Class MethodExpressionImpl
- All Implemented Interfaces:
Externalizable
,Serializable
Expression
that refers to a method on an object.
The ExpressionFactory.createMethodExpression(jakarta.el.ELContext, java.lang.String, java.lang.Class<?>, java.lang.Class<?>[])
method can be used to parse an expression string and
return a concrete instance of MethodExpression
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 getMethodInfo(jakarta.el.ELContext)
and invoke(jakarta.el.ELContext, java.lang.Object[])
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 two 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 on which the method appears. If the base
object is null, a
NullPointerException
must be thrown. At the last resolution, the final property
is then
coerced to a String
, 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 this MethodExpression
).
See the notes about comparison, serialization and immutability in the Expression
javadocs.
- Author:
- Jacob Hookom [jacob@hookom.net]
- See Also:
-
Constructor Summary
ConstructorDescriptionMethodExpressionImpl
(String expr, org.apache.el.parser.Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType, Class<?>[] paramTypes) -
Method Summary
Modifier and TypeMethodDescriptionboolean
Determines whether the specified object is equal to thisExpression
.Returns the original String used to create thisExpression
, unmodified.getMethodInfo
(ELContext context) Evaluates the expression relative to the provided context, and returns information about the actual referenced method.getMethodReference
(ELContext context) Obtain theMethodReference
for the method to which this method expression resolves.int
hashCode()
Returns the hash code for thisExpression
.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
boolean
void
void
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Constructor Details
-
MethodExpressionImpl
public MethodExpressionImpl() -
MethodExpressionImpl
public MethodExpressionImpl(String expr, org.apache.el.parser.Node node, FunctionMapper fnMapper, VariableMapper varMapper, Class<?> expectedType, Class<?>[] paramTypes)
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Method Details
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equals
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:
-
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:
-
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:
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:
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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:
-
invoke
public Object invoke(ELContext context, 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:
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:
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readExternal
- Specified by:
readExternal
in interfaceExternalizable
- Throws:
IOException
ClassNotFoundException
-
writeExternal
- Specified by:
writeExternal
in interfaceExternalizable
- Throws:
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
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getMethodReference
Description copied from class:jakarta.el.MethodExpression
Obtain theMethodReference
for the method to which this method expression resolves.- Overrides:
getMethodReference
in classMethodExpression
- Parameters:
context
- The EL context for this evaluation- Returns:
- This default implementation always returns
null
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