BlobStore


1   /*
2    * Copyright 2004 Outerthought bvba and Schaubroeck nv
3    *
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    *
8    *     http://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  package org.outerj.daisy.blobstore;
17  
18  import EDU.oswego.cs.dl.util.concurrent.Sync;
19  
20  import java.io.InputStream  ;
21  
22  
23  /**
24   * Stores arbitrairy blob ("binary large object") data.
25   *
26   * <p>The store is a write-once, read-many type of store. An existing
27   * blob cannot be updated, rather a new one needs to be written.
28   *
29   * <p>The user of the BlobStore is himself responsible not to retrieve or delete
30   * a blob before it is completely written.
31   */
32  public interface BlobStore {
33      /**
34       * Returns an auto-generated key by which the blob can later be retrieved.
35       */
36      String   store(byte[] data) throws BlobIOException;
37  
38      /**
39       * Returns an auto-generated key by which the blob can later be retrieved.
40       * The InputStream will be closed for you.
41       */
42      String   store(InputStream   is) throws BlobIOException;
43  
44      /**
45       * The caller is responsible himself that a file is not being read before it is completely written.
46       * The caller is also responsible for making sure the stream gets closed, otherwise resource
47       * might leak (thus: always in a try-catch block!).
48       */
49      InputStream   retrieve(String   name) throws BlobIOException, NonExistingBlobException;
50  
51      void delete(String   name) throws NonExistingBlobException;
52  
53      /**
54       * Suspends all write operations to the blob store, after calling this method
55       * only read operation will be allowed. This method only returns after all
56       * active write operations have been finished.
57       *
58       * @param msecs max time to wait for active write operations to finish
59       */
60      boolean suspendWrites(long msecs) throws InterruptedException  ;
61  
62      /**
63       * Resumes write operations (after being suspended with {@link #suspendWrites(long)}.
64       */
65      void resumeWrites();
66  
67      /**
68       * Returns a lock which can be acquired to avoid that the BlobStore can
69       * go into suspension while you have this lock.
70       */
71      Sync getAvoidSuspendLock();
72  }
73
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