org.apache.openjpa.kernel.exps
Class AggregateVal

java.lang.Object
  org.apache.openjpa.kernel.exps.Val
      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, getAlias, getMetaData, getName, getPath, getSelectAs, isVariable, isXPath, setAlias, 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