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

Class SQLSelectValue<T>

java.lang.Object

uk.ac.ed.epcc.webapp.jdbc.expr.SQLSelectValue<T>

Type Parameters:

T -

All Implemented Interfaces:

GroupingSQLValue<T>, SQLValue<T>, Targetted<T>

public class SQLSelectValue<T>
extends java.lang.Object
implements GroupingSQLValue<T>

A SQLValue that returns the first non null result from a set of SQLValues

Constructor Summary

Constructors

Constructor and Description
SQLSelectValue(java.lang.Class<T> target, SQLValue<T>[] accessors)

Method Summary

Modifier and Type	Method and Description
int	add(java.lang.StringBuilder sb, boolean qualify) Add the expression to a StringBuilder
int	addGroup(java.lang.StringBuilder sb, boolean qualify) Add the group-by clause to a query.
boolean	checkContentsCanGroup() return false if this instance is not able to perform grouping.
java.util.List<PatternArgument>	getGroupParameters(java.util.List<PatternArgument> list) Get the parameters for a group-by clause.
java.util.List<PatternArgument>	getParameters(java.util.List<PatternArgument> list) Add parameters for this value to a list.
SQLFilter	getRequiredFilter() Get an SQLFilter required to be added to the filter set.
java.lang.Class<T>	getTarget() Get the type of the returned object as far as it is known.
T	makeObject(java.sql.ResultSet rs, int pos) Extract a result of the expression from a ResultSet into an object of the specified type.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Methods inherited from interface uk.ac.ed.epcc.webapp.jdbc.expr.GroupingSQLValue

groupingIsomorphic

Constructor Detail

SQLSelectValue

public SQLSelectValue(java.lang.Class<T> target,
                      SQLValue<T>[] accessors)

Method Detail

getTarget

public java.lang.Class<T> getTarget()

Description copied from interface: Targetted

Get the type of the returned object as far as it is known. Normally this should be the erasure type corresponding to T.

Specified by:

getTarget in interface Targetted<T>

Returns:

Class object for return type

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

add

public int add(java.lang.StringBuilder sb,
               boolean qualify)

Description copied from interface: SQLValue

Add the expression to a StringBuilder

Specified by:

add in interface SQLValue<T>

Parameters:

sb - StringBuilder to modify

qualify - boolean should fields be qualified with the table name

Returns:

number of fields added

getParameters

public java.util.List<PatternArgument> getParameters(java.util.List<PatternArgument> list)

Description copied from interface: SQLValue

Add parameters for this value to a list.

Specified by:

getParameters in interface SQLValue<T>

Parameters:

list - to modify

Returns:

modified list of parameter objects

makeObject

public T makeObject(java.sql.ResultSet rs,
                    int pos)
             throws DataException,
                    java.sql.SQLException

Description copied from interface: SQLValue

Extract a result of the expression from a ResultSet into an object of the specified type. Note that this method is also used to extract the result of functions over the result type.

Specified by:

makeObject in interface SQLValue<T>

Parameters:

rs - ResultSet

Returns:

produced object

Throws:

DataException

java.sql.SQLException

getRequiredFilter

public SQLFilter getRequiredFilter()

Description copied from interface: SQLValue

Get an SQLFilter required to be added to the filter set. This is usually to implement a join.

Specified by:

getRequiredFilter in interface SQLValue<T>

Returns:

null or SQLFilter

addGroup

public int addGroup(java.lang.StringBuilder sb,
                    boolean qualify)

Description copied from interface: GroupingSQLValue

Add the group-by clause to a query. Note this can be a null operation in which case it will return zero.

Specified by:

addGroup in interface GroupingSQLValue<T>

Returns:

actual number of fields added

getGroupParameters

public java.util.List<PatternArgument> getGroupParameters(java.util.List<PatternArgument> list)

Description copied from interface: GroupingSQLValue

Get the parameters for a group-by clause.

Specified by:

getGroupParameters in interface GroupingSQLValue<T>

Returns:

modified list

checkContentsCanGroup

public boolean checkContentsCanGroup()

Description copied from interface: GroupingSQLValue

return false if this instance is not able to perform grouping.

Specified by:

checkContentsCanGroup in interface GroupingSQLValue<T>

Returns: