uk.ac.ed.epcc.webapp.jdbc.expr

Class CountDistinctMapMapper<K>

java.lang.Object

uk.ac.ed.epcc.webapp.AbstractContexed

uk.ac.ed.epcc.webapp.jdbc.expr.SQLGroupMapper<java.util.Map<K,R>>

uk.ac.ed.epcc.webapp.jdbc.expr.GeneralMapMapper<K,R>

uk.ac.ed.epcc.webapp.jdbc.expr.MapMapper<K,java.lang.Number>

uk.ac.ed.epcc.webapp.jdbc.expr.CountDistinctMapMapper<K>

Type Parameters:

K - key type

All Implemented Interfaces:

Contexed, ResultMapper<java.util.Map<K,java.lang.Number>>

public class CountDistinctMapMapper<K>
extends MapMapper<K,java.lang.Number>

A MapMapper where the data field is Numerical data combined by countign distinct values As the key is a SQLValue rather than a SQLExpression we may have multiple SQL rows mapping to the same key so numerical results may have to be combined.

Field Summary

Fields inherited from class uk.ac.ed.epcc.webapp.jdbc.expr.SQLGroupMapper

qualify, use_alias

Fields inherited from class uk.ac.ed.epcc.webapp.AbstractContexed

conn

Constructor Summary

Constructors

Constructor and Description
CountDistinctMapMapper(AppContext c, GroupingSQLValue<K> key, java.lang.String key_name, SQLExpression<? extends java.lang.Number> val, java.lang.String value_name)

Method Summary

Modifier and Type	Method and Description
protected java.lang.Number	combine(java.lang.Number a, java.lang.Number b) If more than one database value maps to the same key we may have to combine multiple results.

Methods inherited from class uk.ac.ed.epcc.webapp.jdbc.expr.MapMapper

getNullKey, makeKey, makeResult

Methods inherited from class uk.ac.ed.epcc.webapp.jdbc.expr.GeneralMapMapper

makeDefault, makeObject

Methods inherited from class uk.ac.ed.epcc.webapp.jdbc.expr.SQLGroupMapper

addAverage, addClause, addCount, addCount, addKey, addKeyList, addMaxDate, addMaxNumber, addMinDate, addMinNumber, addSQLAverage, addSQLCount, addSum, getModify, getModifyParameters, getRequiredFilter, getTarget, getTargetObject, getTargetParameters, setQualify, setUseAlias

Methods inherited from class uk.ac.ed.epcc.webapp.AbstractContexed

getContext, getLogger, resetLogger

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface uk.ac.ed.epcc.webapp.Contexed

getContext

Constructor Detail

CountDistinctMapMapper

public CountDistinctMapMapper(AppContext c,
                              GroupingSQLValue<K> key,
                              java.lang.String key_name,
                              SQLExpression<? extends java.lang.Number> val,
                              java.lang.String value_name)
                       throws InvalidKeyException

Throws:

InvalidKeyException

Method Detail

combine

protected java.lang.Number combine(java.lang.Number a,
                                   java.lang.Number b)

Description copied from class: GeneralMapMapper

If more than one database value maps to the same key we may have to combine multiple results. This method defines how multiple results are combined. If combination is not possible this method needs to throw CombineException if the first parameter is non-null.

Overrides:

combine in class GeneralMapMapper<K,java.lang.Number>

Parameters:

a - previous value

b - new value

Returns:

combined value