Class ValueExpressionImpl
- java.lang.Object
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- javax.el.Expression
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- javax.el.ValueExpression
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- org.apache.el.ValueExpressionImpl
 
 
 
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- All Implemented Interfaces:
- java.io.Externalizable,- java.io.Serializable
 
 public final class ValueExpressionImpl extends ValueExpression implements java.io.Externalizable AnExpressionthat can get or set a value.In previous incarnations of this API, expressions could only be read. ValueExpressionobjects 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 returntruefromisReadOnly().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 ofValueExpressionthat encapsulates the parsed expression. TheFunctionMapperis used at parse time, not evaluation time, so one is not needed to evaluate an expression using this class. However, theELContextis needed at evaluation time.The getValue(javax.el.ELContext),setValue(javax.el.ELContext, java.lang.Object),isReadOnly(javax.el.ELContext)andgetType(javax.el.ELContext)methods will evaluate the expression each time they are called. TheELResolverin theELContextis used to resolve the top-level variables and to determine the behavior of the.and[]operators. For any of the four methods, theELResolver.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 thebaseobject. At the last resolution, theValueExpressionwill call the correspondingELResolver.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)orELResolver.getType(javax.el.ELContext, java.lang.Object, java.lang.Object)method, depending on which was called on theValueExpression.See the notes about comparison, serialization and immutability in the Expressionjavadocs.- Author:
- Jacob Hookom [jacob@hookom.net]
- See Also:
- ELResolver,- Expression,- ExpressionFactory,- ValueExpression, Serialized Form
 
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Constructor SummaryConstructors Constructor Description ValueExpressionImpl()ValueExpressionImpl(java.lang.String expr, org.apache.el.parser.Node node, FunctionMapper fnMapper, VariableMapper varMapper, java.lang.Class<?> expectedType)
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Method SummaryAll Methods Instance Methods Concrete Methods Modifier and Type Method Description booleanequals(java.lang.Object obj)java.lang.Class<?>getExpectedType()java.lang.StringgetExpressionString()Returns the type the result of the expression will be coerced to after evaluation.java.lang.Class<?>getType(ELContext context)java.lang.ObjectgetValue(ELContext context)ValueReferencegetValueReference(ELContext context)inthashCode()booleanisLiteralText()booleanisReadOnly(ELContext context)voidreadExternal(java.io.ObjectInput in)voidsetValue(ELContext context, java.lang.Object value)java.lang.StringtoString()voidwriteExternal(java.io.ObjectOutput out)
 
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Constructor Detail- 
ValueExpressionImplpublic ValueExpressionImpl() 
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ValueExpressionImplpublic ValueExpressionImpl(java.lang.String expr, org.apache.el.parser.Node node, FunctionMapper fnMapper, VariableMapper varMapper, java.lang.Class<?> expectedType)
 
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Method Detail- 
equalspublic boolean equals(java.lang.Object obj) - Specified by:
- equalsin class- Expression
 
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getExpectedTypepublic java.lang.Class<?> getExpectedType() - Specified by:
- getExpectedTypein class- ValueExpression
 
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getExpressionStringpublic java.lang.String getExpressionString() Returns 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:
- Expression.getExpressionString()
 
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getTypepublic java.lang.Class<?> getType(ELContext context) throws PropertyNotFoundException, ELException - 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
 
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getValuepublic java.lang.Object getValue(ELContext context) throws PropertyNotFoundException, ELException - Specified by:
- getValuein class- ValueExpression
- 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
 
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hashCodepublic int hashCode() - Specified by:
- hashCodein class- Expression
 
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isLiteralTextpublic boolean isLiteralText() - Specified by:
- isLiteralTextin class- Expression
 
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isReadOnlypublic boolean isReadOnly(ELContext context) throws PropertyNotFoundException, ELException - 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
 
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readExternalpublic void readExternal(java.io.ObjectInput in) throws java.io.IOException, java.lang.ClassNotFoundException- Specified by:
- readExternalin interface- java.io.Externalizable
- Throws:
- java.io.IOException
- java.lang.ClassNotFoundException
 
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setValuepublic void setValue(ELContext context, java.lang.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
 
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writeExternalpublic void writeExternal(java.io.ObjectOutput out) throws java.io.IOException- Specified by:
- writeExternalin interface- java.io.Externalizable
- Throws:
- java.io.IOException
 
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toStringpublic java.lang.String toString() - Overrides:
- toStringin class- java.lang.Object
 
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getValueReferencepublic ValueReference getValueReference(ELContext context) - Overrides:
- getValueReferencein class- ValueExpression
- Parameters:
- context- The EL context for this evaluation
- Returns:
- This default implementation always returns null
- Since:
- EL 2.2
 
 
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