AssociationsCriterionBuilder.java

/*
 * The MIT License
 *
 * Copyright 2013 Jakub Jirutka <jakub@jirutka.cz>.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package cz.jirutka.rsql.hibernate;

import cz.jirutka.rsql.parser.model.Comparison;
import org.hibernate.criterion.Criterion;
import org.hibernate.metadata.ClassMetadata;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Criterion Builder that can handle association "dereference". That means you 
 * can specify constraints upon related entities by navigating associations
 * using dot-notation. Builder implicitly creates JOIN for every associated 
 * entity.
 * 
 * <p>For example, we have entity <tt>Course</tt> with property 
 * <tt>department</tt> which is ManyToOne association with entity 
 * <tt>Unit</tt>. That entity contains property <tt>code</tt> of type Integer.
 * When you want to find all courses which are related with department code
 * 18102, you will use query <tt>department.code==18102</tt> on courses 
 * resource.</p>
 *
 * @author Jakub Jirutka <jakub@jirutka.cz>
 */
public class AssociationsCriterionBuilder extends AbstractCriterionBuilder {

    private static final Logger LOG = LoggerFactory.getLogger(AssociationsCriterionBuilder.class);
    
    
    @Override
    public boolean accept(String propertyPath, Class<?> entityClass, CriteriaBuilder builder) {       
        return splitPath(propertyPath).length > 1;
    }

    @Override
    public Criterion createCriterion(String propertyPath, Comparison operator, 
            String argument, Class<?> entityClass, String alias, CriteriaBuilder builder)
            throws ArgumentFormatException, UnknownSelectorException, AssociationsLimitException {
        
        String[] path = splitPath(propertyPath);
        String lastAlias = alias;
        String property = null;
        Class<?> lastClass = entityClass;
        
        // walk through associations
        for (int i = 0; i < path.length -1; i++) {
            ClassMetadata metadata = builder.getClassMetadata(lastClass);
            property = builder.getMapper().translate(path[i], lastClass);
            
            if (!isPropertyName(property, metadata)) {
                throw new UnknownSelectorException(path[i]);
            }
            lastClass = findPropertyType(property, metadata);
            
            LOG.trace("Nesting level {}: property '{}' of entity {}",
                    new Object[]{i, property, lastClass.getSimpleName()});

            lastAlias = builder.createAssociationAlias(lastAlias + property) + '.';
        }
        
        // the last property may by an ordinal property (not an association)
        property = builder.getMapper().translate(path[path.length -1], lastClass);
        
        return builder.delegateToBuilder(property, operator, argument, lastClass, lastAlias);
    }
    
    protected String[] splitPath(String path) {
        return path.split("\\.");
    }
    
}