| java.lang.Object
 org.josql.expressions.Expression
All known Subclasses: org.josql.expressions.SelectItemExpression, org.josql.expressions.ValueExpression, org.josql.expressions.BinaryExpression, org.josql.expressions.AliasedExpression,
| Expression | | abstract public class Expression (Code) | | The base class for all expressions.
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| Method Summary | |
| abstract public Class | getExpectedReturnType(Query q)
Return the class of the object that "should" be returned from a call to the:
Expression.getValue(Object,Query) method. | | abstract public Object | getValue(Object o, Query q)
Get the value for this expression based upon the object passed in. | | abstract public boolean | hasFixedResult(Query q)
Return whether the expression will evaluate to a fixed/constant result.
This allows certain optimisations to be performed when an expression is
evaluated. | | abstract public void | init(Query q)
Perform the necessary initialisation for this expression. | | public boolean | isBracketed()
| | abstract public 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.
Parameters:
o - The current object to evaluate the expression on.
Parameters:
q - The Query object. | | public void | setBracketed(boolean v)
| | abstract public String | toString()
Return a string representation of the expression, making this abstract forces
sub-classes to provide an implementation. |
| getValue | | abstract public Object getValue(Object o, Query q) throws QueryExecutionException(Code) | | 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).
Parameters:
o - The current object that the expression should be evaluated on.
Parameters:
q - The Query object. The value of the expression.
throws:
QueryExecutionException - If something goes wrong with gaining the value. |
| hasFixedResult | | abstract public boolean hasFixedResult(Query q)(Code) | | 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.
Parameters:
q - The Query object. true if the expression evaluates to a fixed/constant result. |
| init | | abstract public void init(Query q) throws QueryParseException(Code) | | Perform the necessary initialisation for this expression.
The exact operations performed are defined by the sub-class.
Parameters:
q - The Query object.
throws:
QueryParseException - If something goes wrong with the initialisation. |
| isBracketed | | public boolean isBracketed()(Code) | | |
| isTrue | | abstract public boolean isTrue(Object o, Query q) throws QueryExecutionException(Code) | | 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.
Parameters:
o - The current object to evaluate the expression on.
Parameters:
q - The Query object. true if the expression evaluates to true (well duh...).
throws:
QueryExecutionException - If there is a problem with the execution of the expression. |
| setBracketed | | public void setBracketed(boolean v)(Code) | | |
| toString | | abstract public String toString()(Code) | | Return a string representation of the expression, making this abstract forces
sub-classes to provide an implementation.
A string representation of the expression. |
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