/*
* =============================================================================
*
* Copyright (c) 2011-2016, 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.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.thymeleaf.TemplateEngine;
import org.thymeleaf.context.IExpressionContext;
import org.thymeleaf.util.StringUtils;
import org.thymeleaf.util.Validate;
/**
* <p>
* Default (if-null-then) complex expression (Thymeleaf Standard Expressions)
* </p>
* <p>
* Note a class with this name existed since 1.1, but it was completely reimplemented
* in Thymeleaf 3.0
* </p>
*
* @author Daniel Fernández
*
* @since 3.0.0
*
*/
public final class DefaultExpression extends ComplexExpression {
private static final Logger logger = LoggerFactory.getLogger(DefaultExpression.class);
private static final long serialVersionUID = 1830867943963082362L;
private static final String OPERATOR = "?:";
// Future proof, just in case in the future we add other tokens as operators
static final String[] OPERATORS = new String[] {String.valueOf(OPERATOR)};
private final Expression queriedExpression;
private final Expression defaultExpression;
public DefaultExpression(final Expression queriedExpression, final Expression defaultExpression) {
super();
Validate.notNull(queriedExpression, "Queried expression cannot be null");
Validate.notNull(defaultExpression, "Default expression cannot be null");
this.queriedExpression = queriedExpression;
this.defaultExpression = defaultExpression;
}
public Expression getQueriedExpression() {
return this.queriedExpression;
}
public Expression getDefaultExpression() {
return this.defaultExpression;
}
@Override
public String getStringRepresentation() {
final StringBuilder sb = new StringBuilder();
if (this.queriedExpression instanceof ComplexExpression) {
sb.append(Expression.NESTING_START_CHAR);
sb.append(this.queriedExpression);
sb.append(Expression.NESTING_END_CHAR);
} else {
sb.append(this.queriedExpression);
}
sb.append(' ');
sb.append(OPERATOR);
sb.append(' ');
if (this.defaultExpression instanceof ComplexExpression) {
sb.append(Expression.NESTING_START_CHAR);
sb.append(this.defaultExpression);
sb.append(Expression.NESTING_END_CHAR);
} else {
sb.append(this.defaultExpression);
}
return sb.toString();
}
static ExpressionParsingState composeDefaultExpression(
final ExpressionParsingState state, final int nodeIndex) {
// Returning "state" means "try next in chain" or "success"
// Returning "null" means parsing error
final String input = state.get(nodeIndex).getInput();
if (StringUtils.isEmptyOrWhitespace(input)) {
return null;
}
// Trying to fail quickly...
final int defaultOperatorPos = input.indexOf(OPERATOR);
if (defaultOperatorPos == -1) {
return state;
}
final String queriedStr = input.substring(0, defaultOperatorPos);
final String defaultStr = input.substring(defaultOperatorPos + 2);
if (defaultStr.contains(OPERATOR)) {
// There are two "?:" operators
return null;
}
final Expression queriedExpr = ExpressionParsingUtil.parseAndCompose(state, queriedStr);
if (queriedExpr == null) {
return null;
}
final Expression defaultExpr = ExpressionParsingUtil.parseAndCompose(state, defaultStr);
if (defaultExpr == null) {
return null;
}
final DefaultExpression defaultExpressionResult = new DefaultExpression(queriedExpr, defaultExpr);
state.setNode(nodeIndex, defaultExpressionResult);
return state;
}
static Object executeDefault(
final IExpressionContext context,
final DefaultExpression expression, final StandardExpressionExecutionContext expContext) {
if (logger.isTraceEnabled()) {
logger.trace("[THYMELEAF][{}] Evaluating default expression: \"{}\"", TemplateEngine.threadIndex(), expression.getStringRepresentation());
}
final Object queriedValue =
expression.getQueriedExpression().execute(context, expContext);
if (queriedValue == null) {
return expression.getDefaultExpression().execute(context, expContext);
}
return queriedValue;
}
}