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