org.josql.expressions
Class SaveValue

java.lang.Object
  org.josql.expressions.Expression
      org.josql.expressions.ValueExpression
          org.josql.expressions.SaveValue

public class SaveValue
extends ValueExpression

Constructor Summary

SaveValue()

Method Summary

Object	evaluate(Object o, Query q)
String	getAccessor()
Class	getExpectedReturnType(Query q) Return the class of the object that "should" be returned from a call to the: Expression.getValue(Object,Query) method.
String	getName()
Object	getValue(Object o, Query q) Get the value for this expression based upon the object passed in.
boolean	hasFixedResult(Query q) Return whether the expression will evaluate to a fixed/constant result.
void	init(Query q) Perform the necessary initialisation for this expression.
boolean	isTrue(Object o, Query q) This method allows ANY expression (including those that extend ValueExpression) to be used in the WHERE and HAVING clauses but ensuring that a boolean value is available for every expression.
void	setAccessor(String acc)
void	setName(String name)
String	toString() Return a string representation of the expression, making this abstract forces sub-classes to provide an implementation.

Methods inherited from class org.josql.expressions.Expression

isBracketed, setBracketed

Methods inherited from class java.lang.Object

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

Constructor Detail

SaveValue

public SaveValue()

Method Detail

getExpectedReturnType

public Class getExpectedReturnType(Query q)
                            throws QueryParseException

Description copied from class: Expression

Return the class of the object that "should" be returned from a call to the: Expression.getValue(Object,Query) method. It may be that repeated executions of a query will return different classes from this method. In general sub-classes should take this variance into account.

Specified by:

getExpectedReturnType in class Expression

Parameters:

q - The Query object.

Returns:

The expected type that will be returned from the Expression.getValue(Object,Query) method.

Throws:

QueryParseException - If something goes wrong with determining the type.

init

public void init(Query q)

Description copied from class: Expression

Perform the necessary initialisation for this expression. The exact operations performed are defined by the sub-class.

Specified by:

init in class Expression

Parameters:

q - The Query object.

getName

public String getName()

setName

public void setName(String name)

getValue

public Object getValue(Object o,
                       Query q)
                throws QueryExecutionException

Description copied from class: Expression

Get the value for this expression based upon the object passed in. In general sub-classes should perform some operation on the object to generate their result. The Query object is provided so that sub-classes can gain access to the bind variables (if required), save values and so on. Whilst it may seem better to have the Query object as a member of this class this would then prevent the expression from being used separately from the Query (a design goal of JoSQL, i.e. independent processing).

Overrides:

getValue in class ValueExpression

Parameters:

o - The current object that the expression should be evaluated on.

q - The Query object.

Returns:

The value of the expression.

Throws:

QueryExecutionException - If something goes wrong with gaining the value.

isTrue

public boolean isTrue(Object o,
                      Query q)
               throws QueryExecutionException

Description copied from class: Expression

This method allows ANY expression (including those that extend ValueExpression) to be used in the WHERE and HAVING clauses but ensuring that a boolean value is available for every expression.

Specified by:

isTrue in class Expression

Parameters:

o - The current object to evaluate the expression on.

q - The Query object.

Returns:

true if the expression evaluates to true (well duh...).

Throws:

QueryExecutionException - If there is a problem with the execution of the expression.

getAccessor

public String getAccessor()

setAccessor

public void setAccessor(String acc)

evaluate

public Object evaluate(Object o,
                       Query q)
                throws QueryExecutionException

Specified by:

evaluate in class ValueExpression

Throws:

QueryExecutionException

toString

public String toString()

Description copied from class: Expression

Return a string representation of the expression, making this abstract forces sub-classes to provide an implementation.

Specified by:

toString in class Expression

Returns:

A string representation of the expression.

hasFixedResult

public boolean hasFixedResult(Query q)

Description copied from class: Expression

Return whether the expression will evaluate to a fixed/constant result. This allows certain optimisations to be performed when an expression is evaluated. A "fixed result" is basically one in which multiple calls to either the: Expression.isTrue(Object,Query) or Expression.getValue(Object,Query) methods will return the same object (or that o1.equals (o2) == true) regardless of the object passed to the method.

Specified by:

hasFixedResult in class Expression

Parameters:

q - The Query object.

Returns:

true if the expression evaluates to a fixed/constant result.