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(jakarta.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(jakarta.el.ELContext), setValue(jakarta.el.ELContext, java.lang.Object), isReadOnly(jakarta.el.ELContext) and getType(jakarta.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(jakarta.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(jakarta.el.ELContext, java.lang.Object, java.lang.Object), ELResolver.setValue(jakarta.el.ELContext, java.lang.Object, java.lang.Object, java.lang.Object), ELResolver.isReadOnly(jakarta.el.ELContext, java.lang.Object, java.lang.Object) or
ELResolver.getType(jakarta.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 Form| Constructor and Description |
|---|
ValueExpressionImpl() |
ValueExpressionImpl(String expr,
Node node,
FunctionMapper fnMapper,
VariableMapper varMapper,
Class<?> expectedType) |
| 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(ELContext context) |
Object |
getValue(ELContext context) |
ValueReference |
getValueReference(ELContext context) |
int |
hashCode() |
boolean |
isLiteralText() |
boolean |
isReadOnly(ELContext context) |
void |
readExternal(ObjectInput in) |
void |
setValue(ELContext context,
Object 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)
equals in class Expressionpublic Class<?> getExpectedType()
getExpectedType in class ValueExpressionpublic String getExpressionString()
getExpressionString in class ExpressionexpectedType passed to the ExpressionFactory.createValueExpression method that
created this ValueExpression.Expression.getExpressionString()public Class<?> getType(ELContext context) throws PropertyNotFoundException, ELException
getType in class ValueExpressionPropertyNotFoundExceptionELExceptionpublic ValueReference getValueReference(ELContext context) throws PropertyNotFoundException, ELException
getValueReference in class ValueExpressionPropertyNotFoundExceptionELExceptionpublic Object getValue(ELContext context) throws PropertyNotFoundException, ELException
getValue in class ValueExpressionPropertyNotFoundExceptionELExceptionpublic int hashCode()
hashCode in class Expressionpublic boolean isLiteralText()
isLiteralText in class Expressionpublic boolean isReadOnly(ELContext context) throws PropertyNotFoundException, ELException
isReadOnly in class ValueExpressionPropertyNotFoundExceptionELExceptionpublic void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
readExternal in interface ExternalizableIOExceptionClassNotFoundExceptionpublic void setValue(ELContext context, Object value) throws PropertyNotFoundException, PropertyNotWritableException, ELException
setValue in class ValueExpressionPropertyNotFoundExceptionPropertyNotWritableExceptionELExceptionpublic void writeExternal(ObjectOutput out) throws IOException
writeExternal in interface ExternalizableIOExceptionComments to: el-dev@eclipse.org.
Copyright © 2018, 2020 Eclipse Foundation. All rights reserved.
Use is subject to license terms.