ActiveWeb allows to render the same values and collections in a variety of formats, such as XML, JSON, etc, as long as they are based on text (not binary).

URL mapping

A URL can have the following structure:

http://host:port/controller.format?param=val

where format is... format which can be detected to match an appropriate view

Mapping URLs to formats

The format portion of the URL is used to map a view automatically:

URL example Format View file location
http://host:port/controller.xml xml /vews/controller/action.xml.ftl
http://host:port/controller.json json /vews/controller/action.json.ftl
http://host:port/controller.xyz xyz /vews/controller/action.xml.ftl

where xyz is just a bogus example, which will work nonetheless!

Format detection in controller

Inside the controller, you can use a method format() n order to detect what format was requested by the client. Here is an example from ActiveWeb-Simple example project:

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public class BooksController extends AppController {
    public void index(){
        if("xml".equals(format())){
            render().noLayout().contentType("text/xml");
        }
        if("json".equals(format())){
            render().noLayout().contentType("application/json");
        }
        view("books", Book.findAll().toMaps());
    }

As you can see, the detection of a format and appropriate logic is easy. The conditional logic in this example is needed only because this controller serves HTML, XML and JSON outputs. Their respective sources are below.

The controller by calling noLayout() method tells the framework to not use a layout for these views. If you are building a controller like this one, that may serve HTML, and in addition, XML or JSON, which do not require a layout, you have to call these methods to prevent your view wrapped in an HTML layout.

If you are building a true webservice, you will not need any layouts. You can then override the getLayout() methods in your controller and simply return null from it. Do it in a a super class of all controllers to concentrate this in one place. Please, see such an example: APIController.

HTML View

Found in a file: src/main/webapp/WEB-INF/views/books/index.ftl:

<table>
    <tr>
        <td>Title</td>
        <td>Author</td>
        <td>Edit</td>
    </tr>
<#list books as book>
    <tr>
        <td>
            <@link_to action="show" id=book.id>${book.title}</@link_to>
        </td>
        <td>
            ${book.author}</td>
        <td>
            <@form  id=book.id action="delete" method="delete" html_id=book.id >
                <button type="submit">delete</button>
            </@form>
        </td>
    </tr>
</#list>
</table>

XML View

Found in a file: src/main/webapp/WEB-INF/views/books/index.xml.ftl:

<books>
<#list books as book>
    <book>
        <id>${book.id}</id>
        <title>${book.title}</title>
        <author>${book.author}</author>
    </book>
</#list>
</books>

JSON View

Found in a file: src/main/webapp/WEB-INF/views/books/index.json.ftl:

[
<#list books as book>
    {
        "id": "${book.id}",
        "title": "${book.title}",
        "author": "${book.author}"
    }
    <#if book_has_next>,</#if>
</#list>
]

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