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java.lang.Objectjavax.el.Expression
javax.el.ValueExpression
org.apache.el.ValueExpressionImpl
public final class ValueExpressionImpl
An 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.
ELResolver
,
Expression
,
ExpressionFactory
,
ValueExpression
,
Serialized FormConstructor Summary | |
---|---|
ValueExpressionImpl()
|
|
ValueExpressionImpl(java.lang.String expr,
Node node,
javax.el.FunctionMapper fnMapper,
javax.el.VariableMapper varMapper,
java.lang.Class expectedType)
|
Method Summary | |
---|---|
boolean |
equals(java.lang.Object obj)
Determines whether the specified object is equal to this Expression . |
java.lang.Class |
getExpectedType()
Returns the type the result of the expression will be coerced to after evaluation. |
java.lang.String |
getExpressionString()
Returns the type the result of the expression will be coerced to after evaluation. |
java.lang.Class |
getType(javax.el.ELContext context)
Evaluates the expression relative to the provided context, and returns the most general type that is acceptable for an object to be passed as the value parameter in a future call
to the ValueExpression.setValue(javax.el.ELContext, java.lang.Object) method. |
java.lang.Object |
getValue(javax.el.ELContext context)
Evaluates the expression relative to the provided context, and returns the resulting value. |
javax.el.ValueReference |
getValueReference(javax.el.ELContext context)
Returns a ValueReference for this expression instance. |
int |
hashCode()
Returns the hash code for this Expression . |
boolean |
isLiteralText()
Returns whether this expression was created from only literal text. |
boolean |
isReadOnly(javax.el.ELContext context)
Evaluates the expression relative to the provided context, and returns true if a call to ValueExpression.setValue(javax.el.ELContext, java.lang.Object) will
always fail. |
void |
readExternal(java.io.ObjectInput in)
|
void |
setValue(javax.el.ELContext context,
java.lang.Object value)
Evaluates the expression relative to the provided context, and sets the result to the provided value. |
java.lang.String |
toString()
|
void |
writeExternal(java.io.ObjectOutput out)
|
Methods inherited from class java.lang.Object |
---|
clone, finalize, getClass, notify, notifyAll, wait, wait, wait |
Constructor Detail |
---|
public ValueExpressionImpl()
public ValueExpressionImpl(java.lang.String expr, Node node, javax.el.FunctionMapper fnMapper, javax.el.VariableMapper varMapper, java.lang.Class expectedType)
Method Detail |
---|
public boolean equals(java.lang.Object obj)
javax.el.Expression
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 javax.el.Expression
obj
- the Object
to test for equality.
true
if obj
equals this
Expression
; false
otherwise.Hashtable
,
Object.equals(java.lang.Object)
public java.lang.Class getExpectedType()
javax.el.ValueExpression
getExpectedType
in class javax.el.ValueExpression
expectedType
passed to the
ExpressionFactory.createValueExpression
method
that created this ValueExpression
.public java.lang.String getExpressionString()
getExpressionString
in class javax.el.Expression
expectedType
passed to the
ExpressionFactory.createValueExpression
method
that created this ValueExpression
.Expression.getExpressionString()
public java.lang.Class getType(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException
javax.el.ValueExpression
value
parameter in a future call
to the ValueExpression.setValue(javax.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, the getType
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.
getType
in class javax.el.ValueExpression
context
- The context of this evaluation.
javax.el.PropertyNotFoundException
- if one of the property
resolutions failed because a specified variable or property
does not exist or is not readable.
javax.el.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.public java.lang.Object getValue(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException
javax.el.ValueExpression
The resulting value is automatically coerced to the type
returned by getExpectedType()
, which was
provided to the ExpressionFactory
when this
expression was created.
getValue
in class javax.el.ValueExpression
context
- The context of this evaluation.
javax.el.PropertyNotFoundException
- if one of the property
resolutions failed because a specified variable or property
does not exist or is not readable.
javax.el.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.public int hashCode()
javax.el.Expression
Expression
.
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 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 javax.el.Expression
Expression
.Expression.equals(java.lang.Object)
,
Hashtable
,
Object.hashCode()
public boolean isLiteralText()
javax.el.Expression
This method must return true
if and only if the
expression string this expression was created from contained no
unescaped EL delimeters (${...}
or
#{...}
).
isLiteralText
in class javax.el.Expression
true
if this expression was created from only
literal text; false
otherwise.public boolean isReadOnly(javax.el.ELContext context) throws javax.el.PropertyNotFoundException, javax.el.ELException
javax.el.ValueExpression
true
if a call to ValueExpression.setValue(javax.el.ELContext, java.lang.Object)
will
always fail.
isReadOnly
in class javax.el.ValueExpression
context
- The context of this evaluation.
true
if the expression is read-only or
false
if not.
javax.el.PropertyNotFoundException
- if one of the property
resolutions failed because a specified variable or property
does not exist or is not readable.
javax.el.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 is null
public void readExternal(java.io.ObjectInput in) throws java.io.IOException, java.lang.ClassNotFoundException
readExternal
in interface java.io.Externalizable
java.io.IOException
java.lang.ClassNotFoundException
public void setValue(javax.el.ELContext context, java.lang.Object value) throws javax.el.PropertyNotFoundException, javax.el.PropertyNotWritableException, javax.el.ELException
javax.el.ValueExpression
setValue
in class javax.el.ValueExpression
context
- The context of this evaluation.value
- The new value to be set.
javax.el.PropertyNotFoundException
- if one of the property
resolutions failed because a specified variable or property
does not exist or is not readable.
javax.el.PropertyNotWritableException
- if the final variable or
property resolution failed because the specified
variable or property is not writable.
javax.el.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.public void writeExternal(java.io.ObjectOutput out) throws java.io.IOException
writeExternal
in interface java.io.Externalizable
java.io.IOException
public javax.el.ValueReference getValueReference(javax.el.ELContext context)
javax.el.ValueExpression
ValueReference
for this expression instance.
getValueReference
in class javax.el.ValueExpression
context
- the context of this evaluation
ValueReference
for this
ValueExpression
, or null
if this
ValueExpression
is not a reference to
a base (null or non-null) and a property.
If the base is null, and the property is a EL variable, return
the ValueReference
for the
ValueExpression
associated with this EL variable.public java.lang.String toString()
toString
in class java.lang.Object
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