| author | lancea |
| Wed, 02 Apr 2014 11:03:10 -0400 | |
| changeset 23708 | fea03b9ae8af |
| parent 5551 | 327690766109 |
| child 24197 | a5c2cff81e25 |
| permissions | -rw-r--r-- |
| 2 | 1 |
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> |
2 |
<html> |
|
3 |
<head> |
|
4 |
<!-- |
|
| 5506 | 5 |
Copyright (c) 2000, 2006, Oracle and/or its affiliates. All rights reserved. |
| 2 | 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 |
|
| 5506 | 10 |
published by the Free Software Foundation. Oracle designates this |
| 2 | 11 |
particular file as subject to the "Classpath" exception as provided |
| 5506 | 12 |
by Oracle in the LICENSE file that accompanied this code. |
| 2 | 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 |
||
|
5551
327690766109
6956202: Fix a few missed rebranding issues, please contact lines etc.
ohair
parents:
5506
diff
changeset
|
24 |
Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
|
327690766109
6956202: Fix a few missed rebranding issues, please contact lines etc.
ohair
parents:
5506
diff
changeset
|
25 |
or visit www.oracle.com if you need additional information or have any |
|
327690766109
6956202: Fix a few missed rebranding issues, please contact lines etc.
ohair
parents:
5506
diff
changeset
|
26 |
questions. |
| 2 | 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> |
|
| 23708 | 299 |
<li><a href="https://jcp.org/en/jsr/detail?id=221">JDBC 4.2 Specification</a> |
| 2 | 300 |
</ul> |
301 |
||
302 |
<h2>Related Documentation</h2> |
|
303 |
||
304 |
The Java Series book published by Addison-Wesley Longman provides detailed |
|
305 |
information about the classes and interfaces in the <code>javax.sql</code> |
|
306 |
package: |
|
307 |
||
308 |
<ul> |
|
| 23708 | 309 |
<li><a href="http://www.oracle.com/technetwork/java/index-142838.html"> |
310 |
<i>JDBC™API Tutorial and Reference, Third Edition</i></a> |
|
| 2 | 311 |
</ul> |
312 |
</body> |
|
313 |
</html> |