Class ValueExpressionImpl
- All Implemented Interfaces:
- Externalizable,- Serializable
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.
- Author:
- Jacob Hookom [jacob@hookom.net]
- See Also:
- 
Constructor SummaryConstructorsConstructorDescriptionValueExpressionImpl(String expr, org.apache.el.parser.Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType) 
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Method SummaryModifier and TypeMethodDescriptionbooleanClass<?>Returns the type the result of the expression will be coerced to after evaluation.Class<?><T> TgetValueReference(ELContext context) inthashCode()booleanbooleanisReadOnly(ELContext context) voidvoidtoString()void
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Constructor Details- 
ValueExpressionImplpublic ValueExpressionImpl()
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ValueExpressionImplpublic ValueExpressionImpl(String expr, org.apache.el.parser.Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType) 
 
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Method Details- 
equals- Specified by:
- equalsin class- Expression
 
- 
getExpectedType- Specified by:
- getExpectedTypein class- ValueExpression
 
- 
getExpressionStringReturns the type the result of the expression will be coerced to after evaluation.- Specified by:
- getExpressionStringin class- Expression
- Returns:
- the expectedTypepassed to theExpressionFactory.createValueExpressionmethod that created thisValueExpression.
- See Also:
 
- 
getType- Specified by:
- getTypein class- ValueExpression
- Parameters:
- context- The EL context for this evaluation
- Returns:
- The type of the result of this value expression
- Throws:
- PropertyNotFoundException- If a property/variable resolution failed because no match was found or a match was found but was not readable
- ELException- Wraps any exception throw whilst resolving a property or variable
 
- 
getValue- Specified by:
- getValuein class- ValueExpression
- Type Parameters:
- T- The expected type for the result of evaluating this value expression
- Parameters:
- context- The EL context for this evaluation
- Returns:
- The result of evaluating this value expression
- Throws:
- PropertyNotFoundException- If a property/variable resolution failed because no match was found or a match was found but was not readable
- ELException- Wraps any exception throw whilst resolving a property or variable
 
- 
hashCodepublic int hashCode()- Specified by:
- hashCodein class- Expression
 
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isLiteralTextpublic boolean isLiteralText()- Specified by:
- isLiteralTextin class- Expression
 
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isReadOnly- Specified by:
- isReadOnlyin class- ValueExpression
- Parameters:
- context- The EL context for this evaluation
- Returns:
- trueif this expression is read only otherwise- false
- Throws:
- PropertyNotFoundException- If a property/variable resolution failed because no match was found or a match was found but was not readable
- ELException- Wraps any exception throw whilst resolving a property or variable
 
- 
readExternal- Specified by:
- readExternalin interface- Externalizable
- Throws:
- IOException
- ClassNotFoundException
 
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setValuepublic void setValue(ELContext context, Object value) throws PropertyNotFoundException, PropertyNotWritableException, ELException - Specified by:
- setValuein class- ValueExpression
- Parameters:
- context- The EL context for this evaluation
- value- The value to set the property to which this value expression refers
- Throws:
- PropertyNotFoundException- If a property/variable resolution failed because no match was found
- PropertyNotWritableException- If a property/variable resolution failed because a match was found but was not writable
- ELException- Wraps any exception throw whilst resolving a property or variable
 
- 
writeExternal- Specified by:
- writeExternalin interface- Externalizable
- Throws:
- IOException
 
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toString
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getValueReference- Overrides:
- getValueReferencein class- ValueExpression
- Parameters:
- context- The EL context for this evaluation
- Returns:
- This default implementation always returns null
- Since:
- EL 2.2
 
 
-