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Modern server-side Java template engine for both web and standalone environments
/*
* =============================================================================
*
* 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.spring5.expression;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.expression.AccessException;
import org.springframework.expression.EvaluationContext;
import org.springframework.expression.PropertyAccessor;
import org.springframework.expression.TypedValue;
import org.thymeleaf.TemplateEngine;
import org.thymeleaf.context.IContext;
import org.thymeleaf.exceptions.TemplateProcessingException;
/**
*
* Property accessor used for allowing Spring EL expression evaluators
* treat {@link IContext} objects correctly (map keys will be accessible
* as object properties).
*
*
* Note that, even if {@link IContext} objects used as expression roots will be accessible as
* {@code java.util.Map}s thanks to {@link SPELContextMapWrapper}, this property accessor
* class is still needed in order to access nested context info like the {@code session} or
* {@code param} maps in web contexts.
*
*
* @author Daniel Fernández
*
* @since 3.0.3
*
*/
public final class SPELContextPropertyAccessor implements PropertyAccessor {
private static final Logger LOGGER = LoggerFactory.getLogger(SPELContextPropertyAccessor.class);
static final SPELContextPropertyAccessor INSTANCE = new SPELContextPropertyAccessor();
private static final String REQUEST_PARAMETERS_RESTRICTED_VARIABLE_NAME = "param";
private static final Class[] TARGET_CLASSES = new Class[] { IContext.class };
SPELContextPropertyAccessor() {
super();
}
public Class[] getSpecificTargetClasses() {
return TARGET_CLASSES;
}
public boolean canRead(final EvaluationContext context, final Object target, final String name)
throws AccessException {
if (context instanceof IThymeleafEvaluationContext) {
if (((IThymeleafEvaluationContext) context).isVariableAccessRestricted()) {
if (REQUEST_PARAMETERS_RESTRICTED_VARIABLE_NAME.equals(name)) {
throw new AccessException(
"Access to variable \"" + name + "\" is forbidden in this context. Note some restrictions apply to " +
"variable access. For example, direct access to request parameters is forbidden in preprocessing and " +
"unescaped expressions, in TEXT template mode, in fragment insertion specifications and " +
"in some specific attribute processors.");
}
}
}
return target != null;
}
public TypedValue read(final EvaluationContext evaluationContext, final Object target, final String name)
throws AccessException {
if (target == null) {
throw new AccessException("Cannot read property of null target");
}
try {
/*
* NOTE we do not check here whether we are being asked for the 'locale', 'request', 'response', etc.
* because there already are specific expression objects for the most important of them, which should
* be used instead: #locale, #httpServletRequest, #httpSession, etc.
* The context should just be used as a map, without exposure of its more-internal methods...
*/
// 'execInfo' translation from context variable to expression object - deprecated and to be removed in 3.1
if ("execInfo".equals(name)) { // Quick check to avoid deprecated method call
final Object execInfoResult = checkExecInfo(name, evaluationContext);
if (execInfoResult != null) {
return new TypedValue(execInfoResult);
}
}
final IContext context = (IContext) target;
return new TypedValue(context.getVariable(name));
} catch (final ClassCastException e) {
// This can happen simply because we're applying the same
// AST tree on a different class (Spring internally caches property accessors).
// So this exception might be considered "normal" by Spring AST evaluator and
// just use it to refresh the property accessor cache.
throw new AccessException("Cannot read target of class " + target.getClass().getName());
}
}
/**
* Translation from 'execInfo' context variable (${execInfo}) to 'execInfo' expression object (${#execInfo}), needed
* since 3.0.0.
*
* Note this is expressed as a separate method in order to mark this as deprecated and make it easily locatable.
*
* @param propertyName the name of the property being accessed (we are looking for 'execInfo').
* @param context the expression context, which should contain the expression objects.
* @deprecated created (and deprecated) in 3.0.0 in order to support automatic conversion of calls to the 'execInfo'
* context variable (${execInfo}) into the 'execInfo' expression object (${#execInfo}), which is its
* new only valid form. This method, along with the infrastructure for execInfo conversion in
* StandardExpressionUtils#mightNeedExpressionObjects(...) will be removed in 3.1.
*/
@Deprecated
static Object checkExecInfo(final String propertyName, final EvaluationContext context) {
if ("execInfo".equals(propertyName)) {
if (!(context instanceof IThymeleafEvaluationContext)) {
throw new TemplateProcessingException(
"Found Thymeleaf Standard Expression containing a call to the context variable " +
"\"execInfo\" (e.g. \"${execInfo.templateName}\"), which has been deprecated. The " +
"Execution Info should be now accessed as an expression object instead " +
"(e.g. \"${#execInfo.templateName}\"). Deprecated use is still allowed (will be removed " +
"in future versions of Thymeleaf) when the SpringEL EvaluationContext implements the " +
IThymeleafEvaluationContext.class + " interface, but the current evaluation context of " +
"class " + context.getClass().getName() + " DOES NOT implement such interface.");
}
LOGGER.warn(
"[THYMELEAF][{}] Found Thymeleaf Standard Expression containing a call to the context variable " +
"\"execInfo\" (e.g. \"${execInfo.templateName}\"), which has been deprecated. The " +
"Execution Info should be now accessed as an expression object instead " +
"(e.g. \"${#execInfo.templateName}\"). Deprecated use is still allowed, but will be removed " +
"in future versions of Thymeleaf.",
TemplateEngine.threadIndex());
return ((IThymeleafEvaluationContext)context).getExpressionObjects().getObject("execInfo");
}
return null;
}
public boolean canWrite(
final EvaluationContext context, final Object target, final String name)
throws AccessException {
// There should never be a need to write on an IContext during a template execution
return false;
}
public void write(
final EvaluationContext context, final Object target, final String name, final Object newValue)
throws AccessException {
// There should never be a need to write on an IContext during a template execution
throw new AccessException("Cannot write to " + IContext.class.getName());
}
}
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