Class ValueExpressionImpl
- All Implemented Interfaces:
Externalizable
,Serializable
Expression
that can get or set a value.
In previous incarnations of this API, expressions could only be read. ValueExpression
objects can now be
used both to retrieve a value and to set a value. Expressions that can have a value set on them are referred to as
l-value expressions. Those that cannot are referred to as r-value expressions. Not all r-value expressions can be
used as l-value expressions (e.g. "${1+1}"
or "${firstName} ${lastName}"
). See the EL
Specification for details. Expressions that cannot be used as l-values must always return true
from
isReadOnly()
.
The ExpressionFactory.createValueExpression(jakarta.el.ELContext, java.lang.String, java.lang.Class<?>)
method can be used to parse an expression string and return a
concrete instance of ValueExpression
that encapsulates the parsed expression. The FunctionMapper
is used at parse time, not evaluation time, so one is not needed to evaluate an expression using this class. However,
the ELContext
is needed at evaluation time.
The getValue(jakarta.el.ELContext)
, setValue(jakarta.el.ELContext, java.lang.Object)
, isReadOnly(jakarta.el.ELContext)
and getType(jakarta.el.ELContext)
methods will evaluate the
expression each time they are called. The ELResolver
in the ELContext
is used to resolve the
top-level variables and to determine the behavior of the .
and []
operators. For any of the
four methods, the ELResolver.getValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object)
method is used to resolve all properties up to but excluding the last
one. This provides the base
object. At the last resolution, the ValueExpression
will call
the corresponding ELResolver.getValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object)
, ELResolver.setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
, ELResolver.isReadOnly(jakarta.el.ELContext, java.lang.Object, java.lang.Object)
or
ELResolver.getType(jakarta.el.ELContext, java.lang.Object, java.lang.Object)
method, depending on which was called on the ValueExpression
.
See the notes about comparison, serialization and immutability in the Expression
javadocs.
- Version:
- $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: dochez $
- See Also:
-
Field Summary
FieldsModifier and TypeFieldDescriptionprivate Class
<?> private String
private FunctionMapper
private Node
private VariableMapper
-
Constructor Summary
ConstructorsConstructorDescriptionValueExpressionImpl
(String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType) -
Method Summary
Modifier and TypeMethodDescriptionboolean
Determines whether the specified object is equal to thisExpression
.Class
<?> Returns the type the result of the expression will be coerced to after evaluation.Returns the type the result of the expression will be coerced to after evaluation.private Node
getNode()
Class
<?> Evaluates the expression relative to the provided context, and returns the most general type that is acceptable for an object to be passed as thevalue
parameter in a future call to theValueExpression.setValue(jakarta.el.ELContext, java.lang.Object)
method.Evaluates the expression relative to the provided context, and returns the resulting value.getValueReference
(ELContext context) Returns aValueReference
for this expression instance.int
hashCode()
Returns the hash code for thisExpression
.boolean
Returns whether this expression was created from only literal text.boolean
isReadOnly
(ELContext context) Evaluates the expression relative to the provided context, and returnstrue
if a call toValueExpression.setValue(jakarta.el.ELContext, java.lang.Object)
will always fail.void
void
Evaluates the expression relative to the provided context, and sets the result to the provided value.toString()
void
-
Field Details
-
expectedType
-
expr
-
fnMapper
-
varMapper
-
node
-
-
Constructor Details
-
ValueExpressionImpl
public ValueExpressionImpl() -
ValueExpressionImpl
public ValueExpressionImpl(String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType)
-
-
Method Details
-
equals
Description copied from class:Expression
Determines whether the specified object is equal to thisExpression
.The result is
true
if and only if the argument is notnull
, is anExpression
object that is the of the same type (ValueExpression
orMethodExpression
), 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 correspondingFunctionMapper
s mappedfn1:foo
andfn2:foo
to the same method.- Specified by:
equals
in classExpression
- Parameters:
obj
- theObject
to test for equality.- Returns:
true
ifobj
equals thisExpression
;false
otherwise.- See Also:
-
getExpectedType
Description copied from class:ValueExpression
Returns the type the result of the expression will be coerced to after evaluation.- Specified by:
getExpectedType
in classValueExpression
- Returns:
- the
expectedType
passed to theExpressionFactory.createValueExpression
method that created thisValueExpression
.
-
getExpressionString
Returns the type the result of the expression will be coerced to after evaluation.- Specified by:
getExpressionString
in classExpression
- Returns:
- the
expectedType
passed to theExpressionFactory.createValueExpression
method that created thisValueExpression
. - See Also:
-
getNode
- Returns:
- The Node for the expression
- Throws:
ELException
-
getType
Description copied from class:ValueExpression
Evaluates the expression relative to the provided context, and returns the most general type that is acceptable for an object to be passed as thevalue
parameter in a future call to theValueExpression.setValue(jakarta.el.ELContext, java.lang.Object)
method.This is not always the same as
getValue().getClass()
. For example, in the case of an expression that references an array element, thegetType
method will return the element type of the array, which might be a superclass of the type of the actual element that is currently in the specified array element.- Specified by:
getType
in classValueExpression
- Parameters:
context
- The context of this evaluation.- Returns:
- the most general acceptable type; otherwise undefined.
- Throws:
PropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.ELException
- if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.
-
getValueReference
public ValueReference getValueReference(ELContext context) throws PropertyNotFoundException, ELException Description copied from class:ValueExpression
Returns aValueReference
for this expression instance.- Overrides:
getValueReference
in classValueExpression
- Parameters:
context
- the context of this evaluation- Returns:
- the
ValueReference
for thisValueExpression
, ornull
if thisValueExpression
is not a reference to a base (null or non-null) and a property. If the base is null, and the property is a Jakarta Expression Language variable, return theValueReference
for theValueExpression
associated with this Jakarta Expression Language variable. - Throws:
PropertyNotFoundException
ELException
-
getValue
Description copied from class:ValueExpression
Evaluates the expression relative to the provided context, and returns the resulting value.The resulting value is automatically coerced to the type returned by
getExpectedType()
, which was provided to theExpressionFactory
when this expression was created.- Specified by:
getValue
in classValueExpression
- Parameters:
context
- The context of this evaluation.- Returns:
- The result of the expression evaluation.
- Throws:
PropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.ELException
- if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.
-
hashCode
public int hashCode()Description copied from class:Expression
Returns the hash code for thisExpression
.See the note in the
Expression.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 theequals(Object)
method, then calling thehashCode
method on each of the two objects must produce the same integer result. Implementations must take special note and implementhashCode
correctly.- Specified by:
hashCode
in classExpression
- Returns:
- The hash code for this
Expression
. - See Also:
-
isLiteralText
public boolean isLiteralText()Description copied from class:Expression
Returns whether this expression was created from only literal text.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#{...}
).- Specified by:
isLiteralText
in classExpression
- Returns:
true
if this expression was created from only literal text;false
otherwise.
-
isReadOnly
Description copied from class:ValueExpression
Evaluates the expression relative to the provided context, and returnstrue
if a call toValueExpression.setValue(jakarta.el.ELContext, java.lang.Object)
will always fail.- Specified by:
isReadOnly
in classValueExpression
- Parameters:
context
- The context of this evaluation.- Returns:
true
if the expression is read-only orfalse
if not.- Throws:
PropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.ELException
- if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available. * @throws NullPointerException if context isnull
-
readExternal
- Specified by:
readExternal
in interfaceExternalizable
- Throws:
IOException
ClassNotFoundException
-
setValue
public void setValue(ELContext context, Object value) throws PropertyNotFoundException, PropertyNotWritableException, ELException Description copied from class:ValueExpression
Evaluates the expression relative to the provided context, and sets the result to the provided value.- Specified by:
setValue
in classValueExpression
- Parameters:
context
- The context of this evaluation.value
- The new value to be set.- Throws:
PropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.PropertyNotWritableException
- if the final variable or property resolution failed because the specified variable or property is not writable.ELException
- if an exception was thrown while attempting to set the property or variable. The thrown exception must be included as the cause property of this exception, if available.
-
writeExternal
- Specified by:
writeExternal
in interfaceExternalizable
- Throws:
IOException
-
toString
-