public final class ValueExpressionImpl extends javax.el.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.
- Version:
- $Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: kchung $
- Author:
- Jacob Hookom [jacob@hookom.net]
- See Also:
ELResolver
,
Expression
,
ExpressionFactory
,
ValueExpression
,
Serialized Form
-
-
Constructor Summary
Constructors
Constructor and Description
ValueExpressionImpl()
ValueExpressionImpl(String expr,
Node node,
javax.el.FunctionMapper fnMapper,
javax.el.VariableMapper varMapper,
Class expectedType)
-
Method Summary
All Methods Instance Methods Concrete Methods
Modifier and Type
Method and Description
boolean
equals(Object obj)
Class
getExpectedType()
String
getExpressionString()
Returns the type the result of the expression will be coerced to after
evaluation.
Class
getType(javax.el.ELContext context)
Object
getValue(javax.el.ELContext context)
int
hashCode()
boolean
isLiteralText()
boolean
isReadOnly(javax.el.ELContext context)
void
readExternal(ObjectInput in)
void
setValue(javax.el.ELContext context,
Object value)
String
toString()
void
writeExternal(ObjectOutput out)
-
-
Method Detail
-
equals
public boolean equals(Object obj)
- Specified by:
equals
in class javax.el.Expression
-
getExpectedType
public Class getExpectedType()
- Specified by:
getExpectedType
in class javax.el.ValueExpression
-
getExpressionString
public String getExpressionString()
Returns the type the result of the expression will be coerced to after
evaluation.
- Specified by:
getExpressionString
in class javax.el.Expression
- Returns:
- the
expectedType
passed to the
ExpressionFactory.createValueExpression
method
that created this ValueExpression
.
- See Also:
Expression.getExpressionString()
-
getType
public Class getType(javax.el.ELContext context)
throws javax.el.ELException
- Specified by:
getType
in class javax.el.ValueExpression
- Throws:
javax.el.ELException
-
getValue
public Object getValue(javax.el.ELContext context)
throws javax.el.ELException
- Specified by:
getValue
in class javax.el.ValueExpression
- Throws:
javax.el.ELException
-
hashCode
public int hashCode()
- Specified by:
hashCode
in class javax.el.Expression
-
isLiteralText
public boolean isLiteralText()
- Specified by:
isLiteralText
in class javax.el.Expression
-
isReadOnly
public boolean isReadOnly(javax.el.ELContext context)
throws javax.el.ELException
- Specified by:
isReadOnly
in class javax.el.ValueExpression
- Throws:
javax.el.ELException
-
readExternal
public void readExternal(ObjectInput in)
throws IOException,
ClassNotFoundException
- Specified by:
readExternal
in interface Externalizable
- Throws:
IOException
ClassNotFoundException
-
setValue
public void setValue(javax.el.ELContext context,
Object value)
throws javax.el.ELException
- Specified by:
setValue
in class javax.el.ValueExpression
- Throws:
javax.el.ELException
-
writeExternal
public void writeExternal(ObjectOutput out)
throws IOException
- Specified by:
writeExternal
in interface Externalizable
- Throws:
IOException
Copyright © 2006–2018 TinyGroup. All rights reserved.