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  • Real-world examples of populating a GWT CellTable using a clean MVP pattern?

    - by piehole
    We are using the GWT-Presenter framework and attempting to use CellTable to put together an updateable grid. It seems as though several of the GWT constructs for CellTable don't lend themselves to easily breaking up the logic into clean view and presenter code. Examples: 1) Within the View's constructor, the CellTable is defined and each column is created by anonymous inner classes that extend the Column class to provide the onValue() method. 2) The FieldUpdater interface must be implemented to provide logic to execute when a user alters data in a cell. This seems like it would best fit in the Presenter's onBind() method, but FieldUpdaters often need access to the Cell or Column which belong in the view. CellTable does not have accessor methods to get hold of the Columns or Cells, so it seems the only way for the Presenter to get them is for me to create a multitude of member variables on the View and accessors on my Display interface. Can anyone provide good examples for dealing with CellTable in GWT-Presenter or a comparable MVP

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  • scala 2.8.0.RC2 compiler problem on pattern matching statement?

    - by gruenewa
    Why does the following module not compile on Scala 2.8.RC[1,2]? object Test { import util.matching.Regex._ val pVoid = """\s*void\s*""".r val pVoidPtr = """\s*(const\s+)?void\s*\*\s*""".r val pCharPtr = """\s*(const\s+)GLchar\s*\*\s*""".r val pIntPtr = """\s*(const\s+)?GLint\s*\*\s*""".r val pUintPtr = """\s*(const\s+)?GLuint\s*\*\s*""".r val pFloatPtr = """\s*(const\s+)?GLfloat\s*\*\s*""".r val pDoublePtr = """\s*(const\s+)?GLdouble\s*\*\s*""".r val pShortPtr = """\s*(const\s+)?GLshort\s*\*\s*""".r val pUshortPtr = """\s*(const\s+)?GLushort\s*\*\s*""".r val pInt64Ptr = """\s*(const\s+)?GLint64\s*\*\s*""".r val pUint64Ptr = """\s*(const\s+)?GLuint64\s*\*\s*""".r def mapType(t: String): String = t.trim match { case pVoid() => "Unit" case pVoidPtr() => "ByteBuffer" case pCharPtr() => "CharBuffer" case pIntPtr() | pUintPtr() => "IntBuffer" case pFloatPtr() => "FloatBuffer" case pShortPtr() | pUshortPtr() => "ShortBuffer" case pDoublePtr() => "DoubleBuffer" case pInt64Ptr() | pUint64Ptr() => "LongBuffer" case x => x } }

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  • Would Python's Twisted library be the best case for an observer type pattern?

    - by beagleguy
    hi all, I'm developing a system where a queue will be filled with millions of items I need a process that reads items from the queue constantly and then sends those items out to registered clients. I'm thinking about using twisted for this, having the queue reader be a twisted server listening on a tcp port then clients can connect on that port and when an item is pulled from the queue the server writes it out to all the clients. Does that sound like something that twisted would be ideal for? Does anyone know of any sample code out there that may do something similar? thanks

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  • Where does the query language sit within the MVC pattern?

    - by weesilmania
    I'd assume that since the query language sits within the controller (typically) that it belongs to that component, but if I play devil's advocate I'd argue that the query language is execute within the domain of the model, and is tightly coupled to that component so it might also be a part of it. Anyone know the answer? Is there a straight answer or is it technology specific?

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  • Post-back + Page Refresh. Post/Redirect/Get pattern alternatives?

    - by Andrew Florko
    When user posts back a web form and then tries to refresh the page - dialog "would you like to resend information" pops up (Opera works silently though). To avoid this we can redirect browser to the page we'd like to show after postback. Now, when user refreshes the page, he duplicates get-request and no pop-ups. Everything is ok but post/redirect/get approach requires additional roundtrip. Is there better alternatives. Send form data with ajax aynchronously, for example? Thank you in advance!

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  • Scala, represent pattern of boolean tuple into something else.

    - by Berlin Brown
    This is a cellular automata rule (input Boolean == Left, Center, Right Cell) and output Boolean . What is a better way to represent this in Scala. trait Rule { def ruleId() : Int def rule(inputState:(Boolean, Boolean, Boolean)) : Boolean override def toString : String = "Rule:" + ruleId } class Rule90 extends Rule { def ruleId() = 90 def rule(inputState:(Boolean, Boolean, Boolean)) : Boolean = { // Verbose version, show all 8 states inputState match { case (true, true, true) => false case (true, false, true) => false case (false, true, false) => false case (false, false, false) => false case _ => true } } }

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  • How to implement the API/SPI Pattern in Java?

    - by Adam Tannon
    I am creating a framework that exposes an API for developers to use: public interface MyAPI { public void doSomeStuff(); public int getWidgets(boolean hasRun); } All the developers should have to do is code their projects against these API methods. I also want them to be able to place different "drivers"/"API bindings" on the runtime classpath (the same way JDBC or SLF4J work) and have the API method calls (doSomeStuff(), etc.) operate on different 3rd party resources (files, servers, whatever). Thus the same code and API calls will map to operations on different resources depending on what driver/binding the runtime classpath sees (i.e. myapi-ftp, myapi-ssh, myapi-teleportation). How do I write (and package) an SPI that allows for such runtime binding, and then maps MyAPI calls to the correct (concrete) implementation? In other words, if myapi-ftp allows you to getWidgets(boolean) from an FTP server, how would I could this up (to make use of both the API and SPI)? Bonus points for concrete, working Java code example! Thanks in advance!

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  • MVC design pattern in complex iPad app: is one fat controller acceptable?

    - by nutsmuggler
    I am building a complex iPad application; think of it as a scrapbook. For the purpose of this question, let's consider a page with two images over it. My main view displays my doc data rendered as a single UIImage; this because I need to do some global manipulation over them. This is my DisplayView. When editing I need to instantiate an EditorView with my two images as subviews; this way I can interact with a single image, (rotate it, scale it, move it). When editing is triggered, I hide my DisplayView and show my EditorView. In a iPhone app, I'd associate each main view (that is, a view filling the screen) to a view controller. The problem is here there is just one view controller; I've considered passing the EditorView via a modal view controller, but it's not an option (there a complex layout with a mask covering everything and palettes over it; rebuilding it in the EditorView would create duplicate code). Presently the EditorView incorporates some logic (loads data from the model, invokes some subviews for fine editing, saves data back to the model); EditorView subviews also incorporate some logic (I manipulate images and pass them back to the main EditorView). I feel this logic belongs more to a controller. On the other hand, I am not sure making my only view controller so fat a good idea. What is the best, cocoa-ish implementation of such a class structure? Feel free to ask for clarifications. Cheers.

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  • UI Design - design pattern for city/country drop down? (ASP.NET MVC)

    - by JK
    What is the best way to do a city/country dropdown pair in ASP.NET MVC? I see lots of places with country above city, but that's unnatural: in real life we write city/country. I've used city, then country, but the problem is that the user then has to go backwards after changing the country. The other problem is what do you do about cities/countries not in your list? If city/country are both drop downs, then the user cant type their own city if it is missing. But if you have a dropdown and a textbox, that makes it unwieldy (you end up with 4 controls to enter 2 pieces of data). Are there any examples websites where the city/country dropdown pair are done in a very useable and clear manner?

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  • About presenter pattern in rails. is a better way to do it?

    - by Totty
    I have in my model: def presenter @presenter ||= ProfilePresenter.new(self) @presenter end The ProfilePresenter is a class that has methods like, get_link(), get_img_url(size), get_sex(), get_relationship_status() and other methods that have not to do with the model, not even with the controller but is used multiple times in the view. So now i use them by doing this: Profile.presenter.get_link # or Profile.presenter.get_img_url('thumb') # returns the path of the image. is not used to make a db query

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  • How to make URL pattern like app.example.com?

    - by abc
    I have my domain say "example.com" (java, GlassFish Web Server) Now I have 3 application.. say A,B,C. Now what I want is, if user hit a.example.com OR example.com/X then A application should get invoked. similarly for B and C. b.example.com or example.com/B, c.example.com or example.com/C. like mail.google.com news.google.com. How to configure this? I couldn't query it in Google as I didn't know how to query for this exactly. So posted here. Thankx guyz in advance.

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  • What is Rails way to DRY up the controller pattern of verifying :id is for a valid object (else redirect to error page)

    - by jpwynn
    One of my controllers has close to 100 methods (eg routes) and nearly every one starts out the same code to redirect to an error page if the id param is invalid, followed by a similar check if the user that id doesn't belong in the user's account: def something @foo = Foo.find_by_guid(params[:id]) unless @foo @msg ||= { :title => 'No such page!', :desc => "There is no such page!" } render :action => "error" and return end unless @foo.owner_id == current_user.id @msg ||= { :title => 'Really?', :desc => "There is no such page." } render :action => "error" and return end What is the best way to DRY up that sort of page id and owner id validation, given the code is doing a render ... and return? What I don't want to do at this point is offload it to a blackbox roles and permissions library like CanCan... my goal is simply to have the in-app code to handle this be as clean as possible.

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  • Retrieve Performance Data from SOA Infrastructure Database

    - by fip
    My earlier blog posting shows how to enable, retrieve and interpret BPEL engine performance statistics to aid performance troubleshooting. The strength of BPEL engine statistics at EM is its break down per request. But there are some limitations with the BPEL performance statistics mentioned in that blog posting: The statistics were stored in memory instead of being persisted. To avoid memory overflow, the data are stored to a buffer with limited size. When the statistic entries exceed the limitation, old data will be flushed out to give ways to new statistics. Therefore it can only keep the last X number of entries of data. The statistics 5 hour ago may not be there anymore. The BPEL engine performance statistics only includes latencies. It does not provide throughputs. Fortunately, Oracle SOA Suite runs with the SOA Infrastructure database and a lot of performance data are naturally persisted there. It is at a more coarse grain than the in-memory BPEL Statistics, but it does have its own strengths as it is persisted. Here I would like offer examples of some basic SQL queries you can run against the infrastructure database of Oracle SOA Suite 11G to acquire the performance statistics for a given period of time. You can run it immediately after you modify the date range to match your actual system. 1. Asynchronous/one-way messages incoming rates The following query will show number of messages sent to one-way/async BPEL processes during a given time period, organized by process names and states select composite_name composite, state, count(*) Count from dlv_message where receive_date >= to_timestamp('2012-10-24 21:00:00','YYYY-MM-DD HH24:MI:SS') and receive_date <= to_timestamp('2012-10-24 21:59:59','YYYY-MM-DD HH24:MI:SS') group by composite_name, state order by Count; 2. Throughput of BPEL process instances The following query shows the number of synchronous and asynchronous process instances created during a given time period. It list instances of all states, including the unfinished and faulted ones. The results will include all composites cross all SOA partitions select state, count(*) Count, composite_name composite, component_name,componenttype from cube_instance where creation_date >= to_timestamp('2012-10-24 21:00:00','YYYY-MM-DD HH24:MI:SS') and creation_date <= to_timestamp('2012-10-24 21:59:59','YYYY-MM-DD HH24:MI:SS') group by composite_name, component_name, componenttype order by count(*) desc; 3. Throughput and latencies of BPEL process instances This query is augmented on the previous one, providing more comprehensive information. It gives not only throughput but also the maximum, minimum and average elapse time BPEL process instances. select composite_name Composite, component_name Process, componenttype, state, count(*) Count, trunc(Max(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MaxTime, trunc(Min(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MinTime, trunc(AVG(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) AvgTime from cube_instance where creation_date >= to_timestamp('2012-10-24 21:00:00','YYYY-MM-DD HH24:MI:SS') and creation_date <= to_timestamp('2012-10-24 21:59:59','YYYY-MM-DD HH24:MI:SS') group by composite_name, component_name, componenttype, state order by count(*) desc;   4. Combine all together Now let's combine all of these 3 queries together, and parameterize the start and end time stamps to make the script a bit more robust. The following script will prompt for the start and end time before querying against the database: accept startTime prompt 'Enter start time (YYYY-MM-DD HH24:MI:SS)' accept endTime prompt 'Enter end time (YYYY-MM-DD HH24:MI:SS)' Prompt "==== Rejected Messages ===="; REM 2012-10-24 21:00:00 REM 2012-10-24 21:59:59 select count(*), composite_dn from rejected_message where created_time >= to_timestamp('&&StartTime','YYYY-MM-DD HH24:MI:SS') and created_time <= to_timestamp('&&EndTime','YYYY-MM-DD HH24:MI:SS') group by composite_dn; Prompt " "; Prompt "==== Throughput of one-way/asynchronous messages ===="; select state, count(*) Count, composite_name composite from dlv_message where receive_date >= to_timestamp('&StartTime','YYYY-MM-DD HH24:MI:SS') and receive_date <= to_timestamp('&EndTime','YYYY-MM-DD HH24:MI:SS') group by composite_name, state order by Count; Prompt " "; Prompt "==== Throughput and latency of BPEL process instances ====" select state, count(*) Count, trunc(Max(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MaxTime, trunc(Min(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) MinTime, trunc(AVG(extract(day from (modify_date-creation_date))*24*60*60 + extract(hour from (modify_date-creation_date))*60*60 + extract(minute from (modify_date-creation_date))*60 + extract(second from (modify_date-creation_date))),4) AvgTime, composite_name Composite, component_name Process, componenttype from cube_instance where creation_date >= to_timestamp('&StartTime','YYYY-MM-DD HH24:MI:SS') and creation_date <= to_timestamp('&EndTime','YYYY-MM-DD HH24:MI:SS') group by composite_name, component_name, componenttype, state order by count(*) desc;  

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  • Nagios plugin script not working as expected

    - by Linker3000
    I have modified an off-the-shelf Nagios plugin perl script to (in theory) return a one or zero according to the existence, or not, of a file on a remote linux server. The script runs a remote ssh session and logs in as the nagios user. The remote linux servers have private keys setup for that user, and on the bash command line the script works as expected, but when run as a plugin it always returns '1' (true) even if the file does not exist. Some help with the logic or a comment on why things are not working as expected within Nagios would be appreciated. I'd prefer to use this ssh login method rather than having to install nrpe on all the linux servers. To run from a command line (assuming remote server has a user called nagios with a valid private key): ./check_reboot_required -e ssh -H remote-servers-ip-addr -p 'filename-to-check' -v Ta. #! /usr/bin/perl -w # # # License Information: # This program is free software; you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation; either version 2 of the License, or # (at your option) any later version. # # This program is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with this program; if not, write to the Free Software # Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. # ############################################################################ use POSIX; use strict; use Getopt::Long; use lib "/usr/lib/nagios/plugins" ; use vars qw($host $opt_V $opt_h $opt_v $verbose $PROGNAME $pattern $opt_p $mmin $opt_e $opt_t $opt_H $status $state $msg $msg_q $MAILQ $SHELL $device $used $avail $percent $fs $blocks $CMD $RMTOS); use utils qw(%ERRORS &print_revision &support &usage ); sub print_help (); sub print_usage (); sub process_arguments (); $ENV{'PATH'}=''; $ENV{'BASH_ENV'}=''; $ENV{'ENV'}=''; $PROGNAME = "check_reboot_required"; Getopt::Long::Configure('bundling'); $status = process_arguments(); if ($status){ print "ERROR: processing arguments\n"; exit $ERRORS{'UNKNOWN'}; } $SIG{'ALRM'} = sub { print ("ERROR: timed out waiting for $CMD on $host\n"); exit $ERRORS{'WARNING'}; }; $host = $opt_H; $pattern = $opt_p; print "Pattern >" . $pattern . "< " if $verbose; alarm($opt_t); #$CMD = "/usr/bin/find " . $pattern . " -type f 2>/dev/null| /usr/bin/wc -l"; $CMD = "[ -f " . $pattern . " ] && echo 1 || echo 0"; alarm($opt_t); ## get cmd output from remote system if (! open (OUTPUT, "$SHELL $host $CMD|" ) ) { print "ERROR: could not open $CMD on $host\n"; exit $ERRORS{'UNKNOWN'}; } my $perfdata = ""; my $state = "3"; my $msg = "Indeterminate result"; # only first line is relevant in this iteration. while (<OUTPUT>) { my $result = chomp($_); $msg = $result; print "Shell returned >" . $result . "< length is " . length($result) . " " if $verbose; if ( $result == 1 ) { $msg = "Reboot required (NB: Result still not accurate)" . $result ; $state = $ERRORS{'WARNING'}; last; } elsif ( $result == 0 ) { $msg = "No reboot required (NB: Result still not accurate) " . $result ; $state = $ERRORS{'OK'}; last; } else { $msg = "Output received, but it was neither a 1 nor a 0" ; last; } } close (OUTPUT); print "$msg | $perfdata\n"; exit $state; ##################################### #### subs sub process_arguments(){ GetOptions ("V" => \$opt_V, "version" => \$opt_V, "v" => \$opt_v, "verbose" => \$opt_v, "h" => \$opt_h, "help" => \$opt_h, "e=s" => \$opt_e, "shell=s" => \$opt_e, "p=s" => \$opt_p, "pattern=s" => \$opt_p, "t=i" => \$opt_t, "timeout=i" => \$opt_t, "H=s" => \$opt_H, "hostname=s" => \$opt_H ); if ($opt_V) { print_revision($PROGNAME,'$Revision: 1.0 $ '); exit $ERRORS{'OK'}; } if ($opt_h) { print_help(); exit $ERRORS{'OK'}; } if (defined $opt_v ){ $verbose = $opt_v; } if (defined $opt_e ){ if ( $opt_e eq "ssh" ) { if (-x "/usr/local/bin/ssh") { $SHELL = "/usr/local/bin/ssh"; } elsif ( -x "/usr/bin/ssh" ) { $SHELL = "/usr/bin/ssh"; } else { print_usage(); exit $ERRORS{'UNKNOWN'}; } } elsif ( $opt_e eq "rsh" ) { $SHELL = "/usr/bin/rsh"; } else { print_usage(); exit $ERRORS{'UNKNOWN'}; } } else { print_usage(); exit $ERRORS{'UNKNOWN'}; } unless (defined $opt_t) { $opt_t = $utils::TIMEOUT ; # default timeout } unless (defined $opt_H) { print_usage(); exit $ERRORS{'UNKNOWN'}; } return $ERRORS{'OK'}; } sub print_usage () { print "Usage: $PROGNAME -e <shell> -H <hostname> -p <directory/file pattern> [-t <timeout>] [-v verbose]\n"; } sub print_help () { print_revision($PROGNAME,'$Revision: 0.1 $'); print "\n"; print_usage(); print "\n"; print " Checks for the presence of a 'reboot-required' file on a remote host via SSH or RSH\n"; print "-e (--shell) = ssh or rsh (required)\n"; print "-H (--hostname) = remote server name (required)"; print "-p (--pattern) = File pattern for find command (default = /var/run/reboot-required)\n"; print "-t (--timeout) = Plugin timeout in seconds (default = $utils::TIMEOUT)\n"; print "-h (--help)\n"; print "-V (--version)\n"; print "-v (--verbose) = debugging output\n"; print "\n\n"; support(); }

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  • Trying to parse links in an HTML directory listing using Java regex

    - by DiskCrasher
    Ok I know everyone is going to tell me not to use RegEx for parsing HTML, but I'm programming on Android and don't have ready access to an HTML parser (that I'm aware of). Besides, this is server generated HTML which should be more consistent than user-generated HTML. The regex looks like this: Pattern patternMP3 = Pattern.compile( "<A HREF=\"[^\"]+.+\\.mp3</A>", Pattern.CASE_INSENSITIVE | Pattern.UNICODE_CASE); Matcher matcherMP3 = patternMP3.matcher(HTML); while (matcherMP3.find()) { ... } The input HTML is all on one line, which is causing the problem. When the HTML is on separate lines this pattern works. Any suggestions?

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  • JavaScript Class Patterns

    - by Liam McLennan
    To write object-oriented programs we need objects, and likely lots of them. JavaScript makes it easy to create objects: var liam = { name: "Liam", age: Number.MAX_VALUE }; But JavaScript does not provide an easy way to create similar objects. Most object-oriented languages include the idea of a class, which is a template for creating objects of the same type. From one class many similar objects can be instantiated. Many patterns have been proposed to address the absence of a class concept in JavaScript. This post will compare and contrast the most significant of them. Simple Constructor Functions Classes may be missing but JavaScript does support special constructor functions. By prefixing a call to a constructor function with the ‘new’ keyword we can tell the JavaScript runtime that we want the function to behave like a constructor and instantiate a new object containing the members defined by that function. Within a constructor function the ‘this’ keyword references the new object being created -  so a basic constructor function might be: function Person(name, age) { this.name = name; this.age = age; this.toString = function() { return this.name + " is " + age + " years old."; }; } var john = new Person("John Galt", 50); console.log(john.toString()); Note that by convention the name of a constructor function is always written in Pascal Case (the first letter of each word is capital). This is to distinguish between constructor functions and other functions. It is important that constructor functions be called with the ‘new’ keyword and that not constructor functions are not. There are two problems with the pattern constructor function pattern shown above: It makes inheritance difficult The toString() function is redefined for each new object created by the Person constructor. This is sub-optimal because the function should be shared between all of the instances of the Person type. Constructor Functions with a Prototype JavaScript functions have a special property called prototype. When an object is created by calling a JavaScript constructor all of the properties of the constructor’s prototype become available to the new object. In this way many Person objects can be created that can access the same prototype. An improved version of the above example can be written: function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { toString: function() { return this.name + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); In this version a single instance of the toString() function will now be shared between all Person objects. Private Members The short version is: there aren’t any. If a variable is defined, with the var keyword, within the constructor function then its scope is that function. Other functions defined within the constructor function will be able to access the private variable, but anything defined outside the constructor (such as functions on the prototype property) won’t have access to the private variable. Any variables defined on the constructor are automatically public. Some people solve this problem by prefixing properties with an underscore and then not calling those properties by convention. function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { _getName: function() { return this.name; }, toString: function() { return this._getName() + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); Note that the _getName() function is only private by convention – it is in fact a public function. Functional Object Construction Because of the weirdness involved in using constructor functions some JavaScript developers prefer to eschew them completely. They theorize that it is better to work with JavaScript’s functional nature than to try and force it to behave like a traditional class-oriented language. When using the functional approach objects are created by returning them from a factory function. An excellent side effect of this pattern is that variables defined with the factory function are accessible to the new object (due to closure) but are inaccessible from anywhere else. The Person example implemented using the functional object construction pattern is: var personFactory = function(name, age) { var privateVar = 7; return { toString: function() { return name + " is " + age * privateVar / privateVar + " years old."; } }; }; var john2 = personFactory("John Lennon", 40); console.log(john2.toString()); Note that the ‘new’ keyword is not used for this pattern, and that the toString() function has access to the name, age and privateVar variables because of closure. This pattern can be extended to provide inheritance and, unlike the constructor function pattern, it supports private variables. However, when working with JavaScript code bases you will find that the constructor function is more common – probably because it is a better approximation of mainstream class oriented languages like C# and Java. Inheritance Both of the above patterns can support inheritance but for now, favour composition over inheritance. Summary When JavaScript code exceeds simple browser automation object orientation can provide a powerful paradigm for controlling complexity. Both of the patterns presented in this article work – the choice is a matter of style. Only one question still remains; who is John Galt?

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  • JavaScript Class Patterns

    - by Liam McLennan
    To write object-oriented programs we need objects, and likely lots of them. JavaScript makes it easy to create objects: var liam = { name: "Liam", age: Number.MAX_VALUE }; But JavaScript does not provide an easy way to create similar objects. Most object-oriented languages include the idea of a class, which is a template for creating objects of the same type. From one class many similar objects can be instantiated. Many patterns have been proposed to address the absence of a class concept in JavaScript. This post will compare and contrast the most significant of them. Simple Constructor Functions Classes may be missing but JavaScript does support special constructor functions. By prefixing a call to a constructor function with the ‘new’ keyword we can tell the JavaScript runtime that we want the function to behave like a constructor and instantiate a new object containing the members defined by that function. Within a constructor function the ‘this’ keyword references the new object being created -  so a basic constructor function might be: function Person(name, age) { this.name = name; this.age = age; this.toString = function() { return this.name + " is " + age + " years old."; }; } var john = new Person("John Galt", 50); console.log(john.toString()); Note that by convention the name of a constructor function is always written in Pascal Case (the first letter of each word is capital). This is to distinguish between constructor functions and other functions. It is important that constructor functions be called with the ‘new’ keyword and that not constructor functions are not. There are two problems with the pattern constructor function pattern shown above: It makes inheritance difficult The toString() function is redefined for each new object created by the Person constructor. This is sub-optimal because the function should be shared between all of the instances of the Person type. Constructor Functions with a Prototype JavaScript functions have a special property called prototype. When an object is created by calling a JavaScript constructor all of the properties of the constructor’s prototype become available to the new object. In this way many Person objects can be created that can access the same prototype. An improved version of the above example can be written: function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { toString: function() { return this.name + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); In this version a single instance of the toString() function will now be shared between all Person objects. Private Members The short version is: there aren’t any. If a variable is defined, with the var keyword, within the constructor function then its scope is that function. Other functions defined within the constructor function will be able to access the private variable, but anything defined outside the constructor (such as functions on the prototype property) won’t have access to the private variable. Any variables defined on the constructor are automatically public. Some people solve this problem by prefixing properties with an underscore and then not calling those properties by convention. function Person(name, age) { this.name = name; this.age = age; } Person.prototype = { _getName: function() { return this.name; }, toString: function() { return this._getName() + " is " + this.age + " years old."; } }; var john = new Person("John Galt", 50); console.log(john.toString()); Note that the _getName() function is only private by convention – it is in fact a public function. Functional Object Construction Because of the weirdness involved in using constructor functions some JavaScript developers prefer to eschew them completely. They theorize that it is better to work with JavaScript’s functional nature than to try and force it to behave like a traditional class-oriented language. When using the functional approach objects are created by returning them from a factory function. An excellent side effect of this pattern is that variables defined with the factory function are accessible to the new object (due to closure) but are inaccessible from anywhere else. The Person example implemented using the functional object construction pattern is: var john = new Person("John Galt", 50); console.log(john.toString()); var personFactory = function(name, age) { var privateVar = 7; return { toString: function() { return name + " is " + age * privateVar / privateVar + " years old."; } }; }; var john2 = personFactory("John Lennon", 40); console.log(john2.toString()); Note that the ‘new’ keyword is not used for this pattern, and that the toString() function has access to the name, age and privateVar variables because of closure. This pattern can be extended to provide inheritance and, unlike the constructor function pattern, it supports private variables. However, when working with JavaScript code bases you will find that the constructor function is more common – probably because it is a better approximation of mainstream class oriented languages like C# and Java. Inheritance Both of the above patterns can support inheritance but for now, favour composition over inheritance. Summary When JavaScript code exceeds simple browser automation object orientation can provide a powerful paradigm for controlling complexity. Both of the patterns presented in this article work – the choice is a matter of style. Only one question still remains; who is John Galt?

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  • Exclude filter from certain url's

    - by Mads Mobæk
    I'm using a filter in web.xml to check if a user is logged in or not: <filter> <filter-name>LoginFilter</filter-name> <filter-class>com.mycompany.LoginFilter</filter-class> </filter> <filter-mapping> <filter-name>LoginFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> And this works like a charm until I have a stylesheet or image I want to exclude from this filter. I know one approach is to put everything that's protected inside /privateor similar, and then set the url-pattern to: <url-pattern>/private/*</url-pattern>. The downside to this is my URLs now looking like: http://www.mycompany.com/private/mypage instead of http://www.mycompany.com/mypage. Is there another solution to this problem, that let me keep my pretty-urls?

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  • Replace named group in regex

    - by Tomas Voracek
    I want to use regular expression same way as string.Format. I will explain I have: string pattern = "^(?<PREFIX>abc_)(?<ID>[0-9])+(?<POSTFIX>_def)$"; string input = "abc_123_def"; Regex regex = new Regex(pattern, RegexOptions.IgnoreCase); string replacement = "456"; Console.WriteLine(regex.Replace(input, string.Format("${{PREFIX}}{0}${{POSTFIX}}", replacement))); This works, but i must provide "input" to regex.Replace. I do not want that. I want to use pattern for matching but also for creating strings same way as with string format, replacing named group "ID" with value. Is that possible? I'm looking for something like: string pattern = "^(?<PREFIX>abc_)(?<ID>[0-9])+(?<POSTFIX>_def)$"; string result = ReplaceWithFormat(pattern, "ID", 999); Result will contain "abc_999_def". How to accomplish this?

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  • Java File and ByteArray or InputStream - please quick help

    - by Peter Perhác
    I want to use jFuge to play some MIDI music in an applet. There's a class for the MIDI pattern - Pattern - and the only method to load the pattern is from a File. Now, I don't know how applets load files and what not, but I am using a framework (PulpCore) that makes loading assets a simple task. If I need to grab an asset from a ZIP catalogue, I can use the Assets class which provides get() and getAsStream() methods. get() returns the given asset as a ByteArray, the other as an InputStream. I need jFuge to load the pattern from either ByteArray or InputStream. In pseudo-code, I would like to do this: Pattern.load(new File(Assets.get("mymidifile.midi"))); however there is no File constructor that would take a ByteArray. Suggestions, please?

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  • What is the C# equivalent of java.util.regex?

    - by peter.murray.rust
    I am converting Java code to C# and need to replace the use of Java's regex. A typical use is import java.util.regex.Matcher; import java.util.regex.Pattern; //... String myString = "B12"; Pattern pattern = Pattern.compile("[A-Za-z](\\d+)"); Matcher matcher = Pattern.matcher(myString); String serial = (matcher.matches()) ? matcher.group(1) : null; which should extract a capture group from a matched target string. I'd be grateful for simple examples. EDIT: I have now added the C# equivalent of the code as an answer. EDIT: Here is a tutorial on the use of the actual expressions. EDIT: Here is a useful comparison of C# and Java (and Perl.)

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  • Session Report - Modern Software Development Anti-Patterns

    - by Janice J. Heiss
    In this standing-room-only session, building upon his 2011 JavaOne Rock Star “Diabolical Developer” session, Martijn Verburg, this time along with Ben Evans, identified and explored common “anti-patterns” – ways of doing things that keep developers from doing their best work. They emphasized the importance of social interaction and team communication, along with identifying certain psychological pitfalls that lead developers astray. Their emphasis was less on technical coding errors and more how to function well and to keep one’s focus on what really matters. They are the authors of the highly regarded The Well-Grounded Java Developer and are both movers and shakers in the London JUG community and on the Java Community Process. The large room was packed as they gave a fast-moving, witty presentation with lots of laughs and personal anecdotes. Below are a few of the anti-patterns they discussed.Anti-Pattern One: Conference-Driven DeliveryThe theme here is the belief that “Real pros hack code and write their slides minutes before their talks.” Their response to this anti-pattern is an expression popular in the military – PPPPPP, which stands for, “Proper preparation prevents piss-poor performance.”“Communication is very important – probably more important than the code you write,” claimed Verburg. “The more you speak in front of large groups of people the easier it gets, but it’s always important to do dry runs, to present to smaller groups. And important to be members of user groups where you can give presentations. It’s a great place to practice speaking skills; to gain new skills; get new contacts, to network.”They encouraged attendees to record themselves and listen to themselves giving a presentation. They advised them to start with a spouse or friends if need be. Learning to communicate to a group, they argued, is essential to being a successful developer. The emphasis here is that software development is a team activity and good, clear, accessible communication is essential to the functioning of software teams. Anti-Pattern Two: Mortgage-Driven Development The main theme here was that, in a period of worldwide recession and economic stagnation, people are concerned about keeping their jobs. So there is a tendency for developers to treat knowledge as power and not share what they know about their systems with their colleagues, so when it comes time to fix a problem in production, they will be the only one who knows how to fix it – and will have made themselves an indispensable cog in a machine so you cannot be fired. So developers avoid documentation at all costs, or if documentation is required, put it on a USB chip and lock it in a lock box. As in the first anti-pattern, the idea here is that communicating well with your colleagues is essential and documentation is a key part of this. Social interactions are essential. Both Verburg and Evans insisted that increasingly, year by year, successful software development is more about communication than the technical aspects of the craft. Developers who understand this are the ones who will have the most success. Anti-Pattern Three: Distracted by Shiny – Always Use the Latest Technology to Stay AheadThe temptation here is to pick out some obscure framework, try a bit of Scala, HTML5, and Clojure, and always use the latest technology and upgrade to the latest point release of everything. Don’t worry if something works poorly because you are ahead of the curve. Verburg and Evans insisted that there need to be sound reasons for everything a developer does. Developers should not bring in something simply because for some reason they just feel like it or because it’s new. They recommended a site run by a developer named Matt Raible with excellent comparison spread sheets regarding Web frameworks and other apps. They praised it as a useful tool to help developers in their decision-making processes. They pointed out that good developers sometimes make bad choices out of boredom, to add shiny things to their CV, out of frustration with existing processes, or just from a lack of understanding. They pointed out that some code may stay in a business system for 15 or 20 years, but not all code is created equal and some may change after 3 or 6 months. Developers need to know where the code they are contributing fits in. What is its likely lifespan? Anti-Pattern Four: Design-Driven Design The anti-pattern: If you want to impress your colleagues and bosses, use design patents left, right, and center – MVC, Session Facades, SOA, etc. Or the UML modeling suite from IBM, back in the day… Generate super fast code. And the more jargon you can talk when in the vicinity of the manager the better.Verburg shared a true story about a time when he was interviewing a guy for a job and asked him what his previous work was. The interviewee said that he essentially took patterns and uses an approved book of Enterprise Architecture Patterns and applied them. Verburg was dumbstruck that someone could have a job in which they took patterns from a book and applied them. He pointed out that the idea that design is a separate activity is simply wrong. He repeated a saying that he uses, “You should pay your junior developers for the lines of code they write and the things they add; you should pay your senior developers for what they take away.”He explained that by encouraging people to take things away, the code base gets simpler and reflects the actual business use cases developers are trying to solve, as opposed to the framework that is being imposed. He told another true story about a project to decommission a very long system. 98% of the code was decommissioned and people got a nice bonus. But the 2% remained on the mainframe so the 98% reduction in code resulted in zero reduction in costs, because the entire mainframe was needed to run the 2% that was left. There is an incentive to get rid of source code and subsystems when they are no longer needed. The session continued with several more anti-patterns that were equally insightful.

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