A simple activity is made of simple text. An extension point has been created at the level of activities rendering for two cases:
* support more HTML tags.
* support @mentions.

But you may want to support a special syntax, for example:
* #hashtags to feel like Twitter.
* smileys to look like Skype.
* [Markdown|http://en.wikipedia.org/wiki/Markdown] to experience Buzz.

You can have more sophisticated cases to process, such as parsing the link that include in the activity's content. Because a process actually has the full access to the Activity, you can very well process based on the owner, app, and media item.

After reading this section, you will know how to extend the activities rendering via 2 topics:

* [Write an ActivityProcessor|#SOCref.DeveloperReferences.how_extend_the_activities_rendering._write_ActivityProcessor]
* [Configure the processor|#SOCref.DeveloperReferences.how_extend_the_activities_rendering.Configure_Processor]

{note}
To understand this section, the knowledge of Java and eXo Kernel (component model and its XML configuration) is prerequisite.
{note}

{docbook}
<para xml:id="SOCref.DeveloperReferences.how_extend_the_activities_rendering._write_ActivityProcessor">
<citetitle>
<emphasis role="bold">
Write an ActivityProcessor
</emphasis>
</citetitle>
</para>
{docbook}

Social lets you pre-process an activity before it is returned by the ActivityManager. To do this, you simply need to implement the interface ActivityProcessor:

{code:java}
/**
 * An activity processor is responsible to pre-process an activity before it is returned by the {@link ActivityManager}
 */
public interface ActivityProcessor {

  /**
   * Process an activity
   * @param activity the activity. It can be modified
   */
  void processActivity(Activity activity);

  /**
   * Priority of this processor.
   * All activity processors will be executed in ascending priority order
   * @return
   */
  int getPriority();

}
{code}


For example, the following shows you how to implement a _SmileyProcessor_ that will replace text smileys by icons:

{code:java}
public class SmileyProcessor implements ActivityProcessor {

  String smiley =  "<img src='/images/smiley.gif'/>";

  public void processActivity(Activity activity) {
    String title = activity.getTitle();
     activity.setTitle(title.replaceAll(":-\\)", smiley));
  }

  public int getPriority() {
    return 100;
  }

}
{code}

{docbook}
<para xml:id="SOCref.DeveloperReferences.how_extend_the_activities_rendering.Configure_Processor">
<citetitle>
<emphasis role="bold">
Configure the processor
</emphasis>
</citetitle>
</para>
{docbook}

Now, you have a nice procesor, so need to hook it to the system.
At runtime, the processors can be attached to _ActivityManager_ via the _addProcessor(ActivityProcessor)_ method.

But there is also a component plugin hooked for it: _public void addProcessorPlugin(BaseActivityProcessorPlugin plugin)_.

So, to make your processor easy to hook, you simply need to let him extend the BaseActivityProcessorPlugin.

{code:java}
public class SmileyProcessor extends BaseActivityProcessorPlugin {

  String smiley =  "<img src='/images/smiley.gif'/>";

  public SmileyProcessor(InitParams params) {
    super(params);
  }

  public void processActivity(Activity activity) {
    String title = activity.getTitle();
      activity.setTitle(title.replaceAll(":-\\)", smiley));
  }
}
{code}

It will have the additional benefit to make the priority field configurable, so you do not need to implement _getPriorty()_.

Then your processor can be configured as a component plugin like this:

{code:xml}
<external-component-plugins>
  <target-component>org.exoplatform.social.core.activitystream.ActivityManager</target-component>
  <component-plugin>
    <name>SmileyProcessor</name>
    <set-method>addProcessorPlugin</set-method>
    <type>org.example.SmileyProcessor</type>
    <init-params>
      <value-param>
        <name>priority</name>
        <description>priority of this processor (lower are executed first)</description>
        <value>2</value>
      </value-param>
    </init-params>
  </component-plugin>
</external-component-plugins>
{code}

Restart, then place the smiley images on the server.