Source Code Cross Referenced for SingleConnectionDataSource.java in  » J2EE » spring-framework-2.5 » org » springframework » jdbc » datasource » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » J2EE » spring framework 2.5 » org.springframework.jdbc.datasource 
Source Cross Referenced  Class Diagram Java Document (Java Doc) 


001:        /*
002:         * Copyright 2002-2006 the original author or authors.
003:         *
004:         * Licensed under the Apache License, Version 2.0 (the "License");
005:         * you may not use this file except in compliance with the License.
006:         * You may obtain a copy of the License at
007:         *
008:         *      http://www.apache.org/licenses/LICENSE-2.0
009:         *
010:         * Unless required by applicable law or agreed to in writing, software
011:         * distributed under the License is distributed on an "AS IS" BASIS,
012:         * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013:         * See the License for the specific language governing permissions and
014:         * limitations under the License.
015:         */
016:
017:        package org.springframework.jdbc.datasource;
018:
019:        import java.lang.reflect.InvocationHandler;
020:        import java.lang.reflect.InvocationTargetException;
021:        import java.lang.reflect.Method;
022:        import java.lang.reflect.Proxy;
023:        import java.sql.Connection;
024:        import java.sql.SQLException;
025:
026:        import org.springframework.beans.factory.DisposableBean;
027:        import org.springframework.jdbc.CannotGetJdbcConnectionException;
028:        import org.springframework.util.Assert;
029:        import org.springframework.util.ObjectUtils;
030:
031:        /**
032:         * Implementation of SmartDataSource that wraps a single Connection which is not
033:         * closed after use. Obviously, this is not multi-threading capable.
034:         *
035:         * <p>Note that at shutdown, someone should close the underlying Connection via the
036:         * <code>close()</code> method. Client code will never call close on the Connection
037:         * handle if it is SmartDataSource-aware (e.g. uses
038:         * <code>DataSourceUtils.releaseConnection</code>).
039:         *
040:         * <p>If client code will call <code>close()</code> in the assumption of a pooled
041:         * Connection, like when using persistence tools, set "suppressClose" to "true".
042:         * This will return a close-suppressing proxy instead of the physical Connection.
043:         * Be aware that you will not be able to cast this to a native OracleConnection
044:         * or the like anymore (you need to use a NativeJdbcExtractor for this then).
045:         *
046:         * <p>This is primarily intended for testing. For example, it enables easy testing
047:         * outside an application server, for code that expects to work on a DataSource.
048:         * In contrast to DriverManagerDataSource, it reuses the same Connection all the
049:         * time, avoiding excessive creation of physical Connections.
050:         *
051:         * @author Rod Johnson
052:         * @author Juergen Hoeller
053:         * @see #getConnection()
054:         * @see java.sql.Connection#close()
055:         * @see DataSourceUtils#releaseConnection
056:         * @see org.springframework.jdbc.support.nativejdbc.NativeJdbcExtractor
057:         */
058:        public class SingleConnectionDataSource extends DriverManagerDataSource
059:                implements  SmartDataSource, DisposableBean {
060:
061:            /** Create a close-suppressing proxy? */
062:            private boolean suppressClose;
063:
064:            /** Override AutoCommit? */
065:            private Boolean autoCommit;
066:
067:            /** Wrapped Connection */
068:            private Connection target;
069:
070:            /** Proxy Connection */
071:            private Connection connection;
072:
073:            /** Synchronization monitor for the shared Connection */
074:            private final Object connectionMonitor = new Object();
075:
076:            /**
077:             * Constructor for bean-style configuration.
078:             */
079:            public SingleConnectionDataSource() {
080:            }
081:
082:            /**
083:             * Create a new SingleConnectionDataSource with the given standard
084:             * DriverManager parameters.
085:             * @param driverClassName the JDBC driver class name
086:             * @param url the JDBC URL to use for accessing the DriverManager
087:             * @param username the JDBC username to use for accessing the DriverManager
088:             * @param password the JDBC password to use for accessing the DriverManager
089:             * @param suppressClose if the returned Connection should be a
090:             * close-suppressing proxy or the physical Connection
091:             * @see java.sql.DriverManager#getConnection(String, String, String)
092:             */
093:            public SingleConnectionDataSource(String driverClassName,
094:                    String url, String username, String password,
095:                    boolean suppressClose)
096:                    throws CannotGetJdbcConnectionException {
097:
098:                super (driverClassName, url, username, password);
099:                this .suppressClose = suppressClose;
100:            }
101:
102:            /**
103:             * Create a new SingleConnectionDataSource with the given standard
104:             * DriverManager parameters.
105:             * @param url the JDBC URL to use for accessing the DriverManager
106:             * @param username the JDBC username to use for accessing the DriverManager
107:             * @param password the JDBC password to use for accessing the DriverManager
108:             * @param suppressClose if the returned Connection should be a
109:             * close-suppressing proxy or the physical Connection
110:             * @see java.sql.DriverManager#getConnection(String, String, String)
111:             */
112:            public SingleConnectionDataSource(String url, String username,
113:                    String password, boolean suppressClose)
114:                    throws CannotGetJdbcConnectionException {
115:
116:                super (url, username, password);
117:                this .suppressClose = suppressClose;
118:            }
119:
120:            /**
121:             * Create a new SingleConnectionDataSource with the given standard
122:             * DriverManager parameters.
123:             * @param url the JDBC URL to use for accessing the DriverManager
124:             * @param suppressClose if the returned Connection should be a
125:             * close-suppressing proxy or the physical Connection
126:             * @see java.sql.DriverManager#getConnection(String, String, String)
127:             */
128:            public SingleConnectionDataSource(String url, boolean suppressClose)
129:                    throws CannotGetJdbcConnectionException {
130:
131:                super (url);
132:                this .suppressClose = suppressClose;
133:            }
134:
135:            /**
136:             * Create a new SingleConnectionDataSource with a given Connection.
137:             * @param target underlying target Connection
138:             * @param suppressClose if the Connection should be wrapped with a Connection that
139:             * suppresses <code>close()</code> calls (to allow for normal <code>close()</code>
140:             * usage in applications that expect a pooled Connection but do not know our
141:             * SmartDataSource interface)
142:             */
143:            public SingleConnectionDataSource(Connection target,
144:                    boolean suppressClose) {
145:                Assert.notNull(target, "Connection must not be null");
146:                this .target = target;
147:                this .suppressClose = suppressClose;
148:                this .connection = (suppressClose ? getCloseSuppressingConnectionProxy(target)
149:                        : target);
150:            }
151:
152:            /**
153:             * Set whether the returned Connection should be a close-suppressing proxy
154:             * or the physical Connection.
155:             */
156:            public void setSuppressClose(boolean suppressClose) {
157:                this .suppressClose = suppressClose;
158:            }
159:
160:            /**
161:             * Return whether the returned Connection will be a close-suppressing proxy
162:             * or the physical Connection.
163:             */
164:            protected boolean isSuppressClose() {
165:                return suppressClose;
166:            }
167:
168:            /**
169:             * Set whether the returned Connection's "autoCommit" setting should be overridden.
170:             */
171:            public void setAutoCommit(boolean autoCommit) {
172:                this .autoCommit = (autoCommit ? Boolean.TRUE : Boolean.FALSE);
173:            }
174:
175:            /**
176:             * Return whether the returned Connection's "autoCommit" setting should be overridden.
177:             * @return the "autoCommit" value, or <code>null</code> if none to be applied
178:             */
179:            protected Boolean getAutoCommitValue() {
180:                return autoCommit;
181:            }
182:
183:            public Connection getConnection() throws SQLException {
184:                synchronized (this .connectionMonitor) {
185:                    if (this .connection == null) {
186:                        // No underlying Connection -> lazy init via DriverManager.
187:                        initConnection();
188:                    }
189:                    if (this .connection.isClosed()) {
190:                        throw new SQLException(
191:                                "Connection was closed in SingleConnectionDataSource. Check that user code checks "
192:                                        + "shouldClose() before closing Connections, or set 'suppressClose' to 'true'");
193:                    }
194:                    return this .connection;
195:                }
196:            }
197:
198:            /**
199:             * Specifying a custom username and password doesn't make sense
200:             * with a single Connection. Returns the single Connection if given
201:             * the same username and password; throws a SQLException else.
202:             */
203:            public Connection getConnection(String username, String password)
204:                    throws SQLException {
205:                if (ObjectUtils.nullSafeEquals(username, getUsername())
206:                        && ObjectUtils.nullSafeEquals(password, getPassword())) {
207:                    return getConnection();
208:                } else {
209:                    throw new SQLException(
210:                            "SingleConnectionDataSource does not support custom username and password");
211:                }
212:            }
213:
214:            /**
215:             * This is a single Connection: Do not close it when returning to the "pool".
216:             */
217:            public boolean shouldClose(Connection con) {
218:                synchronized (this .connectionMonitor) {
219:                    return (con != this .connection && con != this .target);
220:                }
221:            }
222:
223:            /**
224:             * Close the underlying Connection.
225:             * The provider of this DataSource needs to care for proper shutdown.
226:             * <p>As this bean implements DisposableBean, a bean factory will
227:             * automatically invoke this on destruction of its cached singletons.
228:             */
229:            public void destroy() {
230:                synchronized (this .connectionMonitor) {
231:                    closeConnection();
232:                }
233:            }
234:
235:            /**
236:             * Initialize the underlying Connection via the DriverManager.
237:             */
238:            public void initConnection() throws SQLException {
239:                if (getUrl() == null) {
240:                    throw new IllegalStateException(
241:                            "'url' property is required for lazily initializing a Connection");
242:                }
243:                synchronized (this .connectionMonitor) {
244:                    closeConnection();
245:                    this .target = getConnectionFromDriverManager();
246:                    prepareConnection(this .target);
247:                    if (logger.isInfoEnabled()) {
248:                        logger.info("Established shared JDBC Connection: "
249:                                + this .target);
250:                    }
251:                    this .connection = (isSuppressClose() ? getCloseSuppressingConnectionProxy(this .target)
252:                            : this .target);
253:                }
254:            }
255:
256:            /**
257:             * Reset the underlying shared Connection, to be reinitialized on next access.
258:             */
259:            public void resetConnection() {
260:                synchronized (this .connectionMonitor) {
261:                    closeConnection();
262:                    this .target = null;
263:                    this .connection = null;
264:                }
265:            }
266:
267:            /**
268:             * Prepare the given Connection before it is exposed.
269:             * <p>The default implementation applies the auto-commit flag, if necessary.
270:             * Can be overridden in subclasses.
271:             * @param con the Connection to prepare
272:             * @see #setAutoCommit
273:             */
274:            protected void prepareConnection(Connection con)
275:                    throws SQLException {
276:                Boolean autoCommit = getAutoCommitValue();
277:                if (autoCommit != null
278:                        && con.getAutoCommit() != autoCommit.booleanValue()) {
279:                    con.setAutoCommit(autoCommit.booleanValue());
280:                }
281:            }
282:
283:            /**
284:             * Close the underlying shared Connection.
285:             */
286:            private void closeConnection() {
287:                if (this .target != null) {
288:                    try {
289:                        this .target.close();
290:                    } catch (Throwable ex) {
291:                        logger.warn("Could not close shared JDBC Connection",
292:                                ex);
293:                    }
294:                }
295:            }
296:
297:            /**
298:             * Wrap the given Connection with a proxy that delegates every method call to it
299:             * but suppresses close calls.
300:             * @param target the original Connection to wrap
301:             * @return the wrapped Connection
302:             */
303:            protected Connection getCloseSuppressingConnectionProxy(
304:                    Connection target) {
305:                return (Connection) Proxy.newProxyInstance(
306:                        ConnectionProxy.class.getClassLoader(),
307:                        new Class[] { ConnectionProxy.class },
308:                        new CloseSuppressingInvocationHandler(target));
309:            }
310:
311:            /**
312:             * Invocation handler that suppresses close calls on JDBC Connections.
313:             */
314:            private static class CloseSuppressingInvocationHandler implements 
315:                    InvocationHandler {
316:
317:                private final Connection target;
318:
319:                public CloseSuppressingInvocationHandler(Connection target) {
320:                    this .target = target;
321:                }
322:
323:                public Object invoke(Object proxy, Method method, Object[] args)
324:                        throws Throwable {
325:                    // Invocation on ConnectionProxy interface coming in...
326:
327:                    if (method.getName().equals("getTargetConnection")) {
328:                        // Handle getTargetConnection method: return underlying Connection.
329:                        return this .target;
330:                    } else if (method.getName().equals("equals")) {
331:                        // Only consider equal when proxies are identical.
332:                        return (proxy == args[0] ? Boolean.TRUE : Boolean.FALSE);
333:                    } else if (method.getName().equals("hashCode")) {
334:                        // Use hashCode of Connection proxy.
335:                        return new Integer(hashCode());
336:                    } else if (method.getName().equals("close")) {
337:                        // Handle close method: don't pass the call on.
338:                        return null;
339:                    }
340:
341:                    // Invoke method on target Connection.
342:                    try {
343:                        return method.invoke(this .target, args);
344:                    } catch (InvocationTargetException ex) {
345:                        throw ex.getTargetException();
346:                    }
347:                }
348:            }
349:
350:        }
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