ContentStore


1   /*
2    * Copyright (C) 2005 Alfresco, Inc.
3    *
4    * Licensed under the Mozilla Public License version 1.1 
5    * with a permitted attribution clause. You may obtain a
6    * copy of the License at
7    *
8    *   http://www.alfresco.org/legal/license.txt
9    *
10   * Unless required by applicable law or agreed to in writing,
11   * software distributed under the License is distributed on an
12   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
13   * either express or implied. See the License for the specific
14   * language governing permissions and limitations under the
15   * License.
16   */
17  package org.alfresco.repo.content;
18  
19  import java.util.Date  ;
20  import java.util.Set  ;
21  
22  import org.alfresco.service.cmr.repository.ContentIOException;
23  import org.alfresco.service.cmr.repository.ContentReader;
24  import org.alfresco.service.cmr.repository.ContentStreamListener;
25  import org.alfresco.service.cmr.repository.ContentWriter;
26  
27  /**
28   * Provides low-level retrieval of content
29   * {@link org.alfresco.service.cmr.repository.ContentReader readers} and
30   * {@link org.alfresco.service.cmr.repository.ContentWriter writers}.
31   * <p>
32   * Implementations of this interface should be soley responsible for
33   * providing persistence and retrieval of the content against a
34   * <code>content URL</code>.
35   * <p>
36   * The URL format is <b>store://year/month/day/GUID.bin</b> <br>
37   * <ul>
38   *   <li> <b>store://</b>: prefix identifying an Alfresco content stores
39   *                         regardless of the persistence mechanism. </li>
40   *   <li> <b>year</b>: year </li>
41   *   <li> <b>month</b>: 1-based month of the year </li>
42   *   <li> <b>day</b>: 1-based day of the month </li>
43   *   <li> <b>GUID</b>: A unique identifier </li>
44   * </ul>
45   * The old <b>file://</b> prefix must still be supported - and functionality
46   * around this can be found in the {@link org.alfresco.repo.content.AbstractContentStore}
47   * implementation.
48   * 
49   * @author Derek Hulley
50   */
51  public interface ContentStore
52  {
53      /** <b>store://</b> is the new prefix for all content URLs */
54      public static final String   STORE_PROTOCOL = "store://";
55      
56      /**
57       * Check for the existence of content in the store.
58       * <p>
59       * The implementation of this may be more efficient than first getting a
60       * reader to {@link ContentReader#exists() check for existence}, although
61       * that check should also be performed.
62       * 
63       * @param contentUrl the path to the content
64       * @return Returns true if the content exists.
65       * @throws ContentIOException
66       * 
67       * @see ContentReader#exists()
68       */
69      public boolean exists(String   contentUrl) throws ContentIOException;
70      
71      /**
72       * Get the accessor with which to read from the content
73       * at the given URL.  The reader is <b>stateful</b> and
74       * can <b>only be used once</b>.
75       * 
76       * @param contentUrl the path to where the content is located
77       * @return Returns a read-only content accessor for the given URL.  There may
78       *      be no content at the given URL, but the reader must still be returned.
79       *      The reader may implement the {@link RandomAccessContent random access interface}.
80       * @throws ContentIOException
81       *
82       * @see #exists(String)
83       * @see ContentReader#exists()
84       */
85      public ContentReader getReader(String   contentUrl) throws ContentIOException;
86      
87      /**
88       * Get an accessor with which to write content to a location
89       * within the store.  The writer is <b>stateful</b> and can
90       * <b>only be used once</b>.  The location may be specified but must, in that case,
91       * be a valid and unused URL.
92       * <p>
93       * By supplying a reader to existing content, the store implementation may
94       * enable {@link RandomAccessContent random access}.  The store implementation
95       * can enable this by copying the existing content into the new location
96       * before supplying a writer onto the new content.
97       * 
98       * @param existingContentReader a reader onto any existing content for which
99       *      a writer is required - may be null
100      * @param newContentUrl an unused, valid URL to use - may be null.
101      * @return Returns a write-only content accessor, possibly implementing
102      *      the {@link RandomAccessContent random access interface}
103      * @throws ContentIOException if completely new content storage could not be
104      *      created
105      *
106      * @see ContentWriter#addListener(ContentStreamListener)
107      * @see ContentWriter#getContentUrl()
108      */
109     public ContentWriter getWriter(ContentReader existingContentReader, String   newContentUrl) throws ContentIOException;
110 
111     /**
112      * Get all URLs for the store, regardless of creation time.
113      * 
114      * @see #getUrls(Date, Date)
115      */
116     public Set  <String  > getUrls() throws ContentIOException;
117 
118     /**
119      * Get a set of all content URLs in the store.  This indicates all content
120      * available for reads.
121      * 
122      * @param createdAfter all URLs returned must have been created after this date.  May be null.
123      * @param createdBefore all URLs returned must have been created before this date.  May be null.
124      * @return Returns a complete set of the unique URLs of all available content
125      *      in the store
126      * @throws ContentIOException
127      */
128     public Set  <String  > getUrls(Date   createdAfter, Date   createdBefore) throws ContentIOException;
129     
130     /**
131      * Deletes the content at the given URL.
132      * <p>
133      * A delete cannot be forced since it is much better to have the
134      * file remain longer than desired rather than deleted prematurely.
135      * The store implementation should safeguard files for certain
136      * minimum period, in which case all files younger than a certain
137      * age will not be deleted.
138      * 
139      * @param contentUrl the URL of the content to delete
140      * @return Return true if the content was deleted (either by this or
141      *      another operation), otherwise false
142      * @throws ContentIOException
143      */
144     public boolean delete(String   contentUrl) throws ContentIOException;
145 }
146
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