Jersey REST Fibonacci Sequence

Overview

What is the Fibonacci sequence
Prerequisites
Create a new Java project in using Jersey Grizzly quickstart
Java project skeleton structure
Service implementation
Running
Code

A quickly developed Jersey REST implementation of a Fibonacci sequence ‘service’.

What is the Fibonacci sequence

Wikipedia provides quite a detailed definition of the Fibonacci sequence http://en.wikipedia.org/wiki/Fibonacci_number

By definition, the first two numbers in the Fibonacci sequence are 1 and 1, or 0 and 1, depending on the chosen starting point of the sequence, and each subsequent number is the sum of the previous two:

0 1 1 2 3 5 8 13 21 34 55 89 144 233 377

Prerequisites

You will need to install the following technical components:

Java 1.7.x
Maven 3.0.5
Nexus 2.8.1✝ (optional)

✝ by using Nexus, a repository manager, in conjunction with Maven the required dependencies are easily managed and packaged components will be downloaded as required.

Create a new Java project in using Jersey Grizzly quickstart

To create the Jersey web-app project, execute the following Maven archetype command in the directory where the new project should reside:

mvn archetype:generate -DarchetypeArtifactId=jersey-quickstart-webapp -DarchetypeGroupId=org.glassfish.jersey.archetypes -DinteractiveMode=false -DgroupId=com.addison -DartifactId=jersey-webapp -Dpackage=com.addison -DarchetypeVersion=2.13

Java project skeleton structure

jersey-webapp
│   pom.xml
│
└───src
    ├───main
    │   └───java
    │       └───com
    │           └───addison
    │                   App.java
    ├───resources
    └───webapp
        │   index.jsp
        │
        └───WEB-INF
                web.xml

This essentially creates a very simple REST web-app, which retrieves a static string response.

Service implementation

package com.addison;

import java.math.BigInteger;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.core.MediaType;

/**
 * Root resource (exposed at "fibonacci" path)
 */
@Path("fibonacci")
public class Fibonacci {

    /**
     * Method handling HTTP GET requests. The returned object will be sent to the client as "text/plain" media type.
     * 
     * @return String that will be returned as a text/plain response.
     */
    @GET
    @Produces(MediaType.TEXT_PLAIN)
    public String fibonacci(@QueryParam("num") String number) {
        try {
            long n = Long.parseLong(number);
            StringBuilder series = new StringBuilder("Fibonacci ");
            series.append(number);
            series.append(" : 0");

            if (n > 1)
                series.append(" 1");

            BigInteger prev = BigInteger.valueOf(0L), next = BigInteger.valueOf(1L), result = BigInteger.valueOf(0L);
            for (long i = 1; i < n - 1; i++) {
                result = prev.add(next);
                series.append(" ");
                series.append(result.toString());
                prev = next;
                next = result;
            }

            return series.toString();
        } catch (NumberFormatException err) {
            return "Invald Request:  fibonacci?num=" + number + "\nNumberFormatException: " + err.getMessage();
        }
    }
}

Running

The service has been deployed to a server under apache tomcat

Code

The source code is available from my public Github repository jersey-webapp

Mark Addison