org.apache.openjpa.jdbc.kernel.exps
Class IsEmptyExpression

java.lang.Object
  org.apache.openjpa.jdbc.kernel.exps.IsEmptyExpression

All Implemented Interfaces:

Serializable, Exp, Expression

 class IsEmptyExpression
extends Object
implements Exp

Tests whether the given value is empty.

Author:

Abe White

Constructor Summary

IsEmptyExpression(Val val)
Constructor.

Method Summary

void	acceptVisit(ExpressionVisitor visitor) Accept a visit from a tree visitor.
void	appendTo(Select sel, ExpContext ctx, ExpState state, SQLBuffer buf) Append the SQL for this expression to the given buffer.
ExpState	initialize(Select sel, ExpContext ctx, Map contains) Initialize the expression.
void	selectColumns(Select sel, ExpContext ctx, ExpState state, boolean pks) Select just the columns for this expression.

Methods inherited from class java.lang.Object

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

Constructor Detail

IsEmptyExpression

public IsEmptyExpression(Val val)

Constructor. Supply value to test.

Method Detail

initialize

public ExpState initialize(Select sel,
                           ExpContext ctx,
                           Map contains)

Description copied from interface: Exp

Initialize the expression. This method should recursively initialize any sub-expressions or values.

Specified by:

initialize in interface Exp

contains - map of relation paths to the number of times the paths appear in a contains() expression; used to ensure paths used for contains() within the same AND expression used different aliases

appendTo

public void appendTo(Select sel,
                     ExpContext ctx,
                     ExpState state,
                     SQLBuffer buf)

Description copied from interface: Exp

Append the SQL for this expression to the given buffer. The SQL should optionally include any joins this expression needs.

Specified by:

appendTo in interface Exp

selectColumns

public void selectColumns(Select sel,
                          ExpContext ctx,
                          ExpState state,
                          boolean pks)

Description copied from interface: Exp

Select just the columns for this expression.

Specified by:

selectColumns in interface Exp

acceptVisit

public void acceptVisit(ExpressionVisitor visitor)

Description copied from interface: Expression

Accept a visit from a tree visitor.

Specified by:

acceptVisit in interface Expression