SWF-1136 First cut of Spring Binding adapters for Spring EL. Results verified with same test cases as what is there for the Unified EL adapters.
This commit is contained in:
Rossen Stoyanchev
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/*
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* Copyright 2004-2010 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* 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 org.springframework.binding.expression.spel;
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import java.util.Collections;
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import java.util.HashMap;
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import java.util.Iterator;
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import java.util.Map;
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import org.springframework.binding.expression.EvaluationException;
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import org.springframework.binding.expression.Expression;
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import org.springframework.binding.expression.ValueCoercionException;
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import org.springframework.expression.spel.SpelEvaluationException;
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import org.springframework.expression.spel.SpelMessage;
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import org.springframework.expression.spel.support.StandardEvaluationContext;
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import org.springframework.util.Assert;
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/**
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* <p>
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* A wrapper for a Spring EL {@link org.springframework.expression.Expression} allowing it to be used under the Spring
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* Binding {@link Expression} abstraction.
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* </p>
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*
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* @author Rossen Stoyanchev
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* @since 2.1.0
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*/
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public class SpringELExpression implements Expression {
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private org.springframework.expression.Expression expression;
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private StandardEvaluationContext evaluationContext;
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private Class expectedType;
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private Map expressionVariables;
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/**
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* Constructor for SpringELExpression.
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*
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* @param expression a parsed Spring EL expression instance. Must not be null.
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* @param expressionVariables provides a mapping between variables names and parsed Spring EL expression instances.
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* This parameter is optional (may be null).
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* @param expectedType the target type expected from the evaluation of the expression or null. This parameter is
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* optional (may be null).
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* @param evaluationContext a Spring EL evaluation context.
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*/
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public SpringELExpression(org.springframework.expression.Expression expression, Map expressionVariables,
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Class expectedType, StandardEvaluationContext evaluationContext) {
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Assert.notNull(expression, "The SpelExpression is required for evaluation");
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Assert.notNull(evaluationContext, "The StandardEvaluationContext is required for evaluation");
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this.expression = expression;
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this.expressionVariables = expressionVariables;
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this.expectedType = expectedType;
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this.evaluationContext = evaluationContext;
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}
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public String getExpressionString() {
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return expression.getExpressionString();
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}
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public Object getValue(Object rootObject) throws EvaluationException {
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try {
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updateEvaluationContext(rootObject);
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return expression.getValue(evaluationContext, expectedType);
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} catch (SpelEvaluationException e) {
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if (e.getMessageCode().equals(SpelMessage.TYPE_CONVERSION_ERROR)) {
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throw new ValueCoercionException(rootObject.getClass(), getExpressionString(), null, expectedType, e);
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}
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throw new EvaluationException(rootObject.getClass(), expression.getExpressionString(),
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"An ELException occurred getting the value for expression '" + getExpressionString()
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+ "' on context [" + rootObject.getClass() + "]", e);
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}
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}
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public Class getValueType(Object rootObject) throws EvaluationException {
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evaluationContext.setRootObject(rootObject);
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return expression.getValueType(evaluationContext);
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}
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public void setValue(Object rootObject, Object value) throws EvaluationException {
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try {
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updateEvaluationContext(rootObject);
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expression.setValue(evaluationContext, value);
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} catch (SpelEvaluationException e) {
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if (e.getMessageCode().equals(SpelMessage.EXCEPTION_DURING_PROPERTY_WRITE)) {
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throw new ValueCoercionException(rootObject.getClass(), getExpressionString(), value, expectedType, e);
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}
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throw new EvaluationException(rootObject.getClass(), getExpressionString(),
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"An ELException occurred setting the value of expression '" + getExpressionString()
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+ "' on context [" + rootObject.getClass() + "] to [" + value + "]", e);
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}
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}
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/**
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* Updates the Spring EL evaluation context to reflect the given rootObject.
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*
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* @param rootObject the object for the evaluation.
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*/
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private void updateEvaluationContext(Object rootObject) {
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evaluationContext.setRootObject(rootObject);
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evaluationContext.setVariables(getVariableValues(rootObject));
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}
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/**
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* Turns the map of variable-names-to-expressions into a map of variable-names-to-plain-objects by evaluating each
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* object against the input rootObject.
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*
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* @param rootObject the Object to evaluate variable expressions against.
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* @return a mapping between variables names and plain Object's.
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*/
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private Map getVariableValues(Object rootObject) {
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if (expressionVariables == null) {
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return Collections.EMPTY_MAP;
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}
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Map variableValues = new HashMap(expressionVariables.size());
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for (Iterator iterator = expressionVariables.entrySet().iterator(); iterator.hasNext();) {
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Map.Entry var = (Map.Entry) iterator.next();
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variableValues.put(var.getKey(), ((Expression) var.getValue()).getValue(rootObject));
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}
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return variableValues;
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}
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}
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@@ -0,0 +1,106 @@
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/*
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* Copyright 2004-2010 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* 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 org.springframework.binding.expression.spel;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.List;
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import java.util.Map;
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import org.springframework.binding.expression.Expression;
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import org.springframework.binding.expression.ExpressionParser;
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import org.springframework.binding.expression.ExpressionVariable;
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import org.springframework.binding.expression.ParserContext;
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import org.springframework.binding.expression.ParserException;
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import org.springframework.binding.expression.support.NullParserContext;
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import org.springframework.core.convert.ConversionService;
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import org.springframework.expression.EvaluationContext;
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import org.springframework.expression.PropertyAccessor;
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import org.springframework.expression.TypeConverter;
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import org.springframework.expression.spel.standard.SpelExpressionParser;
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import org.springframework.expression.spel.support.StandardEvaluationContext;
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import org.springframework.expression.spel.support.StandardTypeConverter;
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import org.springframework.util.Assert;
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/**
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* <p>
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* Adapts the Spring EL {@link SpelExpressionParser} to the Spring Binding {@link ExpressionParser} interface.
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* </p>
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*
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* @author Rossen Stoyanchev
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* @since 2.1.0
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*/
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public class SpringELExpressionParser implements ExpressionParser {
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private SpelExpressionParser expressionParser;
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private TypeConverter typeConverter = new StandardTypeConverter();
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private List propertyAccessors = new ArrayList();
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public SpringELExpressionParser(SpelExpressionParser expressionParser) {
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this.expressionParser = expressionParser;
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}
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public void setConversionService(ConversionService conversionService) {
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typeConverter = new StandardTypeConverter(conversionService);
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}
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public void addPropertyAccessor(PropertyAccessor propertyAccessor) {
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propertyAccessors.add(propertyAccessor);
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}
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public Expression parseExpression(String expressionString, ParserContext parserContext) throws ParserException {
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Assert.hasText(expressionString, "The expression string to parse is required and must not be empty");
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parserContext = (parserContext == null) ? NullParserContext.INSTANCE : parserContext;
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StandardEvaluationContext evaluationContext = new StandardEvaluationContext();
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evaluationContext.setTypeConverter(typeConverter);
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evaluationContext.getPropertyAccessors().addAll(propertyAccessors);
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Map spelExpressionVariables = parseSpelExpressionVariables(parserContext.getExpressionVariables());
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return new SpringELExpression(parseSpelExpression(expressionString, parserContext), spelExpressionVariables,
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parserContext.getExpectedEvaluationResultType(), evaluationContext);
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}
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private org.springframework.expression.Expression parseSpelExpression(String expression, ParserContext parserContext) {
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return expressionParser.parseExpression(expression, getSpelParserContext(parserContext));
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}
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private org.springframework.expression.ParserContext getSpelParserContext(ParserContext parserContext) {
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return parserContext.isTemplate() ? org.springframework.expression.ParserContext.TEMPLATE_EXPRESSION : null;
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}
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/**
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* Turns {@link ExpressionVariable}'s (pairs of variable names and string expressions) into a map of variable names
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* and parsed Spring EL expressions. The map will be saved in a Spring EL {@link EvaluationContext} for later use at
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* evaluation time.
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*
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* @param expressionVariables an array of ExpressionVariable instances.
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* @return a Map or null if the input array is empty.
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*/
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private Map parseSpelExpressionVariables(ExpressionVariable[] expressionVariables) {
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if (expressionVariables == null || expressionVariables.length == 0) {
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return null;
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}
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Map spelExpressionVariables = new HashMap(expressionVariables.length);
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for (int i = 0; i < expressionVariables.length; i++) {
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ExpressionVariable var = expressionVariables[i];
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spelExpressionVariables.put(var.getName(),
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parseExpression(var.getValueExpression(), var.getParserContext()));
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}
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return spelExpressionVariables;
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}
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}
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