org.apache.jasper.runtime
类 ExpressionEvaluatorImpl

java.lang.Object
  javax.servlet.jsp.el.ExpressionEvaluator
      org.apache.jasper.runtime.ExpressionEvaluatorImpl

public class ExpressionEvaluatorImpl
extends ExpressionEvaluator

This is the implementation of ExpreesioEvaluator using implementation of JSP2.1.

版本：

$Change: 181177 $$DateTime: 2001/06/26 08:45:09 $$Author: hmalphett $

作者：

Kin-man Chung

构造方法摘要

ExpressionEvaluatorImpl(PageContext pageContext)
Constructor

方法摘要

Object	evaluate(String expression, Class expectedType, VariableResolver vResolver, FunctionMapper fMapper) Evaluates an expression.
Expression	parseExpression(String expression, Class expectedType, FunctionMapper fMapper) Prepare an expression for later evaluation.

从类 java.lang.Object 继承的方法

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

构造方法详细信息

ExpressionEvaluatorImpl

public ExpressionEvaluatorImpl(PageContext pageContext)

Constructor

方法详细信息

parseExpression

public Expression parseExpression(String expression,
                                  Class expectedType,
                                  FunctionMapper fMapper)
                           throws ELException

从类 ExpressionEvaluator 复制的描述

Prepare an expression for later evaluation. This method should perform syntactic validation of the expression; if in doing so it detects errors, it should raise an ELParseException.

指定者：

类 ExpressionEvaluator 中的 parseExpression

参数：

expression - The expression to be evaluated.

expectedType - The expected type of the result of the evaluation

fMapper - A FunctionMapper to resolve functions found in the expression. It can be null, in which case no functions are supported for this invocation. The ExpressionEvaluator must not hold on to the FunctionMapper reference after returning from parseExpression(). The Expression object returned must invoke the same functions regardless of whether the mappings in the provided FunctionMapper instance change between calling ExpressionEvaluator.parseExpression() and Expression.evaluate().

返回：

The Expression object encapsulating the arguments.

抛出：

ELException - Thrown if parsing errors were found.

evaluate

public Object evaluate(String expression,
                       Class expectedType,
                       VariableResolver vResolver,
                       FunctionMapper fMapper)
                throws ELException

从类 ExpressionEvaluator 复制的描述

Evaluates an expression. This method may perform some syntactic validation and, if so, it should raise an ELParseException error if it encounters syntactic errors. EL evaluation errors should cause an ELException to be raised.

指定者：

类 ExpressionEvaluator 中的 evaluate

参数：

expression - The expression to be evaluated.

expectedType - The expected type of the result of the evaluation

vResolver - A VariableResolver instance that can be used at runtime to resolve the name of implicit objects into Objects.

fMapper - A FunctionMapper to resolve functions found in the expression. It can be null, in which case no functions are supported for this invocation.

返回：

The result of the expression evaluation.

抛出：

ELException - Thrown if the expression evaluation failed.