REST API for URL shortening

##Description

URL Shortener is a REST service used for representing long URL-s with a possibly small set of characters.

###URL shortening

URL shortening is a procedure based on assigning a unique number, a hash, to each URL that is to be shortened. This hash is essentially a key that is used to retrieve a long URL assigned to it. For this to be possible, each hash is encoded using a set URL permissible characters. This encoded hash can be prefixed with server address or application domain and used as a short URL itself. So each time a short URL is referenced, it is used as a key to find and redirect to a long URL mapped to it.

This service uses a number of registered long URL-s as a hash. A hash is encoded using a set of case sensitive alphanumeric characters and digits, a total of 62 characters. Encoding procedure is basically a decimal number to base-62 conversion, where base-62 uses sixty two distinct symbols from these range of characters: a-z, A-Z, 0-9.

####Example

Long URL to shorten:

• https://github.com/swagger-api/swagger-core/wiki/Annotations-1.5.X#authorization-authorizationscope

Hash:

• 68719476736 (two to the power of thirty six)

Base-62 conversion:

• 68719476736 is represented as bnaN5hc (with seven characters) in base-62

The result short URL:

• http://my-short-domain.com/bnaN5hc

###URL shortening REST service

The shortening API offers:

• user registration into the service by opening an account
• long URL registration and shortening
• registered short URL usage statistic retrieval

where URL registration and usage statistic is available only to authorized users with an account. Basic authentication is used and user's account ID and password need to be provided in the Authorization header. Each registered URL can be referenced with a given short URL by anyone.

###Installation & setup

This application is built upon:

1. Java Development Kit (JDK) 8
2. Apache Maven build automation tool
3. Spring framework and
4. H2 in-memory database

Application is packaged as a web application archive (war file) and it can be deployed on any web or application server.

However, Jetty Maven plugin included in project's pom.xml file can be used for running Jetty web container in Maven life-cycle. To run this service using Jetty Maven plugin, Apache Maven and JDK 8 need to be downloaded and installed.

###Usage

To run Jetty web container using Jetty Maven plugin in terminal, from the project's root folder, use:
mvn package jetty:run-war
or to start the service in scattered mode (for testing/development purposes):
mvn jetty:run
This will start one instance of Jetty web container and the shortening service will be available at the URL: http://localhost:8080/

To change the port, Jetty Maven plugin can be invoked using the jetty.port option, for example: -Djetty.port=8090 to change the port to 8090.
This can be useful if standard 8080 port is already taken or if you want to run multiple Jetty instances in parallel.

To stop the Jetty web container, use: stop.key and stop.port configured in the project's pom.xml file:
mvn -Dstop.key=STOP -Dstop.port=9999 jetty:stop

For detailed description of the entire service, and how to use it, visit Help page which is available at /help

####Example

• Opening an account

/account

• Long URL registration and shortening

/register

• registered short URL usage statistic retrieval

/statistic/Merry