javax.el: abstract public class: MethodExpression

javax.el
abstract public class: MethodExpression [javadoc | source]

java.lang.Object
   javax.el.Expression
      javax.el.MethodExpression

All Implemented Interfaces:
Serializable

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 #getMethodInfo and #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.

Also see:

ELResolver

Expression

ExpressionFactory

since: JSP - 2.1

Method from javax.el.MethodExpression Summary:
getMethodInfo, invoke

Methods from javax.el.Expression:
equals, getExpressionString, hashCode, isLiteralText

Methods from java.lang.Object:
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method from javax.el.MethodExpression Detail:
abstract public MethodInfo getMethodInfo(ELContext context) Evaluates the expression relative to the provided context, and returns information about the actual referenced method.
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. 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.

Method from javax.el.MethodExpression Detail:

 abstract public MethodInfo getMethodInfo(ELContext context)Evaluates the expression relative to the provided context, and
returns information about the actual referenced method.

 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. 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.