Recently i needed to post data using node.js, I was not trying to post a long string of data but rather parameters from a form. But the Node.js help page isn’t too helpful, it just say use request.write() to write data to the streamThis is the first interation i got.

var http=require('http');
var post=http.createClient(80,'localhost');
var request=post.request('POST',/test.php'.{'host':'localhost'});
request.write('test=10'); request.end();
request.on('response',function(response){
response.setEncoding('utf8');
reponse.on('data',function(chunk){ console.log(chunk); } });

test.php is a simple php script that prints out the parameter value.

I got nothing… nothing was printed out. What was wrong?

Using curl and Fiddler, i did a little investigating about what went wrong, what was missing was the Content-Length and the Content-Type which needs to be application/x-www-form-urlencoded.

Adding these 2 parameters to the script, results in

var http=require('http');
var post=http.createClient(80,'localhost');
var request=post.request('POST',/test.php'.{'host':'localhost','Content-Length':'7','Content-Type':'application/x-www-form-urlencoded'});
request.write('test=10');
request.end();
request.on('response',function(response){
response.setEncoding('utf8');
reponse.on('data',function(chunk){
console.log(chunk); } });

And yeah ! It works ! 

 However looking at the code from Vijay (http://www.vijaykiran.com/2006/09/05/using-jrex-in-eclipse-rcp/
), i got it working and it seems to work fine, but Vijay dosen’t really go into how to setup the project like where to download the jars and where to put the dll and so on, and I did have some hard time trying to find out where to find the jars.

 Downloads
1. At first i took apart the jnlp file on jrex.mozdev.org to find out what are the dependencies, but after looking around the mozdev site, i finally found the downloads for the jars, source and docs in here (http://www.mozdev.org/source/browse/jrex/downloads/#dirlist).

 2. But it dosen’t include the jrex_gre files that are in the jnlp, those you can get them here (http://www.mozdev.org/source/browse/jrex/www/releases/jrex-1.0b1_dom3/). Look for the jrex_gre.jar

 Setting up your eclipse.
Put the jrex.dll in your eclipse directory, if not you will get a UnsatisfiedLinkError when you try to run the view. Put the jrex.jar in your lib folder of your project.

 Unzip the jrex_gre.jar contents to a nice location you can remember.  You will see in Vijay’s code a place that you will need to supply the path to the file in org/mozilla/jrex/jrex_gre files.

 That should fill up the missing pieces in Vijay’s writeup.

I will try to package the source code into github at some later time.
&n bsp;
]]> http://stephensoftware.wordpress.com/2011/01/11/jrex-embedding-gecko-firefox-in-eclipse/feed/ 0 sljm http://stephensoftware.wordpress.com/2011/01/06/fedora-14-using-the-dvd-as-a-software-repository/ http://stephensoftware.wordpress.com/2011/01/06/fedora-14-using-the-dvd-as-a-software-repository/#comments Thu, 06 Jan 2011 01:32:10 +0000 sljm http://stephensoftware.wordpress.com/2011/01/06/fedora-14-using-the-dvd-as-a-software-repository/ ]]> Installed Fedora today at office in order to try out some web acceleration stuff lile squid and varnish. I used the DVD iso version, so that i can have most of the essential software already.

  When i rebooted i found that the dvd is not recongnised as a software repository, because there is no entry in /etc/yum.repos.d/.

No biggie, just mount the dvd, in the root of the dvd there is a file media.repo, jus copy the file to /etc/yum.repos.d/ as packagekit-media.repo and you are all set, your dvd becomes a software repository.
]]> http://stephensoftware.wordpress.com/2011/01/06/fedora-14-using-the-dvd-as-a-software-repository/feed/ 0 sljm http://stephensoftware.wordpress.com/2011/01/05/resolutions-2011/ http://stephensoftware.wordpress.com/2011/01/05/resolutions-2011/#comments Wed, 05 Jan 2011 01:53:24 +0000 sljm http://stephensoftware.wordpress.com/2011/01/05/resolutions-2011/ ]]> My resolutions for 2011.

The Blog-Health-o-Meter™ reads This blog is on fire!.

Crunchy numbers

The average container ship can carry about 4,500 containers. This blog was viewed about 20,000 times in 2010. If each view were a shipping container, your blog would have filled about 4 fully loaded ships.

In 2010, there were 9 new posts, growing the total archive of this blog to 53 posts.

The busiest day of the year was June 4th with 297 views. The most popular post that day was Terms in Functional Programming.

Where did they come from?

The top referring sites in 2010 were dzone.com, google.com, google.co.in, info4tech.wordpress.com, and jdon.com.

Some visitors came searching, mostly for ljava.lang.string, extjs form validation, ljava.lang.string; cannot be cast to java.lang.string, and [ljava.lang.string; cannot be cast to java.lang.string.

Attractions in 2010

These are the posts and pages that got the most views in 2010.

Terms in Functional Programming June 2010
1 comment

java.lang.ClassCastException: [Ljava.lang.String; cannot be cast to java.lang.String When using HttpServletRequest getParameters() January 2009
1 comment

Ext JS – Disabling FormPanel submit if validation fails March 2009
1 comment

JAX-WS and Http Proxy July 2009

Getting the gBrowser object in Firefox August 2009
1 comment

For those who are following me using RSS please use the new RSS address. http://feeds.feedburner.com/StephenOnSoftware

Closure

As defined in Wikipedia “a closure is a first-class function with free variables that are bound in the lexical environment. Such a function is said to be “closed over” its free variables”

Let see an example,

var digit_names=function(){
    var digits=["zero","one","two","three",...];
    return function(n){
        return digits[n];
    }
}

In this case the digit_name are the free variables, and it returns a new function with one parameter “n”, that will display the text representation of the number. Notice that even when the function extits, it still maintain the digit_name array in the new function, so the new function is closed over the digit_name array.

Another javascript example this time in jQuery.

var add_link=function(id,text){
$("#"+id).click(function(){
alert("Hello World"+text);
});
}

Java Proposal for closures

Functions as first class arguments

What the hell is this ? Basically first class objects are things that you can pass them into function/methods and also return them from methods. In Java that means primitives like int,char and objects like Strings, Integer and your own custom objects.

So if a language supports first class functions that means you can pass functions as a argument and also returns functions from functions.

Exampls of such languages are Common Lisp, Scheme, Clojure, Javascript.

(defn is10? [b]
    (if (= b 10) true nil))

(filter a [1 2 3 4 5 10])

The above example in clojure defines a is10? that checks if a number is equals to 10. We then pass the is10? to a filter function that will remove all numbers except where the number is 10. The filter function coincidentally is called a HIgher level function.

Metaprogramming

Sounds quite abstract, programming is programming what the hell is the “meta” word doing there. Metaprogramming simply said are programs that write or manipulate other programs as data.

An example in Bash from Wikipedia.

#!/bin/bash
# metaprogram
echo '#!/bin/bash' >program
for ((I=1; I<=992; I++)) do
    echo "echo $I" >>program
done
chmod +x program

This one is a program that writes a program that prints 1 to 992.

Compliers are another examples of metaprogramming, translating programs into bits and bytes that can be executed. C++ templates are another example.

ROR ActiveRecord patterns, Hibernate frameworks are examples of frameworks that use metaprogramming to generate code base on your database structure/definations.

Homoiconicity

Basically it means that the program you are writing is actually some primitive data structure in the language itself.  Sounds weird right.

Languages that have this property include LISP,Clojure, Prolog, XSLT, Xquery (not exhaustive).

For example a primitive structure in LISP is the list. You can represent code in list data structure and it can be evaluated. The advantage is that it makes meta programming easier, that means it makes it easy to write programs that manipulate other programs  as their data.

Below examples taken from Wikipedia.

(setf expression  (list '* (list 'sin 1.1) (list 'cos 2.03)) )
-> (* (SIN 1.1) (COS 2.03))    ; Lisp returns and prints the result

(third expression)    ; the third element of the expression
-> (COS 2.03)

You can see that the sin 1.1 * cos 2.03 code is represented is a list structure in LISP and LISP is able to process that “data” and evaluates the result of that data.

Immutable

It just means that the data cannot be changed after it has been created, the opposite is mutable. In an object orientated world most of the data is mutable that means we allow data or properties in the objects to change state. That’s why we need locking in order to access the data and make sure no one can change the data while we are changing it.

If all your data is immutable, there wouldn’t need to be locks since all data is read only. Erlang,Haskell,OCaml has only single assignment for its variables, most other languages have some keyword or syntax to denote the variable as read only, example Java uses the final keyword.

Data immutability is said to reduce the number of side effects and also makes programs easy to debug.

If you like this post and would like to support my site feel free to buy me a beer !