ServerClient_Java

A project we are developing during the coming year in Advanced software development course. The project is written in Java about generic server-side that given a problem, he could solve it.

Introduction

As said in the main description, this project is about a general server, in which the programmer can decide how and what the server will do given a general problem and how he should solve it.

We want to write a general server, a server that can be used again and again in various projects. To do so, he must make a fundamental and important separation: separating what changes between a project and a project, and what is not.

We will define the functionality of the server through an interface, and each project can have another class that will implement the same functionality in a different way. In that way, we kept the Open / Close principle.

Server

We have Server interface that has quite simple functionality:

• A method that receives a port for listening and its function will be to open the server and wait for clients.
• A method to close the server.

For this project we will use a class called MySerialServer that will be a type of Server.

ClinetHandler

Imagine a situation in which the MySerialServer would also define the client-server call protocol. In different projects, there may be a different conversations in a different format and with different expectations between the client and the server. So we wouldn't be able to use this class in other projects.

Therefore, we need to separate the server mechanism implemented in MySerialServer from different forms of conversation with the client. We will create an interface called ClientHandler to determine the type of call with the client and its handling, which leads to only two Server classes that should be done MySerialServer and MyParallelServer, and each class can inject any desired implementation for ClientHandler.

For example, for every implementation of a Server we can inject a call of inversion of strings or solving equations. In the same way if tomorrow we would like to implement additional protocols then we will only need to add the an implementation of ClientHandler without changing or copying again the code of the various implementations to the Server.

In this method, we maintained both the Single Responsibility and Open / Close principles.

Caching

This system has also caching system, it may take a lot of time to calculate some solutions. It would be superfluous to calculate a solution for a problem that we have already solved. Instead, we can save solutions we've already calculated in a file, or a database. If there is a problem, we will have to check quickly if we have already solved it. If so, we will extract the solution from the disk instead of calculating it. At this point, we already understand that there may be several different implementations to save the solutions, for example in files or in a database. Therefore, we will again implement the same interface use tactic to preserve the various SOLID principles.

We will deploy CacheManager interface to manage the cache for us. with the following functionality:

• Checks whether the solution already exists in the database.
• Extracts the data from the database.
• Saves the solution for the problem.

Currently, only FileCacheManager is implemented.

UML

Running some examples and tests

The specific problem and solution in the project I created is a server that given a matrix is able to solve it and say the cheapest path from point A to point B using BestFirstSearch algorithm.

For example: lets assume we have this matrix:

114	93	164	123
109	27	40	15
156	175	189	5
160	186	153	38

If we'll set the start point to be 114 (0,0) and the end point to be 38 (3,3) then the path ( the output ) will be:

Right, Down, Right, Right, Down, Down.

(Marked in bold)

Getting Started

These instructions will get you a copy of the project up and running on your local machine for development and testing purposes. See deployment for notes on how to deploy the project on a live system.

Prerequisites

What things you need to install the software and how to install them

• Only updated Java Development Kit ( JDK )

Installing

The main page where you can configure the server, what is the problem, and what solution it should provide, can be found in the file:

testserver/TestSetter.java

Then, in order to program the clinets to request or communicate in some particular way with the server, it can be done in this file:

testserver/TestServer.java

And then, we can run the server and clinets in that file ( no need to edit it ) :

testserver/MainTrain.java

Let's end with an code example of getting some data out of the system

Server Side

Server s = new MySerialServer(port);
try {
  SearchableClientHandler<String, Position> ch = new SearchableClientHandler<>(
      new SearcherSolver<MatrixProblem, String, Position>(new BestFirstSearch<Position>()),
      new FileCacheManager<MatrixProblem, String>("./maze.xml")
  );

  System.out.println("Server is running...!");
  s.start(ch, "end");
} catch (Exception e) {
  e.printStackTrace();
}

Client Side The procedures that occur within the client file TestServer.java :

• The client sends line by line until you get a row with the value "end"
• Each row applies numeric values separated by a comma, so the row collection creates a matrix of values.
• The customer then sends two more lines. Each line has two values separated by a comma: a row Row, Col., And Column
• The values in the first line indicate the entrance to the area
• The values in the second line indicate the exit from the field

Then the server will return only one string, with comma-separated values. Values will be of the type of words {Right, Left, Down, Up} indicating the direction to move in order to cross the area, the cheapest route.

Authors

• Daniel Paz - Entire work - Profile
• Omer Nahum - Co-Worker