JavaWeb预习（jdbc）

基础

1.驱动程序接口Driver

每种数据库都提供了数据库驱动程序，并且都提供了一个实现java.sql.Driver接口的类，称为Driver

对于MySql，其Driver类为com.mysql.jdbc.Driver，加载该类的语句为：

Class.forName("com.mysql.jdbc.Driver")

2.驱动程序管理器DriverManager

DriverManager类用来建立数据库连接

Connection getConnection(String url,String user,String password)

URL语法格式为:

jdbc:子协议:数据源

eg:

String url = "jdbc:mysql:localhost:3306/user";
Connection con = DriverManager.getConnection(url,"root","123456");

3.数据库连接接口Connection

Java程序对数据库的操作都在该对象上进行

eg：

Statement stmt = con.createStatement();

该语句不需要SQL语句，在执行时加上SQL就行

还有PreparedStatement，直接在括号加上sql执行

4.执行SQL语句接口Statement

用来执行静态SQL语句，并返回执行结果，

executeQuery(String sql)执行select

executeUpdate(String sql)执行insert，update，delete

增加

JDBC连接数据库

<%@page import="java.sql.PreparedStatement"%>
<%@page import="java.sql.DriverManager" %>
<%@page import="java.sql.Connection" %>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<%
	String driverName = "com.mysql.jdbc.Driver";
	String userName = "root";
	String userPwd = "1234";
	String dbName = "students";
	String url1 = "jdbc:mysql://localhost:3306/"+dbName;
	String url2 = "?user="+userName+"&password="+userPwd;
	String url3 = "&useUnicode=true&characterEncoding=UTF-8";
	String url = url1+url2+url3;
	Class.forName(driverName);
	Connection conn = DriverManager.getConnection(url);
	
	String sql = "Insert into stu_info(id,name,sex,age,weight,hight) values(?,?,?,?,?,?)";
	PreparedStatement pstmt = conn.prepareStatement(sql);
	pstmt.setInt(1,16);
	pstmt.setString(2,"张三");
	pstmt.setString(3,"男");
	pstmt.setInt(4,20);
	pstmt.setFloat(5,70);
	pstmt.setFloat(6,175);
	int n = pstmt.executeUpdate();
	if(n == 1){%> 数据插入成功<br> <%}
	else{%> 数据插入失败<br><%}
	if(pstmt != null){pstmt.close();}
	if(conn != null){conn.close();}
	%>
</body>
</html>


<%@page import="java.sql.PreparedStatement"%>
<%@page import="java.sql.DriverManager"%>
<%@page import="java.sql.Connection"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<%
	String driverName = "com.mysql.jdbc.Driver";
	String dbName = "students";
	String userName = "root";
	String userPwd = "1234";
	String url1 = "jdbc:mysql://localhost:3306/"+dbName;
	String url2 = "?user="+userName+"&password="+userPwd;
	String url3 = "&useUnicode=true&characterEncoding=UTF-8";
	String url = url1+url2+url3;
	Class.forName(driverName);
	Connection conn = DriverManager.getConnection(url);
	
	String sql = "Insert into stu_info(id,name,sex,age,weight,hight) values(17,'王五','男',21,80,170)";
	PreparedStatement pstmt = conn.prepareStatement(sql);
	pstmt.executeUpdate();
	
	
	
	%>
</body>
</html>

实例：

1.表单：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>添加学生</title>
</head>
<body>
	<form action="sjk.jsp" method="post">
		<table>
			<tr>
				<td>学号</td>
				<td><input type="text" name="id"></td>
			</tr>
			<tr>
				<td>姓名</td>
				<td><input type="text" name="name"></td>
			</tr>
			<tr>
				<td>性别</td>
				<td><input type="text" name="sex"></td>
			</tr>
			<tr>
				<td>年龄</td>
				<td><input type="text" name="age"></td>
			</tr>
			<tr>
				<td>体重</td>
				<td><input type="text" name="weight"></td>
			</tr>
			<tr>
				<td>身高</td>
				<td><input type="text" name="hight"></td>
			</tr>
			<tr>
				<td colspan="2" align="center">
					<input type="submit" value="提交">&nbsp;
					<input type="reset" value="取消">
				</td>
			</tr>
		
		</table>
	</form>	
</body>
</html>

2.连接数据库：


<%@page import="java.sql.PreparedStatement"%>
<%@page import="java.sql.DriverManager"%>
<%@page import="java.sql.Connection"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<%
	String driverName = "com.mysql.jdbc.Driver";
	String dbName = "students";
	String userName = "root";
	String userPwd = "1234";
	String url1 = "jdbc:mysql://localhost:3306/"+dbName;
	String url2 = "?user="+userName+"&password="+userPwd;
	String url3 = "&useUnicode=true&characterEncoding=UTF-8";
	String url = url1+url2+url3;
	Class.forName(driverName);
	Connection conn = DriverManager.getConnection(url);
	
	String sql = "Insert into stu_info(id,name,sex,age,weight,hight) values(?,?,?,?,?,?)";
	PreparedStatement pstmt = conn.prepareStatement(sql);
	
	request.setCharacterEncoding("UTF-8");
	int id = Integer.parseInt(request.getParameter("id"));
	String name = request.getParameter("name");
	String sex = request.getParameter("sex");
	int age = Integer.parseInt(request.getParameter("age"));
	float weight = Float.parseFloat(request.getParameter("weight"));
	float hight = Float.parseFloat(request.getParameter("hight"));
	
	pstmt.setInt(1,id);
	pstmt.setString(2,name);
	pstmt.setString(3,sex);
	pstmt.setInt(4,age);
	pstmt.setFloat(5,weight);
	pstmt.setFloat(6,hight);
	
	try{
		int n = pstmt.executeUpdate();
		if(n==1){%>
			数据插入成功<br><%
		}else {
			%>数据插入失败<br><%
		}
	}catch(Exception e){%>
		更新过程出现异常错误！<br>
		<%=e.getMessage() %>
		<%
	}
	
	%>
</body>
</html>

3.回显

<%@page import="java.sql.ResultSet"%>
<%@page import="java.sql.PreparedStatement"%>
<%@page import="java.sql.DriverManager"%>
<%@page import="java.sql.Connection"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>学生数据表</title>
</head>
<body>
    <%
    String driverName = "com.mysql.jdbc.Driver";
    String userName = "root";
    String userPwd = "1234";
    String dbName = "students";
    String url1 = "jdbc:mysql://localhost:3306/" + dbName;
    String url2 = "?user=" + userName + "&password=" + userPwd;
    String url3 = "&useUnicode=true&characterEncoding=UTF-8";
    String url = url1 + url2 + url3;
    
    Connection conn = null;
    PreparedStatement pstmt = null;
    ResultSet rs = null;
    
    try {
        Class.forName(driverName);
        conn = DriverManager.getConnection(url);
        
        // 创建可滚动的 PreparedStatement
        String sql = "select * from stu_info";
        pstmt = conn.prepareStatement(sql, ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
        rs = pstmt.executeQuery();
        
        // 获取记录总数
        rs.last();
        int totalRows = rs.getRow();
    %>
    你要查询的学生数据表中共有
    <%= totalRows %> 人
    <center>
    <table border="1">
        <tr>
            <td>记录条数</td>
            <td>学号</td>
            <td>姓名</td>
            <td>性别</td>
            <td>年龄</td>
            <td>体重</td>
            <td>身高</td>
        </tr>
        <%
        // 将光标移动到结果集的开始位置
        rs.beforeFirst(); 
        while(rs.next()){%>
        <tr>
            <td><%= rs.getRow() %></td>
            <td><%= rs.getString("id") %></td>
            <td><%= rs.getString("name") %></td>
            <td><%= rs.getString("sex") %></td>
            <td><%= rs.getString("age") %></td>
            <td><%= rs.getString("weight") %></td>
            <td><%= rs.getString("hight") %></td>
        </tr>
        <%}%>
    </table></center>
    <%
    } catch (Exception e) {
        e.printStackTrace();
    %>
    <p style="color:red">发生错误: <%= e.getMessage() %></p>
    <%
    } finally {
        // 确保资源被关闭
        try {
            if (rs != null) rs.close();
            if (pstmt != null) pstmt.close();
            if (conn != null) conn.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    } // 确保 finally 块正确闭合
    %>
</body>
</html>

4.带条件的回显

<%@page contentType="text/html" pageEncoding="UTF-8" import="java.sql.*"%>
<html>
    <head>
    <title>查询满足条件的学生页面</title> 
    
    <style>
    .style1 {
    	border-collapse: collapse;
    	border-spacing: 0px;
    }
    </style>
    </head>
    <body>

		<%
		String dbName = "students";
		String driverName = "com.mysql.jdbc.Driver";
		String userName = "root";
		String userPwd = "1234";
		String url1 = "jdbc:mysql://localhost:3306/"+dbName;
		String url2 = "?user="+userName+"&password="+userPwd;
		String url3 = "&useUnicode=true&characterEncoding=UTF-8";
		String url = url1+url2+url3;
		
		Class.forName(driverName);
		Connection conn = DriverManager.getConnection(url);
		
		String sql = "select * from stu_info where weight>=? and weight<=?";
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		pstmt = conn.prepareStatement(sql,ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
		pstmt.setFloat(1, 60);
		pstmt.setFloat(2,80);
		
		rs = pstmt.executeQuery();
		rs.last();
		%>
		共有<%=rs.getRow() %>人
		<center>
		<table border="1" class="style1">
			<tr>
				<td>记录条数</td>
				<td>学号</td>
				<td>姓名</td>
				<td>性别</td>
				<td>年龄</td>
				<td>身高</td>
				<td>体重</td>
			</tr>
			
		<%
		rs.beforeFirst();
		while(rs.next()){%>
			<tr>
				<td><%=rs.getRow() %></td>
				<td><%=rs.getString("id") %></td>
				<td><%=rs.getString("name") %></td>
				<td><%=rs.getString("sex") %></td>
				<td><%=rs.getString("age") %></td>
				<td><%=rs.getString("hight") %></td>
				<td><%=rs.getString("weight") %></td>
			</tr>
		<%}%>
		</table>
		</center>
		<%
		if(rs!=null){rs.close();}
		if(conn!=null){conn.close();}
		if(pstmt!=null){pstmt.close();}
		%>
     
    </body>
</html>

5.加客户端的条件查询

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>条件查询页面</title>

<style>
.css1 {
	width: 40px;
}
</style>
</head>
<body>
	<form action="huixian2.jsp" method="post">
		性别:男<input type="radio" value="男" name="sex" checked="checked"> 女<input type="radio" value="女" name="sex">
		<br>
		体重范围：最小<input type="text" name="w1" class="css1"> &nbsp;&nbsp;最大<input type="text" name="w2" class="css1">
		<br>
		<input type="submit" value="提交">&nbsp;&nbsp;<input type="reset" value="取消">



	</form>
</body>
</html>

<%@page contentType="text/html" pageEncoding="UTF-8" import="java.sql.*"%>
<html>
    <head>
    <title>查询满足条件的学生页面</title> 
    
    <style>
    .style1 {
    	border-collapse: collapse;
    	border-spacing: 0px;
    }
    </style>
    </head>
    <body>

		<%
		String dbName = "students";
		String driverName = "com.mysql.jdbc.Driver";
		String userName = "root";
		String userPwd = "1234";
		String url1 = "jdbc:mysql://localhost:3306/"+dbName;
		String url2 = "?user="+userName+"&password="+userPwd;
		String url3 = "&useUnicode=true&characterEncoding=UTF-8";
		String url = url1+url2+url3;
		
		Class.forName(driverName);
		Connection conn = DriverManager.getConnection(url);
		
		String sql = "select * from stu_info where sex=? and weight>=? and weight<=?";
		PreparedStatement pstmt = null;
		ResultSet rs = null;
		pstmt = conn.prepareStatement(sql,ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY);
		request.setCharacterEncoding("UTF-8");
		
		pstmt.setString(1,request.getParameter("sex"));
		pstmt.setFloat(2,Float.parseFloat(request.getParameter("w1")));
		pstmt.setFloat(3,Float.parseFloat(request.getParameter("w2")));
		
		rs = pstmt.executeQuery();
		rs.last();
		%>
		共有<%=rs.getRow() %>人
		<center>
		<table border="1" class="style1">
			<tr>
				<td>记录条数</td>
				<td>学号</td>
				<td>姓名</td>
				<td>性别</td>
				<td>年龄</td>
				<td>身高</td>
				<td>体重</td>
			</tr>
			
		<%
		rs.beforeFirst();
		while(rs.next()){%>
			<tr>
				<td><%=rs.getRow() %></td>
				<td><%=rs.getString("id") %></td>
				<td><%=rs.getString("name") %></td>
				<td><%=rs.getString("sex") %></td>
				<td><%=rs.getString("age") %></td>
				<td><%=rs.getString("hight") %></td>
				<td><%=rs.getString("weight") %></td>
			</tr>
		<%}%>
		</table>
		</center>
		<%
		if(rs!=null){rs.close();}
		if(conn!=null){conn.close();}
		if(pstmt!=null){pstmt.close();}
		%>
     
    </body>
</html>

删除

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" import="java.sql.*"%>
<!DOCTYPE html> 
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
	<%
	request.setCharacterEncoding("UTF-8");
	String driverName = "com.mysql.jdbc.Driver";
	String dbName = "students";
	String userName = "root";
	String userPwd = "1234";
	String url1 = "jdbc:mysql://localhost:3306/"+dbName;
	String url2 = "?user="+userName+"&password="+userPwd;
	String url3 = "&useUnicode=true&characterEncoding=UTF-8";	
	String url = url1+url2+url3;
	
	Class.forName(driverName);
	Connection conn = DriverManager.getConnection(url);
	
	String sql = "Delete from stu_info where name = ?";
	PreparedStatement pstmt = conn.prepareStatement(sql);
	
	pstmt.setString(1, request.getParameter("name"));
	
	try{ 
        int n= pstmt.executeUpdate();
        if(n>=1){%>
            数据删除操作成功！<br>
        <%}
        else{%>
           数据删除操作失败！<br>
        <%} 
   }catch(Exception e){%>
         删除更新过程出现异常错误！<br>
         <%=e.getMessage()%>
   <%            
   }

	if(conn!=null){
		conn.close();
	}
	if(pstmt!=null){
		pstmt.close();
	}
	
	
	
	%>
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

<form action="delete.jsp" method="post">
请输入要删除数据的姓名：
<input type="text" name="name"><br>
<input type="submit" value="提交">
</form>

</body>
</html>