JAVA eXpress in English

JAVA eXpress, Polish magazine about (yes, you guessed it right) Java, from now on is accessible in English. You can get it from http://www.javaexpress.pl/

In this issue:

• Introduction to Grails
• Problems of large J2EE applications
• Graphical Modelling Framework
• J2ME: Objects Serialization
• XML in JAVA - XStream Library
• TeamCity: pre-tested commit
• Express killers, part III
• GroovyMag review - June 2009
• Layering

Check it out and have a nice reading :)

Google Chrome on Linux with Flash

For some time now I am using Google Chrome. I like it, because it is extremely fast. Quite a blocker for using it as a preferred browser was lack of Flash plugin. Now I have Flash thanks to author of this blog.

All you need to do:
1. Download and extract Adobe Flash player plugin for Firefox from here. Download 32bit version, even if you are using 64bit linux.
2. Go to /opt/google/chrome and create directory plugins.
3. Copy libflashplayer.so to this directory
4. Run google-chrome --enable-plugins

Enjoy :)

Setting up backup by rsync

I want to backup my files on another server. So I go to another server, and create file /etc/rsyncd.conf:

secrets file = /etc/rsyncd.secrets
#Global properties
read only = yes
list = yes
#User on server
uid = backup
#User's group
gid = backup

#Protected share for backups.
[files]
comment = For your eyes only
path = /home/backup/
auth users = franek
read only = no
hosts allow = 192.168.1.64
hosts deny = *
list = yes

We are using user backup as rsync files owner. Don't forget to create him.

So now we need to create entry for franek in rsyncd.secrets:

franek:his_password

rsyncd.secrets cannot be readable for all. In such case rsync daemon will not allow access to protected shares. Set permissions to 600.

We need to do one more thing before starting the daemon. Go to /etc/default/rsync and set RSYNC_ENABLE=true

Ok, issue sudo /etc/init.d/rsync start and rsync deamon is running.

Now go to the client machine. The one we want to make backups from. I want to backup whole /home, so my command looks like this:

sudo rsync -aXAvz --delete --delete-excluded --exclude-from=$DIR/backup.excludes --password-file=$DIR/rsync-pass /home franek@moon::files

So there is sudo rsync, and then some options:

-a the same as -rlptgoD, which is:
-r recurse into directories
-l copy symlinks as symlinks
-p preserve permissions
-t preserve modification times
-g preserve group
-o preserve owner
-D preserve device files, preserve special files
-X preserve extended attributes
-A preserve ACLs
-v be verbose
-z use compression

Then there is --delete and --delete-excluded. It means if there is some file on copy, but there is no such file on source, delete file from copy. --delete-excluded means delete all excluded files from copy.

I keep exclusions patterns in separate file. Format is quite simple:

lost+found
*/.Trash/
*/.thumbnails/
cache/
Cache/
.Cache/
.cache/

My share is password protected. Only user franek can access it, and he needs to give his password. If you want to do it by system (e.g. cron), you don't have the possibility to type the password. However, you can put it into file and make file readable only for user (permissions 700). Then you can just point to that file with --password-file option.

Next there is just source and destination. Just like in cp or smb. Source is pretty simple in my example. Destination is a bit more complicated: <user>@<server>::<share-name>

Setting samba on ubuntu server for sharing files

I am building home server, so now I want to configure it in a way so I could put photos there, and everyone could access them.

I assume samba is already initialized.

Guest access
We want everybody to be able to store files there, and everybody to be able to read them. So let's give guest access to it. But somebody has to be the owner of the files, right? (In terms of Unix file ownership, chown). So we neet to tell who guest user maps to. Lets call our Unix user henry:

sudo adduser henry

Set some password too.

Now, let's tell samba that guest should map to henry. In /etc/samba/smb.conf in [global] section:

guest account = henry

We are ready to create share for everybody now. Again, in /etc/samba/smb.conf:

[for-all]
path = /home/henry
browsable = yes
read only = no
guest ok = yes
create mask = 644

Now we created share called "for-all", it is stored at /home/henry, and everybody can read and write it. Files put to server into for-all share are going to be read-write for owner (henry), and read for everyone. However, it is not so important as everybody can access them like owner through samba.

Users access
We can also make it available only for users. Let's say we want samba user henry:

sudo smbpasswd -a henry

Set password. User created.

Now we need to disable guest access:

guest ok = no

Now we can connect from another machine by smbclient:

smbclient //192.168.1.1/for-all -U henry

Of course put your server's IP instead of 192.168.1.1

Mount as fs for users manually
You can mount samba share to some directory on your client machine. Just like some filesystem. Install smbfs package:

sudo apt-get install smbfs

If you have sudo access, you can mount samba share. First, create directory to mount it:

mkdir smb-share

Now, mount share:

sudo mount -t cifs //192.168.1.1/for-all smb-share -o username=henry,noexec,uid=local_user,gid=local_group

noexec means you'll be not able to run any executable files from that share. uid and gid will render all files in mounted share to belong to user local_user and group local_group on client.

If you want more users to be able to mount the share, you can create group for them:

sudo addgroup samba

Now let's give this group rights to mount remote samba shares. Run:

sudo visudo

And in the group section add following line:

%samba   ALL=(ALL) /bin/mount,/bin/umount,/sbin/mount.cifs,/sbin/umount.cifs

Add user frank to that group:

sudo adduser frank samba

From now on, frank can mount samba shares.

Configure postfix to send emails for root to your account

Goal: make our small ubuntu server forward email which has "to: root" to your private mail.

Install postfix.

sudo apt-get install postfix

Some console app for sending emails can be handy too:

sudo apt-get install mutt

Edit /etc/postfix/main.cf. In mydestination enter host, host.domain, localhost.domain, and also empty domain:

mydestination = serverek.przepompownia.com, localhost.przepompownia.com, , localhost

Restart postfix. I'm not sure if it is really needed, but won't hurt ;)

sudo /etc/init.d/postfix restart

Ok, now edit /etc/aliases. Add something like this:

root: franek
franek: mickey@my.mail.com

Dont forget to run:

sudo newaliases

This way everything sent to root is forwarded to franek, and everything sent to franek is forwarded to mickey@my.mail.com

Now you can try sending some mail to "root". You can use mutt for this.
UPDATE:
Recently my ISP (neostrada, TPSA) blocked outgoing connections to port 25 (standard port for connecting with SMTP servers). What to do to send emails to port 587 is well described here. Author only forgot to add that you also need this:

transport_maps = hash:/etc/postfix/transport

in your main.cf

JavaFX - Operations on Strings

Use any quote you like

Ok, so let's start with Strings. You can use both single and double quote to define simple String. Both works:

var a = 'Single';
var b = "Double";

Also you can use another quote in String as part of this String. I.e. if you use single quote to declare String, you can put double quote inside, and if you use double one, you can put single one inside.

var a = 'This is String "with double quote" inside';
var b = "This is String 'with single quote' inside";

Both are valid Strings. However, if you need to use both types in your String, you have to escape it:

var a = 'Here we have "double quotes" and \'single quotes\' in one String';
var b = "And 'here' \"too!\""

Expressions in String

In JavaFX you can also embed expressions in Strings. To do it, put expression in curly brackets:

println("2 + 3 = {2+3}");

This code prints: 2 + 3 = 5 By the way, you can see new println function here. It is in javafx.lang.Builtins, which is included automatically in all JavaFX scripts.

As expression, you can use also variables, function calls, operations on variables (like in example above) etc.

Concatenation

You don't need any operator to concatenate Strings. If you split String over few lines, you don't have to add "+" at the end of each line.

var one = "This" 'is'
"one"
'String';
println(one);

And it outputs: ThisisoneString

Formatting

You can quite easy format Strings in JavaFX. It is based on java.util.Formatter class.

println("{%x 12}");
println("{%c 120}");
var d = Date{};    //Here new java.util.Date is created
println("{%tH d}:{%tM d}:{%tS d}")

And it prints:
c x 23:12:18 First there is 12 in hex, then there is character, which code in Unicode is 120, and then it is Date object, first we get hour from it, then minute, and then second.

Localization

Localization in JFX is realized by properties files. It's name is connected with your script (file with your JFX code) by name convention. If your script is House.fx, then your localization file is House_en.fxproperties and it has to be somewhere in the classpath. fxproperties file looks like this:

"dog"="pies"
"cat"="kot"

And then, to use it in script:

println(##"dog");
println(##[cat]"Cat");

If there is fxproperties found, it is used. If not found, default is used. Default is either properties key (like "dog" in above example) or another word (like "Cat", not "cat" which is only fxproperties key).

JavaFX - Defining simple variables.

Ok, so I thought to write JavaFX tutorial. Hope it's going to be useful for somebody. Welcome to part one, about language basics, defining variables and values.

First, you should know what variables/value types are available. There are all the familiar ones (String, Long, Double etc.), but no primitives (long, double etc.). Well, in JavaFX everything is an object. Really. There is also one new type: Duration. It is especially useful in animations, but we'll get to it later.

So there are variables and values. Values are a little like final constants in Java, but only a little. Value of value ( ;) ) can change, but you can't change it explicitly. It can be changed by binding - we'll talk about it in some later part.

So how do you define variables and values? Quite simple:

var a:Float = 5;

Defines variable a of type Float. We can also do something like this:

var a = 5;

Where is variable's type? Well, you don't need to specify it in such case. Type is inferred automatically by JavaFX Script compiler from value assigned to this variable. Isn't it obvious that it is Integer? It could be also Float, yes, and if you want it to be Float, please specify it like in first example.

What about "almost-like-java-constants" values? You define it like that:

def a:Float = 5;

So now there is value defined, and you can't change it. a = 6 will not compile.

Ok, let's look at this new Duration type. Few examples:

var s = 5s;
var m = 2m;
var h = 4h;

s is 5 seconds, m is 2 minutes and h is 4 hours. Quite simple, isn't it? Also arithmetics like adding, multiplying etc works here:

var s = 5s * 4;
var m = 2m + 3m;
var h = (2h + 3m) * 4;

Ok, that's all in this part. In the next one I'll write something about String operations and sequences. Stay tuned!