biz.chitec.quarterback.util.logic
Class EqualsExpr

java.lang.Object
  biz.chitec.quarterback.util.logic.EqualsExpr

All Implemented Interfaces:

java.lang.Cloneable, LogicExpr

public class EqualsExpr

extends java.lang.Object

implements LogicExpr

Tests for equality between the representation of the left argument in the universe and the constant in the right argument. Equality test uses java.lang.Object.equals(). null is allowed and is equal to null only. SQL checking uses "=" and takes the escaped toString() result of the constant value.

Version:

$Id: a577dcd3b196fd94ae2c476b80b98733cbd23da0 $

Author:

chitec/Dirk Hillbrecht 2001, cantamen/Dirk Hillbrecht 2004. Distributed under the terms of the GNU LGPL.

Nested Class Summary

Nested classes inherited from class biz.chitec.quarterback.util.logic.LogicExpr

LogicExpr.Converter, LogicExpr.UniverseGenerator

Field Summary

private java.lang.Object	key
private java.lang.Object	value

Constructor Summary

EqualsExpr(java.lang.Object kx, java.lang.Object vx)

Method Summary

java.lang.Object	clone() Deep-copy the logic expression.
void	convertValues(LogicExpr.Converter c) Conversion of values in the expressions (e.g. for replacing external representations of database entries with their internal key)
boolean	equals(java.lang.Object o)
boolean	evaluate(java.lang.Object universe) Is the expression valid in the given universe
java.lang.Object[]	getInternalVars() Only for GJSA class parsers: get class variables to create object from a parsed string.
java.lang.Object	getKey()
int[]	getResultSet(LogicExpr.UniverseGenerator generator) Equals operation cannot be mapped sensibly onto universe subset selection.
java.lang.Object	getValue()
boolean	isReady() Returns if the expression is actually evaluable, i.e. any of the evaluating methods can be called.
boolean	isTreeReady() Returns whether this and all deeper expressions are evaluable.
java.lang.String	sqlString(java.util.Map identifiers) Returns an SQL representation of the expression with the constant names replaced by the ones in the given Map.

Methods inherited from class java.lang.Object

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

Field Detail

key

private java.lang.Object key

value

private java.lang.Object value

Constructor Detail

EqualsExpr

public EqualsExpr(java.lang.Object kx,
                  java.lang.Object vx)

Method Detail

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Description copied from interface: LogicExpr

Deep-copy the logic expression. The contract for this method says the the logic expression must be deep-copied. I.e. if clone() is called for the root expression of a certain expression tree, a completely independent tree is returned.

Note: This method must be defined in a way that makes it quite complicated to call it for simply cloning a logic expression tree: It returns an Object (which always happens to be a LogicExpr) and it might throw a CloneNotSupportedException - which will (a) never happen and is (b) no RuntimeException, so a caller would always have to catch it.

To make life simpler, there is a static method LogicExprUtilties.cloneLogicExpr() which will call clone() on the root object and take care of return value and exceptions.

Specified by:

clone in interface LogicExpr

Throws:

java.lang.CloneNotSupportedException

equals

public boolean equals(java.lang.Object o)

isReady

public boolean isReady()

Description copied from interface: LogicExpr

Returns if the expression is actually evaluable, i.e. any of the evaluating methods can be called. If this method returns false, the expression should not be evaluated. Note that this method does not care for the evaluation state of any potential children of this LogicExpr. Use isTreeEvaluable() for this test.

Specified by:

isReady in interface LogicExpr

Returns:

True if an evaluation is possible, false if not.

isTreeReady

public boolean isTreeReady()

Description copied from interface: LogicExpr

Returns whether this and all deeper expressions are evaluable. Walks through the the expression tree and returns only true if all expressions below are evaluable.

Specified by:

isTreeReady in interface LogicExpr

Returns:

True if this and all expressions below are evaluable, false otherwise.

getKey

public java.lang.Object getKey()

getValue

public java.lang.Object getValue()

evaluate

public boolean evaluate(java.lang.Object universe)

Is the expression valid in the given universe

Specified by:

evaluate in interface LogicExpr

getResultSet

public int[] getResultSet(LogicExpr.UniverseGenerator generator)

Equals operation cannot be mapped sensibly onto universe subset selection.

Specified by:

getResultSet in interface LogicExpr

sqlString

public java.lang.String sqlString(java.util.Map identifiers)

Description copied from interface: LogicExpr

Returns an SQL representation of the expression with the constant names replaced by the ones in the given Map.

Specified by:

sqlString in interface LogicExpr

getInternalVars

public java.lang.Object[] getInternalVars()

Description copied from interface: LogicExpr

Only for GJSA class parsers: get class variables to create object from a parsed string.

Specified by:

getInternalVars in interface LogicExpr

convertValues

public void convertValues(LogicExpr.Converter c)

Description copied from interface: LogicExpr

Conversion of values in the expressions (e.g. for replacing external representations of database entries with their internal key)

Specified by:

convertValues in interface LogicExpr