Class ValueExpressionImpl
- java.lang.Object
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- org.zkoss.zel.Expression
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- org.zkoss.zel.ValueExpression
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- org.zkoss.zel.impl.ValueExpressionImpl
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- All Implemented Interfaces:
java.io.Externalizable
,java.io.Serializable
- Direct Known Subclasses:
ValueExpressionImplEx
public class ValueExpressionImpl extends ValueExpression implements java.io.Externalizable
AnExpression
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 returntrue
fromisReadOnly()
.The
ExpressionFactory.createValueExpression(org.zkoss.zel.ELContext, java.lang.String, java.lang.Class<?>)
method can be used to parse an expression string and return a concrete instance ofValueExpression
that encapsulates the parsed expression. TheFunctionMapper
is used at parse time, not evaluation time, so one is not needed to evaluate an expression using this class. However, theELContext
is needed at evaluation time.The
getValue(org.zkoss.zel.ELContext)
,setValue(org.zkoss.zel.ELContext, java.lang.Object)
,isReadOnly(org.zkoss.zel.ELContext)
andgetType(org.zkoss.zel.ELContext)
methods will evaluate the expression each time they are called. TheELResolver
in theELContext
is used to resolve the top-level variables and to determine the behavior of the.
and[]
operators. For any of the four methods, theELResolver.getValue(org.zkoss.zel.ELContext, java.lang.Object, java.lang.Object)
method is used to resolve all properties up to but excluding the last one. This provides thebase
object. At the last resolution, theValueExpression
will call the correspondingELResolver.getValue(org.zkoss.zel.ELContext, java.lang.Object, java.lang.Object)
,ELResolver.setValue(org.zkoss.zel.ELContext, java.lang.Object, java.lang.Object, java.lang.Object)
,ELResolver.isReadOnly(org.zkoss.zel.ELContext, java.lang.Object, java.lang.Object)
orELResolver.getType(org.zkoss.zel.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
Expression
javadocs.- 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, 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 boolean
equals(java.lang.Object obj)
java.lang.Class<?>
getExpectedType()
java.lang.String
getExpressionString()
Returns the type the result of the expression will be coerced to after evaluation.java.lang.Class<?>
getType(ELContext context)
java.lang.Object
getValue(ELContext context)
ValueReference
getValueReference(ELContext context)
int
hashCode()
boolean
isLiteralText()
boolean
isReadOnly(ELContext context)
void
readExternal(java.io.ObjectInput in)
void
setValue(ELContext context, java.lang.Object value)
java.lang.String
toString()
void
writeExternal(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, 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:
equals
in classExpression
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getExpectedType
public java.lang.Class<?> getExpectedType()
- Specified by:
getExpectedType
in 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:
getExpressionString
in classExpression
- Returns:
- the
expectedType
passed to theExpressionFactory.createValueExpression
method that created thisValueExpression
. - See Also:
Expression.getExpressionString()
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getType
public java.lang.Class<?> getType(ELContext context) throws PropertyNotFoundException, ELException
- Specified by:
getType
in 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:
getValue
in 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:
hashCode
in classExpression
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isLiteralText
public boolean isLiteralText()
- Specified by:
isLiteralText
in classExpression
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isReadOnly
public boolean isReadOnly(ELContext context) throws PropertyNotFoundException, ELException
- Specified by:
isReadOnly
in classValueExpression
- Parameters:
context
- The EL context for this evaluation- Returns:
true
if 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:
readExternal
in interfacejava.io.Externalizable
- Throws:
java.io.IOException
java.lang.ClassNotFoundException
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setValue
public void setValue(ELContext context, java.lang.Object value) throws PropertyNotFoundException, PropertyNotWritableException, ELException
- Specified by:
setValue
in 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:
writeExternal
in interfacejava.io.Externalizable
- Throws:
java.io.IOException
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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getValueReference
public ValueReference getValueReference(ELContext context)
- Overrides:
getValueReference
in classValueExpression
- Parameters:
context
- The EL context for this evaluation- Returns:
- This default implementation always returns
null
- Since:
- EL 2.2
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