public final class ValueExpressionImpl extends ValueExpression implements Externalizable
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 and Description |
---|
ValueExpressionImpl() |
ValueExpressionImpl(String expr,
Node node,
FunctionMapper fnMapper,
VariableMapper varMapper,
Class<?> expectedType) |
Modifier and Type | Method and Description |
---|---|
boolean |
equals(Object obj)
Determines whether the specified object is equal to this
Expression . |
Class<?> |
getExpectedType()
Returns the type the result of the expression will be coerced to after evaluation.
|
String |
getExpressionString()
Returns the type the result of the expression will be coerced to after evaluation.
|
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(javax.el.ELContext, java.lang.Object) method. |
Object |
getValue(ELContext context)
Evaluates the expression relative to the provided context, and returns the resulting value.
|
ValueReference |
getValueReference(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(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(ObjectInput in) |
void |
setValue(ELContext context,
Object value)
Evaluates the expression relative to the provided context, and sets the result to the provided value.
|
String |
toString() |
void |
writeExternal(ObjectOutput out) |
public ValueExpressionImpl()
public ValueExpressionImpl(String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType)
public boolean equals(Object obj)
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 Expression
obj
- the Object
to test for equality.true
if obj
equals this Expression
; false
otherwise.Hashtable
,
Object.equals(java.lang.Object)
public Class<?> getExpectedType()
ValueExpression
getExpectedType
in class ValueExpression
expectedType
passed to the ExpressionFactory.createValueExpression
method that
created this ValueExpression
.public String getExpressionString()
getExpressionString
in class Expression
expectedType
passed to the ExpressionFactory.createValueExpression
method that
created this ValueExpression
.Expression.getExpressionString()
public Class<?> getType(ELContext context) throws PropertyNotFoundException, ELException
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 ValueExpression
context
- 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 ValueReference getValueReference(ELContext context) throws PropertyNotFoundException, ELException
ValueExpression
ValueReference
for this expression instance.getValueReference
in class ValueExpression
context
- the context of this evaluationValueReference
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 Jakarta Expression Language variable, return the ValueReference
for the
ValueExpression
associated with this Jakarta Expression Language variable.PropertyNotFoundException
ELException
public Object getValue(ELContext context) throws PropertyNotFoundException, ELException
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 ValueExpression
context
- 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 int hashCode()
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 Expression
Expression
.Expression.equals(java.lang.Object)
,
Hashtable
,
Object.hashCode()
public boolean isLiteralText()
Expression
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 #{...}
).
isLiteralText
in class Expression
true
if this expression was created from only literal text; false
otherwise.public boolean isReadOnly(ELContext context) throws PropertyNotFoundException, ELException
ValueExpression
true
if a call to
ValueExpression.setValue(javax.el.ELContext, java.lang.Object)
will always fail.isReadOnly
in class ValueExpression
context
- 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(ObjectInput in) throws IOException, ClassNotFoundException
readExternal
in interface Externalizable
IOException
ClassNotFoundException
public void setValue(ELContext context, Object value) throws PropertyNotFoundException, PropertyNotWritableException, ELException
ValueExpression
setValue
in class ValueExpression
context
- 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(ObjectOutput out) throws IOException
writeExternal
in interface Externalizable
IOException
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