javax.servlet.jsp.el.ExpressionEvaluator Maven / Gradle / Ivy
/*
* 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;
/**
*
* The abstract base class for an expression-language evaluator. Classes that
* implement an expression language expose their functionality via this abstract
* class.
*
*
* An instance of the ExpressionEvaluator can be obtained via the JspContext /
* PageContext
*
*
* 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.
*
*
* Only a single EL expression, starting with '${' and ending with '}', can be
* parsed or evaluated at a time. EL expressions cannot be mixed with static
* text. For example, attempting to parse or evaluate "
* abc${1+1}def${1+1}ghi" or even "${1+1}${1+1}" will
* cause an ELException to be thrown.
*
*
* The following are examples of syntactically legal EL expressions:
*
* ${person.lastName}${8 * 8}${my:reverse('hello')}
*
*
* @since 2.0
* @deprecated
*/
@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
* 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().
* @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;
}