Source Code Cross Referenced for DatabaseReader.java in  » Content-Management-System » apache-lenya-2.0 » org » apache » cocoon » reading » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Content Management System » apache lenya 2.0 » org.apache.cocoon.reading 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Licensed to the Apache Software Foundation (ASF) under one or more
003:         * contributor license agreements.  See the NOTICE file distributed with
004:         * this work for additional information regarding copyright ownership.
005:         * The ASF licenses this file to You under the Apache License, Version 2.0
006:         * (the "License"); you may not use this file except in compliance with
007:         * the License.  You may obtain a copy of the License at
008:         *
009:         *      http://www.apache.org/licenses/LICENSE-2.0
010:         *
011:         * Unless required by applicable law or agreed to in writing, software
012:         * distributed under the License is distributed on an "AS IS" BASIS,
013:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014:         * See the License for the specific language governing permissions and
015:         * limitations under the License.
016:         */
017:        package org.apache.cocoon.reading;
018:
019:        import java.io.BufferedInputStream;
020:        import java.io.IOException;
021:        import java.io.InputStream;
022:        import java.sql.Connection;
023:        import java.sql.PreparedStatement;
024:        import java.sql.ResultSet;
025:        import java.sql.SQLException;
026:        import java.sql.Timestamp;
027:        import java.util.Map;
028:
029:        import org.apache.avalon.excalibur.datasource.DataSourceComponent;
030:        import org.apache.avalon.framework.activity.Disposable;
031:        import org.apache.avalon.framework.configuration.Configurable;
032:        import org.apache.avalon.framework.configuration.Configuration;
033:        import org.apache.avalon.framework.configuration.ConfigurationException;
034:        import org.apache.avalon.framework.parameters.Parameters;
035:        import org.apache.avalon.framework.service.ServiceException;
036:        import org.apache.avalon.framework.service.ServiceManager;
037:        import org.apache.avalon.framework.service.ServiceSelector;
038:        import org.apache.cocoon.ProcessingException;
039:        import org.apache.cocoon.ResourceNotFoundException;
040:        import org.apache.cocoon.caching.CacheableProcessingComponent;
041:        import org.apache.cocoon.environment.ObjectModelHelper;
042:        import org.apache.cocoon.environment.Request;
043:        import org.apache.cocoon.environment.Response;
044:        import org.apache.cocoon.environment.SourceResolver;
045:        import org.apache.excalibur.source.SourceValidity;
046:        import org.apache.excalibur.source.impl.validity.NOPValidity;
047:        import org.apache.excalibur.source.impl.validity.TimeStampValidity;
048:        import org.xml.sax.SAXException;
049:
050:        /**
051:         * This Reader pulls a resource from a database.  It is configured with
052:         * the Connection to use, parameters specify the table and column
053:         * to pull the image from, and source specifies the source key information.
054:         *
055:         * @author <a href="mailto:bloritsch@apache.org">Berin Loritsch</a>
056:         * @version CVS $Id: DatabaseReader.java 452159 2006-10-02 18:20:45Z vgritsenko $
057:         */
058:        public class DatabaseReader extends ServiceableReader implements 
059:                Configurable, Disposable, CacheableProcessingComponent {
060:
061:            private ServiceSelector datasourceSelector;
062:            private DataSourceComponent datasource;
063:
064:            private int typeColumn;
065:            private boolean defaultCache = true;
066:
067:            private Connection connection;
068:            private PreparedStatement statement;
069:            private ResultSet resultSet;
070:            private InputStream resource; // because HSQL doesn't yet implement getBlob()
071:            private String mimeType;
072:            private long lastModified = System.currentTimeMillis();
073:            private boolean doCommit;
074:
075:            public void service(final ServiceManager manager)
076:                    throws ServiceException {
077:                super .service(manager);
078:                this .datasourceSelector = (ServiceSelector) manager
079:                        .lookup(DataSourceComponent.ROLE + "Selector");
080:            }
081:
082:            /**
083:             * Configure the <code>Reader</code> so that we can use the same database
084:             * for all instances.
085:             */
086:            public void configure(Configuration conf)
087:                    throws ConfigurationException {
088:                this .defaultCache = conf.getChild("invalidate").getValue(
089:                        "never").equals("always");
090:
091:                String datasourceName = conf.getChild("use-connection")
092:                        .getValue();
093:                try {
094:                    this .datasource = (DataSourceComponent) datasourceSelector
095:                            .select(datasourceName);
096:                } catch (ServiceException e) {
097:                    throw new ConfigurationException("Datasource '"
098:                            + datasourceName + "' is not available.", e);
099:                }
100:            }
101:
102:            /**
103:             * Set the <code>SourceResolver</code> the object model <code>Map</code>,
104:             * the source and sitemap <code>Parameters</code> used to process the request.
105:             */
106:            public void setup(SourceResolver resolver, Map objectModel,
107:                    String src, Parameters par) throws ProcessingException,
108:                    SAXException, IOException {
109:                super .setup(resolver, objectModel, src, par);
110:
111:                try {
112:                    this .connection = datasource.getConnection();
113:                    if (this .connection.getAutoCommit()) {
114:                        this .connection.setAutoCommit(false);
115:                    }
116:
117:                    statement = connection.prepareStatement(getQuery());
118:                    statement.setString(1, this .source);
119:
120:                    resultSet = statement.executeQuery();
121:                    if (!resultSet.next()) {
122:                        throw new ResourceNotFoundException(
123:                                "There is no resource with that key");
124:                    }
125:
126:                    Response response = ObjectModelHelper
127:                            .getResponse(objectModel);
128:                    Request request = ObjectModelHelper.getRequest(objectModel);
129:
130:                    if (modifiedSince(resultSet, request, response)) {
131:                        this .resource = resultSet.getBinaryStream(1);
132:                        if (this .resource == null) {
133:                            throw new ResourceNotFoundException(
134:                                    "There is no resource with that key");
135:                        }
136:
137:                        if (this .typeColumn != 0) {
138:                            this .mimeType = resultSet
139:                                    .getString(this .typeColumn);
140:                        }
141:                    }
142:
143:                    this .doCommit = true;
144:                } catch (Exception e) {
145:                    this .doCommit = false;
146:                    throw new ResourceNotFoundException(
147:                            "DatabaseReader error:", e);
148:                }
149:            }
150:
151:            /**
152:             * Generates the resource we need to retrieve verbatim from the
153:             * database.  Granted, this can be used for any resource from a
154:             * database, so we may want to get rid of the bias toward images.
155:             * This reader requires a number of parameters:
156:             *
157:             * <pre>
158:             *   &lt;parameter name="table" value="database_table_name"/&gt;
159:             *   &lt;parameter name="image" value="database_resource_column_name"/&gt;
160:             *   &lt;parameter name="key" value="database_lookup_key_column_name"/&gt;
161:             * </pre>
162:             *
163:             * Please note that if any of those parameters are missing, this
164:             * <code>Reader</code> cannot function.  There are a number of other
165:             * parameters that allow you to provide hints for the reader to
166:             * optimize resource use:
167:             *
168:             * <pre>
169:             *   &lt;parameter name="last-modified" value="database_timestamp_column_name"/&gt;
170:             *   &lt;parameter name="content-type" value="content_mime_type"/&gt;
171:             *   &lt;parameter name="type-column" value="database_content_mime_type_column"/&gt;
172:             *   &lt;parameter name="expires" value="number_of_millis_before_refresh"/&gt;
173:             *   &lt;parameter name="where" value="alternate_key = 'foo'"/&gt;
174:             *   &lt;parameter name="order-by" value="alternate_key DESC"/&gt;
175:             * </pre>
176:             *
177:             * Lastly, the <code>key</code> value is derived from the value of
178:             * the <code>source</code> string.
179:             */
180:            public void generate() throws ProcessingException, SAXException,
181:                    IOException {
182:                try {
183:                    Response response = ObjectModelHelper
184:                            .getResponse(objectModel);
185:                    serialize(response);
186:                } catch (IOException e) {
187:                    getLogger().warn("Assuming client reset stream");
188:                    this .doCommit = false;
189:                } catch (Exception e) {
190:                    this .doCommit = false;
191:                    throw new ResourceNotFoundException(
192:                            "DatabaseReader error:", e);
193:                }
194:            }
195:
196:            /**
197:             * This method builds the query string used for accessing the database.
198:             * If the required parameters do not exist, then we cannot build a
199:             * correct query.
200:             */
201:            protected String getQuery() throws ProcessingException {
202:                String table = this .parameters.getParameter("table", null);
203:                String column = this .parameters.getParameter("image", null);
204:                String key = this .parameters.getParameter("key", null);
205:                String where = this .parameters.getParameter("where", null);
206:                String orderBy = this .parameters.getParameter("order-by", null);
207:                String typeColumn = this .parameters.getParameter("type-column",
208:                        null);
209:
210:                if (table == null || column == null || key == null) {
211:                    throw new ProcessingException(
212:                            "We are missing a required parameter.  Please include 'table', 'image', and 'key'");
213:                }
214:
215:                String date = this .parameters.getParameter("last-modified",
216:                        null);
217:                StringBuffer query = new StringBuffer("SELECT ");
218:
219:                int columnNo = 1;
220:                query.append(column);
221:                columnNo++;
222:
223:                if (date != null) {
224:                    query.append(", ").append(date);
225:                    columnNo++;
226:                }
227:
228:                if (null != orderBy) {
229:                    query.append(", ");
230:
231:                    if (orderBy.endsWith(" DESC")) {
232:                        query
233:                                .append(orderBy.substring(0,
234:                                        orderBy.length() - 5));
235:                    } else {
236:                        query.append(orderBy);
237:                    }
238:                    columnNo++;
239:                }
240:
241:                if (null != typeColumn) {
242:                    query.append(", ").append(typeColumn);
243:                    this .typeColumn = columnNo;
244:                }
245:
246:                query.append(" FROM ").append(table);
247:                query.append(" WHERE ").append(key).append(" = ?");
248:
249:                if (null != where) {
250:                    query.append(" AND ").append(where);
251:                }
252:
253:                if (null != orderBy) {
254:                    query.append(" ORDER BY ").append(orderBy);
255:                }
256:
257:                return query.toString();
258:            }
259:
260:            /**
261:             * Tests whether a resource has been modified or not.  As Blobs and
262:             * database columns usually do not have intrinsic dates on them (at
263:             * least easily accessible), we have to have a database column that
264:             * holds a date for the resource.  Please note, that the database
265:             * column <strong>must</strong> be a <code>Timestamp</code> column.
266:             *
267:             * In the absence of such a column this method <em>always</em>
268:             * returns <code>true</code>.  This is because databases are much
269:             * more prone to change than filesystems, and don't have intrinsic
270:             * timestamps on column updates.
271:             */
272:            protected boolean modifiedSince(ResultSet set, Request request,
273:                    Response response) throws SQLException {
274:                String lastModified = this .parameters.getParameter(
275:                        "last-modified", null);
276:                if (lastModified != null) {
277:                    Timestamp modified = set.getTimestamp(lastModified, null);
278:                    if (null != modified) {
279:                        this .lastModified = modified.getTime();
280:                    } else {
281:                        // assume it has never been modified
282:                    }
283:
284:                    response.setDateHeader("Last-Modified", this .lastModified);
285:                    return this .lastModified > request
286:                            .getDateHeader("if-modified-since");
287:                }
288:
289:                // if we have nothing to compare to, then we must assume it
290:                // has been modified
291:                return true;
292:            }
293:
294:            /**
295:             * This method actually performs the serialization.
296:             */
297:            public void serialize(Response response) throws IOException,
298:                    SQLException {
299:                if (this .resource == null) {
300:                    throw new SQLException("The Blob is empty!");
301:                }
302:
303:                InputStream is = new BufferedInputStream(this .resource);
304:
305:                long expires = parameters.getParameterAsInteger("expires", -1);
306:                if (expires > 0) {
307:                    response.setDateHeader("Expires", System
308:                            .currentTimeMillis()
309:                            + expires);
310:                }
311:
312:                response.setHeader("Accept-Ranges", "bytes");
313:
314:                byte[] buffer = new byte[8192];
315:                int length;
316:                while ((length = is.read(buffer)) > -1) {
317:                    out.write(buffer, 0, length);
318:                }
319:                is.close();
320:                out.flush();
321:            }
322:
323:            /**
324:             * Generate the unique key.
325:             * This key must be unique inside the space of this component.
326:             *
327:             * @return The generated key hashes the src
328:             */
329:            public java.io.Serializable getKey() {
330:                return this .source;
331:            }
332:
333:            /**
334:             * Generate the validity object.
335:             *
336:             * @return The generated validity object or <code>null</code> if the
337:             *         component is currently not cacheable.
338:             */
339:            public SourceValidity getValidity() {
340:                if (this .lastModified > 0) {
341:                    return new TimeStampValidity(this .lastModified);
342:                } else {
343:                    if (this .defaultCache) {
344:                        return NOPValidity.SHARED_INSTANCE;
345:                    } else {
346:                        return null;
347:                    }
348:                }
349:            }
350:
351:            public void recycle() {
352:                super .recycle();
353:                this .resource = null;
354:                this .lastModified = 0;
355:                this .mimeType = null;
356:                this .typeColumn = 0;
357:
358:                try {
359:                    if (resultSet != null) {
360:                        resultSet.close();
361:                    }
362:                } catch (SQLException e) { /* ignored */
363:                }
364:                resultSet = null;
365:
366:                try {
367:                    if (statement != null) {
368:                        statement.close();
369:                    }
370:                } catch (SQLException e) { /* ignored */
371:                }
372:                statement = null;
373:
374:                if (this .connection != null) {
375:                    try {
376:                        if (this .doCommit) {
377:                            this .connection.commit();
378:                        } else {
379:                            this .connection.rollback();
380:                        }
381:                    } catch (SQLException e) {
382:                        getLogger().warn(
383:                                "Could not commit or rollback connection", e);
384:                    }
385:
386:                    try {
387:                        this .connection.close();
388:                    } catch (SQLException e) { /* ignored */
389:                    }
390:                    this .connection = null;
391:                }
392:            }
393:
394:            public void dispose() {
395:                recycle();
396:                if (datasource != null) {
397:                    datasourceSelector.release(datasource);
398:                    datasource = null;
399:                }
400:                if (datasourceSelector != null) {
401:                    manager.release(datasourceSelector);
402:                    datasourceSelector = null;
403:                }
404:                manager = null;
405:            }
406:
407:            public String getMimeType() {
408:                if (mimeType != null) {
409:                    return mimeType;
410:                }
411:
412:                return this .parameters.getParameter("content-type", super
413:                        .getMimeType());
414:            }
415:        }
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