uk.ac.sheffield.vtts.model

Class Parameter

java.lang.Object

uk.ac.sheffield.vtts.model.Element

uk.ac.sheffield.vtts.model.Named

uk.ac.sheffield.vtts.model.Expression

uk.ac.sheffield.vtts.model.Parameter

Direct Known Subclasses:

Constant, Failure, Input, Output, Variable

public abstract class Parameter
extends Expression

Parameter is a kind of expression denoting a named and typed parameter. Parameter is the ancestor of Constant, Variable, Input and Output, which are the actual kinds of Parameter used in model specifications. A Parameter may be supplied with an XML content string, which is converted to a strongly-typed object when the Parameter is first evaluated. With the exception of Constant, all other kinds of Parameter may either be bound or unbound. When a Parameter is unbound, its value is null and evaluating will return null. When a Parameter is bound, evaluating will always return a non-null strongly-typed object. This will either be the cached value, or a value created from the XML content string, possibly using default initialisation rules if no content exists.

Version:

Broker@Cloud 1.0

Author:

Anthony J H Simons

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	bound Flag denoting whether this Parameter is currently bound.
protected java.lang.String	content The textual printed representation of the value, or null.
protected java.lang.Object	value The strongly-typed bound value of this Parameter, or null.

Fields inherited from class uk.ac.sheffield.vtts.model.Expression

factory, type

Fields inherited from class uk.ac.sheffield.vtts.model.Named

name

Constructor Summary

Constructors

Constructor and Description
Parameter() Creates a default parameter.
Parameter(java.lang.String name, java.lang.String type) Creates a parameter of the given name and type.

Method Summary

Methods

Modifier and Type	Method and Description
void	assign(java.lang.Object value) Assigns a new bound value to this Parameter.
java.lang.Object	evaluate() Evaluates this Parameter expression.
java.lang.Boolean	getBound() Optionally returns the value of the bound flag for marshalling.
java.lang.String	getContent() Returns the content of this Parameter.
boolean	isAssignable() Reports whether this Parameter is re-assignable.
boolean	isBound() Reports whether this Parameter is bound.
void	rebind() Rebinds this Parameter to its default value.
void	rebind(java.lang.Object value) Rebinds this Parameter to the given value.
Parameter	resolve(Scope scope) Degenerate method to resolve Parameter references in this Parameter.
Parameter	setBound(boolean value) Sets whether this Parameter is bound.
Parameter	setContent(java.lang.String content) Sets the content of this Parameter.
Parameter	snapshot() Takes a snapshot of this Parameter, fixing its current bound value.
java.lang.String	toString() The printable representation of a parameter is its name.
void	unbind() Unbinds this Parameter.

Methods inherited from class uk.ac.sheffield.vtts.model.Expression

equals, getName, getType, hashCode, isBottom, isOrdered, setType

Methods inherited from class uk.ac.sheffield.vtts.model.Named

setName, setName

Methods inherited from class uk.ac.sheffield.vtts.model.Element

safeEquals, safeHashCode, semanticError

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

bound

protected boolean bound

Flag denoting whether this Parameter is currently bound. Initially false for all Parameters, except Constants, which are always bound, this may be set to true by Assignment of some value, and may also be affected by calls to rebind, or unbind.

value

protected java.lang.Object value

The strongly-typed bound value of this Parameter, or null.

content

protected java.lang.String content

The textual printed representation of the value, or null.

Constructor Detail

Parameter

public Parameter()

Creates a default parameter.

Parameter

public Parameter(java.lang.String name,
         java.lang.String type)

Creates a parameter of the given name and type.

Parameters:

name - the name of this parameter.

type - the type of this parameter.

Method Detail

isAssignable

public boolean isAssignable()

Reports whether this Parameter is re-assignable. By default, the result is true, since most Parameters may be re-assigned new values in an Assignment expression. This method is overridden in Constant, to return false, since a Constant may not be re-assigned, but may only be initialised.

Specified by:

isAssignable in class Expression

Returns:

true, by default.

evaluate

public java.lang.Object evaluate()

Evaluates this Parameter expression. Returns the bound value of this Parameter, if it is currently bound. If a bound value exists, returns this; otherwise creates the bound value from the specified textual content and caches it. If no content is specified, performs default initialisation to false, zero, null byte, empty String, empty List, Set or Map, etc. according to type. If this Parameter is not bound, returns null.

Specified by:

evaluate in class Expression

Returns:

the bound value of this Parameter.

setBound

public Parameter setBound(boolean value)

Sets whether this Parameter is bound. Initially this Parameter is not bound, unless it is a Constant.

Parameters:

value - true, if this Parameter is bound.

Returns:

this Parameter.

getBound

public java.lang.Boolean getBound()

Optionally returns the value of the bound flag for marshalling. This returns true only if this Parameter is assignable and also bound to a value; otherwise returns null. Redefined in Constant to return null, to reduce XML clutter, since Constants are always bound.

Returns:

the Boolean object true, or null.

isBound

public boolean isBound()

Reports whether this Parameter is bound. Returns the value of the bound flag. Use this in preference to getBound() when testing the bound status, since this is the proper query method.

Specified by:

isBound in class Expression

Returns:

true if this Parameter is bound.

unbind

public void unbind()

Unbinds this Parameter. Sets the bound flag to false, and deletes any cached copy of this Parameter's strongly-typed bound value. This is invoked during protocol checking, when searching for values that may satisfy a compound condition.

Specified by:

unbind in class Expression

rebind

public void rebind()

Rebinds this Parameter to its default value. Sets the bound flag to true, so that any subsequent evaluation will create and cache a default value, according to type. This is invoked during protocol checking, when searching for values that may satisfy a compound condition.

Specified by:

rebind in class Expression

rebind

public void rebind(java.lang.Object value)

Rebinds this Parameter to the given value. Sets the bound flag to true. Assumes that the value is in fact of the correct type.

Specified by:

rebind in class Expression

Parameters:

value - the value to bind.

resolve

public Parameter resolve(Scope scope)

Degenerate method to resolve Parameter references in this Parameter. This is a null operation, since a Parameter is an atomic expression and contains no further embedded Parameter references that need to be resolved.

Specified by:

resolve in class Expression

Parameters:

scope - a table of global and local Parameters currently in scope.

Returns:

this Expression.

assign

public void assign(java.lang.Object value)

Assigns a new bound value to this Parameter. The value is the result of evaluating some other Expression, which is now being bound to this Parameter. The value is cached and the bound flag is set to true. This method is overridden in Constant, which may not reassign values.

Specified by:

assign in class Expression

Parameters:

value - the value to assign.

toString

public java.lang.String toString()

The printable representation of a parameter is its name.

Overrides:

toString in class Named

Returns:

the name of this parameter.

setContent

public Parameter setContent(java.lang.String content)

Sets the content of this Parameter.

Parameters:

content - the content, as a String.

Returns:

this Parameter.

getContent

public java.lang.String getContent()

Returns the content of this Parameter.

Returns:

the content of this Parameter.

snapshot

public Parameter snapshot()

Takes a snapshot of this Parameter, fixing its current bound value. Clones this Parameter, whether it is a Constant, Variable, Input or output, creating a true copy. Converts its current bound value back to a String value, so that the snapshot is ready to be marshalled as XML data. This is used during test generation, to create snapshots of Parameters that are shared by other test cases, before they are rebound in the next test case.

Returns:

a clone of this Parameter, with a snapshot of its value.