jpa/org.eclipse.persistence.jpa.jpql/src/main/java/org/eclipse/persistence/jpa/jpql/tools/resolver/CollectionValuedFieldResolver.java

/*
 * Copyright (c) 2006, 2021 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Oracle - initial API and implementation
//
package org.eclipse.persistence.jpa.jpql.tools.resolver;

import org.eclipse.persistence.jpa.jpql.tools.spi.IManagedType;
import org.eclipse.persistence.jpa.jpql.tools.spi.IManagedTypeProvider;
import org.eclipse.persistence.jpa.jpql.tools.spi.IManagedTypeVisitor;
import org.eclipse.persistence.jpa.jpql.tools.spi.IMapping;
import org.eclipse.persistence.jpa.jpql.tools.spi.IType;
import org.eclipse.persistence.jpa.jpql.tools.spi.ITypeDeclaration;
import org.eclipse.persistence.jpa.jpql.tools.utility.iterable.EmptyIterable;

/**
 * This {@link Resolver} is responsible to resolve the type of a collection-valued field.
 *
 * @version 2.5
 * @since 2.3
 * @author Pascal Filion
 */
public class CollectionValuedFieldResolver extends AbstractPathResolver {

    /**
     * Creates a new <code>CollectionValuedFieldResolver</code>.
     *
     * @param parent The parent {@link Resolver}, which is never <code>null</code>
     * @param path A single segment of the collection-valued path expression
     */
    public CollectionValuedFieldResolver(Resolver parent, String path) {
        super(parent, path);
    }

    @Override
    protected IType buildType() {

        ITypeDeclaration typeDeclaration = getTypeDeclaration();
        IType type = typeDeclaration.getType();

        // For a collection type, return the first type parameter
        if (getTypeHelper().isCollectionType(type)) {
            ITypeDeclaration[] typeParameters = typeDeclaration.getTypeParameters();
            if (typeParameters.length > 0) {
                type = typeParameters[0].getType();
            }
        }
        // For a map type, by default the value is the actual type to return
        else if (getTypeHelper().isMapType(type)) {
            ITypeDeclaration[] typeParameters = typeDeclaration.getTypeParameters();
            if (typeParameters.length == 2) {
                type = typeParameters[1].getType();
            }
        }

        // A collection-valued path expression should not reference a primitive,
        // however, in an invalid query, this could potentially happen and the API
        // only deals with the primitive wrapper type
        return getTypeHelper().convertPrimitive(type);
    }

    @Override
    protected IManagedType resolveManagedType(IMapping mapping) {

        ITypeDeclaration typeDeclaration = mapping.getTypeDeclaration();
        IType type = typeDeclaration.getType();

        // Collection type cannot be traversed
        if (getTypeHelper().isCollectionType(type)) {
            ITypeDeclaration[] typeParameters = typeDeclaration.getTypeParameters();
            if (typeParameters.length == 0) {
                return null;
            }
            type = typeParameters[0].getType();
        }
        // Wrap the Map into a virtual IManagedType so it can be returned and the
        // IType for the Map can be used to retrieve the type of the key and value
        else if (getTypeHelper().isMapType(type)) {
            ITypeDeclaration[] typeParameters = typeDeclaration.getTypeParameters();
            if (typeParameters.length != 2) {
                return null;
            }
            type = typeParameters[1].getType();
        }

        // Retrieve the corresponding managed type for the mapping's type
        return getProvider().getManagedType(type);
    }

    protected static class MapManagedType implements IManagedType {

        protected final IType mapType;
        protected final IManagedTypeProvider provider;

        protected MapManagedType(IManagedTypeProvider provider, IType mapType) {
            super();

            this.provider = provider;
            this.mapType  = mapType;
        }

        @Override
        public void accept(IManagedTypeVisitor visitor) {
        }

        @Override
        public int compareTo(IManagedType managedType) {
            return getType().getName().compareTo(managedType.getType().getName());
        }

        @Override
        public IMapping getMappingNamed(String name) {
            return null;
        }

        @Override
        public IManagedTypeProvider getProvider() {
            return provider;
        }

        @Override
        public IType getType() {
            return mapType;
        }

        @Override
        public Iterable<IMapping> mappings() {
            return EmptyIterable.instance();
        }

        @Override
        public String toString() {
            return getType().getName();
        }
    }
}