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(javax.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(javax.el.ELContext)
, setValue(javax.el.ELContext, java.lang.Object)
, isReadOnly(javax.el.ELContext)
and
getType(javax.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(javax.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(javax.el.ELContext, java.lang.Object, java.lang.Object)
,
ELResolver.setValue(javax.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
, ELResolver.isReadOnly(javax.el.ELContext, java.lang.Object, java.lang.Object)
or
ELResolver.getType(javax.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 $
- Author:
- Jacob Hookom [jacob@hookom.net]
- See Also:
-
Constructor Summary
ConstructorsConstructorDescriptionValueExpressionImpl
(String expr, Node node, javax.el.FunctionMapper fnMapper, javax.el.VariableMapper varMapper, Class expectedType) -
Method Summary
Modifier and TypeMethodDescriptionboolean
Returns the type the result of the expression will be coerced to after evaluation.getType
(javax.el.ELContext context) getValue
(javax.el.ELContext context) javax.el.ValueReference
getValueReference
(javax.el.ELContext context) int
hashCode()
boolean
boolean
isReadOnly
(javax.el.ELContext context) void
void
toString()
void
-
Constructor Details
-
ValueExpressionImpl
public ValueExpressionImpl() -
ValueExpressionImpl
-
-
Method Details
-
equals
- Specified by:
equals
in classjavax.el.Expression
-
getExpectedType
- Specified by:
getExpectedType
in classjavax.el.ValueExpression
-
getExpressionString
Returns the type the result of the expression will be coerced to after evaluation.- Specified by:
getExpressionString
in classjavax.el.Expression
- Returns:
- the
expectedType
passed to theExpressionFactory.createValueExpression
method that created thisValueExpression
. - See Also:
-
getType
public Class getType(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException - Specified by:
getType
in classjavax.el.ValueExpression
- Throws:
javax.el.PropertyNotFoundException
javax.el.ELException
-
getValueReference
public javax.el.ValueReference getValueReference(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException - Overrides:
getValueReference
in classjavax.el.ValueExpression
- Throws:
javax.el.PropertyNotFoundException
javax.el.ELException
-
getValue
public Object getValue(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException - Specified by:
getValue
in classjavax.el.ValueExpression
- Throws:
javax.el.PropertyNotFoundException
javax.el.ELException
-
hashCode
public int hashCode()- Specified by:
hashCode
in classjavax.el.Expression
-
isLiteralText
public boolean isLiteralText()- Specified by:
isLiteralText
in classjavax.el.Expression
-
isReadOnly
public boolean isReadOnly(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException - Specified by:
isReadOnly
in classjavax.el.ValueExpression
- Throws:
javax.el.PropertyNotFoundException
javax.el.ELException
-
readExternal
- Specified by:
readExternal
in interfaceExternalizable
- Throws:
IOException
ClassNotFoundException
-
setValue
public void setValue(javax.el.ELContext context, Object value) throws javax.el.PropertyNotFoundException, javax.el.PropertyNotWritableException, javax.el.ELException - Specified by:
setValue
in classjavax.el.ValueExpression
- Throws:
javax.el.PropertyNotFoundException
javax.el.PropertyNotWritableException
javax.el.ELException
-
writeExternal
- Specified by:
writeExternal
in interfaceExternalizable
- Throws:
IOException
-
toString
-