1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> 2 <html> 3 <head> 4 <!-- 5 Copyright (c) 2000, 2006, Oracle and/or its affiliates. All rights reserved. 6 DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 7 8 This code is free software; you can redistribute it and/or modify it 9 under the terms of the GNU General Public License version 2 only, as 10 published by the Free Software Foundation. Oracle designates this 11 particular file as subject to the "Classpath" exception as provided 12 by Oracle in the LICENSE file that accompanied this code. 13 14 This code is distributed in the hope that it will be useful, but WITHOUT 15 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 16 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 17 version 2 for more details (a copy is included in the LICENSE file that 18 accompanied this code). 19 20 You should have received a copy of the GNU General Public License version 21 2 along with this work; if not, write to the Free Software Foundation, 22 Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 23 24 Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 25 or visit www.oracle.com if you need additional information or have any 26 questions. 27 --> 28 29 </head> 30 31 32 33 <body bgcolor="white"> 34 35 Provides the API for server side data source access and processing from 36 the Java<sup><font size=-2>TM</font></sup> programming language. 37 This package supplements the <code>java.sql</code> 38 package and, as of the version 1.4 release, is included in the 39 Java Platform, Standard Edition 40 (Java SE<sup><font size=-2>TM</sup></font>). 41 It remains an essential part of the Java Platform, Enterprise Edition 42 (Java EE<sup><font size=-2>TM</sup></font>). 43 <P> 44 The <code>javax.sql</code> package provides for the following: 45 <OL> 46 <LI>The <code>DataSource</code> interface as an alternative to the 47 <code>DriverManager</code> for establishing a 48 connection with a data source 49 <LI>Connection pooling and Statement pooling 50 <LI>Distributed transactions 51 <LI>Rowsets 52 </OL> 53 <P> 54 Applications use the <code>DataSource</code> and <code>RowSet</code> 55 APIs directly, but the connection pooling and distributed transaction 56 APIs are used internally by the middle-tier infrastructure. 57 58 <H2>Using a <code>DataSource</code> Object to Make a Connection</H2> 59 60 The <code>javax.sql</code> package provides the preferred 61 way to make a connection with a data source. The <code>DriverManager</code> 62 class, the original mechanism, is still valid, and code using it will 63 continue to run. However, the newer <code>DataSource</code> mechanism 64 is preferred because it offers many advantages over the 65 <code>DriverManager</code> mechanism. 66 <P> 67 These are the main advantages of using a <code>DataSource</code> object to 68 make a connection: 69 <UL> 70 71 <LI>Changes can be made to a data source's properties, which means 72 that it is not necessary to make changes in application code when 73 something about the data source or driver changes. 74 <LI>Connection and Statement pooling and distributed transactions are available 75 through a <code>DataSource</code> object that is 76 implemented to work with the middle-tier infrastructure. 77 Connections made through the <code>DriverManager</code> 78 do not have connection and statement pooling or distributed transaction 79 capabilities. 80 </UL> 81 <P> 82 Driver vendors provide <code>DataSource</code> implementations. A 83 particular <code>DataSource</code> object represents a particular 84 physical data source, and each connection the <code>DataSource</code> object 85 creates is a connection to that physical data source. 86 <P> 87 A logical name for the data source is registered with a naming service that 88 uses the Java Naming and Directory Interface<sup><font size=-2>TM</font></sup> 89 (JNDI) API, usually by a system administrator or someone performing the 90 duties of a system administrator. An application can retrieve the 91 <code>DataSource</code> object it wants by doing a lookup on the logical 92 name that has been registered for it. The application can then use the 93 <code>DataSource</code> object to create a connection to the physical data 94 source it represents. 95 <P> 96 A <code>DataSource</code> object can be implemented to work with the 97 middle tier infrastructure so that the connections it produces will be 98 pooled for reuse. An application that uses such a <code>DataSource</code> 99 implementation will automatically get a connection that participates in 100 connection pooling. 101 A <code>DataSource</code> object can also be implemented to work with the 102 middle tier infrastructure so that the connections it produces can be 103 used for distributed transactions without any special coding. 104 105 <H2>Connection Pooling and Statement Pooling</H2> 106 107 Connections made via a <code>DataSource</code> 108 object that is implemented to work with a middle tier connection pool manager 109 will participate in connection pooling. This can improve performance 110 dramatically because creating new connections is very expensive. 111 Connection pooling allows a connection to be used and reused, 112 thus cutting down substantially on the number of new connections 113 that need to be created. 114 <P> 115 Connection pooling is totally transparent. It is done automatically 116 in the middle tier of a Java EE configuration, so from an application's 117 viewpoint, no change in code is required. An application simply uses 118 the <code>DataSource.getConnection</code> method to get the pooled 119 connection and uses it the same way it uses any <code>Connection</code> 120 object. 121 <P> 122 The classes and interfaces used for connection pooling are: 123 <UL> 124 <LI><code>ConnectionPoolDataSource</code> 125 <LI><code>PooledConnection</code> 126 <LI><code>ConnectionEvent</code> 127 <LI><code>ConnectionEventListener</code> 128 <LI><code>StatementEvent</code> 129 <LI><code>StatementEventListener</code> 130 </UL> 131 The connection pool manager, a facility in the middle tier of 132 a three-tier architecture, uses these classes and interfaces 133 behind the scenes. When a <code>ConnectionPoolDataSource</code> object 134 is called on to create a <code>PooledConnection</code> object, the 135 connection pool manager will register as a <code>ConnectionEventListener</code> 136 object with the new <code>PooledConnection</code> object. When the connection 137 is closed or there is an error, the connection pool manager (being a listener) 138 gets a notification that includes a <code>ConnectionEvent</code> object. 139 <p> 140 If the connection pool manager supports <code>Statement</code> pooling, for 141 <code>PreparedStatements</code>, which can be determined by invoking the method 142 <code>DatabaseMetaData.supportsStatementPooling</code>, the 143 connection pool manager will register as a <code>StatementEventListener</code> 144 object with the new <code>PooledConnection</code> object. When the 145 <code>PreparedStatement</code> is closed or there is an error, the connection 146 pool manager (being a listener) 147 gets a notification that includes a <code>StatementEvent</code> object. 148 <p> 149 150 <H2>Distributed Transactions</H2> 151 152 As with pooled connections, connections made via a <code>DataSource</code> 153 object that is implemented to work with the middle tier infrastructure 154 may participate in distributed transactions. This gives an application 155 the ability to involve data sources on multiple servers in a single 156 transaction. 157 <P> 158 The classes and interfaces used for distributed transactions are: 159 <UL> 160 <LI><code>XADataSource</code> 161 <LI><code>XAConnection</code> 162 </UL> 163 These interfaces are used by the transaction manager; an application does 164 not use them directly. 165 <P> 166 The <code>XAConnection</code> interface is derived from the 167 <code>PooledConnection</code> interface, so what applies to a pooled connection 168 also applies to a connection that is part of a distributed transaction. 169 A transaction manager in the middle tier handles everything transparently. 170 The only change in application code is that an application cannot do anything 171 that would interfere with the transaction manager's handling of the transaction. 172 Specifically, an application cannot call the methods <code>Connection.commit</code> 173 or <code>Connection.rollback</code>, and it cannot set the connection to be in 174 auto-commit mode (that is, it cannot call 175 <code>Connection.setAutoCommit(true)</code>). 176 <P> 177 An application does not need to do anything special to participate in a 178 distributed transaction. 179 It simply creates connections to the data sources it wants to use via 180 the <code>DataSource.getConnection</code> method, just as it normally does. 181 The transaction manager manages the transaction behind the scenes. The 182 <code>XADataSource</code> interface creates <code>XAConnection</code> objects, and 183 each <code>XAConnection</code> object creates an <code>XAResource</code> object 184 that the transaction manager uses to manage the connection. 185 186 187 <H2>Rowsets</H2> 188 The <code>RowSet</code> interface works with various other classes and 189 interfaces behind the scenes. These can be grouped into three categories. 190 <OL> 191 <LI>Event Notification 192 <UL> 193 <LI><code>RowSetListener</code><br> 194 A <code>RowSet</code> object is a JavaBeans<sup><font size=-2>TM</font></sup> 195 component because it has properties and participates in the JavaBeans 196 event notification mechanism. The <code>RowSetListener</code> interface 197 is implemented by a component that wants to be notified about events that 198 occur to a particular <code>RowSet</code> object. Such a component registers 199 itself as a listener with a rowset via the <code>RowSet.addRowSetListener</code> 200 method. 201 <P> 202 When the <code>RowSet</code> object changes one of its rows, changes all of 203 it rows, or moves its cursor, it also notifies each listener that is registered 204 with it. The listener reacts by carrying out its implementation of the 205 notification method called on it. 206 <P> 207 <LI><code>RowSetEvent</code><br> 208 As part of its internal notification process, a <code>RowSet</code> object 209 creates an instance of <code>RowSetEvent</code> and passes it to the listener. 210 The listener can use this <code>RowSetEvent</code> object to find out which rowset 211 had the event. 212 </UL> 213 <P> 214 <LI>Metadata 215 <UL> 216 <LI><code>RowSetMetaData</code><br> 217 This interface, derived from the 218 <code>ResultSetMetaData</code> interface, provides information about 219 the columns in a <code>RowSet</code> object. An application can use 220 <code>RowSetMetaData</code> methods to find out how many columns the 221 rowset contains and what kind of data each column can contain. 222 <P> 223 The <code>RowSetMetaData</code> interface provides methods for 224 setting the information about columns, but an application would not 225 normally use these methods. When an application calls the <code>RowSet</code> 226 method <code>execute</code>, the <code>RowSet</code> object will contain 227 a new set of rows, and its <code>RowSetMetaData</code> object will have been 228 internally updated to contain information about the new columns. 229 <P> 230 </UL> 231 <LI>The Reader/Writer Facility<br> 232 A <code>RowSet</code> object that implements the <code>RowSetInternal</code> 233 interface can call on the <code>RowSetReader</code> object associated with it 234 to populate itself with data. It can also call on the <code>RowSetWriter</code> 235 object associated with it to write any changes to its rows back to the 236 data source from which it originally got the rows. 237 A rowset that remains connected to its data source does not need to use a 238 reader and writer because it can simply operate on the data source directly. 239 240 <UL> 241 <LI><code>RowSetInternal</code><br> 242 By implementing the <code>RowSetInternal</code> interface, a 243 <code>RowSet</code> object gets access to 244 its internal state and is able to call on its reader and writer. A rowset 245 keeps track of the values in its current rows and of the values that immediately 246 preceded the current ones, referred to as the <i>original</i> values. A rowset 247 also keeps track of (1) the parameters that have been set for its command and 248 (2) the connection that was passed to it, if any. A rowset uses the 249 <code>RowSetInternal</code> methods behind the scenes to get access to 250 this information. An application does not normally invoke these methods directly. 251 <P> 252 <LI><code>RowSetReader</code><br> 253 A disconnected <code>RowSet</code> object that has implemented the 254 <code>RowSetInternal</code> interface can call on its reader (the 255 <code>RowSetReader</code> object associated with it) to populate it with 256 data. When an application calls the <code>RowSet.execute</code> method, 257 that method calls on the rowset's reader to do much of the work. Implementations 258 can vary widely, but generally a reader makes a connection to the data source, 259 reads data from the data source and populates the rowset with it, and closes 260 the connection. A reader may also update the <code>RowSetMetaData</code> object 261 for its rowset. The rowset's internal state is also updated, either by the 262 reader or directly by the method <code>RowSet.execute</code>. 263 264 265 <LI><code>RowSetWriter</code><br> 266 A disconnected <code>RowSet</code> object that has implemented the 267 <code>RowSetInternal</code> interface can call on its writer (the 268 <code>RowSetWriter</code> object associated with it) to write changes 269 back to the underlying data source. Implementations may vary widely, but 270 generally, a writer will do the following: 271 272 <P> 273 <UL> 274 <LI>Make a connection to the data source 275 <LI>Check to see whether there is a conflict, that is, whether 276 a value that has been changed in the rowset has also been changed 277 in the data source 278 <LI>Write the new values to the data source if there is no conflict 279 <LI>Close the connection 280 </UL> 281 282 283 </UL> 284 </OL> 285 <P> 286 The <code>RowSet</code> interface may be implemented in any number of 287 ways, and anyone may write an implementation. Developers are encouraged 288 to use their imaginations in coming up with new ways to use rowsets. 289 <P> 290 <B>IMPORTANT NOTE:</B> Code that uses API marked "Since 1.6" must be run using a 291 JDBC technology driver that implements the JDBC 4.0 API. 292 You must check your driver documentation to be sure that it implements 293 the particular features you want to use. 294 <P> 295 296 <h2>Package Specification</h2> 297 298 <ul> 299 <li><a href="http://java.sun.com/products/jdbc/download.html">Specification of the 300 JDBC 4.0 API</a> 301 </ul> 302 303 <h2>Related Documentation</h2> 304 305 The Java Series book published by Addison-Wesley Longman provides detailed 306 information about the classes and interfaces in the <code>javax.sql</code> 307 package: 308 309 <ul> 310 <li><a href="http://java.sun.com/docs/books/jdbc"><i>JDBC<sup><font size=-2>TM</font></sup> 311 API Tutorial and Reference, Third Edition:</i></a> 312 </ul> 313 <P> 314 @since 1.4 315 </body> 316 </html> 317
