org.jboss.byteman.rule.expression
Class Expression

java.lang.Object
  extended by org.jboss.byteman.rule.RuleElement
      extended by org.jboss.byteman.rule.expression.Expression
Direct Known Subclasses:
AssignableExpression, BooleanLiteral, 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
protected  int charPos
           
protected  int line
           
protected  Rule rule
           
protected  ParseNode token
           
protected  Type type
           
 
Constructor Summary
protected Expression(Rule rule, Type type, ParseNode token)
          Create a new expression.
 
Method Summary
abstract  void bind()
          verify that variables mentioned in this expression are actually available in the rule bindings list
 java.lang.String getPos()
           
 Type getType()
           
abstract  java.lang.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(java.io.StringWriter stringWriter)
           
 
Methods inherited from class org.jboss.byteman.rule.RuleElement
compile, compileBooleanConversion, compileBox, compileNumericConversion, compileObjectConversion, compilePrimitiveConversion, compileStringConversion, compileTypeConversion, compileUnbox, getBindings, getTypeGroup, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

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:
type - the current type 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

getPos

public java.lang.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:
Throws:
TypeException

interpret

public abstract java.lang.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

writeTo

public abstract void writeTo(java.io.StringWriter stringWriter)
Specified by:
writeTo in class RuleElement