/* * 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 jakarta.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 JSP 2.0 * * @deprecated As of JSP 2.1, replaced by jakarta.el.ExpressionFactory
*/
@Deprecated publicabstractclass 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.
*/ publicabstract Expression parseExpression(String expression, 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.
*/ publicabstract Object evaluate(String expression, Class<?> expectedType, VariableResolver vResolver,
FunctionMapper fMapper) throws ELException;
}
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