public abstract class MethodExpression extends Expression
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.
ELResolver
,
Expression
,
ExpressionFactory
,
Serialized FormConstructor and Description |
---|
MethodExpression() |
Modifier and Type | Method and Description |
---|---|
abstract MethodInfo |
getMethodInfo(ELContext context)
Evaluates the expression relative to the provided context, and
returns information about the actual referenced method.
|
abstract Object |
invoke(ELContext context,
Object[] params)
If a String literal is specified as the expression, returns the
String literal coerced to the expected return type of the method
signature.
|
boolean |
isParmetersProvided()
Return whether this MethodExpression was created with parameters.
|
equals, getExpressionString, hashCode, isLiteralText
public abstract MethodInfo getMethodInfo(ELContext context)
context
- The context of this evaluationMethodInfo
containing information
about the method the expression evaluated to.NullPointerException
- if context is null
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.public abstract Object invoke(ELContext context, Object[] params)
ELException
is thrown if
expectedReturnType
is void or if the coercion of the String literal
to the expectedReturnType
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 isParametersProvided() is true.context
- The context of this evaluation.params
- The parameters to pass to the method, or
null
if no parameters.null
if
the method has a void
return type).NullPointerException
- if context is null
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 an
InvocationTargetException
, extract its
cause
and pass it to the
ELException
constructor.public boolean isParmetersProvided()
This method must return true
if and only if
parameters are specified in the EL, using the
expr-a.expr-b(...) syntax.
true
if the MethodExpression was created with
parameters, false
otherwise.Copyright © 2012 JBoss by Red Hat. All Rights Reserved.