DWR

This is all you have to do to your back-end, so now you can start using DWR on the front end of your application.

The DWR framework allows you to call methods on your Java classes directly from JavaScript code.

At this point, I'm ready to deploy my dwr. xml to my Web application's WEB-INF directory, where the DWR servlet will pick it up.

DWR makes it easy to enable Ajax on the back-end of an application.

For this configuration we create a dwr. xml file that we place in the WEB-INF directory of the application.

Now, take a look at a specific example to see how DWR works.

Three-layer laminated soft shell upper is water and wind resistant, breathable, and treated with a DWR (durable water repellent) finish.

This is a DWR annotation that lets DWR know this class can be automatically marshaled and sent across the wire as part of an Ajax response.

While DWR has many features that I haven't covered, the article source code is a good starting point for taking DWR for a spin.

We also need to configure the DWR client side engine to use active Reverse Ajax, so we need to call dwr. engine. setActiveReverseAjax(true).

Finally, you need to remember that DWR Ajax calls are asynchronous and should not be expected to return in the order they were dispatched.

A few of the most promising and well-designed toolkits that we have used are: Dojo, Rico, and DWR (see Resources).

You can switch freely among the Comet, polling, or even piggyback methods, simply by altering DWR's configuration.

You can configure DWR to call the server synchronously or asynchronously in the background.

In a larger application, DWR's Spring integration could be leveraged to provide DWR with Spring-created beans.

DWR is an open source, Apache licensed solution consisting of server-side Java libraries, a DWR servlet, and JavaScript libraries.

And best of all, DWR can auto-detect when it's running under Jetty and switch to using Continuations for nonblocking Comet.

The JSP file, fileupload-view. jsp, is shown in Listing 5 to illustrate how DWR helps to retrieve file upload progress from the server side.

The starting point of a DWR application is writing your server-side object model.

DWR automatically mediates simple data types between Java and JavaScript representations.

In the simplest terms, DWR is an engine that exposes methods of server-side Java objects to JavaScript code.

To get around this, you might use wrapper classes to add extra DWR-specific methods to your plain-old JavaBeans.

Effectively, with DWR, you can eliminate all of the machinery of the Ajax request-response cycle from your application code.

This article shows how you can use the Jetty servlet engine and DWR together to implement a Comet Web application simply and efficiently.

In this version of dwr. xml, I've added both a creator and a convertor for Cart.

DWR operates and maintains the State Water Project, including the California Aqueduct.

DWR does have its own solution to the latency issue in call batching (see the sidebar Call batching).

Before explaining DWR in more detail, I'll introduce a simple example scenario.

This string-keyed map representation can simply be converted into JavaScript by DWR's built-in convertors.

You can download the complete code for our sample application, including DWR, from the Download section.

DWR. Detailed instructions for experimenting with DWR are included in this tutorial.

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Configure a converter in dwr. xml file which specifies ProductSubtype as a bean converter.

The classes param is a comma-separated list of all classes that are annotated with DWR annotations.

DWR also provides JavaScript utility functions that help perform common UI tasks.

The data model is greatly simplified so you can concentrate on the DWR-brokered Ajax interactions.

The creator attribute here is set to the value new, meaning that DWR should call the class's default constructor to obtain an instance.

Herein lies the beauty of DWR: The client is communicating with the server-side Java object.

DWR is deployed as a servlet within your Web application.

If the DWRServlet's web. xml definition sets the init-param debug to true, then DWR's extremely helpful test mode is enabled.

The members are specified using the JavaBean naming convention, so DWR will call the corresponding get methods.

DWR (durable water repellent) finish sheds moisture.

DWR is a Java library, open sourced under the Apache license, for building Ajax-based Web applications.

To improve the user experience and ease of development, author designed and implemented timely validation of form based on DWR.

These classes don't implement any DWR specific interfaces or classes.

To download DWR before proceeding with the examples.

The page loads the data asynchronously using your DWR-enabled Ajax.

Element, which specifies the classes that DWR will remote.

The integration of DWR framework and the SSH framework, gives full play to their strengths.

JSF-based Apache Shale and servlet-based DWR are two that you'll want to keep an eye on.

With DWR taking care of all the communication, the add-to-cart behavior on the client is literally a one-line function.

There is one more thing you need to do to setup DWR on your back-end.

For the latter cases, DWR is a turnkey solution.

The DWR test page for CatalogDAO is shown in Figure 2.

So, framework like DWR, ICEFaces and Bindows all added native support and abstracted a layer in order to support different Comet API.

An easy way to combine the two with Java technology is to use the DWR library.

This is the DWR configuration file, which tells the container which classes are available in JavaScript.

When you click Add Message, you use DWR's utility method dwr. util. getValue to get the data from your form.

Download DWR: Get the latest DWR jar distribution.

In Listing 4, FileUploadProgressListener is defined for DWR so that the client can call this auto-generated JavaScript.

Figure 7 shows the format of the data that DWR sends across.

This article shows you how to leverage DWR to simplify Ajax development.

Include DWR-related JavaScript code in fileupload-view. jsp (see Listing 5).

DWR has been designed with security in mind.

All you must do is add some declarations and activate the DWR servlet.

Create a file called dwr. xml in the WEB-INF directory using the code in Listing 2.

DWR 2. 0 has been out for 6 months or so.

Figure 3 shows my DWR-based Ajax application in action, displaying items retrieved by a search with the user's shopping cart on the right

The following configuration information from dwr. xml shows how a Java class is configured

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Tells DWR to use its reflection-based bean convertor for the

Listing 6 is the extended dwr. xml config file that includes the extra config info for remoting the Cart class

this listing also uses convenience functions from dwr s

By default, when an Ajax request to DWR invokes a