public final class ValueExpressionImpl
extends ValueExpression
implements java.io.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
javax.el.ExpressionFactory#createValueExpression
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(ELContext)
, setValue(ELContext, java.lang.Object)
, isReadOnly(ELContext)
and
getType(ELContext)
methods will evaluate the expression each time they are
called. The javax.el.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 javax.el.ELResolver#getValue
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
javax.el.ELResolver#getValue
, javax.el.ELResolver#setValue
,
javax.el.ELResolver#isReadOnly
or javax.el.ELResolver#getType
method, depending on which was called on the ValueExpression
.
See the notes about comparison, serialization and immutability in
the javax.el.Expression
javadocs.
javax.el.ELResolver
,
javax.el.Expression
,
javax.el.ExpressionFactory
,
javax.el.ValueExpression
Constructor and Description |
---|
ValueExpressionImpl() |
ValueExpressionImpl(java.lang.String expr,
Node node,
FunctionMapper fnMapper,
VariableMapper varMapper,
java.lang.Class<?> expectedType) |
Modifier and Type | Method and Description |
---|---|
boolean |
equals(java.lang.Object obj) |
java.lang.Class<?> |
getExpectedType() |
java.lang.String |
getExpressionString()
Returns the type the result of the expression will be coerced to after
evaluation.
|
java.lang.Class<?> |
getType(ELContext context) |
java.lang.Object |
getValue(ELContext context) |
ValueReference |
getValueReference(ELContext context) |
int |
hashCode() |
boolean |
isLiteralText() |
boolean |
isReadOnly(ELContext context) |
void |
readExternal(java.io.ObjectInput in) |
void |
setValue(ELContext context,
java.lang.Object value) |
java.lang.String |
toString() |
void |
writeExternal(java.io.ObjectOutput out) |
public ValueExpressionImpl()
public ValueExpressionImpl(java.lang.String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, java.lang.Class<?> expectedType)
public boolean equals(java.lang.Object obj)
public java.lang.Class<?> getExpectedType()
public java.lang.String getExpressionString()
expectedType
passed to the
ExpressionFactory.createValueExpression
method
that created this ValueExpression
.javax.el.Expression#getExpressionString()
public java.lang.Class<?> getType(ELContext context) throws PropertyNotFoundException, ELException
PropertyNotFoundException
ELException
public java.lang.Object getValue(ELContext context) throws PropertyNotFoundException, ELException
PropertyNotFoundException
ELException
public int hashCode()
public boolean isLiteralText()
public boolean isReadOnly(ELContext context) throws PropertyNotFoundException, ELException
PropertyNotFoundException
ELException
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(ELContext context, java.lang.Object value) throws PropertyNotFoundException, PropertyNotWritableException, ELException
PropertyNotFoundException
PropertyNotWritableException
ELException
public void writeExternal(java.io.ObjectOutput out) throws java.io.IOException
writeExternal
in interface java.io.Externalizable
java.io.IOException
public java.lang.String toString()
public ValueReference getValueReference(ELContext context)