javax.el

Class LambdaExpression

java.lang.Object

javax.el.LambdaExpression

public class LambdaExpression
extends Object

Encapsulates a parameterized ValueExpression.

A LambdaExpression is a representation of the EL Lambda expression syntax. It consists of a list of the formal parameters and a body, represented by a ValueExpression. The body can be any valid Expression, including another LambdaExpression.

A LambdaExpression is created when an EL expression containing a Lambda expression is evaluated.

A LambdaExpression can be invoked by calling invoke(javax.el.ELContext, java.lang.Object...), with an ELContext and a list of the actual arguments. Alternately, a LambdaExpression can be invoked without passing a ELContext, in which case the ELContext previously set by calling setELContext(javax.el.ELContext) will be used. The evaluation of the ValueExpression in the body uses the ELContext to resolve references to the parameters, and to evaluate the lambda expression. The result of the evaluation is returned.

See Also:

ELContext.getLambdaArgument(java.lang.String), ELContext.enterLambdaScope(java.util.Map<java.lang.String, java.lang.Object>), ELContext.exitLambdaScope()

Constructor Summary

Constructors

Constructor and Description
LambdaExpression(List<String> formalParameters, ValueExpression expression) Creates a new LambdaExpression.

Method Summary

Methods

Modifier and Type	Method and Description
Object	invoke(ELContext elContext, Object... args) Invoke the encapsulated Lambda expression.
Object	invoke(Object... args) Invoke the encapsulated Lambda expression.
void	setELContext(ELContext context) Set the ELContext to use in evaluating the LambdaExpression.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LambdaExpression

public LambdaExpression(List<String> formalParameters,
                ValueExpression expression)

Creates a new LambdaExpression.

Parameters:

formalParameters - The list of String representing the formal parameters.

expression - The ValueExpression representing the body.

Method Detail

setELContext

public void setELContext(ELContext context)

Set the ELContext to use in evaluating the LambdaExpression. The ELContext must to be set prior to the invocation of the LambdaExpression, unless it is supplied with invoke(javax.el.ELContext, java.lang.Object...).

Parameters:

context - The ELContext to use in evaluating the LambdaExpression.

invoke

public Object invoke(ELContext elContext,
            Object... args)
              throws ELException

Invoke the encapsulated Lambda expression.

The supplied arguments are matched, in the same order, to the formal parameters. If there are more arguments than the formal parameters, the extra arguments are ignored. If there are less arguments than the formal parameters, an ELException is thrown.

The actual Lambda arguments are added to the ELContext and are available during the evaluation of the Lambda expression. They are removed after the evaluation.

Parameters:

elContext - The ELContext used for the evaluation of the expression The ELContext set by setELContext(javax.el.ELContext) is ignored.

args - The arguments to invoke the Lambda expression. For calls with no arguments, an empty array must be provided. A Lambda argument can be null.

Returns:

The result of invoking the Lambda expression

Throws:

ELException - if not enough arguments are provided

NullPointerException - is elContext is null

invoke

public Object invoke(Object... args)

Invoke the encapsulated Lambda expression.

The supplied arguments are matched, in the same order, to the formal parameters. If there are more arguments than the formal parameters, the extra arguments are ignored. If there are less arguments than the formal parameters, an ELException is thrown.

The actual Lambda arguments are added to the ELContext and are available during the evaluation of the Lambda expression. They are removed after the evaluation.

The ELContext set by setELContext(javax.el.ELContext) is used in the evaluation of the lambda Expression.

Parameters:

args - The arguments to invoke the Lambda expression. For calls with no arguments, an empty array must be provided. A Lambda argument can be null.

Returns:

The result of invoking the Lambda expression

Throws:

ELException - if not enough arguments are provided