Method: PersistenceProviderResolverHolder()

1: /*
2: * JOPA
3: * Copyright (C) 2024 Czech Technical University in Prague
4: *
5: * This library is free software; you can redistribute it and/or
6: * modify it under the terms of the GNU Lesser General Public
7: * License as published by the Free Software Foundation; either
8: * version 3.0 of the License, or (at your option) any later version.
9: *
10: * This library is distributed in the hope that it will be useful,
11: * but WITHOUT ANY WARRANTY; without even the implied warranty of
12: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13: * Lesser General Public License for more details.
14: *
15: * You should have received a copy of the GNU Lesser General Public
16: * License along with this library.
17: */
18: package cz.cvut.kbss.jopa.model;
19:
20: import java.util.Objects;
21:
22: /**
23: * Holds the global {@link PersistenceProviderResolver} instance.
24: * <p>
25: * If no {@code PersistenceProviderResolver} is set by the environment, the default {@code PersistenceProviderResolver}
26: * is used. Implementations must be thread-safe.
27: */
28: public class PersistenceProviderResolverHolder {
29:
30: private static PersistenceProviderResolver instance = new DefaultPersistenceProviderResolver();
31:
32: private PersistenceProviderResolverHolder() {
33: throw new AssertionError();
34: }
35:
36: /**
37: * Returns the current persistence provider resolver.
38: *
39: * @return the current persistence provider resolver
40: */
41: public static synchronized PersistenceProviderResolver getPersistenceProviderResolver() {
42: return instance;
43: }
44:
45: /**
46: * Defines the persistence provider resolver used.
47: *
48: * @param resolver persistence provider resolver to be used
49: */
50: public static synchronized void setPersistenceProviderResolver(final PersistenceProviderResolver resolver) {
51: instance = Objects.requireNonNullElseGet(resolver, DefaultPersistenceProviderResolver::new);
52: }
53: }