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java.lang.Objectorg.jdesktop.el.Expression
org.jdesktop.el.ValueExpression
org.jdesktop.el.impl.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(org.jdesktop.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(org.jdesktop.el.ELContext), setValue(org.jdesktop.el.ELContext, java.lang.Object), isReadOnly(org.jdesktop.el.ELContext) and
getType(org.jdesktop.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(org.jdesktop.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(org.jdesktop.el.ELContext, java.lang.Object, java.lang.Object),
ELResolver.setValue(org.jdesktop.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object), ELResolver.isReadOnly(org.jdesktop.el.ELContext, java.lang.Object, java.lang.Object) or
ELResolver.getType(org.jdesktop.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.
javax.el.ELResolver,
javax.el.Expression,
javax.el.ExpressionFactory,
javax.el.ValueExpression,
Serialized Form| Nested Class Summary |
|---|
| Nested classes/interfaces inherited from class org.jdesktop.el.Expression |
|---|
Expression.ResolvedProperty, Expression.Result |
| Constructor Summary | |
|---|---|
ValueExpressionImpl()
|
|
ValueExpressionImpl(java.lang.String expr,
Node node,
FunctionMapper fnMapper,
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. |
Expression.Result |
getResult(ELContext context,
boolean trackResolvedObjects)
|
java.lang.Class |
getType(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(org.jdesktop.el.ELContext, java.lang.Object) method. |
java.lang.Object |
getValue(ELContext context)
Evaluates the expression relative to the provided context, and returns the resulting value. |
int |
hashCode()
Returns the hash code for this Expression. |
boolean |
isLiteralText()
Returns whether this expression was created from only literal text. |
boolean |
isReadOnly(ELContext context)
Evaluates the expression relative to the provided context, and returns true if a call to ValueExpression.setValue(org.jdesktop.el.ELContext, java.lang.Object) will
always fail. |
void |
readExternal(java.io.ObjectInput in)
|
void |
setValue(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 org.jdesktop.el.ValueExpression |
|---|
getSource, setSource |
| 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,
FunctionMapper fnMapper,
VariableMapper varMapper,
java.lang.Class expectedType)
| Method Detail |
|---|
public boolean equals(java.lang.Object obj)
ExpressionExpression.
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 Expressionobj - 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()
ValueExpression
getExpectedType in class ValueExpressionexpectedType passed to the
ExpressionFactory.createValueExpression method
that created this ValueExpression.public java.lang.String getExpressionString()
getExpressionString in class ExpressionexpectedType passed to the
ExpressionFactory.createValueExpression method
that created this ValueExpression.javax.el.Expression#getExpressionString()
public java.lang.Class getType(ELContext context)
throws PropertyNotFoundException,
ELException
ValueExpressionvalue parameter in a future call
to the ValueExpression.setValue(org.jdesktop.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 ValueExpressioncontext - The context of this evaluation.
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.
public java.lang.Object getValue(ELContext context)
throws PropertyNotFoundException,
ELException
ValueExpressionThe 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 ValueExpressioncontext - The context of this evaluation.
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.
public Expression.Result getResult(ELContext context,
boolean trackResolvedObjects)
throws PropertyNotFoundException,
ELException
getResult in class ValueExpressionPropertyNotFoundException
ELExceptionpublic int hashCode()
ExpressionExpression.
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 ExpressionExpression.Expression.equals(java.lang.Object),
Hashtable,
Object.hashCode()public boolean isLiteralText()
ExpressionThis 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 Expressiontrue if this expression was created from only
literal text; false otherwise.
public boolean isReadOnly(ELContext context)
throws PropertyNotFoundException,
ELException
ValueExpressiontrue if a call to ValueExpression.setValue(org.jdesktop.el.ELContext, java.lang.Object) will
always fail.
isReadOnly in class ValueExpressioncontext - The context of this evaluation.
true if the expression is read-only or
false if not.
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 is null
public void readExternal(java.io.ObjectInput in)
throws java.io.IOException,
java.lang.ClassNotFoundException
readExternal in interface java.io.Externalizablejava.io.IOException
java.lang.ClassNotFoundException
public void setValue(ELContext context,
java.lang.Object value)
throws PropertyNotFoundException,
PropertyNotWritableException,
ELException
ValueExpression
setValue in class ValueExpressioncontext - The context of this evaluation.value - The new value to be set.
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.
public void writeExternal(java.io.ObjectOutput out)
throws java.io.IOException
writeExternal in interface java.io.Externalizablejava.io.IOExceptionpublic java.lang.String toString()
toString in class java.lang.Object
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