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54
55 package org.apache.jetspeed.portlet.event;
56
57 import org.apache.jetspeed.portlet.Portlet;
58 import org.apache.jetspeed.portlet.PortletRequest;
59 import org.apache.jetspeed.portlet.PortletConfig;
60
61 /**
62  * The <CODE>Event</CODE> is the base interface for all events
63  * that can occur whithin the portlet container. To be informed
64  * of events, a listener has to be registered with the respective
65  * event source.
66  *
67  * <P>
68  * The portlet container delivers all events to the respective
69  * event listeners (and thereby the portlets) before the content
70  * generation is started. Should a listener, while processing the
71  * event, find that another event needs to be generated, that
72  * event will be queued by the portlet container and delivered
73  * at a point of time that is at the discretion of the portlet
74  * container. It is only guarantued that it will be deliverd
75  * and that it will happen before the content generation phase.
76  * </P>
77  * <P>
78  * This also means, that no further events will be delivered
79  * once the content generation phase has started. For example,
80  * message cannot be sent from within the service() methods.
81  * The resulting message event will not be delivered and
82  * essentially discarded.
83  * </P>
84  * <P>
85  * Intelligent portlet containers should provide a cyclic event
86  * detection mechanism, so that the portlet container does not
87  * come to a screaming halt, if two or more portlets happen
88  * to send each other events that are triggered by each other.
89  * </P>
90  *
91  * @author <A HREF="mailto:tboehme@us.ibm.com">Thomas F. Boehme</A>
92  */
93 public interface Event
94 {
95     /**
96      ** Returns the portlet request that has caused this event.
97      ** If this event is not triggered by a request,
98      ** this methods returns <CODE>null</CODE>.
99      **
100      ** @return the portlet request
101      **/
102
103     public PortletRequest getRequest ();
104
105     /**
106      ** Returns the virtual instance of the portlet
107      ** that receives this event.
108      **
109      ** @return the virtual instance of the portlet
110      **/
111
112     public Portlet getPortlet ();
113
114     /**
115      ** Returns the portlet config of the virtual instance
116      ** that receives this event.
117      **
118      ** @return the portlet config
119      **/
120
121     public PortletConfig getConfig ();
122
123 }
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