Class ValueExpressionImpl
- java.lang.Object
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- jakarta.el.Expression
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- jakarta.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(jakarta.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(jakarta.el.ELContext),setValue(jakarta.el.ELContext, java.lang.Object),isReadOnly(jakarta.el.ELContext)andgetType(jakarta.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(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 thebaseobject. At the last resolution, theValueExpressionwill call the correspondingELResolver.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)orELResolver.getType(jakarta.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 Summary
Constructors 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 Summary
All 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
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ValueExpressionImpl
public ValueExpressionImpl()
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ValueExpressionImpl
public 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
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equals
public boolean equals(java.lang.Object obj)
- Specified by:
equalsin classExpression
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getExpectedType
public java.lang.Class<?> getExpectedType()
- Specified by:
getExpectedTypein classValueExpression
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getExpressionString
public java.lang.String getExpressionString()
Returns the type the result of the expression will be coerced to after evaluation.- Specified by:
getExpressionStringin classExpression- Returns:
- the
expectedTypepassed to theExpressionFactory.createValueExpressionmethod that created thisValueExpression. - See Also:
Expression.getExpressionString()
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getType
public java.lang.Class<?> getType(ELContext context) throws PropertyNotFoundException, ELException
- Specified by:
getTypein classValueExpression- 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 readableELException- Wraps any exception throw whilst resolving a property or variable
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getValue
public java.lang.Object getValue(ELContext context) throws PropertyNotFoundException, ELException
- Specified by:
getValuein classValueExpression- 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 readableELException- Wraps any exception throw whilst resolving a property or variable
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hashCode
public int hashCode()
- Specified by:
hashCodein classExpression
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isLiteralText
public boolean isLiteralText()
- Specified by:
isLiteralTextin classExpression
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isReadOnly
public boolean isReadOnly(ELContext context) throws PropertyNotFoundException, ELException
- Specified by:
isReadOnlyin classValueExpression- Parameters:
context- The EL context for this evaluation- Returns:
trueif this expression is read only otherwisefalse- Throws:
PropertyNotFoundException- If a property/variable resolution failed because no match was found or a match was found but was not readableELException- Wraps any exception throw whilst resolving a property or variable
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readExternal
public void readExternal(java.io.ObjectInput in) throws java.io.IOException, java.lang.ClassNotFoundException- Specified by:
readExternalin interfacejava.io.Externalizable- Throws:
java.io.IOExceptionjava.lang.ClassNotFoundException
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setValue
public void setValue(ELContext context, java.lang.Object value) throws PropertyNotFoundException, PropertyNotWritableException, ELException
- Specified by:
setValuein classValueExpression- Parameters:
context- The EL context for this evaluationvalue- The value to set the property to which this value expression refers- Throws:
PropertyNotFoundException- If a property/variable resolution failed because no match was foundPropertyNotWritableException- If a property/variable resolution failed because a match was found but was not writableELException- Wraps any exception throw whilst resolving a property or variable
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writeExternal
public void writeExternal(java.io.ObjectOutput out) throws java.io.IOException- Specified by:
writeExternalin interfacejava.io.Externalizable- Throws:
java.io.IOException
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toString
public java.lang.String toString()
- Overrides:
toStringin classjava.lang.Object
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getValueReference
public ValueReference getValueReference(ELContext context)
- Overrides:
getValueReferencein classValueExpression- Parameters:
context- The EL context for this evaluation- Returns:
- This default implementation always returns
null - Since:
- EL 2.2
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