org.riotfamily.common.web.collaboration
Class SharedProperties

java.lang.Object
  org.riotfamily.common.web.collaboration.SharedProperties

public class SharedProperties
extends Object

Class that facilitates collaboration between controllers.

The Spring DispatcherServlet performs an attribute clean-up after an include so included controllers can't expose request attributes to other controllers unless you turn this feature off, which usually isn't a good idea.

Another level of complexity comes into play when you want to cache the output of a controller that contributes information needed by other collaborators. If a cached version is served, the controller's handleRequest() method is not invoked (which after all is the purpose of a cache), therefore the controller has no chance to set any request attributes.

One solution would be to cache the dependent controller too. But in this case we would have to ensure that the cached version of the first controller is invalidated as soon as the dependent cache item is removed from the cache. As there is no easy way to achieve this, the SharedProperites class uses another approach:

The SharedPropertiesInterceptor exposes a HashMap as request attribute before the top-level handler is executed. A controller that wants to hand data on to a subsequent controller can use the setProperty(HttpServletRequest, String, String) method to add entries to this map. Because the map is already present before the the include is performed, it won't be cleaned up by the DispatcherServlet. Another controller can now invoke getProperty(HttpServletRequest, String) to retrieve the previously set values.

Currently shared properties are limited to Strings. The reason for this is that Cachius is aware of shared properties and caches them along with the actual output. It's basically a precaution to prevent users from caching their business objects. The fact that Cachius knows about shared properties allows us to serve cached content and still expose data to others.

A common use case for this is when you want to add information to the document title (or a meta-tag) that is provided by a controller which is deeply nested inside a template and would be processed too late. An elegant solution is to use the push-up feature of the TemplateController, which takes the nested controller out of the regular rendering flow and processes it first. This pushed-up controller can now expose shared properties which are then available everywhere else on the page, even if the pushed-up content comes from the cache.

Note: You can easily access shared properties in your FreeMarker views via the common.getSharedProperty() function and the common.setSharedProperty() macro.

Since:

6.5

Author:

Felix Gnass [fgnass at neteye dot de]

Constructor Summary

SharedProperties()

Method Summary

static Map<String,String>	getDiff(HttpServletRequest request, Map<String,String> snapshot) Returns a map containing all properties that have been added or modified since the snapshot was made.
static String	getProperty(HttpServletRequest request, String key) Retrieves a shared property.
static Map<String,String>	getSnapshot(HttpServletRequest request) Returns all shared properties currently set.
static void	setProperties(HttpServletRequest request, Map<String,String> properties) Sets multiple shared property at once.
static void	setProperty(HttpServletRequest request, String key, String value) Sets a shared property.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

SharedProperties

public SharedProperties()

Method Detail

setProperty

public static void setProperty(HttpServletRequest request,
                               String key,
                               String value)

Sets a shared property.

Throws:

IllegalStateException - if no properties map is found in the request

setProperties

public static void setProperties(HttpServletRequest request,
                                 Map<String,String> properties)

Sets multiple shared property at once.

getProperty

public static String getProperty(HttpServletRequest request,
                                 String key)

Retrieves a shared property.

Throws:

IllegalStateException - if no properties map is found in the request

getSnapshot

public static Map<String,String> getSnapshot(HttpServletRequest request)

Returns all shared properties currently set.

getDiff

public static Map<String,String> getDiff(HttpServletRequest request,
                                         Map<String,String> snapshot)

Returns a map containing all properties that have been added or modified since the snapshot was made.