| java.lang.Object
 javax.el.Expression
javax.el.MethodExpression
| MethodExpression | | abstract public class MethodExpression extends Expression (Code) | | An Expression that refers to a method on an object.
The
ExpressionFactory.createMethodExpression 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
MethodExpression.getMethodInfo and
MethodExpression.invoke 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
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.
See Also: ELResolver
See Also: Expression
See Also: ExpressionFactory
since:
JSP 2.1 |
| Method Summary | |
| abstract public MethodInfo | getMethodInfo(ELContext context)
Evaluates the expression relative to the provided context, and
returns information about the actual referenced method.
Parameters:
context - The context of this evaluation an instance of MethodInfo containing informationabout the method the expression evaluated to.
throws:
NullPointerException - if context is null
throws:
PropertyNotFoundException - if one of the propertyresolutions failed because a specified variable or property does not exist or is not readable.
throws:
MethodNotFoundException - if no suitable method can be found.
throws:
ELException - if an exception was thrown while performingproperty or variable resolution. | | abstract public 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. |
| getMethodInfo | | abstract public MethodInfo getMethodInfo(ELContext context)(Code) | | Evaluates the expression relative to the provided context, and
returns information about the actual referenced method.
Parameters:
context - The context of this evaluation an instance of MethodInfo containing informationabout the method the expression evaluated to.
throws:
NullPointerException - if context is null
throws:
PropertyNotFoundException - if one of the propertyresolutions failed because a specified variable or property does not exist or is not readable.
throws:
MethodNotFoundException - if no suitable method can be found.
throws:
ELException - if an exception was thrown while performingproperty or variable resolution. The thrown exceptionmust be included as the cause property of this exception, ifavailable. |
| invoke | | abstract public Object invoke(ELContext context, Object[] params)(Code) | | If a String literal is specified as the expression, returns the
String literal coerced to the expected return type of the method
signature. An 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()
is true.
Parameters:
context - The context of this evaluation.
Parameters:
params - The parameters to pass to the method, ornull if no parameters. the result of the method invocation (null ifthe method has a void return type).
throws:
NullPointerException - if context is null
throws:
PropertyNotFoundException - if one of the propertyresolutions failed because a specified variable or property does not exist or is not readable.
throws:
MethodNotFoundException - if no suitable method can be found.
throws:
ELException - if a String literal is specified andexpectedReturnType of the MethodExpression is void or if the coercion of the String literal to the expectedReturnType yields an error (see Section "1.18 TypeConversion").
throws:
ELException - if an exception was thrown while performingproperty or variable resolution. The thrown exception must beincluded as the cause property of this exception, ifavailable. If the exception thrown is anInvocationTargetException, extract itscause and pass it to theELException constructor. |
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