;

import javafx.scene.Scene;
import javafx.stage.Stage;
import javafx.scene.control.*;

Stage {
title: "HyperLink to URL"
width: 240
height: 320
scene: Scene {
content: [
translateY: 160
translateX: 40
width: 150
text: bind "Visit javafx Samples! "
action: function():Void{
java.awt.Desktop.getDesktop().browse(new URI(""));

So, 2 things for running this code. First,Desktop API has been added in JDK6, so this code won't run on JDK5. Second, Add rt.jar(rt.jar of JDK6) file in the Libraries if you are using Netbeans

No2 : For only JavaFX code, we can use AppletStageExtension like this :

package sample1;

import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.control.Hyperlink;
import javafx.stage.AppletStageExtension;

Stage {
title: "Hyperlink to URL"
width: 250
height: 80
scene: Scene {
content: [
Hyperlink {
text: "JavaFX Samples !"
action: function() {

In this case, you cant send hyperlink from Desktop Application, but it will work fine for applet or Browser application. So, best is to use this and then use our normal funda : if {__PROFILE__}" != "browser") --> use the Desktop API code. What you say :).

Please let me know if there is any issue in the code ! Or also if there is any better way to do this.

Java Debugging basics

Some simple debugging tools related to Java. These are for those who are new to Java.

1. Application is crashing : Most miserable one. Get your log file, try to analysis log. How to write log file, use Java Logger API. Java Logger had been introduced in JDK 1.4.2. The most awesome feature of Logger API is that you can use it in production without much overhead. The overhead is controlled by something called level in API. Level goes from FINEST to SEVERE. You can refer to O'Relly Book "Java, In a NutShell". I guess, it covers Logging API into a great detail.

Lot many things to know: Standalone application is crashing or web application. Its crashing with -client or -server option, appletviewer or browser, plugin or plugin2.

2. Application Hang: Most prominent reason for Hang is thread related. I don't know too many language but Java handles thread in most graceful way. What we can do when a Java Process or Application Hang:

- Hmm, get stack trace at Java and native level.
- Get to know current thread conditions and their status.
- Try to get core dump. Sometime, application will refuse to give you.
- Get to know machine detail. Almost all OS, use different thread model. Not only that in Solaris, 8 and 9 use different models. Sometime, it narrow down the problem, if you are luck :).

How to get all these information. Easy actually. Take help of Java Debugger, jdb(which is a part of JDK). In jdb, you can run the command like threads, thread, dump and many more. Take help of Windbg, if its a windows machine for native level. I find it useful and painful.

3. Your application is drinking memory: There is some memory leak. Best is to use jhat(part of JDK). First take a heap dump by using jmap, jconsole hprof. Pass that heap dump to jhat and it will bring a server and

dump all the information. Analyze where most of the memory is going. Writing to track the place from where memory is going. What is GC response on it. Change some arguments of GC and then give a try.

There are lot of JDK tools that help in analyzing JVM, threads, memory, process. See the list :

Garbage collector play important role in all of them, so always get to know what is best for what:- (Even you know less about GC, you can't resist yourself finishing this page, this is so interesting). In terms of GC, everything is improving day be day and we have new GC, Garbage First aka G1 ready. With Vikram, I had one presentation on G1 in Sun tech days -

If you have any wired debugging story related to Java, please share :). Also, visit Visual VM which is meant to integrate all the command line tools of JDK.