java barcode library Not enough REST in Java

Generation Denso QR Bar Code in Java Not enough REST

For more background information on REST take a look at its Wikipedia page. The official JavaFX site also hosts a Media Browser project that demonstrates a RESTful service. http://en.wikipedia.org/wiki/Representational_State_Transfer http://javafx.com/docs/tutorials/mediabrowser/

Before we can go any further, you ll need to register yourself as a Flickr developer, assuming you don t have an account already.

You must register with Flickr so you can call its web service, which is a necessary part of this project. Signing up is relatively quick to do and totally free for nonprofessional use. Once your account is created you ll be assigned a key (a long hexadecimal string) for use in any software you write accessing the service. The necessity for a key, it seems, is primarily to stop a single developer from flooding the site with requests. Go to http://www.flickr.com/services/api/ and click the Sign Up link at the head of the page to begin the process of creating your account. The site will walk you through what you need to do, which shouldn t take long. Once your account is created, a Your

view your developer account details, including the all-important key. The site contains plenty of API documentation and tutorials. We ll be using only a tiny subset of the full API, but once you ve seen an example of one web service call, it should be clear how to apply the documentation to call another. So, if you don t already have a Flickr developer account, put this book down and register one right now, before you read any further. You can t run the project code without one, and the very next section will throw us straight into web service coding.

At the heart of JavaFX s web service support are three classes. In the javafx.io.http package there s the HttpRequest class, used to make the HTTP request; in javafx.data.pull there s PullParser and Event, used to parse the reply. Our application also uses three classes itself: FlickrService handles the request (using HttpRequest), FlickrResult processes the result (using PullParser and Event), and FlickrPhoto stores the details of the photos as they are pulled from the result. In the sections ahead we ll examine each of these classes.

We ll start, naturally enough, with the FlickrService. You ll find it in listing 8.1. As in previous chapters, the listing has been broken into stages to aid explanation.

Listing 8.1 FlickrService.fx (part 1)

package jfxia.chapter8; import import import import javafx.io.http.HttpRequest; javafx.data.pull.PullParser; java.io.InputStream; java.lang.Exception;

def REST:String = "http://api.flickr.com/services/rest/"; function createArgList(args:String[]) : String { var ret=""; var sep=""; for(i in [0..<sizeof args step 2]) { ret="{ret}{sep}{args[i]}={args[i+1]}"; sep="&"; } return ret; } // ** Part 2 is listing 8.2; part 3 is listing 8.3

We begin with one variable and one function, at the script level. The variable, REST, is the base URL for the web service we ll be addressing. Onto this we ll add our request and its parameters. The function createArgList() is a useful utility for building the argument string appended to the end of REST. It takes a sequence of

key/value pairs and combines each into a query string using the format key=value, separated by ampersands. Listing 8.2 shows the top of the FlickrService class itself.

Listing 8.2 FlickrService.fx (part 2)

// ** Part 1 is listing 8.1 public class FlickrService { public var apiKey:String; public var userId:String; public var photosPerPage:Integer = 10; public-read var page:Integer = 0; public var onSuccess:function(:FlickrResult); public var onFailure:function(:String); var valid:Boolean; init { valid = isInitialized(apiKey); if(not valid) println("API key required."); } // ** Part 3 is listing 8.3

At the head of the class we see several variables:

apiKey holds the developer key (the one associated with your Flickr account). userId is for the account identifier of the person whose gallery we ll be viewing. photosPerPage and page determine the page size (how many thumbs are

fetched at once) and which page was previously fetched. onSuccess and onFailure are function types, permitting us to run code on the success or failure of our web service request.

In the init block we test for apiKey initialization; if it s unset we print an error message. A professional application would do something more useful with the error, of course, but for our project a simple error report like this will suffice (it keeps the class free of too much off-topic detail). We conclude the code with listing 8.3.

Listing 8.3 FlickrService.fx (part 3)

// ** Part 1 is listing 8.1; part 2 is listing 8.2 public function loadPage(p:Integer) : Void { if(not valid) throw new Exception("API key not set."); page = p; var args = [ "method", "api_key", "user_id", "per_page", "page", ]; "flickr.people.getPublicPhotos", apiKey, userId, photosPerPage.toString(), page.toString()