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 |
isParametersProvided()
Return whether this MethodExpression was created with parameters.
|
boolean |
isParmetersProvided()
Deprecated.
|
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 Jakarta Expression Language 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.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 isParametersProvided()
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.@Deprecated public boolean isParmetersProvided()
true
if the MethodExpression was created with parameters, false
otherwise.Copyright © 2021 JBoss by Red Hat. All rights reserved.