public abstract class MethodExpression extends Expression
Expression that refers to a method on an object.
The ExpressionFactory.createMethodExpression(jakarta.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(jakarta.el.ELContext) and invoke(jakarta.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(jakarta.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 Form| Constructor 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.
|
MethodReference |
getMethodReference(ELContext context)
Obtain the
MethodReference for the method to which this method
expression resolves. |
abstract java.lang.Object |
invoke(ELContext context,
java.lang.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.
|
equals, getExpressionString, hashCode, isLiteralTextpublic abstract MethodInfo getMethodInfo(ELContext context)
context - The context of this evaluationMethodInfo containing information about the method the expression evaluated to.java.lang.NullPointerException - if context is nullPropertyNotFoundException - 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 java.lang.Object invoke(ELContext context, java.lang.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 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).java.lang.NullPointerException - if context is nullPropertyNotFoundException - 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.public MethodReference getMethodReference(ELContext context)
MethodReference for the method to which this method
expression resolves.context - The EL context for this evaluationnulljava.lang.NullPointerException - If the supplied context is nullPropertyNotFoundException - If a property/variable resolution failed because no match
was found or a match was found but was not readableMethodNotFoundException - If no matching method can be foundELException - Wraps any exception throw whilst resolving the property