Package org.jboss.byteman.rule.expression

Class Expression

java.lang.Object

org.jboss.byteman.rule.RuleElement

org.jboss.byteman.rule.expression.Expression

Direct Known Subclasses:

ArrayInitExpression, AssignableExpression, BooleanLiteral, ClassLiteralExpression, MethodExpression, NewExpression, NullLiteral, NumericLiteral, OperExpression, ReturnExpression, StringLiteral, ThrowExpression

public abstract class Expression
extends RuleElement

abstract class representing an evaluable expression. this is used in all 3 elements of ECA rules: as the value part of each of the event bindings in the binding list comprising an ECA rule event; as the condition expression of an ECA rule condition;and as an element of the actions list in an ECA rule action.

Field Summary

Fields

Modifier and Type	Field	Description
protected int	charPos
protected int	line
protected Rule	rule
protected ParseNode	token
protected Type	type

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Expression(Rule rule, Type type, ParseNode token)	Create a new expression.

Method Summary

Modifier and Type	Method	Description
abstract void	bind()	verify that variables mentioned in this expression are actually available in the rule bindings list
String	getPos()
Type	getType()
abstract Object	interpret(HelperAdapter helper)	evaluate the expression by interpreting the expression tree
abstract Type	typeCheck(Type expected)	ensure that all type references in the expression and its component expressions can be resolved, that the type of the expression is well-defined and that it is compatible with the type expected in the context in which it occurs.
abstract void	writeTo(StringWriter stringWriter)

Methods inherited from class java.lang.Object

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

Methods inherited from class org.jboss.byteman.rule.RuleElement

compile, getBindings, getTypeGroup, rebox, toString

Field Detail

rule

protected Rule rule

type

protected Type type

charPos

protected int charPos

line

protected int line

token

protected ParseNode token

Constructor Detail

Expression

protected Expression(Rule rule,
                     Type type,
                     ParseNode token)

Create a new expression.

Parameters:

rule - the rule for this expression

type - the type for this expression

token - the token for this expression

Method Detail

bind

public abstract void bind()
                   throws TypeException

verify that variables mentioned in this expression are actually available in the rule bindings list

Throws:

TypeException - if any variable is missing or has the wrong type

getPos

public String getPos()

getType

public Type getType()

typeCheck

public abstract Type typeCheck(Type expected)
                        throws TypeException

ensure that all type references in the expression and its component expressions can be resolved, that the type of the expression is well-defined and that it is compatible with the type expected in the context in which it occurs.

Specified by:

typeCheck in class RuleElement

Parameters:

expected - the type expected for the expression in the contxet in which it occurs. this may be void but should not be undefined at the point where type checking is performed.

Returns:

the type of the expression

Throws:

TypeException - if a type check failure occurs

interpret

public abstract Object interpret(HelperAdapter helper)
                          throws ExecuteException

evaluate the expression by interpreting the expression tree

Specified by:

interpret in class RuleElement

Parameters:

helper - an execution context associated with the rule which contains a map of current bindings for rule variables and another map of their declared types both of which are indexed by variable name. This includes entries for the helper (name "-1"), the recipient if the trigger method is not static (name "0") and the trigger method arguments (names "1", ...)

Returns:

the result of evaluation as an Object

Throws:

ExecuteException - if an error occurs during execution

writeTo

public abstract void writeTo(StringWriter stringWriter)

Specified by:

writeTo in class RuleElement