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Posts Tagged ‘HEAD’

BD-review

July 29th, 2009 bodom_lx No comments

BD-review is a dynamic website to allow people to review releases (albums, demos, EPs, singles) of (young, unsigned) music bands. The project is the outcome of the Internet Technologies course at the Faculty of Computer Science of the Free University of Bolzano.  The requirements of the project were to build a website using a small subset of JavaEE technologies, without the use of web-frameworks.

Therefore, this project is not really meant for production use. It was made as a strong, working and correct base for studying JavaEE academically. It should be useful for every student (also non-student) willing to have an overview on JSP and study it. The code is well-written, uses MVC, and the whole project is documented in detail in a 20+ pages report.

A screenshot of a Review

A screenshot of a Review

I encourage to read the PDF report of the project. It contains detailed information about the analysis and design phases, as well as the architecture description, screenshots, problems found etc. Please read also the README file. It contains configuration instructions.

There is a running demo located on the evaluation server of the course, but I think it will be removed soon.

Quick Jump:

Vision

Requirements Implemented

Technologies Overview

Download

License

Vision

The aim of the project is to build a dynamic website to allow people to review releases (albums, demos, EPs, singles) of (young, unsigned) music bands. Users will be able to signal interesting materials and review them, while other users will be able to comment the reviews, too.
This web 2.0-oriented application should allow unknown talented musicians to achieve a higher notoriety but also to improve their productions.

Screenshot of the personal user page

Screenshot of the personal user page

Requirements Implemented

I report here the requirements of the course, all implemented by BD-review:
What BD-review implements is:

  • User Management
    • List existing users of the system
    • Creation of a new user
    • Deletion of the existing user
  • List and modify access rights of the users
    • check boxes with some capabilities (min 3)
  • User registration and login to the system
  • Items management
    • Users add, edit or remove items
    • Users comments or reviews items
    • Administrator can manage the comments (edit,remove, add)
  • Personalization
    • Salutation for a returning user
    • List resources that are new from the last visit
    • Customization of the layout for a class of users.
  • Techniques – MUST be used
    • Static HTML
    • CSS: all the look and feel must be in CSS files
    • Javascript: check input and manage menus
    • Servlet: Reading (parameters and headers) and writing headers and resulting page
    • Servlet: Session management with cookies and session object
    • Servlet: Redirect the client
    • Servlet: Forward to another page or servlet
    • JSP: Expressions, scriptlets and declarations Beans
    • DBMS access trough JDBC
    • Integration of JSP and Servlets (forward and include) using MVC pattern.

In addition, BD-review implements two Filters and plays with Regular Expressions.

Technologies Overview

  • J2EE technologies (JSP, Servlets and JavaBeans)
  • Database support (PostgreSQL 8.3) through JDBC 4
  • XHTML Strict 1.0 + Cascading Style Sheets 2.1 for presentation
  • Apache Commons for conversion and Bean population routines
  • Some utility methods found on Books and Internet (their provenience is cited in the sourcecode)
  • Javascript for confirmation system and form validation
  • Regular Expressions
  • TinyMCE rich WYSIWYG HTML editor
Screenshot: modifying a Review

Screenshot: modifying a Review

Download

PDF report of the project
Complete Source Code and Documentation (as Netbeans Project)

The Future

There will not be future developments for the project. It was not a real-life project but I will be very proud if you find it an useful example for learning JSP. You can also use it as a basis for developing a real project (also a University Project). You can do anything you want with BD-review, but please respect the license. I would be happy if you send me an email about your experience in using BD-review.

License

BD-review is released under The Gnu Affero GPL version 3! This is different from the license of the contents of the blog

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 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 Affero General Public License for more details.

You should have received a copy of the GNU Affero General Public License
along with this program. If not, see < http ://www.gnu.org/licenses/ >.

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Heap vs. Stack in C++

March 20th, 2009 bodom_lx 4 comments

After the study of pointers versus references, the second natural question that comes in head of a ex Java developer turning to C++ is:

“What are the difference between static and dynamic memory allocation in C++?”

which can be translated as:

“When should I use the stack and when do I have to use the heap in C++?”

that can be further simplified to:

“When should I use the new operator in C++?”

I could simply summarize the answer to: “Use stack when possible”, but I think that this time there is the need of more explanations. Let’s have the following model for a process in the system:

A simplified model for a process

A simplified model for a process

I’m not really interested in an real representation of a process (see Modern Operating Systems by A. S. Tanenbaum for a very good explanation on processes), but focus on the stack and on the heap.
In reality the heap is a software abstraction but you can also imagine it like the stack.
In C++ programs there are also several other memory areas in which objects and non-object values may be stored (see this article on GotW for further details).

Why then choose between stack or heap? Quoting my publication on object-oriented memory management in Java:

Stack-based variables have their extent determined by their scope, so the former is constrained by the structure of the code at compile-time .

Sometimes there is a need for the variables with unconstrained extent in order to cope with
problems where lifetime of a variable can only be known at run-time.
In this case heap-based variables, whose extent is strictly under control of the programmer, are used. [..]

I promise that I will update my 17 pages about OO-memory management to cover also C++ by the end of June. By the way, following some forums, wikipedia, my publication and GotW, I also summarized pros and cons of stack and heap use in C++:

Stack Heap
Its size is determined at compile-time Size determined at run-time
Therefore, it is less expensive and quick Therefore, it is more expensive and slower than stack
The preferred way to store objects and variables if their size is limited. To be used only if needed: the amount of memory needed is variable and unknown, and may increase rapidly.
There is an AUTOMATIC CLEANUP of objects when they go out of their scope Objects STAY IN MEMORY even when you don’t use them anymore.
Programmers don’t have to bother to free resources Therefore, programmers HAVE TO CLEAN memory manually. However, all modern OS free the resources when the program exits.

Update 2009-07-03
After 4 months of heavy GUI and Database C++ programming, here are my thoughts: if you are planning to write a program with something more than a couple of objects interacting, using associations and therefore, objects as attributes, use the heap. Every serious program, even if not really big, uses heap for object allocation. Just take care to delete the objects when you don’t need them anymore. Objects on the heap are dynamically allocated and it is more comfortable to pass them through other objects using pointers. The use of the heap assures the live of objects even if the method that generated them runs out of scope ( =dies ). If you also plan to write GUIs, solid toolkits like QT recommend the use of heap to create graphical objects.

In some Operating Systems, stack is also very limited while heap is usually not.

Here are listed the sources I used for writing this article:

  • http://www.velocityreviews.com/forums/t278261-stack-vs-heap.html
  • http://www.computing.net/answers/programming/stackheap-c/2293.html
  • http://www.codeguru.com/forum/showthread.php?p=1186307#post1186307
  • http://www.codeguru.com/forum/showthread.php?t=350945
  • http://www.gotw.ca/gotw/009.htm
  • http://en.wikipedia.org/wiki/Process_(computing)#Representation
  • http://task3.cc/object-oriented-memory-management/

Hope that this article helped you to clearly understand the differences between stack and heap allocation in C++, write me if there are other issues or you need more explanations!

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Introduction to HTTP mind-map

March 1st, 2009 bodom_lx No comments

As I promised about 4 hours ago, here is my introduction to Hyper Text Transfer Protocol in form of a mind map.
It is to be intended as a really short introduction to this protocol. Like the previous one about computer networks, the mindmap summarizes materials copyrighted by Tanenbaum and also material taken from Wikipedia.

The topics covered are:

  • Scope of the protocol
  • HTTP connection
    • HTTP/1.0
    • HTTP/1.1
  • HTTP request methods:
    • GET
    • HEAD
    • PUT
    • POST
    • DELETE
    • TRACE
    • CONNECT
    • OPTIONS
  • Message Headers
    • Request Headers – all
    • Response Headers – all
  • Status Codes:
    • 1xx Information
    • 2xx Success
    • 3xx Redirection
    • 4xx Client error
    • 5xx Server Error
  • Sessions:
    • Cookies
    • Server-Side sessions
  • Secure HTTP – HTTPS:
    • By URI scheme
    • HTTP Upgrade Header
    • SSL/TLS

You can browse an HTML version online.

You can download:

As always, you are free and encouraged to contact me in case of errors or anything else.
Hope you like it!

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Fedora 10, thank you very much! (macbook review and fixes)

November 29th, 2008 bodom_lx 3 comments

I’ve never been a big fan of rpm-based Gnu/Linux distributions, since I’ve always preferred the stability of Debian and Debian based distros, with their great dpkg system.
The problem with Debian on Macbooks is that I do not see both the stability and performance anymore, as I have to use Lenny/Sid. Etch is too old and I don’t have the time (*sic*) to play with it to make it work well. Lenny should be next to be released but I don’t feel the very famous stability AND lightness of Debian distributions on this release, like I was accustomed in the past years. Is this because I own a Macbook? Maybe, but a Macbook Santa Rosa is nothing more than an Intel-powered notebook with some strange input devices and a strange non-bios system :-)

Regarding Ubuntu, I believe that this distribution has become naff and really slow. See this Slashdot discussion on this topic.

Yesterday I stumbled to Scientechie review of Fedora 10, which convinced me to try it out.
The software shipped with Fedora 10 is aligned with the one provided with the other distributions: Gnome 2.24.0, kernel 2.6.27.5, NetworkManager 0.7.0 (svn) and so on. Read the release notes for more information.

Fedora 10 really surprises me, as it is the first Gnu/Linux distribution in many, many years that makes me feel again the great stability and performance of the Penguin. Therefore I’m writing this review that is also a how-to, as it contains some fixes for Fedora 10 and Macbooks.

Read more…

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BD-shell

April 21st, 2008 bodom_lx No comments

BD-shell (a.k.a. bdsh) is a tiny Unix shell written in C. It’s a project required for the Operating System Course at my University.
It is written using a clean coding style, following xP coding standard philosophy.
Version 1.0 is the release that satisfies all the course requirements!

Quick Jump:
Features
Download
License

Features

Cool Features

  • Lightweight
  • Implements real Job Control
  • Clear and understandable code, ideal for Academic (and personal) studies
  • Makes use of various system calls, signals, signal handlers, user input handling, data structures implementation
  • Free Software!

Cool Features NOT present (but may be in future)

  • No command history present
  • No command/filename auto completion
  • No wildcars
  • No command piping, just a single command can be launched at a time
  • Put everything else here.
These are the requirements asked by the teaching professor. The complete project description page is located at http://www.inf.unibz.it/~david/os/project.html
The shell must be able to do the following:

  1. to read commands from standard input and execute them in a loop until a
    built-in command exit is issued (we call these processes the foreground processes; there is always at most one of these at any particular time);
  2. be able to redirect the standard input and output of commands by prefixing them with built-in commands in file and out file;
  3. be able to terminate (involuntarily) the foreground process when user presses ^C and return back to the mini-shell;
  4. be able to interrupt the foreground process temporarily, when user presses ^Z, returning to the mini-shell;
  5. be able to execute any number of processes in background (i.e., in parallel with the foreground process), including in particular, the ability to start another process while a process has been temporarily suspended;
  6. inform the user when the background process finishes or is
    waiting for an input from the terminal;
  7. be able to inform the user what commands are executing in the background by issuing the built-in command jobs, this should include information about the state of the process (i.e., suspended, background, waiting for input, etc.) and about what file(s) is the background process using for standard input and output);
  8. be able to terminate involuntarily a background processes by issuing the built-in command kill job-number.
  9. to be able to resume a process or to make a background process into the foreground process (i.e., the one that currently interacts with the terminal) by issuing the fg job-number command.

Download:

  • 2008-09-14 – version 1.0.0.
    • fixed synchronization bug in putJobBackground() that made not notify background processes requesting input (in some situations)

    Known Bugs:

    • Lots of! I consider bdsh-1.0.0 stable because it covers ALL requirements of the course and does them whell on various Unix systems. So it works, but commands like “in non_existent_file cat” won’t work and will crash it!

    What will be next?

    • I don’t know. I may consider a 1.0.1 release to fix future bugs. I may also think to add cool features to make the shell complete. I hope I will have the time for it. You can also do it by yourself and send me the code
  • 2008-09-13 – version 1.0.0 Release Candidate 2.
    Changes from beta 1 / release candidate 1

    • removed gcc O3 flag from makefile
    • lots of bugs fixed in functions operating on the list of jobs
    • improvements in launchJob() when dealing with background commands
    • bug in putJobBackground() that made the shell crash has been fixed
    • killJob() now sends a SIGKILL
    • bugs fixed in signalHandler_child()
    • Code formatted using astyle (linux style)
    • A couple of variables renamed
    • Various usleep() removed

    Known Bugs:

    • So many =) This is a shell made for Academic purposes, not for production use!
  • 2008-07-30 – version 1.0.0 beta1.
    Characteristics:

    • First beta release of the final version
    • Every requirement has been covered
    • Real Job-Control implemented
    • About every function of bdsh.c has been rewritten
    • New source directory layout, very clean
    • Some documentation and makefile
    • IMPORTANT! this has to be considered a bug hunting release! Please report me any bugs
  • 2008-06-05 – version 0.7.1, corrects the linked list bug of version 0.7.0
  • 2008-05-09 – version 0.7.0.
    UPDATE 2008-06-05: there is a bug in the list handling, the shell crashes when using the standard input redirection. Please download version 0.7.1, which corrects the problem.
    Characteristics:
    • Cleaner code!
    • Lots of bugs fixed!
    • reads commands from standard input and executes them in a loop until a built-in command exit is issued
    • redirects STDIN and STDOUT of commands by prefixing them with built-in commands in file and out file
    • terminates (involuntarily) the foreground process when user presses ^C and return back to the shell
    • executes any number of processes in background (i.e., in parallel with the foreground process)
    • informs the user when the background process finishes
    • informs the user what commands are executing in the background by issuing the built-in command jobs
    • terminates involuntarily a background processes by issuing the built-in command kill job-number.
  • Due to a lots of compatibility issues with Gnu/Linux (the shell has been developed under Mac Os X), the final released has been delayed to mid-September. Sorry for this, I encountered so many problems the day before project presentation, that I decided to present it during the next exam session. I switched back to Gnu/Linux, too :)
  • Final release is scheduled on 2008-06-26, as the project deadline is 2008-06-25. The release will
    satisfy all the requirements, and as addition:

    • Execution system totally rewritten (e.g. one single short function that handles everything)
    • A Job Control will be implemented
    • Processes in foreground will really be in foreground, there are a lot of things that we did not learn during the course, like tcsetpgrp()
    • Some functions in utils.h will be deleted and optimized
    • Cleaner and clearer code!
  • 2008-04-21 – version 0.0.1
    Characteristics:
    • Modular code, divided in 3 files: bdsh.c, utils.h, headers.h
    • Clean user input from a char buffer to an array of strings
    • Built-in commands: exit (exits from the shell), cd (changes directory), in <filename> command (redirects STDIN of command from <filename>), out <filename> command (redirects STDOUT of command to <filename>)
    • Makes use of fork() to read commands from standard input and execute them

License:

BD-shell is released under The Gnu GPL version 3! This is different from the license of the contents of the blog

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 3 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, see <http ://www.gnu.org/licenses/>>.

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BD-theme

January 24th, 2008 bodom_lx No comments

BD-theme is a widget ready, two columns Wordpress theme, written using the default Wordpress theme as php/xhtml base. The theme is inspired by TorrentFreak rounded layout, and some little ideas are inspired by Curved Theme, which was the old BD-blog theme.
I just wanted to write my own Wordpress theme.
This is my first theme, and my first try to design something nice. Source code is available below.

If you like BD-blog theme, then download BD-theme =)

Download:

  • 2008-12-08 – version 1.0
    Changes from 1.0 beta 1:
    • Remove_filter(‘the_content’, ‘wptexturize’); added for better posts regarding coding
    • If you decide to create a “Archives” page and/or a “Blogroll” page for listing links and archives, those pages are not listed in the rounded menu
    • Related tags of a post are no more links, for a more polished site
    • Better caption for images
    • Works with IE6, IE7, Firefox 2, Firefox 3, Opera, Google Chrome
    • Valid XHTML 1.0 Strict
    • Valid CSS 2.1
    • Screenshot:
      BD-theme 1.0

      BD-theme 1.0

  • 2008-11-27 – version 1.0 beta 1
    Changes from 0.9:
    • Change of dtd: from xhtml 1.0 transitional to xhtml 1.0 strict
    • Yes it’s VALID Xhtml :-)
    • Navigation links now present in every section of the theme (archive,single, index etc)
    • Ready for Get Recent Comments and Recent Posts, both recommended and displayed at the page footer if installed
    • New logo system that checks if IE6 is present and presents an alternative page without logo
    • More space for content is given
    • Post headers (title and date) are fixed for every browser
    • Fixed some css bugs for those wo do not use the sidebar
    • Lighter css! more standard but still not finished
    • Screenshot:
      BD-theme 1.0 beta 1 screenshot

      BD-theme 1.0 beta 1 screenshot

    What will be next:

    • CSS fixes for IE6
    • Cleaner Code
  • 2008-09-19 – version 0.9
    Changes from 0.8-experiment:
    • Fully Compatible with Mozilla Firefox 2/3, Internet Explorer 6,7,8, Google Chrome, Apple Safari
    • More harmonious and stable
    • Links to pages are now rounded corner buttons
    • Buttons for pages moved over main layout, added a button for accessing the blog posts
    • The current page link button gets the same background color of the content page
    • Post header layout changed: a very nice band contains the title of the post and the date of posting exits the main layout
    • Various CSS fixes
    • Screenshot:
      BD-theme 0.9 Screenshot

      BD-theme 0.9 Screenshot

    What will be next:

    • CSS bugs totally fixed (I hope :D )
    • Theme has to pass w3c’s xhtml/css validations
    • Theme has to remain compatible with all browsers
  • 2008-08-21 – version 0.8 – experiment
    About:
    • Quite everything changed in the last 6 months, but the colors
    • This is the source code of the experiments done from the post of 06-06-2008: BD-theme’s new look
    • NOT to be considered as a stable release, code is very dirty (but almost functional)
    • It’s the base I’ve been using since 7 days for the final release, It’s available because somebody may like it more than the next version, or to modify it
    • An image helps more than a thousand words:
      BD-theme 0.8, the Experiment

      BD-theme 0.8, the Experiment


      BD-theme 0.2 - Classic

      BD-theme 0.2 - Classic

  • 2008-02-21 – version 0.2
    Changes:
    • fixed a:hover transparency bug in #pages
    • fixed .entry links and img
    • added a stlye for blockqoute
    • fixed some values of the searchform in the sidebar (safari fix)
    • added a style for the links inside the #footer section
  • 2008-01-24 – version 0.1
    First version, download it just if you want to customize it or to create a new theme based on this one. I’m testing it on my blog. It may contain “useless” code from the default Wordpress Theme

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