1 | /* |
2 | * Copyright 2006-2007 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 | package org.springframework.batch.item.database; |
17 | |
18 | import org.hibernate.Query; |
19 | import org.hibernate.ScrollMode; |
20 | import org.hibernate.ScrollableResults; |
21 | import org.hibernate.Session; |
22 | import org.hibernate.SessionFactory; |
23 | import org.hibernate.StatelessSession; |
24 | import org.springframework.batch.item.ItemReader; |
25 | import org.springframework.batch.item.ItemStream; |
26 | import org.springframework.batch.item.support.AbstractBufferedItemReaderItemStream; |
27 | import org.springframework.beans.factory.InitializingBean; |
28 | import org.springframework.util.Assert; |
29 | import org.springframework.util.ClassUtils; |
30 | |
31 | /** |
32 | * {@link ItemReader} for reading database records built on top of Hibernate. |
33 | * |
34 | * It executes the HQL {@link #setQueryString(String)} when initialized and |
35 | * iterates over the result set as {@link #read()} method is called, returning |
36 | * an object corresponding to current row. |
37 | * |
38 | * The reader can be configured to use either {@link StatelessSession} |
39 | * sufficient for simple mappings without the need to cascade to associated |
40 | * objects or standard hibernate {@link Session} for more advanced mappings or |
41 | * when caching is desired. |
42 | * |
43 | * When stateful session is used it will be cleared after successful commit |
44 | * without being flushed (no inserts or updates are expected). |
45 | * |
46 | * Reset(rollback) functionality is implemented by item buffering allowing the |
47 | * cursor used to be forward-only. |
48 | * |
49 | * The implementation is *not* thread-safe. |
50 | * |
51 | * @author Robert Kasanicky |
52 | * @author Dave Syer |
53 | */ |
54 | public class HibernateCursorItemReader extends AbstractBufferedItemReaderItemStream implements ItemStream, |
55 | InitializingBean { |
56 | |
57 | private SessionFactory sessionFactory; |
58 | |
59 | private StatelessSession statelessSession; |
60 | |
61 | private Session statefulSession; |
62 | |
63 | private ScrollableResults cursor; |
64 | |
65 | private String queryString; |
66 | |
67 | private boolean useStatelessSession = true; |
68 | |
69 | private boolean initialized = false; |
70 | |
71 | private int fetchSize = 0; |
72 | |
73 | public HibernateCursorItemReader() { |
74 | setName(ClassUtils.getShortName(HibernateCursorItemReader.class)); |
75 | } |
76 | |
77 | /** |
78 | * Open appropriate type of hibernate session and create the query. |
79 | */ |
80 | private Query createQuery() { |
81 | if (useStatelessSession) { |
82 | statelessSession = sessionFactory.openStatelessSession(); |
83 | return statelessSession.createQuery(queryString); |
84 | } |
85 | else { |
86 | statefulSession = sessionFactory.openSession(); |
87 | return statefulSession.createQuery(queryString); |
88 | } |
89 | } |
90 | |
91 | /** |
92 | * @param sessionFactory hibernate session factory |
93 | */ |
94 | public void setSessionFactory(SessionFactory sessionFactory) { |
95 | this.sessionFactory = sessionFactory; |
96 | } |
97 | |
98 | public void afterPropertiesSet() throws Exception { |
99 | Assert.notNull(sessionFactory); |
100 | Assert.hasLength(queryString); |
101 | Assert.isTrue(fetchSize >= 0, "fetchSize must not be negative"); |
102 | } |
103 | |
104 | /** |
105 | * @param queryString HQL query string |
106 | */ |
107 | public void setQueryString(String queryString) { |
108 | this.queryString = queryString; |
109 | } |
110 | |
111 | /** |
112 | * Can be set only in uninitialized state. |
113 | * |
114 | * @param useStatelessSession <code>true</code> to use |
115 | * {@link StatelessSession} <code>false</code> to use standard hibernate |
116 | * {@link Session} |
117 | */ |
118 | public void setUseStatelessSession(boolean useStatelessSession) { |
119 | Assert.state(!initialized); |
120 | this.useStatelessSession = useStatelessSession; |
121 | } |
122 | |
123 | /** |
124 | * Mark is supported as long as this {@link ItemStream} is used in a |
125 | * single-threaded environment. The state backing the mark is a single |
126 | * counter, keeping track of the current position, so multiple threads |
127 | * cannot be accommodated. |
128 | * |
129 | * @see org.springframework.batch.item.ItemReader#mark() |
130 | */ |
131 | public void mark() { |
132 | |
133 | super.mark(); |
134 | |
135 | if (!useStatelessSession) { |
136 | statefulSession.clear(); |
137 | } |
138 | } |
139 | |
140 | /** |
141 | * Gives the JDBC driver a hint as to the number of rows that should be |
142 | * fetched from the database when more rows are needed for this |
143 | * <code>ResultSet</code> object. If the fetch size specified is zero, the |
144 | * JDBC driver ignores the value. |
145 | * |
146 | * @param fetchSize the number of rows to fetch, 0 by default |
147 | * @see Query#setFetchSize(int) |
148 | */ |
149 | public void setFetchSize(int fetchSize) { |
150 | this.fetchSize = fetchSize; |
151 | } |
152 | |
153 | protected Object doRead() throws Exception { |
154 | if (cursor.next()) { |
155 | Object[] data = cursor.get(); |
156 | Object item; |
157 | |
158 | if (data.length > 1) { |
159 | item = data; |
160 | } |
161 | else { |
162 | item = data[0]; |
163 | } |
164 | |
165 | return item; |
166 | } |
167 | return null; |
168 | } |
169 | |
170 | /** |
171 | * Open hibernate session and create a forward-only cursor for the |
172 | * {@link #setQueryString(String)}. |
173 | */ |
174 | protected void doOpen() throws Exception { |
175 | Assert.state(!initialized, "Cannot open an already opened ItemReader, call close first"); |
176 | |
177 | cursor = createQuery().setFetchSize(fetchSize).scroll(ScrollMode.FORWARD_ONLY); |
178 | |
179 | initialized = true; |
180 | |
181 | } |
182 | |
183 | /** |
184 | * Close the cursor and hibernate session. |
185 | */ |
186 | protected void doClose() throws Exception { |
187 | initialized = false; |
188 | |
189 | if (cursor != null) { |
190 | cursor.close(); |
191 | } |
192 | if (useStatelessSession) { |
193 | if (statelessSession != null) { |
194 | statelessSession.close(); |
195 | } |
196 | } |
197 | else { |
198 | if (statefulSession != null) { |
199 | statefulSession.close(); |
200 | } |
201 | } |
202 | |
203 | } |
204 | } |