org.apache.openjpa.kernel.exps
Class AggregateVal

java.lang.Object
  extended by org.apache.openjpa.kernel.exps.Val
      extended by org.apache.openjpa.kernel.exps.AggregateVal
All Implemented Interfaces:
Serializable, Value
Direct Known Subclasses:
Avg, Count, Max, Min, Sum

abstract class AggregateVal
extends Val

An aggregate of some value.

Author:
Abe White

Constructor Summary
AggregateVal(Val val)
          Constructor.
 
Method Summary
 void acceptVisit(ExpressionVisitor visitor)
          Accept a visit from a tree visitor.
protected  Collection eval(Collection candidates, Object orig, StoreContext ctx, Object[] params)
          Return a list of values resulting from evaluating each given candidate.
protected  Object eval(Object candidate, Object orig, StoreContext ctx, Object[] params)
          Return this value for the given candidate.
 Class getType()
          Return the expected type for this value, or Object if the type is unknown.
protected abstract  Class getType(Class c)
          Return the type of this aggregate based on the value type.
 boolean isAggregate()
          Return true if this value is an aggregate.
protected abstract  Object operate(Collection os, Class c)
          Aggregate the given values.
 void setImplicitType(Class type)
          Set the implicit type of the value, based on how it is used in the filter.
 
Methods inherited from class org.apache.openjpa.kernel.exps.Val
evaluate, evaluate, getMetaData, isVariable, isXPath, setMetaData
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

AggregateVal

public AggregateVal(Val val)
Constructor. Supply value to aggregate.

Method Detail

isAggregate

public boolean isAggregate()
Description copied from interface: Value
Return true if this value is an aggregate.

Specified by:
isAggregate in interface Value
Overrides:
isAggregate in class Val

getType

public Class getType()
Description copied from interface: Value
Return the expected type for this value, or Object if the type is unknown.


setImplicitType

public void setImplicitType(Class type)
Description copied from interface: Value
Set the implicit type of the value, based on how it is used in the filter. This method is only called on values who return Object from Value.getType().


eval

protected Object eval(Object candidate,
                      Object orig,
                      StoreContext ctx,
                      Object[] params)
Description copied from class: Val
Return this value for the given candidate.

Specified by:
eval in class Val

eval

protected Collection eval(Collection candidates,
                          Object orig,
                          StoreContext ctx,
                          Object[] params)
Description copied from class: Val
Return a list of values resulting from evaluating each given candidate. By default, this implementation invokes #eval(Object,Object,StoreContext,Map) for each instance and packs the return value into a new list. Aggregates should override.

Overrides:
eval in class Val

getType

protected abstract Class getType(Class c)
Return the type of this aggregate based on the value type.


operate

protected abstract Object operate(Collection os,
                                  Class c)
Aggregate the given values.


acceptVisit

public void acceptVisit(ExpressionVisitor visitor)
Description copied from interface: Value
Accept a visit from a tree visitor.

Specified by:
acceptVisit in interface Value
Overrides:
acceptVisit in class Val


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