org.josql.expressions
Class SelectItemExpression

java.lang.Object
  org.josql.expressions.Expression
      org.josql.expressions.SelectItemExpression

public class SelectItemExpression
extends Expression

Field Summary

static String	KEY
static String	VALUE

Constructor Summary

SelectItemExpression()

Method Summary

Collection	getAddItems(Object v)
String	getAlias()
Class	getExpectedReturnType(Query q) Return the class of the object that "should" be returned from a call to the: Expression.getValue(Object,Query) method.
Expression	getExpression()
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	isAddItemsFromCollectionOrMap()
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	setAddItemsType(Class c)
void	setAddMapType(String t)
void	setAlias(String a)
void	setExpression(Expression exp)
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

Field Detail

KEY

public static final String KEY

See Also:

Constant Field Values

VALUE

public static final String VALUE

See Also:

Constant Field Values

Constructor Detail

SelectItemExpression

public SelectItemExpression()

Method Detail

getAlias

public String getAlias()

setAlias

public void setAlias(String a)

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.

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)
          throws QueryParseException

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.

Throws:

QueryParseException - If something goes wrong with the initialisation.

setAddMapType

public void setAddMapType(String t)

getAddItems

public Collection getAddItems(Object v)

isAddItemsFromCollectionOrMap

public boolean isAddItemsFromCollectionOrMap()

setAddItemsType

public void setAddItemsType(Class c)

getExpression

public Expression getExpression()

setExpression

public void setExpression(Expression exp)

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.

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).

Specified by:

getValue in class Expression

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.

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.