public abstract class Expression
extends java.lang.Object
implements java.io.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.
Expressions 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(java.lang.Object obj)
Determines whether the specified object is equal to this
Expression. |
abstract java.lang.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 java.lang.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(java.lang.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 ${fn2:foo()} are equal if their corresponding FunctionMappers
mapped fn1:foo and fn2:foo to the same method.
equals in class java.lang.Objectobj - the Object to test for equality.true if obj equals this Expression; false otherwise.Hashtable,
Object.equals(java.lang.Object)public abstract int hashCode()
Expression.
See the note in the equals(java.lang.Object) method on how two expressions can be equal if their expression Strings are
different. Recall that if two objects are equal according to the equals(Object) method, then calling the
hashCode method on each of the two objects must produce the same integer result. Implementations must
take special note and implement hashCode correctly.
hashCode in class java.lang.ObjectExpression.equals(java.lang.Object),
Hashtable,
Object.hashCode()public abstract boolean isLiteralText()
This method must return true if and only if the expression string this expression was created from
contained no unescaped Jakarta Expression Language delimeters (${...} or #{...}).
true if this expression was created from only literal text; false otherwise.