目录

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

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 年龄
100ZaraAli18
101MahnazFatma25
102ZaidKhan30
103SumitMittal28

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 年龄
100ZaraAli18
101MahnazFatma25
102ZaidKhan30
103SumitMittal28
104NuhaAli2

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 年龄
100ZaraAli18
101MahnazFatma25
102ZaidKhan30

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 年龄
100ZaraAli18
101MahnazFatma25
102ZaidAli30
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