JSP jstl-<sql:param> 标记

jstl-<sql:param> 标记

<sql:param>标记用作嵌套动作标签<：查询SQL>标记和<sql:query>标记为一个值的占位符提供一个值。如果提供空值，则将占位符的值设置为SQL NULL。

属性

属性	描述	必需	默认值
Value	设置的参数的值	否	Body

示例

首先，让我们在TEST数据库中创建一个Employees表，并在该表中创建一些记录，如下所示：请按照以下步骤创建雇员表-

第1步 - 打开命令提示符，然后更改为安装目录，如下所示：


C:\>
C:\>cd Program Files\MySQL\bin
C:\Program Files\MySQL\bin>

第2步 - 登录数据库如下


C:\Program Files\MySQL\bin>mysql -u root -p
Enter password: ********
mysql>

第3步 - 在TEST数据库中创建Employee表，如下所示：


mysql> use TEST;
mysql> create table Employees
   (
      id int not null,
      age int not null,
      first varchar (255),
      last varchar (255)
   );
Query OK, 0 rows affected (0.08 sec)
mysql>

创建数据记录 - 现在，我们将在Employee表中创建一些记录，如下所示：


mysql> INSERT INTO Employees VALUES (100, 18, 'Zara', 'Ali');
Query OK, 1 row affected (0.05 sec)
 
mysql> INSERT INTO Employees VALUES (101, 25, 'Mahnaz', 'Fatma');
Query OK, 1 row affected (0.00 sec)
 
mysql> INSERT INTO Employees VALUES (102, 30, 'Zaid', 'Khan');
Query OK, 1 row affected (0.00 sec)
 
mysql> INSERT INTO Employees VALUES (103, 28, 'Sumit', 'Mittal');
Query OK, 1 row affected (0.00 sec)
 
mysql>

现在让我们编写一个JSP，它将利用<sql：update>标记执行一条SQL DELETE语句，从表中删除ID = 103的一条记录，如下所示-


<%@ page import = "java.io.*,java.util.*,java.sql.*"%>
<%@ page import = "javax.servlet.http.*,javax.servlet.*" %>
<%@ 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:param Tag</title>
   </head>

   <body>
      <sql:setDataSource var = "snapshot" driver = "com.mysql.jdbc.Driver"
         url = "jdbc:mysql://localhost/TEST"
         user = "root"  password = "pass123"/>

      <c:set var = "empId" value = "103"/>

      <sql:update dataSource = "${snapshot}" var = "count">
         DELETE FROM Employees WHERE Id = ?
         <sql:param value = "${empId}" />
      </sql:update>

      <sql:query dataSource = "${snapshot}" var = "result">
         SELECT * from Employees;
      </sql:query>
 
      <table border = "1" width = "100%">
         <tr>
            <th>Emp ID</th>
            <th>First Name</th>
            <th>Last Name</th>
            <th>Age</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.age}"/></td>
            </tr>
         </c:forEach>
      </table>

   </body>
</html>

访问上面的JSP，它将显示以下结果-


+-------------+----------------+-----------------+-----------------+
|    Emp ID   |    First Name  |     Last Name   |       Age       |
+-------------+----------------+-----------------+-----------------+
|     100     |    Zara        |     Ali         |       18        |
|     101     |    Mahnaz      |     Fatma       |       25        |
|     102     |    Zaid        |     Khan        |       30        |
+-------------+----------------+-----------------+-----------------+

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