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XML/XHTML/HTML5 template engine for Java
/*
* =============================================================================
*
* Copyright (c) 2011-2013, 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.spring4.expression;
import java.util.List;
import java.util.Map;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.spel.standard.SpelExpression;
import org.springframework.expression.spel.standard.SpelExpressionParser;
import org.springframework.expression.spel.support.StandardEvaluationContext;
import org.springframework.web.servlet.support.BindStatus;
import org.springframework.web.servlet.tags.form.ValueFormatterWrapper;
import org.thymeleaf.Configuration;
import org.thymeleaf.TemplateEngine;
import org.thymeleaf.cache.ICache;
import org.thymeleaf.cache.ICacheManager;
import org.thymeleaf.context.IContext;
import org.thymeleaf.context.IContextVariableRestriction;
import org.thymeleaf.context.IProcessingContext;
import org.thymeleaf.context.IWebContext;
import org.thymeleaf.context.VariablesMap;
import org.thymeleaf.exceptions.TemplateProcessingException;
import org.thymeleaf.expression.ExpressionEvaluatorObjects;
import org.thymeleaf.spring4.util.FieldUtils;
import org.thymeleaf.standard.expression.IStandardConversionService;
import org.thymeleaf.standard.expression.IStandardVariableExpressionEvaluator;
import org.thymeleaf.standard.expression.StandardExpressionExecutionContext;
import org.thymeleaf.standard.expression.StandardExpressions;
import org.thymeleaf.standard.expression.StandardVariableRestrictions;
/**
*
* @author Daniel Fernández
* @author Guven Demir
*
* @since 2.0.9
*
*/
public class SpelVariableExpressionEvaluator
implements IStandardVariableExpressionEvaluator {
public static final SpelVariableExpressionEvaluator INSTANCE = new SpelVariableExpressionEvaluator();
private static final String SPEL_CACHE_PREFIX = "{spel}";
public static final String FIELDS_EVALUATION_VARIABLE_NAME = "fields";
public static final String THEMES_EVALUATION_VARIABLE_NAME = "themes";
private static final Logger logger = LoggerFactory.getLogger(SpelVariableExpressionEvaluator.class);
private static final SpelExpressionParser PARSER = new SpelExpressionParser();
protected SpelVariableExpressionEvaluator() {
super();
}
public final Object evaluate(final Configuration configuration, final IProcessingContext processingContext,
final String spelExpression, final StandardExpressionExecutionContext expContext, final boolean useSelectionAsRoot) {
if (logger.isTraceEnabled()) {
logger.trace("[THYMELEAF][{}] SpringEL expression: evaluating expression \"{}\" on target", TemplateEngine.threadIndex(), spelExpression);
}
try {
if (expContext.getPerformTypeConversion()) {
// This is a {{...}} expression, so we should use binding info (if available) for formatting.
if (useSelectionAsRoot || !isLocalVariableOverriding(processingContext, spelExpression)) {
// The "local variable override" check avoid scenarios where a locally defined variable
// (e.g. the iterated variable in a th:each) has the same name as a bound object (e.g. a
// form-backing bean). If this was not detected, the bound object value would be always used
// instead of the local variable's
final BindStatus bindStatus =
FieldUtils.getBindStatusFromParsedExpression(
configuration, processingContext, true, useSelectionAsRoot, spelExpression);
if (bindStatus != null) {
// The expression goes against a bound object! Let Spring do its magic for displaying it...
return ValueFormatterWrapper.getDisplayString(bindStatus.getValue(), bindStatus.getEditor(), false);
}
}
}
final Map contextVariables =
computeExpressionObjects(configuration, processingContext);
EvaluationContext baseEvaluationContext =
(EvaluationContext) processingContext.getContext().getVariables().
get(ThymeleafEvaluationContext.THYMELEAF_EVALUATION_CONTEXT_CONTEXT_VARIABLE_NAME);
if (baseEvaluationContext == null) {
// Using a standard one as base: we are losing bean resolution and conversion service!!
baseEvaluationContext = new StandardEvaluationContext();
}
final ThymeleafEvaluationContextWrapper evaluationContext =
new ThymeleafEvaluationContextWrapper(baseEvaluationContext, contextVariables);
final SpelExpression exp = getExpression(configuration, spelExpression);
final Object evaluationRoot =
(useSelectionAsRoot?
processingContext.getExpressionSelectionEvaluationRoot() :
processingContext.getExpressionEvaluationRoot());
setVariableRestrictions(expContext, evaluationRoot, contextVariables);
if (!expContext.getPerformTypeConversion()) {
return exp.getValue(evaluationContext, evaluationRoot);
}
final IStandardConversionService conversionService =
StandardExpressions.getConversionService(configuration);
if (conversionService instanceof SpringStandardConversionService) {
// The conversion service is a mere bridge with the Spring ConversionService, therefore
// this makes use of the complete Spring type conversion infrastructure, without needing
// to manually execute the conversion.
return exp.getValue(evaluationContext, evaluationRoot, String.class);
}
// We need type conversion, but conversion service is not a mere bridge to the Spring one,
// so we need manual execution.
final Object result = exp.getValue(evaluationContext, evaluationRoot);
return conversionService.convert(configuration, processingContext, result, String.class);
} catch (final TemplateProcessingException e) {
throw e;
} catch(final Exception e) {
throw new TemplateProcessingException(
"Exception evaluating SpringEL expression: \"" + spelExpression + "\"", e);
}
}
private static SpelExpression getExpression(final Configuration configuration, final String spelExpression) {
SpelExpression exp = null;
ICache cache = null;
final ICacheManager cacheManager = configuration.getCacheManager();
if (cacheManager != null) {
cache = cacheManager.getExpressionCache();
if (cache != null) {
exp = (SpelExpression) cache.get(SPEL_CACHE_PREFIX + spelExpression);
}
}
if (exp == null) {
exp = (SpelExpression) PARSER.parseExpression(spelExpression);
if (cache != null && null != exp) {
cache.put(SPEL_CACHE_PREFIX + spelExpression, exp);
}
}
return exp;
}
public Map computeExpressionObjects(
final Configuration configuration, final IProcessingContext processingContext) {
// IProcessingContext.getExpressionObjects() cannot return null, and cannot return an unmodifiable object
final Map expressionObjects = processingContext.getExpressionObjects();
final Fields fields = new Fields(configuration, processingContext);
expressionObjects.put(FIELDS_EVALUATION_VARIABLE_NAME, fields);
if (processingContext.getContext() instanceof IWebContext) {
final VariablesMap variables = processingContext.getContext().getVariables();
if (!variables.containsKey(THEMES_EVALUATION_VARIABLE_NAME)) {
variables.put(THEMES_EVALUATION_VARIABLE_NAME, new Themes(processingContext));
}
expressionObjects.put(THEMES_EVALUATION_VARIABLE_NAME, variables.get(THEMES_EVALUATION_VARIABLE_NAME));
}
final Map additionalExpressionObjects = computeAdditionalExpressionObjects(processingContext);
if (additionalExpressionObjects != null) {
expressionObjects.putAll(additionalExpressionObjects);
}
return expressionObjects;
}
/*
* Meant to be overwritten
*/
protected Map computeAdditionalExpressionObjects(
@SuppressWarnings("unused") final IProcessingContext processingContext) {
return null;
}
protected void setVariableRestrictions(final StandardExpressionExecutionContext expContext,
final Object evaluationRoot, final Map contextVariables) {
final List restrictions =
(expContext.getForbidRequestParameters()?
StandardVariableRestrictions.REQUEST_PARAMETERS_FORBIDDEN : null);
final Object context = contextVariables.get(ExpressionEvaluatorObjects.CONTEXT_VARIABLE_NAME);
if (context != null && context instanceof IContext) {
final VariablesMap variablesMap = ((IContext)context).getVariables();
variablesMap.setRestrictions(restrictions);
}
if (evaluationRoot != null && evaluationRoot instanceof VariablesMap) {
((VariablesMap)evaluationRoot).setRestrictions(restrictions);
}
}
private static boolean isLocalVariableOverriding(final IProcessingContext processingContext, final String expression) {
if (!processingContext.hasLocalVariables()) {
return false;
}
final int dotPos = expression.indexOf('.');
if (dotPos == -1) {
return false;
}
final String expressionFirstComponent = expression.substring(0,dotPos);
return processingContext.hasLocalVariable(expressionFirstComponent);
}
@Override
public String toString() {
return "SpringEL";
}
}