public abstract class Expression extends Object implements Serializable
ValueExpression
and MethodExpression
, implementing
characteristics 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 and Description |
---|
Expression() |
Modifier and Type | Method and Description |
---|---|
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.
|
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 ${fn2:foo()}
are equal if their corresponding FunctionMapper
s
mapped fn1:foo
and fn2:foo
to the same method.
equals
in class Object
obj
- the Object
to test for equality.true
if obj
equals this Expression
; false
otherwise.Hashtable
,
Object.equals(java.lang.Object)
public abstract int hashCode()
Expression
.
See the note in the equals(java.lang.Object)
method on how two expressions can be equal if their expression Strings are
different. Recall that if two objects are equal according to the equals(Object)
method, then calling the
hashCode
method on each of the two objects must produce the same integer result. Implementations must
take special note and implement hashCode
correctly.
hashCode
in class Object
Expression
.equals(java.lang.Object)
,
Hashtable
,
Object.hashCode()
public abstract boolean isLiteralText()
This method must return true
if and only if the expression string this expression was created from
contained no unescaped Jakarta Expression Language delimeters (${...}
or #{...}
).
true
if this expression was created from only literal text; false
otherwise.Comments to: el-dev@eclipse.org.
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Use is subject to license terms.