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/*
 * =============================================================================
 *
 *   Copyright (c) 2011-2018, The THYMELEAF team (http://www.thymeleaf.org)
 *
 *   Licensed 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 org.thymeleaf.standard.expression;

import org.thymeleaf.IEngineConfiguration;
import org.thymeleaf.exceptions.TemplateProcessingException;


/**
 * 

* Utility class for the easy obtention of objects relevant to the parsing and execution of Thymeleaf * Standard Expressions. *

*

* Note a class with this name existed since 2.1.0, but it was completely reimplemented * in Thymeleaf 3.0 *

* * @author Daniel Fernández * * @since 3.0.0 * */ public final class StandardExpressions { /** * Name used for registering the Standard Variable Expression Evaluator object as an * execution attribute at the Standard Dialects. */ public static final String STANDARD_VARIABLE_EXPRESSION_EVALUATOR_ATTRIBUTE_NAME = "StandardVariableExpressionEvaluator"; /** * Name used for registering the Standard Expression Parser object as an * execution attribute at the Standard Dialects. */ public static final String STANDARD_EXPRESSION_PARSER_ATTRIBUTE_NAME = "StandardExpressionParser"; /** * Name used for registering the Standard Conversion Service object as an * execution attribute at the Standard Dialects. */ public static final String STANDARD_CONVERSION_SERVICE_ATTRIBUTE_NAME = "StandardConversionService"; private StandardExpressions() { super(); } /** *

* Obtain the expression parser (implementation of {@link IStandardExpressionParser}) registered by * the Standard Dialect that is being currently used. *

* * @param configuration the configuration object for the current template execution environment. * @return the parser object. */ public static IStandardExpressionParser getExpressionParser(final IEngineConfiguration configuration) { final Object parser = configuration.getExecutionAttributes().get(STANDARD_EXPRESSION_PARSER_ATTRIBUTE_NAME); if (parser == null || (!(parser instanceof IStandardExpressionParser))) { throw new TemplateProcessingException( "No Standard Expression Parser has been registered as an execution argument. " + "This is a requirement for using Standard Expressions, and might happen " + "if neither the Standard or the SpringStandard dialects have " + "been added to the Template Engine and none of the specified dialects registers an " + "attribute of type " + IStandardExpressionParser.class.getName() + " with name " + "\"" + STANDARD_EXPRESSION_PARSER_ATTRIBUTE_NAME + "\""); } return (IStandardExpressionParser) parser; } /** *

* Obtain the variable expression evaluator (implementation of {@link IStandardVariableExpressionEvaluator}) * registered by the Standard Dialect that is being currently used. *

*

* Normally, there should be no need to obtain this object from the developers' code (only internally from * {@link IStandardExpression} implementations). *

* * @param configuration the configuration object for the current template execution environment. * @return the variable expression evaluator object. */ public static IStandardVariableExpressionEvaluator getVariableExpressionEvaluator(final IEngineConfiguration configuration) { final Object expressionEvaluator = configuration.getExecutionAttributes().get(STANDARD_VARIABLE_EXPRESSION_EVALUATOR_ATTRIBUTE_NAME); if (expressionEvaluator == null || (!(expressionEvaluator instanceof IStandardVariableExpressionEvaluator))) { throw new TemplateProcessingException( "No Standard Variable Expression Evaluator has been registered as an execution argument. " + "This is a requirement for using Standard Expressions, and might happen " + "if neither the Standard or the SpringStandard dialects have " + "been added to the Template Engine and none of the specified dialects registers an " + "attribute of type " + IStandardVariableExpressionEvaluator.class.getName() + " with name " + "\"" + STANDARD_VARIABLE_EXPRESSION_EVALUATOR_ATTRIBUTE_NAME + "\""); } return (IStandardVariableExpressionEvaluator) expressionEvaluator; } /** *

* Obtain the conversion service (implementation of {@link IStandardConversionService}) registered by * the Standard Dialect that is being currently used. *

* * @param configuration the configuration object for the current template execution environment. * @return the conversion service object. */ public static IStandardConversionService getConversionService(final IEngineConfiguration configuration) { final Object conversionService = configuration.getExecutionAttributes().get(STANDARD_CONVERSION_SERVICE_ATTRIBUTE_NAME); if (conversionService == null || (!(conversionService instanceof IStandardConversionService))) { throw new TemplateProcessingException( "No Standard Conversion Service has been registered as an execution argument. " + "This is a requirement for using Standard Expressions, and might happen " + "if neither the Standard or the SpringStandard dialects have " + "been added to the Template Engine and none of the specified dialects registers an " + "attribute of type " + IStandardConversionService.class.getName() + " with name " + "\"" + STANDARD_CONVERSION_SERVICE_ATTRIBUTE_NAME + "\""); } return (IStandardConversionService) conversionService; } }




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