Class MethodExpression
- All Implemented Interfaces:
Serializable
Expression
that refers to a method on an object.
The ExpressionFactory.createMethodExpression(javax.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(javax.el.ELContext)
and invoke(javax.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(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 the base
object on which the method
appears. If the base
object is null, a
PropertyNotFoundException
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.
- Since:
- JSP 2.1
- See Also:
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Constructor Summary
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Method Summary
Modifier and TypeMethodDescriptionabstract MethodInfo
getMethodInfo
(ELContext context) Evaluates the expression relative to the provided context, and returns information about the actual referenced method.abstract Object
If a String literal is specified as the expression, returns the String literal coerced to the expected return type of the method signature.boolean
Return whether this MethodExpression was created with parameters.boolean
Deprecated.Methods inherited from class javax.el.Expression
equals, getExpressionString, hashCode, isLiteralText
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Constructor Details
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MethodExpression
public MethodExpression()
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Method Details
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getMethodInfo
Evaluates the expression relative to the provided context, and returns information about the actual referenced method.- 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
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.
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invoke
If a String literal is specified as the expression, returns the String literal coerced to the expected return type of the method signature. AnELException
is thrown ifexpectedReturnType
is void or if the coercion of the String literal to theexpectedReturnType
yields an error (see Section "1.18 Type Conversion" of the EL specification). If not a String literal, 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. Any parameters passed to this method is ignored if isLiteralText() or isParmetersProvided() is true.- 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
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 a String literal is specified and expectedReturnType of the MethodExpression is void or if the coercion of the String literal to the expectedReturnType yields an error (see Section "1.18 Type Conversion").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.
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isParametersProvided
public boolean isParametersProvided()Return whether this MethodExpression was created with parameters.This method must return
true
if and only if parameters are specified in the EL, using the expr-a.expr-b(...) syntax.- Returns:
true
if the MethodExpression was created with parameters,false
otherwise.- Since:
- EL 2.2
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isParmetersProvided
Deprecated.Use isParametersProvided instead.
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