This plugin is only available with Struts 2.1.1 or later
The REST Plugin simplifies REST-style resources to be consumed by both human and machine clients. The goals are to 100% follow Ruby on Rails-style REST URL conventions and enable XML-free resource development. It builds on the Convention Plugin to support automatic configuration of both actions and results.
Or, expressed as a table:
HTTP method |
URI |
Class.method |
parameters |
---|---|---|---|
GET |
/movie |
Movie.index |
|
POST |
/movie |
Movie.create |
|
PUT |
/movie/Thrillers |
Movie.update |
id="Thrillers" |
DELETE |
/movie/Thrillers |
Movie.destroy |
id="Thrillers" |
GET |
/movie/Thrillers |
Movie.show |
id="Thrillers" |
GET |
/movie/Thrillers/edit |
Movie.edit |
id="Thrillers" |
GET |
/movie/new |
Movie.editNew |
|
In addition to being a REST-style URL mapper, this plugin provides built-in support for multiple content types, switchable through the URL extension. In this way, a single resource can be exposed as multiple content types without any extra work.
For example, by exposing an "orders" resource, clients can immediately access it via:
http://my.company.com/myapp/orders/1 http://my.company.com/myapp/orders/1.xml http://my.company.com/myapp/orders/1.xhtml http://my.company.com/myapp/orders/1.json
The REST plugin automatically handles serialization to, and deserialization from, each format.
Features
- Fully implements Ruby on Rails REST-style URLs
- Supports XML-free development, without requiring annotations
- Built-in serialization and deserialization support for XML and JSON
- Automatic error handling
- Type-safe configuration of the HTTP response
- Automatic conditional GET support
Usage
Create Java objects ending in "Controller" in the configured package. The "Controller" suffix is used to distinguish REST action resources from regular Struts 2 actions, although it is completely optional and they are functionally the same. Now, add in methods to handle the various requests. For example, the following resource action will support /orders/34
GET and PUT requests:
package org.apache.struts2.rest.example; public class OrdersController implements ModelDriven<Order> { private OrderManager orderManager; private String id; private Order model; // Handles /orders/{id} GET requests public HttpHeaders show() { model = orderManager.findOrder(id); return new DefaultHttpHeaders("show") .withETag(model.getUniqueStamp()) .lastModified(model.getLastModified()); } // Handles /orders/{id} PUT requests public String update() { orderManager.updateOrder(model); return "update"; } // getters and setters }
In this example, the ModelDriven
interface is used to ensure that only my model, the Order object in this case, is returned to the client, otherwise, the whole OrdersController
object would be serialized.
You may wonder why the show()
method returns a HttpHeaders
object and the update()
method returns the expected result code String. The REST Plugin adds support for action methods that return HttpHeaders
objects as a way for the action to have more control over the response. In this example, we wanted to ensure the response included the ETag header and a last modified date so that the information will be cached properly by the client. The HttpHeaders
object is a convenient way to control the response in a type-safe way.
Also, notice we aren't returning the usual "success" result code in either method. This allows us to use the special features of the Codebehind Plugin to intuitively select the result template to process when this resource is accessed with the .xhtml
extension. In this case, we can provide a customized XHTML view of the resource by creating /orders-show.jsp
and /orders-update.jsp
for the respective methods.
Custom ContentTypeHandlers
If you need to handle extensions that aren't supported by the default handlers, you can create your own ContentTypeHandler
implementation and define it in your struts.xml
:
<bean name="yaml" type="org.apache.struts2.rest.handler.ContentTypeHandler" class="com.mycompany.MyYamlContentHandler" />
If the built-in content type handlers don't do what you need, you can override the handling of any extension by providing an alternate handler. First, define your own ContentTypeHandler
and declare with its own alias. For example:
<bean name="myXml" type="org.apache.struts2.rest.handler.ContentTypeHandler" class="com.mycompany.MyXmlContentHandler" />
Then, tell the REST Plugin to override the handler for the desired extension with yours. In struts.properties
, it would look like this:
struts.rest.handlerOverride.xml=myXml
struts.xml
Instruct Struts to use the REST action mapper:
<constant name="struts.mapper.class" value="rest" />
Because the REST plugin uses the Convention plugin, some settings need to be set in struts.xml:
<constant name="struts.convention.action.suffix" value="Controller"/> <constant name="struts.convention.action.mapAllMatches" value="true"/> <constant name="struts.convention.default.parent.package" value="rest-default"/>
and for this example:
<constant name="struts.convention.package.locators" value="example"/>
Example
The plugin ships with a struts2-rest-showcase
application that demonstrates a simple REST web program.
The behavior of the showcase is different with standard development, a controller will be mapped a method that related to HTTP (PUT, DELETE).
See this diagram to make you easily understand, how the REST work.
Settings
The following settings can be customized. See the developer guide.
For more configuration options see the Convention Plugin Documentation
Setting |
Description |
Default |
Possible Values |
---|---|---|---|
|
The alias for the |
N/A |
Any declared alias for a |
|
The default extension to use when none is explicitly specified in the request |
|
Any extension |
|
The HTTP status code to return on validation failure |
|
Any HTTP status code as an integer |
|
Optional parameter to specify namespace for REST services |
|
eg. /rest |
|
Optional parameter, if set to true blocks returning content from any other methods than GET, if set to false, the content can be returned for any kind of method |
|
eg. put struts.rest.content.restrictToGET = false in struts.properties |
Installation
This plugin can be installed by copying the plugin jar into your application's /WEB-INF/lib
directory. The REST plugin is dependent on the Convention Plugin, so if aren't using a build system that supports transitive dependencies like Maven 2, you will need to add that plugin as well.
Resources
- http://www.b-simple.de/documents - Short RESTful Rails tutorial (PDF, multiple languages)
- RESTful Web Services - Highly recommend book from O'Reilly
- Go Light with Apache Struts 2 and REST - Presentation by Don Brown at ApacheCon US 2008
Version History
From Struts 2.1.1+