<sql:transaction >
《sql:transaction》标记用于将《sql:query》和《sql:update》标记分组到事务中。 您可以在《sql:transaction》标记内放置尽可能多的《sql:query》和《sql:update》标记,以创建单个事务。
它确保如果任何嵌套操作引发异常,则嵌套操作执行的数据库修改将被提交或回滚。
属性 (Attribute)
《sql:transaction》标记具有以下属性 -
属性 | 描述 | 需要 | 默认 |
---|---|---|---|
dataSource | 要使用的数据库连接(覆盖默认值) | No | 默认数据库 |
isolation | 事务隔离(READ_COMMITTED,READ_UNCOMMITTED,REPEATABLE_READ或SERIALIZABLE) | No | 数据库的默认值 |
例子 (Example)
要从基本概念开始,让我们在TEST数据库中创建一个Students表,并在该表中创建一些记录,如下所示 -
Step 1
打开Command Prompt并切换到安装目录,如下所示 -
C:\>
C:\>cd Program Files\MySQL\bin
C:\Program Files\MySQL\bin>
Step 2
登录数据库如下 -
C:\Program Files\MySQL\bin>mysql -u root -p
Enter password: ********
mysql>
Step 3
在TEST数据库中创建Employee表,如下所示 -
mysql> use TEST;
mysql> create table Students
(
id int not null,
first varchar (255),
last varchar (255),
dob date
);
Query OK, 0 rows affected (0.08 sec)
mysql>
创建数据记录 (Create Data Records)
我们现在将在Employee表中创建一些记录,如下所示 -
mysql> INSERT INTO Students
VALUES (100, 'Zara', 'Ali', '2002/05/16');
Query OK, 1 row affected (0.05 sec)
mysql> INSERT INTO Students
VALUES (101, 'Mahnaz', 'Fatma', '1978/11/28');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO Students
VALUES (102, 'Zaid', 'Khan', '1980/10/10');
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO Students
VALUES (103, 'Sumit', 'Mittal', '1971/05/08');
Query OK, 1 row affected (0.00 sec)
mysql>
现在让我们编写一个JSP,它将使用《sql:update》标记和《sql:transaction》标记来执行SQL UPDATE语句。 这里《sql:transaction》标签内的代码将完全执行或根本不执行 -
<%@ page import = "java.io.*,java.util.*,java.sql.*"%>
<%@ page import = "javax.servlet.http.*,javax.servlet.*"%>
<%@ page import = "java.util.Date,java.text.*" %>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c"%>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/sql" prefix = "sql"%>
<html>
<head>
<title>JSTL sql:transaction Tag</title>
</head>
<body>
<sql:setDataSource var = "snapshot" driver = "com.mysql.jdbc.Driver"
url = "jdbc:mysql://localhost/TEST" user = "root" password = "cohondob"/>
<%
Date DoB = new Date("2001/12/16");
int studentId = 100;
%>
<sql:transaction dataSource = "${snapshot}">
<sql:update var = "count">
UPDATE Students SET last = 'Ali' WHERE Id = 102
</sql:update>
<sql:update var = "count">
UPDATE Students SET last = 'Shah' WHERE Id = 103
</sql:update>
<sql:update var = "count">
INSERT INTO Students
VALUES (104,'Nuha', 'Ali', '2010/05/26');
</sql:update>
</sql:transaction>
<sql:query dataSource = "${snapshot}" var = "result">
SELECT * from Students;
</sql:query>
<table border = "1" width = "100%">
<tr>
<th>Emp ID</th>
<th>First Name</th>
<th>Last Name</th>
<th>DoB</th>
</tr>
<c:forEach var = "row" items = "${result.rows}">
<tr>
<td> <c:out value = "${row.id}"/></td>
<td> <c:out value = "${row.first}"/></td>
<td> <c:out value = "${row.last}"/></td>
<td> <c:out value = "${row.dob}"/></td>
</tr>
</c:forEach>
</table>
</body>
</html>
访问上面的JSP,将显示以下结果 -
+-------------+----------------+-----------------+-----------------+
| Emp ID | First Name | Last Name | DoB |
+-------------+----------------+-----------------+-----------------+
| 100 | Zara | Ali | 2001-12-16 |
| 101 | Mahnaz | Fatma | 1978-11-28 |
| 102 | Zaid | Ali | 1980-10-10 |
| 103 | Sumit | Mittal | 1971-05-08 |
| 104 | Nuha | Ali | 2010-05-26 |
+-------------+----------------+-----------------+-----------------+