Class MethodExpressionImpl
- java.lang.Object
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- org.zkoss.zel.Expression
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- org.zkoss.zel.MethodExpression
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- org.zkoss.zel.impl.MethodExpressionImpl
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- All Implemented Interfaces:
java.io.Externalizable
,java.io.Serializable
public final class MethodExpressionImpl extends MethodExpression implements java.io.Externalizable
AnExpression
that refers to a method on an object.The
ExpressionFactory.createMethodExpression(org.zkoss.zel.ELContext, java.lang.String, java.lang.Class<?>, java.lang.Class<?>[])
method can be used to parse an expression string and return a concrete instance ofMethodExpression
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
getMethodInfo(org.zkoss.zel.ELContext)
andinvoke(org.zkoss.zel.ELContext, java.lang.Object[])
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 two 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 on which the method appears. If thebase
object is null, aNullPointerException
must be thrown. At the last resolution, the finalproperty
is then coerced to aString
, which provides the name of the method to be found. A method matching the name and expected parameters provided at parse time is found and it is either queried or invoked (depending on the method called on thisMethodExpression
).See the notes about comparison, serialization and immutability in the
Expression
javadocs.- Author:
- Jacob Hookom [jacob@hookom.net]
- See Also:
ELResolver
,Expression
,ExpressionFactory
,MethodExpression
, Serialized Form
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Constructor Summary
Constructors Constructor Description MethodExpressionImpl()
MethodExpressionImpl(java.lang.String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, java.lang.Class<?> expectedType, java.lang.Class<?>[] paramTypes)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description boolean
equals(java.lang.Object obj)
Determines whether the specified object is equal to thisExpression
.java.lang.String
getExpressionString()
Returns the original String used to create thisExpression
, unmodified.MethodInfo
getMethodInfo(ELContext context)
Evaluates the expression relative to the provided context, and returns information about the actual referenced method.int
hashCode()
Returns the hash code for thisExpression
.java.lang.Object
invoke(ELContext context, java.lang.Object[] params)
Evaluates the expression relative to the provided context, invokes the method that was found using the supplied parameters, and returns the result of the method invocation.boolean
isLiteralText()
boolean
isParametersProvided()
boolean
isParmetersProvided()
void
readExternal(java.io.ObjectInput in)
void
writeExternal(java.io.ObjectOutput out)
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Constructor Detail
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MethodExpressionImpl
public MethodExpressionImpl()
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MethodExpressionImpl
public MethodExpressionImpl(java.lang.String expr, Node node, FunctionMapper fnMapper, VariableMapper varMapper, java.lang.Class<?> expectedType, java.lang.Class<?>[] paramTypes)
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Method Detail
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equals
public boolean equals(java.lang.Object obj)
Determines whether the specified object is equal to thisExpression
.The result is
true
if and only if the argument is notnull
, is anExpression
object that is the of the same type (ValueExpression
orMethodExpression
), and has an identical parsed representation.Note that two expressions can be equal if their expression Strings are different. For example,
${fn1:foo()}
and${fn2:foo()}
are equal if their correspondingFunctionMapper
s mappedfn1:foo
andfn2:foo
to the same method.- Specified by:
equals
in classExpression
- Parameters:
obj
- theObject
to test for equality.- Returns:
true
ifobj
equals thisExpression
;false
otherwise.- See Also:
Hashtable
,Object.equals(java.lang.Object)
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getExpressionString
public java.lang.String getExpressionString()
Returns the original String used to create thisExpression
, unmodified.This is used for debugging purposes but also for the purposes of comparison (e.g. to ensure the expression in a configuration file has not changed).
This method does not provide sufficient information to re-create an expression. Two different expressions can have exactly the same expression string but different function mappings. Serialization should be used to save and restore the state of an
Expression
.- Specified by:
getExpressionString
in classExpression
- Returns:
- The original expression String.
- See Also:
Expression.getExpressionString()
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getMethodInfo
public MethodInfo getMethodInfo(ELContext context) throws PropertyNotFoundException, MethodNotFoundException, ELException
Evaluates the expression relative to the provided context, and returns information about the actual referenced method.- Specified by:
getMethodInfo
in classMethodExpression
- Parameters:
context
- The context of this evaluation- Returns:
- an instance of
MethodInfo
containing information about the method the expression evaluated to. - Throws:
java.lang.NullPointerException
- if context isnull
or the base object isnull
on the last resolution.PropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.MethodNotFoundException
- if no suitable method can be found.ELException
- if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available.- See Also:
MethodExpression.getMethodInfo(org.zkoss.zel.ELContext)
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hashCode
public int hashCode()
Returns the hash code for thisExpression
.See the note in the
equals(java.lang.Object)
method on how two expressions can be equal if their expression Strings are different. Recall that if two objects are equal according to theequals(Object)
method, then calling thehashCode
method on each of the two objects must produce the same integer result. Implementations must take special note and implementhashCode
correctly.- Specified by:
hashCode
in classExpression
- Returns:
- The hash code for this
Expression
. - See Also:
equals(java.lang.Object)
,Hashtable
,Object.hashCode()
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invoke
public java.lang.Object invoke(ELContext context, java.lang.Object[] params) throws PropertyNotFoundException, MethodNotFoundException, ELException
Evaluates the expression relative to the provided context, invokes the method that was found using the supplied parameters, and returns the result of the method invocation.- Specified by:
invoke
in classMethodExpression
- Parameters:
context
- The context of this evaluation.params
- The parameters to pass to the method, ornull
if no parameters.- Returns:
- the result of the method invocation (
null
if the method has avoid
return type). - Throws:
java.lang.NullPointerException
- if context isnull
or the base object isnull
on the last resolution.PropertyNotFoundException
- if one of the property resolutions failed because a specified variable or property does not exist or is not readable.MethodNotFoundException
- if no suitable method can be found.ELException
- if an exception was thrown while performing property or variable resolution. The thrown exception must be included as the cause property of this exception, if available. If the exception thrown is anInvocationTargetException
, extract itscause
and pass it to theELException
constructor.- See Also:
MethodExpression.invoke(org.zkoss.zel.ELContext, java.lang.Object[])
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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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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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isLiteralText
public boolean isLiteralText()
- Specified by:
isLiteralText
in classExpression
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isParametersProvided
public boolean isParametersProvided()
- Overrides:
isParametersProvided
in classMethodExpression
- Returns:
- This default implementation always returns
false
- Since:
- EL 3.0
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isParmetersProvided
public boolean isParmetersProvided()
- Since:
- EL 2.2 Note: The spelling mistake is deliberate. isParmetersProvided() - Specification definition isParametersProvided() - Corrected spelling
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