Part $1.$ URL Parsing$(10$ Marks$)$

Web URL$$s are made of many parts. Take the following url for example:

https:$//$acs$.$uwinnipeg.ca$/$search$?$hello$=$world&x$=50$

We have the following parts:

$1.$ Scheme: https

$2.$ subdomain: acs

$3.$ domain: uwinnipeg

$4.$ top$-$level domain: ca

$5.$ subdirectory $($or route$)$: search

$6.$ query parameters: everything following the $?$

The query parameters are variables in the url that follow

a $?.$ These parameters are values that get passed to a webpage, like we would pass variables to a Java method. The parameter name and value are always separated by a $=,$ while different

parameters are separated by &$$s$.$ For the sample url we have two parameters: hello $=$ world,

and x $=50.$

make the following changes in the java file given below :

a$.(3$ Marks$)$ Complete the parseParams$()$ method. This method will accept a url $($String$)$ as

input, and the parse out all of the parameters from the url. The parameters should be

returned as a $2$D array of Strings. Where the array holds the pairs or parameter names and

values. Use the split$()$ method from the String class to answer this question.

eg: Our example url would return $\{\{$hello$,$world$\},\{$x$,50\}\}$

b$.(1$ Mark$)$ URL$$s will often need to encode many special characters in the query params. $($If

you$$ve ever noticed urls with things like hello$\%20$world, this is why.$)$ Use the decode

method from the URLDecoder class to decode your urls in the parseParams method.

c$.(1$ Mark$)$ A url should contain at most one unencoded $?.$ Include validation in your

parseParams$()$ method to check that the url argument is valid.

d$.(3$ Marks$)$ Complete the buildQuery$()$ method. This method will take a $2$D array of Strings

that represent query params. This array is the same format as the output of part a$.$ Your

method will return the rebuilt query part of the url. You must use StringBuilder to rebuild

your result.

For example $\{\{$hello$,$world$\},\{$x$,50\}\}$ would return $?$hello$=$world&x$=50$

e$.(2$ Marks$)$ As mentioned, url$$s often need to encode special characters in their query

parameters. Use the URLEncoder class to ensure that all of your values are encoded while

building the query again.

Java file:

import java.net.URLDecoder;

import java.net.URLEncoder;

import java.util.Arrays;

public class Lab$03$

$\{$

public static void main$($String$[]$ args$)\{$

$//$ A list of various urls

String$[]$ completeUrls $=\{$

$"$https:$//$github$.$com$/$search$?$q$=$machine$+$learning&type$=$repositories&l$=$Python",

$"$https:$//$github$.$com$/$search$?$q$=$stringbuilder&type$=$discussions",

$"$https:$//$github$.$com$/$search$?$q$=$date$+$parser$+$language$\%3$AJavaScript$+$created$\%3$A$\%3$E$2024-01-21$&type$=$repositories",

$"$https:$//$github$.$com$/",$

$"$https:$//$www$.$google.com$/$search$?$q$=$java$+$docs$+$stringbuilder",

$"$https:$//$www$.$uwinnipeg.ca$/$search$-$results.html$?$q$=$applied$+$computer$+$science",

$"$https:$//$www$.$bestbuy.ca$/$en$-$ca$/$search$?$search$=$cool$+$computer$+$stuff&sort$=$highestRated",

$"$https:$//$docs$.$oracle.com$/$search$/?$q$=$stringbuilder&pg$=1$&size$=10$&product$=$en$\%2$Fjava$\%2$Fjavase$\%2$F$21$&category$=$en$\%2$Fjava&showfirstpage$=$true&cType$=$WM$178623$&lang$=$en$",$

$"$https:$//$www$.$youtube.com$/$watch$?$v$=$dQw$4$w$9$WgXcQ$",$

$"$https:$//$www$.$google.com$/$search$?$q$=$shouldthrowexception?toomanyquestionmarks",

$\}$;

System.out.println$("$Parsing params..."$)$;

for$($String url : completeUrls$)\{$

System.out.println$($url$)$;

$//$ This try$-$catch block will stop our code from crashing if an IllegalArgumentException occurs

$//$ We'll learn more about these try$-$catch blocks later in the course :$)$

try$\{$

$//$ Parse the URL to get the query parameters

String$[][]$ params $=$ parseParams$($url$)$;

System.out.println$("\backslash$tParams: $"+$ Arrays.deepToString$($params$))$;

$//$ Using the query params, rebuild the query from the URL

String rebuiltQuery $=$ buildQuery$($params$)$;

System.out.println$("\backslash$tRebuilt: $"+$ rebuiltQuery$)$;

$\}$catch$($IllegalArgumentException e$)\{$

$//$ If illegal argument exception occurs, print it out

System.out.println$("\backslash$tException: $"+$ e$)$;

$\}$

System.out.print$("$

$")$;

$\}$

$\}$

public static String$[][]$ parseParams$($String url$)\{$

$//$ Hint $?$ is a special character!

$//$ Your code goes here

$\}$

public static String buildQuery$($String$[][]$ params$)\{$

$//$ Your code goes here

$//$ Use StringBuilder

$\}$

$\}$