net.esper.view.std
Class MergeView

java.lang.Object
  extended by net.esper.view.ViewSupport
      extended by net.esper.view.std.MergeView
All Implemented Interfaces:
java.lang.Iterable<EventBean>, ContextAwareView, EventCollection, ParentAwareView, View, Viewable

public final class MergeView
extends ViewSupport
implements ParentAwareView, ContextAwareView

The merge view works together with a group view that splits the data in a stream to multiple subviews, based on a key index. Every group view requires a merge view to merge the many subviews back into a single view. Typically the last view in a chain containing a group view is a merge view. The merge view has no other responsibility then becoming the single last instance in the chain to which external listeners for updates can be attached to receive updates for the many subviews that have this merge view as common child views. The parent view of this view is generally the AddPropertyValueView that adds the grouped-by information back into the data.


Field Summary
 
Fields inherited from class net.esper.view.ViewSupport
parent
 
Constructor Summary
MergeView()
          Default constructor - required by all views to adhere to the Java bean specification.
MergeView(java.lang.String groupFieldName)
          Constructor.
MergeView(java.lang.String[] groupFieldNames)
          Constructor.
 
Method Summary
 void addParentView(AddPropertyValueView parentView)
          Add a parent data merge view.
 java.lang.String attachesTo(Viewable parentView)
          Return null if the view will accept being attached to a particular object.
 EventType getEventType()
          Provides metadata information about the type of object the event collection contains.
 java.lang.String[] getGroupFieldNames()
          Returns the field name that contains the values to group by.
 java.lang.Class[] getGroupFieldTypes()
          Returns types of fields used in the group-by.
 ViewServiceContext getViewServiceContext()
          Returns the context instances used by the view.
 java.util.Iterator<EventBean> iterator()
          Allows iteration through all elements in this event collection.
 void setEventType(EventType eventType)
          Sets event type - required for successful view copy.
 void setGroupFieldNames(java.lang.String[] groupFieldNames)
          Sets the field name that contains the values to group by.
 void setGroupFieldType(java.lang.Class[] groupFieldTypes)
          Sets types of fields used in the group-by.
 void setParentAware(java.util.List<View> parentViews)
          Called to indicate the parent views.
 void setViewServiceContext(ViewServiceContext viewServiceContext)
          Set the services context containing service handles.
 java.lang.String toString()
           
 void update(EventBean[] newData, EventBean[] oldData)
          Notify that data has been added or removed from the Viewable parent.
 
Methods inherited from class net.esper.view.ViewSupport
addView, dumpChildViews, dumpUpdateParams, findDescendent, getParent, getViews, hasViews, removeView, setParent, shallowCopyView, updateChildren, updateChildren
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

MergeView

public MergeView()
Default constructor - required by all views to adhere to the Java bean specification.


MergeView

public MergeView(java.lang.String groupFieldName)
Constructor.

Parameters:
groupFieldName - is the field from which to pull the value to group by

MergeView

public MergeView(java.lang.String[] groupFieldNames)
Constructor.

Parameters:
groupFieldNames - is the fields from which to pull the value to group by
Method Detail

getGroupFieldNames

public final java.lang.String[] getGroupFieldNames()
Returns the field name that contains the values to group by.

Returns:
field name providing group key value

getViewServiceContext

public ViewServiceContext getViewServiceContext()
Description copied from interface: ContextAwareView
Returns the context instances used by the view.

Specified by:
getViewServiceContext in interface ContextAwareView
Returns:
context instance

setViewServiceContext

public void setViewServiceContext(ViewServiceContext viewServiceContext)
Description copied from interface: ContextAwareView
Set the services context containing service handles.

Specified by:
setViewServiceContext in interface ContextAwareView
Parameters:
viewServiceContext - with service handles

setGroupFieldNames

public final void setGroupFieldNames(java.lang.String[] groupFieldNames)
Sets the field name that contains the values to group by.

Parameters:
groupFieldNames - is the field names providing group key values

setEventType

public void setEventType(EventType eventType)
Sets event type - required for successful view copy.

Parameters:
eventType - is the event type

getGroupFieldTypes

public java.lang.Class[] getGroupFieldTypes()
Returns types of fields used in the group-by.

Returns:
types for group-by fields

setGroupFieldType

public void setGroupFieldType(java.lang.Class[] groupFieldTypes)
Sets types of fields used in the group-by.

Parameters:
groupFieldTypes - - types for group-by fields

addParentView

public final void addParentView(AddPropertyValueView parentView)
Add a parent data merge view.

Parameters:
parentView - is the parent data merge view to add

attachesTo

public final java.lang.String attachesTo(Viewable parentView)
Description copied from interface: View
Return null if the view will accept being attached to a particular object.

Specified by:
attachesTo in interface View
Parameters:
parentView - is the potential parent for this view
Returns:
null if this view can successfully attach to the parent, an error message if it cannot.

setParentAware

public void setParentAware(java.util.List<View> parentViews)
Description copied from interface: ParentAwareView
Called to indicate the parent views.

Specified by:
setParentAware in interface ParentAwareView
Parameters:
parentViews - is a list of parent views in top-down order

getEventType

public final EventType getEventType()
Description copied from interface: EventCollection
Provides metadata information about the type of object the event collection contains.

Specified by:
getEventType in interface EventCollection
Returns:
metadata for the objects in the collection

update

public final void update(EventBean[] newData,
                         EventBean[] oldData)
Description copied from interface: View
Notify that data has been added or removed from the Viewable parent. The last object in the newData array of objects would be the newest object added to the parent view. The first object of the oldData array of objects would be the oldest object removed from the parent view. If the call to update contains new (inserted) data, then the first argument will be a non-empty list and the second will be empty. Similarly, if the call is a notification of deleted data, then the first argument will be empty and the second will be non-empty. Either the newData or oldData will be non-null. This method won't be called with both arguments being null, but either one could be null. The same is true for zero-length arrays. Either newData or oldData will be non-empty. If both are non-empty, then the update is a modification notification. When update() is called on a view by the parent object, the data in newData will be in the collection of the parent, and its data structures will be arranged to reflect that. The data in oldData will not be in the parent's data structures, and any access to the parent will indicate that that data is no longer there.

Specified by:
update in interface View
Parameters:
newData - is the new data that has been added to the parent view
oldData - is the old data that has been removed from the parent view

iterator

public final java.util.Iterator<EventBean> iterator()
Description copied from interface: EventCollection
Allows iteration through all elements in this event collection. The iterator will return the elements in the collection in their natural order, or, if there is no natural ordering, in some unpredictable order.

Specified by:
iterator in interface java.lang.Iterable<EventBean>
Specified by:
iterator in interface EventCollection
Returns:
an iterator which will go through all current elements in the collection.

toString

public final java.lang.String toString()
Overrides:
toString in class java.lang.Object