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How to use parameterized SQL query in a JSP?
The <sql:param> tag used as a nested action for the <sql:query> tag and the <sql:update> tag to supply a value for a value placeholder. If a null value is provided, the value is set to SQL NULL for the placeholder.
Attribute
The <sql:param> tag has the following attributes −
| Attribute | Description | Required | Default |
|---|---|---|---|
| Value | Value of the parameter to set | No | Body |
Example
To start with the basic concept, let us create an Employees table in the TEST database and create few records in that table as follows −
Step 1
Open a Command Prompt and change to the installation directory as follows −
C:\> C:\>cd Program Files\MySQL\bin C:\Program Files\MySQL\bin>
Step 2
Login to the database as follows −
C:\Program Files\MySQL\bin>mysql -u root -p Enter password: ******** mysql>
Step 3
Create the Employee table in the TEST database as follows −
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>Create Data Records
We will now create a few records in the Employee table as follows −
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>
Let us now write a JSP which will make use of the <sql:update> tag to execute an SQL DELETE statement to delete one record with id = 103 from the table as follows −
<%@ 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>Access the above JSP, the following result will be displayed −
+-------------+----------------+-----------------+-----------------+ | Emp ID | First Name | Last Name | Age | +-------------+----------------+-----------------+-----------------+ | 100 | Zara | Ali | 18 | | 101 | Mahnaz | Fatma | 25 | | 102 | Zaid | Khan | 30 | +-------------+----------------+-----------------+-----------------+
You can try the <sql:param> tag with the SQL UPDATE and the SELECT statements as well in the same way as we have used it with the DELETE statement.
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