AbstractLobStreamingResultSetExtractor


1   /*
2    * Copyright 2002-2005 the original author or authors.
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  
17  package org.springframework.jdbc.core.support;
18  
19  import java.io.IOException  ;
20  import java.sql.ResultSet  ;
21  import java.sql.SQLException  ;
22  
23  import org.springframework.dao.DataAccessException;
24  import org.springframework.dao.EmptyResultDataAccessException;
25  import org.springframework.dao.IncorrectResultSizeDataAccessException;
26  import org.springframework.jdbc.LobRetrievalFailureException;
27  import org.springframework.jdbc.core.ResultSetExtractor;
28  
29  /**
30   * Abstract ResultSetExtractor implementation that assumes streaming of LOB data.
31   * Typically used as inner class, with access to surrounding method arguments.
32   *
33   * <p>Delegates to the <code>streamData</code> template method for streaming LOB
34   * content to some OutputStream, typically using a LobHandler. Converts an
35   * IOException thrown during streaming to a LobRetrievalFailureException.
36   *
37   * <p>A usage example with JdbcTemplate:
38   *
39   * <pre class="code">JdbcTemplate jdbcTemplate = new JdbcTemplate(dataSource);  // reusable object
40   * final LobHandler lobHandler = new DefaultLobHandler();  // reusable object
41   *
42   * jdbcTemplate.query(
43   *       "SELECT content FROM imagedb WHERE image_name=?", new Object[] {name},
44   *       new AbstractLobStreamingResultSetExtractor() {
45   *           public void streamData(ResultSet rs) throws SQLException, IOException {
46   *               FileCopyUtils.copy(lobHandler.getBlobAsBinaryStream(rs, 1), contentStream);
47   *           }
48   *       }
49   * );</pre>
50   *
51   * @author Juergen Hoeller
52   * @since 1.0.2
53   * @see org.springframework.jdbc.support.lob.LobHandler
54   * @see org.springframework.jdbc.LobRetrievalFailureException
55   */
56  public abstract class AbstractLobStreamingResultSetExtractor implements ResultSetExtractor {
57  
58      /**
59       * Delegates to handleNoRowFound, handleMultipleRowsFound and streamData,
60       * according to the ResultSet state. Converts an IOException thrown by
61       * streamData to a LobRetrievalFailureException.
62       * @see #handleNoRowFound
63       * @see #handleMultipleRowsFound
64       * @see #streamData
65       * @see org.springframework.jdbc.LobRetrievalFailureException
66       */
67      public final Object   extractData(ResultSet   rs) throws SQLException  , DataAccessException {
68          if (!rs.next()) {
69              handleNoRowFound();
70          }
71          else {
72              try {
73                  streamData(rs);
74                  if (rs.next()) {
75                      handleMultipleRowsFound();
76                  }
77              }
78              catch (IOException   ex) {
79                  throw new LobRetrievalFailureException("Couldn't stream LOB content", ex);
80              }
81          }
82          return null;
83      }
84  
85      /**
86       * Handle the case where the ResultSet does not contain a row.
87       * @throws DataAccessException a corresponding exception,
88       * by default an EmptyResultDataAccessException
89       * @see org.springframework.dao.EmptyResultDataAccessException
90       */
91      protected void handleNoRowFound() throws DataAccessException {
92          throw new EmptyResultDataAccessException(
93                  "LobStreamingResultSetExtractor did not find row in database", 1);
94      }
95  
96      /**
97       * Handle the case where the ResultSet contains multiple rows.
98       * @throws DataAccessException a corresponding exception,
99       * by default an IncorrectResultSizeDataAccessException
100      * @see org.springframework.dao.IncorrectResultSizeDataAccessException
101      */
102     protected void handleMultipleRowsFound() throws DataAccessException {
103         throw new IncorrectResultSizeDataAccessException(
104                 "LobStreamingResultSetExtractor found multiple rows in database", 1);
105     }
106 
107     /**
108      * Stream LOB content from the given ResultSet to some OutputStream.
109      * <p>Typically used as inner class, with access to surrounding method arguments
110      * and to a LobHandler instance variable of the surrounding class.
111      * @param rs the ResultSet to take the LOB content from
112      * @throws SQLException if thrown by JDBC methods
113      * @throws IOException if thrown by stream access methods
114      * @throws DataAccessException in case of custom exceptions
115      * @see org.springframework.jdbc.support.lob.LobHandler#getBlobAsBinaryStream
116      * @see org.springframework.util.FileCopyUtils
117      */
118     protected abstract void streamData(ResultSet   rs) throws SQLException  , IOException  , DataAccessException;
119 
120 }
121
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