Welcome to the website of Davis Fiore

It's a monitor equivalent to the use of the "synchronized" keyword, but with added features.

Here's a basic example:

	public void doTask() { 

		lock.lock();                 

		try { 

			// Do the task

		} finally { 
			lock.unlock(); 
		}               
	} 

That's equivalent to:

	public synchronized void doTask() { 

		// Do the task
	} 

However, there are actions that are only possible with ReentrantLock:

• Non-blocking: immediately return if the lock is not available

Passwords have to be stored as hashes, so that they cannot be reversed. In addition to this, before hashing a random generated number is added with a "salt algorithm", so that two equal password for two different users, generate different hashes. This means it's harder to crack multiple passwords.

Here's how the method works, when a user register:

1. A random salt is generated
2. Password and salt are concatenated
3. The password+salt string is hashed for N times.
4. The string iterations+salt+hash is stored into the database

Both authenticate with username and password and both generate a temporary token, called session id in the case of the session-based authentication and token in the case of the token-based authentication.

The main difference is that session authentication is stateful, whereas token-based authentication is stateless. That means that the former can associate many information to the session, on the server side.

Normally token-based authentication doesn't use cookies, whereas session authentication usually uses cookies.

A design pattern is "a general repeatable solution to a commonly occurring problem". That means that if we know the problem, we can determine which pattern is appropriate.

Here's a list of common design patterns, with the problem they solve, and a short description on how they are implemented. This wants to be a sort of map to easily find the right pattern in any situations.

CREATIONAL PATTERNS

Builder pattern

Problem that it solves: you have many constructors to manage optional parameters (telescopic constructor anti-pattern)

Testing goes through a series of standard phases, as follows:

• Unit tests are performed to test and validate small portions of the software, independently. They are run by the developer, or automatically after each commit or daily.
• Integration tests are performed to verify the interaction between components and expose defects in the interfaces. They are performed by developers or testers.

The term 3-tier (or n-tier) refers to an architecture, whereas MVC is an architectural design pattern. The main difference is that the former is distributed among different servers and the latter is located on a single machine.

Another difference is that MVC manages data in a triangular way, whereas 3-tier manages data in sequence, through a middle tier.

• A 3-tier system is separated into presentation, logic and data tiers. Presentation and data tiers never communicate directly.

A value object is an object that is compared by value, not by identity. Dates and money are better represented with value objects, whereas accounts or orders are better represented with reference objects.

There are two requirements for a value object:

• It must be immutable
• It must override equals() and hashCode()

Here's an example of value object class:

	public final class Number {
		
		private final int value;
		
		public Number(int value) {
			this.value = value;
		}
		
		public boolean equals(Object o){

Spring is a dependency injection framework and Powermock a powerful mocking framework. You might want to use both in your unit tests, when you have an hybrid approach. In this case, you might want to mock some objects and inject others.

The integration is a little tricky as Junit only allow us to specify one single runner, either PowerMock or Spring runner. So we need to instantiate a PowerMock runner and delegate to Spring for some operations.

Here's how to do.

1) Create a Spring configuration class:

	package davisfiore.api;

When you rent resources and hardware for your websites or your applications, the provider is hosting your services.

Hosting can take 5 forms:

• Shared server: this is the most common solution for small applications that do not require extensive IT knowledge or for personal websites. You have to share resources with others.
• Dedicated: this is ideal for small business, as you have a dedicated hardware. It can be self-managed or managed by the provider.

Curl is a command line tool for getting and sending data, using URL syntax. It is part of a project with the same name, that also includes liburl, a library with similar purpose.

Here are some examples.

Send an http request with content type "application/x-www-form-urlencoded" (option -d):

	curl -d "key1=val1&key2=val2" https://davisfiore.co.uk/endpoint

Send an http request with content type "multipart/form-data" (option -F):

	curl -F "key1=val1" https://davisfiore.co.uk/endpoint