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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package javax.servlet.jsp.el;
/**
* <p>
* The abstract base class for an expression-language evaluator. Classes that
* implement an expression language expose their functionality via this abstract
* class.
* </p>
* <p>
* An instance of the ExpressionEvaluator can be obtained via the JspContext /
* PageContext
* </p>
* <p>
* The parseExpression() and evaluate() methods must be thread-safe. That is,
* multiple threads may call these methods on the same ExpressionEvaluator
* object simultaneously. Implementations should synchronize access if they
* depend on transient state. Implementations should not, however, assume that
* only one object of each ExpressionEvaluator type will be instantiated; global
* caching should therefore be static.
* </p>
* <p>
* Only a single EL expression, starting with '${' and ending with '}', can be
* parsed or evaluated at a time. EL expressions cannot be mixed with static
* text. For example, attempting to parse or evaluate "
* <code>abc${1+1}def${1+1}ghi</code>" or even "<code>${1+1}${1+1}</code>" will
* cause an <code>ELException</code> to be thrown.
* </p>
* <p>
* The following are examples of syntactically legal EL expressions:
* </p>
* <ul>
* <li><code>${person.lastName}</code></li>
* <li><code>${8 * 8}</code></li>
* <li><code>${my:reverse('hello')}</code></li>
* </ul>
*
* @since 2.0
* @deprecated As of JSP 2.1, replaced by javax.el.ExpressionFactory
*/
@SuppressWarnings("dep-ann")
// TCK signature test fails with annotation
public abstract class ExpressionEvaluator {
/**
* 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.
*
* @param expression
* The expression to be evaluated.
* @param expectedType
* The expected type of the result of the evaluation
* @param 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
* <code>parseExpression()</code>. The <code>Expression</code>
* object returned must invoke the same functions regardless of
* whether the mappings in the provided
* <code>FunctionMapper</code> instance change between calling
* <code>ExpressionEvaluator.parseExpression()</code> and
* <code>Expression.evaluate()</code>.
* @return The Expression object encapsulating the arguments.
* @exception ELException
* Thrown if parsing errors were found.
*/
public abstract Expression parseExpression(String expression,
@SuppressWarnings("rawtypes")// TCK signature fails with generics
Class expectedType, FunctionMapper fMapper) throws ELException;
/**
* 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.
*
* @param expression
* The expression to be evaluated.
* @param expectedType
* The expected type of the result of the evaluation
* @param vResolver
* A VariableResolver instance that can be used at runtime to
* resolve the name of implicit objects into Objects.
* @param fMapper
* A FunctionMapper to resolve functions found in the expression.
* It can be null, in which case no functions are supported for
* this invocation.
* @return The result of the expression evaluation.
* @exception ELException
* Thrown if the expression evaluation failed.
*/
public abstract Object evaluate(
String expression,
@SuppressWarnings("rawtypes")// TCK signature fails with generics
Class expectedType, VariableResolver vResolver,
FunctionMapper fMapper) throws ELException;
}
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