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 {
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 public abstract void close();
78
79 /**
80 * Does the requested object exist in this database?
81 * <p>
82 * This is a one-shot call interface which may be faster than allocating a
83 * {@link #newReader()} to perform the lookup.
84 *
85 * @param objectId
86 * identity of the object to test for existence of.
87 * @return true if the specified object is stored in this database.
88 * @throws java.io.IOException
89 * the object store cannot be accessed.
90 */
91 public boolean has(AnyObjectId objectId) throws IOException {
92 try (ObjectReader or = newReader()) {
93 return or.has(objectId);
94 }
95 }
96
97 /**
98 * Open an object from this database.
99 * <p>
100 * This is a one-shot call interface which may be faster than allocating a
101 * {@link #newReader()} to perform the lookup.
102 *
103 * @param objectId
104 * identity of the object to open.
105 * @return a {@link org.eclipse.jgit.lib.ObjectLoader} for accessing the object.
106 * @throws MissingObjectException
107 * the object does not exist.
108 * @throws java.io.IOException
109 * the object store cannot be accessed.
110 */
111 public ObjectLoader open(AnyObjectId objectId)
112 throws IOException {
113 return open(objectId, ObjectReader.OBJ_ANY);
114 }
115
116 /**
117 * Open an object from this database.
118 * <p>
119 * This is a one-shot call interface which may be faster than allocating a
120 * {@link #newReader()} to perform the lookup.
121 *
122 * @param objectId
123 * identity of the object to open.
124 * @param typeHint
125 * hint about the type of object being requested, e.g.
126 * {@link org.eclipse.jgit.lib.Constants#OBJ_BLOB};
127 * {@link org.eclipse.jgit.lib.ObjectReader#OBJ_ANY} if the
128 * object type is not known, or does not matter to the caller.
129 * @return a {@link org.eclipse.jgit.lib.ObjectLoader} for accessing the
130 * object.
131 * @throws org.eclipse.jgit.errors.MissingObjectException
132 * the object does not exist.
133 * @throws org.eclipse.jgit.errors.IncorrectObjectTypeException
134 * typeHint was not OBJ_ANY, and the object's actual type does
135 * not match typeHint.
136 * @throws java.io.IOException
137 * the object store cannot be accessed.
138 */
139 public ObjectLoader open(AnyObjectId objectId, int typeHint)
140 throws MissingObjectException, IncorrectObjectTypeException,
141 IOException {
142 try (ObjectReader or = newReader()) {
143 return or.open(objectId, typeHint);
144 }
145 }
146
147 /**
148 * Create a new cached database instance over this database. This instance might
149 * optimize queries by caching some information about database. So some modifications
150 * done after instance creation might fail to be noticed.
151 *
152 * @return new cached database instance
153 */
154 public ObjectDatabase newCachedDatabase() {
155 return this;
156 }
157 }