JSP - 数据库访问( Database Access)
在本章中,我们将讨论如何使用JSP访问数据库。 我们假设您对JDBC应用程序的工作原理有很好的理解。 在通过JSP开始数据库访问之前,请确保您具有正确的JDBC环境设置以及数据库。
有关如何使用JDBC及其环境设置访问数据库的更多详细信息,您可以浏览我们的JDBC教程 。
从基本概念开始,让我们创建一个表并在该表中创建一些记录,如下所示 -
Create Table
要在EMP数据库中创建Employees表,请使用以下步骤 -
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 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 (Create Data Records)
现在让我们在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>
选择操作 (SELECT Operation)
以下示例显示了如何在JSP编程中使用JTSL执行SQL SELECT语句 -
<%@ 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>SELECT Operation</title>
</head>
<body>
<sql:setDataSource var = "snapshot" driver = "com.mysql.jdbc.Driver"
url = "jdbc:mysql://localhost/TEST"
user = "root" password = "pass123"/>
<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,将显示以下结果 -
None
Emp ID | 名字 | 姓 | 年龄 |
---|---|---|---|
100 | Zara | Ali | 18 |
101 | Mahnaz | Fatma | 25 |
102 | Zaid | Khan | 30 |
103 | Sumit | Mittal | 28 |
插入操作
以下示例显示了如何在JSP编程中使用JTSL执行SQL INSERT语句 -
<%@ 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>JINSERT Operation</title>
</head>
<body>
<sql:setDataSource var = "snapshot" driver = "com.mysql.jdbc.Driver"
url = "jdbc:mysql://localhost/TEST"
user = "root" password = "pass123"/>
<sql:update dataSource = "${snapshot}" var = "result">
INSERT INTO Employees VALUES (104, 2, 'Nuha', 'Ali');
</sql:update>
<sql:query dataSource = "${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 = "${row.age}"/></td>
</tr>
</c:forEach>
</table>
</body>
</html>
访问上面的JSP,将显示以下结果 -
None
Emp ID | 名字 | 姓 | 年龄 |
---|---|---|---|
100 | Zara | Ali | 18 |
101 | Mahnaz | Fatma | 25 |
102 | Zaid | Khan | 30 |
103 | Sumit | Mittal | 28 |
104 | Nuha | Ali | 2 |
删除操作
以下示例显示了如何在JSP编程中使用JTSL执行SQL DELETE语句 -
<%@ page import = "java.io.*,java.util.*,java.sql.*"%>
<%@ page import = "javax.servlet.http.*,javax.servlet.*" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix = "c"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/sql" prefix = "sql"%>
<html>
<head>
<title>DELETE Operation</title>
</head>
<body>
<sql:setDataSource var = "snapshot" driver = "com.mysql.jdbc.Driver"
url = "jdbc:mysql://localhost/TEST"
user = "root" password = "pass123"/>
<c:set var = "empId" value = "103"/>
<sql:update dataSource = "${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 = "${row.age}"/></td>
</tr>
</c:forEach>
</table>
</body>
</html>
访问上面的JSP,将显示以下结果 -
None
Emp ID | 名字 | 姓 | 年龄 |
---|---|---|---|
100 | Zara | Ali | 18 |
101 | Mahnaz | Fatma | 25 |
102 | Zaid | Khan | 30 |
更新操作
以下示例显示了如何在JSP编程中使用JTSL执行SQL UPDATE语句 -
<%@ page import = "java.io.*,java.util.*,java.sql.*"%>
<%@ page import = "javax.servlet.http.*,javax.servlet.*" %>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c"%>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/sql" prefix = "sql"%>
<html>
<head>
<title>DELETE Operation</title>
</head>
<body>
<sql:setDataSource var = "snapshot" driver = "com.mysql.jdbc.Driver"
url = "jdbc:mysql://localhost/TEST"
user = "root" password = "pass123"/>
<c:set var = "empId" value = "102"/>
<sql:update dataSource = "${snapshot}" var = "count">
UPDATE Employees SET WHERE last = 'Ali'
<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,将显示以下结果 -
None
Emp ID | 名字 | 姓 | 年龄 |
---|---|---|---|
100 | Zara | Ali | 18 |
101 | Mahnaz | Fatma | 25 |
102 | Zaid | Ali | 30 |