Java Reference
In-Depth Information
Interacting with a Resource Using a Custom Reader
and Writer
Problem
You want to create a web page that produces a representation of an item with HTML forms
and allows the user to interact with it. You have a real-world compound object, such as a list
of products, and you want to read and write its representation in an interactive HTML form.
Solution
Create a resource, and then create two classes: one that implements
MessageBodyWriter<T>
and another that implements
MessageBodyReader<T>
. Use the
@Produces
and
@Consumes
annotations on them respectively. In the writer, produce the HTML form; in the reader, parse
the incoming form data and create your objects with them.
This gets complex fairly quickly, so we'll look at a complete example in the discussion below.
This example uses only JAX-RS standard code, so it's portable across implementations. I'm
using Jersey here, but this would work in JBoss RESTEasy too.
Discussion
This application consists of four classes: a
Product
class that is a POJO containing two strings
and an integer; a REST
Resource
class that manages the resource on the server; a
Mes-
sageBodyWriter
implementation that writes out the HTML form; and a
MessageBodyReader
implementation that gathers the form data and creates
Product
instances from it.
Figure 8-4
shows a screenshot of the application running in Tomcat, after submitting the form
a few times. Open your browser to
http://localhost:8080/restexamples/resources/order
after
deploying the application to see it working.
