Visualizing REST XML Data in JavaFX controls
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I'm currently working on a number of projects that use JavaFX. One of the characteristics all those projects share, is the requirement to be able to communicate with an enterprise backend. That justifies the work I spend on RedFX and DataFX, two JavaFX libraries that deal with retrieving, rendering and synchronizing data.
The focus of RedFX is the communication between JavaFX Clients and Java EE servers. RedFX allows clients to share data with each other and with backend modules. The original code was based on JavaFX 1.3.1 and has been ported to JavaFX 2.0. A number of brave beta-testers are now working with the new code, and a public release will be available soon.
The DataFX project enables client developers to populate JavaFX controls with data coming from different sources, and to visualize this data in a convenient way without the need of writing lots of boilerplate code.
In this blog entry, I will quickly show how you can use the DataFX library
to retrieve and visualize XML data obtained via a REST call.
Today, many enterprise projects make their data available via REST calls. The result of a REST call is often an XML document, containing lots of information. Not all this information is relevant to the particular JavaFX project. Retrieving the relevant parts and populating a TableView with this information can become rather cumbersome.
For this reason, the DataFX project contains the XMLDataSource class. Using this class, developers can populate a TableView with the parts in the XML that they want, without having to parse the XML manually.
<?xml version="1.0" encoding="UTF-8" standalone="yes"?> <CultureEvents xmlns:ns2="http://www.cultuurdatabank.com/XMLSchema/CdbXSD/3.1/FINAL"> <event> <cdbid>77f811ca-ac5d-40a4-9d73-80335b6288cd</cdbid> <discountPrice>5.0</discountPrice> <id>1</id> <item title="Biljarten" cdbid="77f811ca-ac5d-40a4-9d73-80335b6288cd"/> <normalPrice>20.0</normalPrice> <promotion>false</promotion> </event> <event> ... </event> <event> ... </event> </CultureEvents>
The non-relevant parts are already omitted from this example. In the TableView, we want to show the name of the events (in the first event, this is "Biljarten", the normal price (5 EUR) and the discounted price (20 EUR). The following code will achieve this:
NetworkSource ns = new NetworkSource("http://192.168.130.115:8080/uitpas/rest/uitpas/cultureevent?from=2011-11-01&to=2011-11-15"); XMLDataSource dataSource = new XMLDataSource(ns,"event","item/@title","normalPrice", "discountPrice"); TableView tv = new TableView(); tv.setItems(dataSource); tv.getColumns().setAll(dataSource.getColumns());
Rendering the TableView will show a table with 3 columns: the title, the
normal price and the discounted price. Each event will be on a single
row in the table.
The XMLDataSource constructor used in this example takes a number of arguments:
- a DataSourceReader. In this case, this is the URL of a REST endpoint. For my local development, however, I store the returned XML in a local file and I use a FileSource instead of a NetworkSource.
- the tagname that separates the different "rows" we want to visualize. In this case, we want one row for one "event"
- a number of columns we want to show. The XMLDataSource accepts xpath expressions, and can render both XML elements (e.g. the normalPrice) as well as attributes (e.g. the "title" attribute on the "item" element)
The DataFX project contains another very useful part: convenient CellFactories. The Currency CellFactory can be used to render the normal price and the discount price.
I want to stress that there are a number of ways for having interactions between desktop clients and remote backends. There is no single solutions to all problems. Developers should be aware of this. I am convinced that both DataFX and RedFX can contribute to faster development of enterprise JavaFX applications, but we want to hear from developers what they think is missing, or why we should support different patterns.
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