1 /**
2 * This file Copyright (c) 2018 Magnolia International
3 * Ltd. (http://www.magnolia-cms.com). All rights reserved.
4 *
5 *
6 * This file is dual-licensed under both the Magnolia
7 * Network Agreement and the GNU General Public License.
8 * You may elect to use one or the other of these licenses.
9 *
10 * This file is distributed in the hope that it will be
11 * useful, but AS-IS and WITHOUT ANY WARRANTY; without even the
12 * implied warranty of MERCHANTABILITY or FITNESS FOR A
13 * PARTICULAR PURPOSE, TITLE, or NONINFRINGEMENT.
14 * Redistribution, except as permitted by whichever of the GPL
15 * or MNA you select, is prohibited.
16 *
17 * 1. For the GPL license (GPL), you can redistribute and/or
18 * modify this file under the terms of the GNU General
19 * Public License, Version 3, as published by the Free Software
20 * Foundation. You should have received a copy of the GNU
21 * General Public License, Version 3 along with this program;
22 * if not, write to the Free Software Foundation, Inc., 51
23 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
24 *
25 * 2. For the Magnolia Network Agreement (MNA), this file
26 * and the accompanying materials are made available under the
27 * terms of the MNA which accompanies this distribution, and
28 * is available at http://www.magnolia-cms.com/mna.html
29 *
30 * Any modifications to this file must keep this entire header
31 * intact.
32 *
33 */
34 package info.magnolia.ui.editor;
35
36 import java.util.Locale;
37 import java.util.Optional;
38
39 /**
40 * Item provider is an abstraction aiming to give developer a flexible way to specify which item a form or a complex form
41 * field should bind to and how to access that item.
42 *
43 * <ul>
44 * <li>
45 * Item providers allow to bind form views to complex nested data structures and fine tune such bindings. E.g. if a
46 * form binds a contact address as a separate sub-form (in M5 words - e.g. as a composite field), the Magnolia user
47 * might want to use a contact's child node to store the data (item provider that resolves a sub-node can be used),
48 * or store the properties directly on the contact node keeping it flat (self-reference item provider case).</li>
49 * <li>
50 * Item providers get reference items as context. I.e. an address editor from the example upon data binding will get
51 * the root contact node so that it would be trivial to resolve the corresponding sub-node if needed.
52 * </li>
53 * <li>
54 * Item providers kick in the form lifecycle only when the data is fetched from the backend (to populate the form) and
55 * when the updated data needs to be flushed from the Vaadin components back to the backend (on form commit).
56 * </li>
57 * </ul>
58 *
59 * @param <T>
60 * item type.
61 * @param <R>
62 * item type.
63 */
64 public interface ItemProviderStrategy<T, R> {
65
66 Optional<T> read(R reference);
67
68 default Optional<T> read(R reference, Locale locale) {
69 return read(reference);
70 }
71
72 /**
73 * Shortcut interface which does not enforce different
74 * reference type.
75 *
76 * @param <T>
77 * item and reference type
78 */
79 interface WithSameTypeReference<T> extends ItemProviderStrategy<T, T> {
80 }
81 }