1 /*
2 * Copyright (C) 2009, Google Inc. and others
3 *
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Distribution License v. 1.0 which is available at
6 * https://www.eclipse.org/org/documents/edl-v10.php.
7 *
8 * SPDX-License-Identifier: BSD-3-Clause
9 */
10
11 package org.eclipse.jgit.lib;
12
13 import java.io.IOException;
14
15 import org.eclipse.jgit.errors.IncorrectObjectTypeException;
16 import org.eclipse.jgit.errors.MissingObjectException;
17
18 /**
19 * Abstraction of arbitrary object storage.
20 * <p>
21 * An object database stores one or more Git objects, indexed by their unique
22 * {@link org.eclipse.jgit.lib.ObjectId}.
23 */
24 public abstract class ObjectDatabase implements AutoCloseable {
25 /**
26 * Initialize a new database instance for access.
27 */
28 protected ObjectDatabase() {
29 // Protected to force extension.
30 }
31
32 /**
33 * Does this database exist yet?
34 *
35 * @return true if this database is already created; false if the caller
36 * should invoke {@link #create()} to create this database location.
37 */
38 public boolean exists() {
39 return true;
40 }
41
42 /**
43 * Initialize a new object database at this location.
44 *
45 * @throws java.io.IOException
46 * the database could not be created.
47 */
48 public void create() throws IOException {
49 // Assume no action is required.
50 }
51
52 /**
53 * Create a new {@code ObjectInserter} to insert new objects.
54 * <p>
55 * The returned inserter is not itself thread-safe, but multiple concurrent
56 * inserter instances created from the same {@code ObjectDatabase} must be
57 * thread-safe.
58 *
59 * @return writer the caller can use to create objects in this database.
60 */
61 public abstract ObjectInserter newInserter();
62
63 /**
64 * Create a new {@code ObjectReader} to read existing objects.
65 * <p>
66 * The returned reader is not itself thread-safe, but multiple concurrent
67 * reader instances created from the same {@code ObjectDatabase} must be
68 * thread-safe.
69 *
70 * @return reader the caller can use to load objects from this database.
71 */
72 public abstract ObjectReader newReader();
73
74 /**
75 * Close any resources held by this database.
76 */
77 @Override
78 public abstract void close();
79
80 /**
81 * Does the requested object exist in this database?
82 * <p>
83 * This is a one-shot call interface which may be faster than allocating a
84 * {@link #newReader()} to perform the lookup.
85 *
86 * @param objectId
87 * identity of the object to test for existence of.
88 * @return true if the specified object is stored in this database.
89 * @throws java.io.IOException
90 * the object store cannot be accessed.
91 */
92 public boolean has(AnyObjectId objectId) throws IOException {
93 try (ObjectReader or = newReader()) {
94 return or.has(objectId);
95 }
96 }
97
98 /**
99 * Open an object from this database.
100 * <p>
101 * This is a one-shot call interface which may be faster than allocating a
102 * {@link #newReader()} to perform the lookup.
103 *
104 * @param objectId
105 * identity of the object to open.
106 * @return a {@link org.eclipse.jgit.lib.ObjectLoader} for accessing the object.
107 * @throws MissingObjectException
108 * the object does not exist.
109 * @throws java.io.IOException
110 * the object store cannot be accessed.
111 */
112 public ObjectLoader open(AnyObjectId objectId)
113 throws IOException {
114 return open(objectId, ObjectReader.OBJ_ANY);
115 }
116
117 /**
118 * Open an object from this database.
119 * <p>
120 * This is a one-shot call interface which may be faster than allocating a
121 * {@link #newReader()} to perform the lookup.
122 *
123 * @param objectId
124 * identity of the object to open.
125 * @param typeHint
126 * hint about the type of object being requested, e.g.
127 * {@link org.eclipse.jgit.lib.Constants#OBJ_BLOB};
128 * {@link org.eclipse.jgit.lib.ObjectReader#OBJ_ANY} if the
129 * object type is not known, or does not matter to the caller.
130 * @return a {@link org.eclipse.jgit.lib.ObjectLoader} for accessing the
131 * object.
132 * @throws org.eclipse.jgit.errors.MissingObjectException
133 * the object does not exist.
134 * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
135 * typeHint was not OBJ_ANY, and the object's actual type does
136 * not match typeHint.
137 * @throws java.io.IOException
138 * the object store cannot be accessed.
139 */
140 public ObjectLoader open(AnyObjectId objectId, int typeHint)
141 throws MissingObjectException, IncorrectObjectTypeException,
142 IOException {
143 try (ObjectReader or = newReader()) {
144 return or.open(objectId, typeHint);
145 }
146 }
147
148 /**
149 * Create a new cached database instance over this database. This instance might
150 * optimize queries by caching some information about database. So some modifications
151 * done after instance creation might fail to be noticed.
152 *
153 * @return new cached database instance
154 */
155 public ObjectDatabase newCachedDatabase() {
156 return this;
157 }
158 }