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java.lang.Object javax.el.Expression
public abstract class Expression
Base class for the expression subclasses ValueExpression
and
MethodExpression
, implementing characterstics common to both.
All expressions must implement the equals()
and
hashCode()
methods so that two expressions can be compared
for equality. They are redefined abstract in this class to force their
implementation in subclasses.
All expressions must also be Serializable
so that they
can be saved and restored.
Expression
s are also designed to be immutable so
that only one instance needs to be created for any given expression
String / FunctionMapper
. This allows a container to pre-create
expressions and not have to re-parse them each time they are evaluated.
Constructor Summary | |
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Expression()
|
Method Summary | |
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abstract boolean |
equals(Object obj)
Determines whether the specified object is equal to this Expression . |
abstract String |
getExpressionString()
Returns the original String used to create this Expression ,
unmodified. |
abstract int |
hashCode()
Returns the hash code for this Expression . |
abstract boolean |
isLiteralText()
Returns whether this expression was created from only literal text. |
Methods inherited from class java.lang.Object |
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clone, finalize, getClass, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public Expression()
Method Detail |
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public abstract String getExpressionString()
Expression
,
unmodified.
This is used for debugging purposes but also for the purposes of comparison (e.g. to ensure the expression in a configuration file has not changed).
This method does not provide sufficient information to
re-create an expression. Two different expressions can have exactly
the same expression string but different function mappings.
Serialization should be used to save and restore the state of an
Expression
.
public abstract boolean equals(Object obj)
Expression
.
The result is true
if and only if the argument is
not null
, is an Expression
object that
is the of the same type (ValueExpression
or
MethodExpression
), and has an identical parsed
representation.
Note that two expressions can be equal if their expression
Strings are different. For example, ${fn1:foo()}
and ${fn2:foo()}
are equal if their corresponding
FunctionMapper
s mapped fn1:foo
and
fn2:foo
to the same method.
obj
- the Object
to test for equality.
true
if obj
equals this
Expression
; false
otherwise.Hashtable
,
Object.equals(java.lang.Object)
public abstract int hashCode()
Expression
.
See the note in the equals(java.lang.Object)
method on how two expressions
can be equal if their expression Strings are different. Recall that
if two objects are equal according to the equals(Object)
method, then calling the hashCode
method on each of the
two objects must produce the same integer result. Implementations must
take special note and implement hashCode
correctly.
Expression
.equals(java.lang.Object)
,
Hashtable
,
Object.hashCode()
public abstract boolean isLiteralText()
This method must return true
if and only if the
expression string this expression was created from contained no
unescaped EL delimeters (${...}
or
#{...}
).
true
if this expression was created from only
literal text; false
otherwise.
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Copyright 2006 Sun Microsystems, Inc. All rights reserved.