Category: english
Here is a problem I faced those days while programming with JavaFX.
When you perform a click in a JavaFX area, mouse events are called to all nodes through that position. You can see this behavior in this video.
Example 1.
Here is the code.
import javafx.application.*;
import javafx.scene.geometry.*;
import javafx.scene.geometry.Rectangle;
import javafx.scene.paint.Color;
import javafx.input.MouseEvent;
Frame {
width: 200
height: 200
visible: true
stage: Stage {
content: [
Rectangle {
var color1 = Color.BLUE;
x: 10, y: 10, width: 140, height: 90, fill: bind color1
onMouseClicked: function( e: MouseEvent ):Void {
if (color1==Color.BLUE){
color1 = Color.GREEN;
} else {
color1 = Color.BLUE
}
}
},
Circle {
var color2 = Color.RED
centerX: 100, centerY: 100, radius: 40, fill: bind color2
onMouseClicked: function( e: MouseEvent ):Void {
if (color2==Color.YELLOW){
color2 = Color.RED;
} else {
color2 = Color.YELLOW
}
}
}
]
}
}
This is the default behavior. All node are called with a mouse event. Is a expected and robust behavior but sometimes we just don’t want that. We want events called to just one node or a set of nodes.
Example 2.
Is exactly the same code but with blocksMouse: true in the circle node. When blocksMouse is true the mouse event will not be called to others node behind it.
package overlapping;
import javafx.application.*;
import javafx.scene.geometry.*;
import javafx.scene.geometry.Rectangle;
import javafx.scene.paint.Color;
import javafx.input.MouseEvent;
Frame {
width: 200
height: 200
visible: true
stage: Stage {
content: [
Rectangle {
var color1 = Color.BLUE;
x: 10, y: 10, width: 140, height: 90, fill: bind color1
onMouseClicked: function( e: MouseEvent ):Void {
if (color1==Color.BLUE){
color1 = Color.GREEN;
} else {
color1 = Color.BLUE
}
}
},
Circle {
var color2 = Color.RED
centerX: 100, centerY: 100, radius: 40, fill: bind color2
blocksMouse: true
onMouseClicked: function( e: MouseEvent ):Void {
if (color2==Color.YELLOW){
color2 = Color.RED;
} else {
color2 = Color.YELLOW
}
}
}
]
}
}
Thanks guys on the OpenJDK user mail list and at OpenJFX Forum, specially this thread.
Right in this moment you can choose between three options to develop JavaFX:
- Use the old version of JavaFX, interpreted. Not recommended.
- Use the JavaFX Milestone 3. Little bit old but more stable.
- Use the JavaFX Continuous Build. Is more dangerous but give us fresh builds. 🙂
I did this little script to download the last version of JavaFX continuos build and install it for you.
#!/bin/sh
envfile=$HOME/.bash_profile
#download and unpatch the last build of JavaFx
mkdir jfx
cd jfx
wget http://openjfx.java.sun.com/hudson/job/openjfx-compiler/lastBuild/artifact/openjfx-compiler/dist//*zip*/dist.zip
unzip dist.zip
rm dist.zip
#set files at bin folder as executable
chmod +x dist/bin/*
#add those executables to the path
echo "PATH=\$PATH:`pwd`/dist/bin" >> $envfile
Save this script as install_jfx.sh and execute it. Probably you want to execute it at you home directory. If you want to install JavaFX to root change envfile for /root/.bash_profile, if you want to install to all users change for /etc/profile. I tested this script successfully on my Ubuntu 8.04.
After that open a new terminal and try to see if javafx, javafxc and javafxdoc are available. You can test your enviroment with this simple program.
import javafx.ui.*;
import java.lang.*;
Frame {
visible: true
content: FlowPanel {
content: Button {
var n = 0
text: bind Integer.toString(n)
action: function() {
n++;
}
}
}
}
Save it as Counter.fx, compile with javafxc Counter.fx and so execute it with javafx Counter.fx.
To know more, take a look into the preliminary JavaFX API or in the article Using JavaFX GUI Toolkit.
As seen in the Sun Tech Days page, the Sun Tech Days Brazil will happen this September. In a few days we can know exactly the day the event will occurs. Probably we CEJUG will prepare a parallel event and see live the event in São Paulo by video stream. 🙂
Duke Luau Style, under public domain. Source: duke_lual.svg.
import java.util.Calendar;
public class Main {
public static void main(String[] args) {
Calendar today = Calendar.getInstance();
System.out.println("Today is " + today.getTime());
}
}
In this simplest example of Calendar, the output would be
Today is : Tue Jul 01 10:56:14 BRT 2008
In the next example how to get information about the day inside the year, month and week.
import java.util.Calendar;
public class Main {
public static void main(String[] args) {
Calendar today = Calendar.getInstance();
int dof = today.get(Calendar.DAY_OF_YEAR);
int dom = today.get(Calendar.DAY_OF_MONTH);
int dow = today.get(Calendar.DAY_OF_WEEK);
System.out.println("Today is the " + dof +"º day in this year,");
System.out.println("the " + dom +"º day in this month");
System.out.println("and the " + dow +"º day in this week.");
}
}
The output could be
Today is the 183º day in this year,
the 1º day in this month
and the 3º day in this week.
The next example is about how to add (and subtract) a duration from a Calendar.
import java.util.Calendar;
public class Main {
public static void main(String[] args) {
Calendar today = Calendar.getInstance();
System.out.println("Today is " + today.getTime());
Calendar yesterday = (Calendar)today.clone();
yesterday.add(Calendar.DATE, -1);
System.out.println("Yesterday was " + yesterday.getTime());
Calendar tomorow = (Calendar)today.clone();
tomorow.add(Calendar.DATE, 1);
System.out.println("Tomorow will be " + tomorow.getTime());
}
}
A typical output would be
Today is Tue Jul 01 10:44:18 BRT 2008
Yesterday was Mon Jun 30 10:44:18 BRT 2008
Tomorow will be Wed Jul 02 10:44:18 BRT 2008
This week I did another presentation outside my city. This time it was at Maracanau in the Comsolid, a open source and digital inclusion event.
My first presentation was about ZFS filesystem and how you can take benefits from it like pooling storage and self healing. I used as base for examples my last post on it, Trying to corrupt data in a ZFS mirror.
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My next talk was about OpenSolaris. We had a lot of questions and interesting about this. We burned some cds with OpenSolaris 2008.5 and also distributed others versions of OpenSolaris like Solaris 10.
And my last presentation was a quick talk about high performance computing, a short version on that I already did before.
Was a interesting event mainly because the public was composed primarily by young students with few background on TI. It was a challenge to present some new concepts like pooling storage for those who aren’t familiar with filesystems management. I tried to keep my talk as simpler as I could and focus on daily problems and showing that you can avoid them with some open source technologies.
The full album is available at http://flickr.com/photos/silveiraneto/sets/72157605632001295/.
Photos from one unit of many units of Casa Brasil, a Non Governmental Organization, trying OpenSolaris (Solaris 10 distribution).
Thanks Erivelton, Alyne and others for these photos.
More photos in this album.
Casa Brasil is a very interesting project. I had there these days. I belive we can do some good partnerships.
Rafael Carneiro, Tarso Bersa, Rafael Ponte and me, after 8 hours of bus travel, arrived in Juazeiro do Norte to talk at the first JavaDay there.
- Rafael Carneiro talked about Java Certification.
- Tarso Bersa talked about Spring Framework for JEE applications.
- I talked about NetBeans 6.
- Rafael Ponte talked about JavaServer Faces.
We answered a lot of questions and gave lot of gifts. I also showed the Sun Academic Initiative, which they are already subscribed. We also showed several opportunities they can participate with CEJUG like free vouchers or a free travel for Belgium.
Some pictures we took. These ones during the bus travel. We saw a nice sunrise through beautiful landscapes.
We playing guitar hero. 😀 The city have their own shopping with games, restaurant and cinema.
The main atraction at Juazeiro is a statue of Padre (Priest) CÃcero with 7 meters itself and more 8 meters of base. Pilgrimage to this statue takes place in his honour every November, attracting thousands of followers. The city’s economy is highly influenced by those travelers devotes.
There’s a museum with several personal objects from Padre Cicero. People go there in order to thanks for miracles. If you got your a part of your body cured, of place there a wooden replica of that part of your body. If you got a car, you place a wooden car or a photo, and so on. There is thousands, maybe millions, of objects theres.
You can see all photos at Carneiro’s album or in my album.
Ilustrative image 😛
This is the first of a serie of posts I’d like to write while I’m studying more about OpenSolaris. The idea is to create simple posts showing a specific feature through practical examples that you can reproduce in your computer.
One of the most interesting feature on OpenSolaris is the 128-bit filesystem ZFS.
For those who are starting with ZFS, the main diference is the abstraction used for volumes. Unlike traditional file systems, which reside on single devices and thus require a volume manager to use more than one device, ZFS filesystems are built on top of virtual storage pools called zpools. One zpool is constructed of virtual devices (vdevs), which are themselves constructed of block devices: files, hard drive partitions, or entire drives (the recommended usage).
In this first experiment we will construct a mirrored zpool (RAID-1) and so try to corrupt its data and see what happens. In a mirrored pool the data is replicated into many disks and that eliminates the critical point, ie if one disks stops the data is not corrupted. You’ll can create a mirror with two or more disks and inside a pool you can have many mirrors. By example, one pool of 100Gb made by two mirrors, each one with 50Gb and each mirror made by volumes of 25Gb. You’ll scale your pool according your needs and capabilities.
This part of corrupt data make this experiment a little dangerous. You have these options:
- Install OpenSolaris in your disk and have at least two more disks to make a mirrored zpool. I don’t recommend this option because if you don’t know exactly what you are doing you can lose important data if you use the wrong volumes.
- Install OpenSolaris in a virtual machine and create fake volumes for this experiment. If you make some mistake nothing too bad will happen. That’s the option I’m using. Here I’m using VirtualBox with OpenSolaris 2008.5. VirtualBox is a free virtual machine, easy to use and works well with OpenSolaris.
Although there is already a graphical tool for manage ZFS, this is not available at OpenSolaris 2008.5. Also for who are studying ZFS a little bit deeper, know how to manage it by command line tools is interesting.
With your OpenSolaris booted, open a terminal and log yourself as root. Consult your available devices with echo|format.
If you are familiar with Linux, OpenSolaris nomenclature for devices may sound strange. I recommend you to take a look at this document.
To create a pool with the devices c4d1 (80G) and c5d1 (60GB) just type zpool create ourpool mirror c4d1 c5d1.
Explaining this command word by word:
- zpool: for manage ZFS you need to be familiar with only two commands: zpool and zfs. Zpool command is for configure and manage ZFS pools.
- create: the action, in this case, creation.
- ourpool: name I chose for the pool.
- mirror: we want a mirror in ourpool, so the next words will be more devices.
- c4d1 c5d1: devices we want to use.
Diagram of ourpool. Icons from Everaldo Coelho.
If your command works, it’ll works silently e will returns nothing. For check pool’s status do a zpool status ourpool.
This output shows that a pool called ourpool is ONLINE and is made of one only mirror, that is made of two devices c4d1 e c5d1.
We can list all pools with zpool list.
Ourpool has approximately 60Gb size which 900kb is already used for store metadata. As we did a mirror using volume of 60Gb and 80Gb, the mirror size is determined by the smaller volume. The another pool, rpool is a pool that OpenSolaris creates by defaul to place the system.
Now we’ll populate the pool with data. These data could be real important data like data base files, your photo collection or personal documents. For illustrative effect I’m using a 100Mb empty file called data. mkfile 100m data.
While the file creation I did a zpool iostat -v ourpool too see the IO traffic in the pool. Note that there’s traffic on both disks as they form a mirror.
We will create and save a file of md5 checksum of date to be able to check its integrity later, md5sum data > data.md5. Too see if a checksum matches we do a md5sum –check data.md5.
Now comes the critical part of this simulation. We will simulate a physical defect on the disc. Storage devices will fail at some point, but we don’t know when. When it happens it can corrupt your data or stop important applications.
Let’s get 20Mb of garbage from /dev/urandom e throw them in the disk c4d1, dd if=/dev/urandom of=/dev/dsk/c4d1 bs=1024 count=20480. There’s more fun (and expensive) ways to case physical defects in a disk, take a look into this video where they use ZFS and hammers. 🙂
Ready, the damage was done. Let’s look the pool status, zpool status ourpool.
We see no error but the ZFS uses strongly memory cache. Let’s force clean this cache by disabling and enabling the pool. First cd / to assure we are not into the pool, so zpool export ourpool followed by zpool import ourpool.
Checking it’s status again, zpool status ourpool.
Pool remains ONLINE but ZFS noticed that something is wrong.
Let see the data integrity, md5sum –check data.md5.
Data are intact.
This is one of the characteristic of self healing in ZFS. The corruption that occurred in one volume was silently repaired. In a traditional volume manager you would not only lost our data but not event know that a corruption has occurred.
In this point the system administrator should be warmed to take some action on the defective disk. Here some advices:
- Find out the defective disk: if the disk fails once so is probably that it’ll fail again or even take others disks to fail. ZFS have a mechanism called scrubbing that scan blocks finding out checksum erros and trying to correct them using the safe data. A zpool scrub ourpool will force the scrubbing process, that will run in background. After that If you look at the pool status zpool status ourpool you can see which disk is the defective one.
- Look the pool history: you can examine all pool history and understand all that happening before you came. A zpool history ourpool will show all commands that was used since its creation.
- Repair de mirror: a zpool clean ourpool will repair the mirror, but keeps the defective disk, what can be dangerous.
- Turn off the defective disk: you can turn off it using a zpool offline ourpool c4d1 without alter the pool structure.
- Unmirror the pool: with a zpool detach ourpool c4d1 you can remove the device from the pool, but as the mirror was composed of two devices, it’s no longer a mirror.
- Change the defective disk: if you have another disk, like c6d1, you put it in the place of the defective disk and it’ll assume it role in the mirror. For that use a zpool replace c4d1 c6d1. This will start in background a process called resilvering, but that is subject for another post. 🙂
I also did a screencast the resumes the entire process:
Video download: opensolaris_zpool_mirror.mpeg.
Additional Documentation:
- Self Healing with ZFS
- ZFS Best Practices Guide
- OpenSolaris ZFS Documentation Page
- Solaris ZFS Administration Guide
- ZFS, Sun’s Cutting-edge File System
- VÃdeos about OpenSolaris (in portuguese)
This post is a english translation for this post.