第十一节、JDBC详解

其他 2021-11-19 14:28:39 阅读次数: 0

文章目录

JDBC建立过程的4个步骤：
（1）建立数据库的一个连接；
（2）执行SQL语句；
（3）处理数据库返回结果；
（4）关闭数据库的连接。

JDBC的基本操作

建立一张人员信息表：
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数据库操作

查询数据库：在查询数据库时候，记得关闭数据库，否则会占用连接，引发连接异常。
在Java中插入人员信息，主要用到executeUpdate(String sql)方法。该方法用于执行对数据库INSERT、UPDATE、DELETE操作，返回执行语句影响的行数，如果没有影响行数，就返回0。
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package com.eshore;

import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.servlet.annotation.WebServlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

//给当前文件的路径设置为根目录下的GetReaderBody2
@WebServlet(
		urlPatterns = {
    
     "/OperateServlet" },
		name = "operateServlet"
)
public class OperateServlet extends HttpServlet {
    
    
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
    
    
		request.setCharacterEncoding("UTF-8");
        String name = request.getParameter("name");
        String age = request.getParameter("age");
        String sex = request.getParameter("sex");
        String birthday = request.getParameter("birthday");
        String description = request.getParameter("description");
        String sql = "insert into person(name,age,sex,birthday,description) "+
                     "values('"+name+"','"+age+"','"+sex+"','"+birthday+"','"+description+"')";
        Connection con = null;
        Statement st = null;
        int  result = 0;
        try {
    
    
			Class.forName("com.mysql.cj.jdbc.Driver");//注册数据库
			con = DriverManager.
			getConnection("jdbc:mysql://localhost:3306/mydb","root","1234");//获取数据库连接
			st = con.createStatement();            //获取Statement
			result = st.executeUpdate(sql);        //执行查询，返回结果集
			response.setContentType("text/html;charset=utf-8");
			PrintWriter out = response.getWriter();
			out .println("<!DOCTYPE HTML >");
			out.println("<HTML>");
			out.println("  <HEAD><TITLE>列出人员信息表</TITLE></HEAD>");
			out.println("  <BODY>");
			out.println("");
			out.println("<a href=\""+request.getContextPath()+"/listPerson.jsp\">返回人员列表</a>");
			out.println("  </BODY>");
			out.println("</HTML>");
			out.flush();
			out.close();
		 } catch (SQLException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}catch (ClassNotFoundException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
    
    
			try {
    
    //关闭连接
				st.close();
				con.close();
			} catch (SQLException e) {
    
    
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		} 
	}
}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
	String path = request.getContextPath();
%>
<!DOCTYPE HTML >
<html>
  <head>
    <title>增加人员列表</title>
    <!-- 调用日期控件的js -->  
    <script language="javascript" type="text/javascript" src="${pageContext.request.contextPath}/My97DatePicker/WdatePicker.js"></script>
    <script type="text/javascript" src="${pageContext.request.contextPath}/js/jquery-1.8.1.js"></script>
  </head>
  <body>
      <form action="<%=path%>/OperateServlet" method="post">
	      <table>
	            <tr>
	                <td>姓名</td>        
	                <td><input name="name"/></td>     
	            </tr>
	            <tr>
	                <td>性别</td>        
	                <td><select name="sex">
	                       <option value="男">男</option>
	                       <option value="女">女</option>
	                  </select></td>     
	            </tr>
	            <tr>
	                <td>年龄</td>        
	                <td><input name="age"/></td>     
	            </tr>
	            <tr>
	                <td>生日</td>    
	                <!-- 调用日期控件 -->    
	                <td><input id="d11" name="birthday" type="text" onClick="WdatePicker()"/></td>     
	            </tr>
	            <tr>
	                <td>描述</td>        
	                <td><textarea name="description"></textarea></td>     
	            </tr>
	            <tr>
	                <td colspan="2">
	                   <input type="submit" value="提交"/>
	                </td>
	            </tr>
	       </table>
      </form>
  </body>
</html>

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删除人员信息：
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<%@ page language="java" contentType="text/html; charset=UTF-8"%>
<%@ page import="java.sql.*" %>
<!DOCTYPE HTML >
<HTML>
	<HEAD>
		<TITLE>删除人员信息</TITLE>
	</HEAD>
	<BODY>
		<%
		    Connection con = null;
	        Statement st = null;
	        try {
	        	Class.forName("com.mysql.cj.jdbc.Driver");       //注册数据库
				con = DriverManager.getConnection(            //获取数据库连接
				"jdbc:mysql://localhost:3306/mydb","root","1234");
				st = con.createStatement();                  //获取Statement
				request.setCharacterEncoding("UTF-8");
                String id = request.getParameter("id");       //获取页面参数id
                String sql = "delete from Person where id='"+id+"'"; //删除指定人员
		        int  result = st.executeUpdate(sql); 
		     } catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}finally{
				//记住关闭连接
				try {
					st.close();
					con.close();
				} catch (SQLException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		 %>
		 <a href="listPerson.jsp">返回人员信息列表</a>
		 <br/>
	</BODY>
</HTML>

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修改人员信息：
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package com.eshore;

import jakarta.servlet.ServletException;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.servlet.annotation.WebServlet;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;

//给当前文件的路径设置为根目录下的GetReaderBody2
@WebServlet(
		urlPatterns = {
    
     "/OperateServlet" },
		name = "operateServlet"
)
public class OperateServlet extends HttpServlet {
    
    
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
    
    
		request.setCharacterEncoding("UTF-8");
        String name = request.getParameter("name");
        String age = request.getParameter("age");
        String sex = request.getParameter("sex");
        String birthday = request.getParameter("birthday");
        String description = request.getParameter("description");
        String sql = "insert into person(name,age,sex,birthday,description) "+
                     "values('"+name+"','"+age+"','"+sex+"','"+birthday+"','"+description+"')";
        Connection con = null;
        Statement st = null;
        int  result = 0;
        try {
    
    
			Class.forName("com.mysql.cj.jdbc.Driver");//注册数据库
			con = DriverManager.
			getConnection("jdbc:mysql://localhost:3306/mydb","root","1234");//获取数据库连接
			st = con.createStatement();            //获取Statement
			result = st.executeUpdate(sql);        //执行查询，返回结果集
			response.setContentType("text/html;charset=utf-8");
			PrintWriter out = response.getWriter();
			out .println("<!DOCTYPE HTML >");
			out.println("<HTML>");
			out.println("  <HEAD><TITLE>列出人员信息表</TITLE></HEAD>");
			out.println("  <BODY>");
			out.println("");
			out.println("<a href=\""+request.getContextPath()+"/listPerson.jsp\">返回人员列表</a>");
			out.println("  </BODY>");
			out.println("</HTML>");
			out.flush();
			out.close();
		 } catch (SQLException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}catch (ClassNotFoundException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
    
    
			try {
    
    //关闭连接
				st.close();
				con.close();
			} catch (SQLException e) {
    
    
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		} 
	}
}

<%@ page language="java" contentType="text/html; charset=UTF-8"%>
<%@ page import="java.sql.*" %>
<!DOCTYPE HTML >
<HTML>
	<HEAD>
		<TITLE>修改人员信息</TITLE>
	</HEAD>
	<BODY>
		<%
		    Connection con = null;
	        Statement st = null;
	        ResultSet rs = null;
	        try {
				Class.forName("com.mysql.cj.jdbc.Driver");    //注册数据库
				con = DriverManager.getConnection(         //获取数据库连接
				"jdbc:mysql://localhost:3306/mydb","root","1234");
				st = con.createStatement();                //获取Statement
				request.setCharacterEncoding("UTF-8");
				//获得修改人员的主键ID
                String id = request.getParameter("id");
                //查询该人员的SQL语句
                String sql = "select *  from Person where id='"+id+"'";
		        rs = st.executeQuery(sql);
		        if(rs.next()){
		            //往页面传递人员信息参数
		            request.setAttribute("id",rs.getInt("id"));
		            request.setAttribute("name",rs.getString("name"));
		            request.setAttribute("sex",rs.getString("sex"));
		            request.setAttribute("age",rs.getInt("age"));
		            request.setAttribute("birthday",rs.getString("birthday"));
		            request.setAttribute("description",rs.getString("description"));
		            RequestDispatcher rd = request.getRequestDispatcher("update.jsp");
		            rd.forward(request,response);
		        }else{
		        	out.println("没有找到id为"+id+"的人员记录");
		        }
		     } catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}finally{
				try {//记住关闭数据库连接
				    rs.close();
					st.close();
					con.close();
				} catch (SQLException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		 %>
		 <br/>
	</BODY>
</HTML>

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML >
<html>
  <head>
    <title>修改人员</title>
    <!-- 调用日期控件的js -->  
    <script language="javascript" type="text/javascript" src="${pageContext.request.contextPath}/My97DatePicker/WdatePicker.js"></script>
  </head>
  <%
     //获取传递的参数信息
     Integer id = (Integer)request.getAttribute("id");
     String name = (String)request.getAttribute("name");
     Integer age = (Integer)request.getAttribute("age");
     String sex = (String)request.getAttribute("sex");
     String birthday = (String)request.getAttribute("birthday");
     String description = (String)request.getAttribute("description");
   %>
  <body>
      <form action="${pageContext.request.contextPath}/ModifyServlet?id=<%=id%>" method="post">
	      <table>
	            <tr>
	                <td>姓名</td>        
	                <td><input name="name" value="<%=name %>" />
	                </td>     
	            </tr>
	            <tr>
	                <td>性别</td>        
	                <td><select name="sex">
	                        <%
	                          if("男".equals(sex)){
	                       %>
	                       <option value="男" selected>男</option>
	                       <%
	                         }else{
	                        %>
	                        <option value="男" >男</option>
	                        <%
	                         }
	                         %>
	                       <%
	                          if("女".equals(sex)){
	                       %>
	                       <option value="女" selected>女</option>
	                       <%
	                         }else{
	                        %>
	                        <option value="女" >女</option>
	                        <%
	                         }
	                         %>
	                  </select></td>     
	            </tr>
	            <tr>
	                <td>年龄</td>        
	                <td><input name="age" value="<%=age%>"/></td>     
	            </tr>
	            <tr>
	                <td>生日</td>    
	                <!-- 调用日期控件 -->    
	                <td><input id="d11" name="birthday" type="text" onClick="WdatePicker()" value="<%=birthday %>"/></td>     
	            </tr>
	            <tr>
	                <td>描述</td>        
	                <td><textarea name="description" ><%=description %></textarea></td>     
	            </tr>
	            <tr>
	                <td colspan="2">
	                   <input type="submit" value="提交"/>
	                </td>
	            </tr>
	       </table>
      </form>
  </body>
</html>

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使用PreparedStatement:
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package com.eshore;

import jakarta.servlet.ServletException;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.*;
import java.text.ParseException;
import java.text.SimpleDateFormat;

@WebServlet(
		urlPatterns = {
    
     "/ModifyServletPrepared" },
		name = "modifyServletPrepared"
)
public class ModifyServletPrepared extends HttpServlet {
    
    
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
    
    
		request.setCharacterEncoding("UTF-8");
		String id = request.getParameter("id");
        String name = request.getParameter("name");
        String age = request.getParameter("age");
        String sex = request.getParameter("sex");
        String birthday = request.getParameter("birthday");
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        String description = request.getParameter("description");
        String sql = "update Person set name=?,age=?,sex=?,birthday=?,description=? where id=?";
        Connection con = null;
        PreparedStatement prest = null;
        int  result = 0;
        try {
    
    
			Class.forName("com.mysql.cj.jdbc.Driver");            //注册数据库
			con = DriverManager.getConnection(                 //获取数据库连接
					"jdbc:mysql://localhost:3306/mydb","root","1234");
			prest = con.prepareStatement(sql);                 //获取PreparedStatement,并且预编译SQL语句
			prest.setString(1, name); 
			prest.setInt(2, Integer.parseInt(age));            //设定第2个参数
			prest.setString(3, sex);                           //设定第3个参数
			Date date = new Date(sdf.parse(birthday).getTime());
			prest.setDate(4, date);                            //设定第4个参数
			prest.setString(5, description);                   //设定第5个参数
			prest.setInt(6, Integer.parseInt(id));             //设定第6个参数
			result = prest.executeUpdate(sql);           //执行查询，返回结果集
			response.setContentType("text/html;charset=utf-8");
			PrintWriter out = response.getWriter();
			out .println("<!DOCTYPE HTML >");
			//���ҳ������
			out.println("<HTML>");
			out.println("  <HEAD><TITLE>列出人员信息表</TITLE></HEAD>");
			out.println("  <BODY>");
			out.println("");
			out.println("<a href=\""+request.getContextPath()+"/listPerson.jsp\">返回人员列表</a>");
			out.println("  </BODY>");
			out.println("</HTML>");
			out.flush();
			out.close();
		 } catch (SQLException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}catch (ClassNotFoundException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}catch (ParseException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
    
    
			try {
    
    //记住关闭连接
				prest.close();
				con.close();
			} catch (SQLException e) {
    
    
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		} 
	}
}

利用Statement与PreparedStatement批处理SQL：

package com.eshore;

import java.sql.*;

public class PreparedStatementBatch {
    
    
	
    public static void main(String[] args){
    
    
    	String sql = "insert into Person(name,age,sex,birthday,description) values(?,?,?,?,?)";
        Connection con = null;
        PreparedStatement prest = null;
    	try {
    
    
			Class.forName("com.mysql.cj.jdbc.Driver");//注册数据库
			con = DriverManager.getConnection("jdbc:mysql://localhost:3306/mydb","root","1234");//获取数据库连接
			prest = con.prepareStatement(sql);               //获取PreparedStatement,并且预编译SQL语句
			for(int i=0;i<=10;i++){
    
    
				prest.setString(1, "李四"+i);                //设定第1个参数
				prest.setInt(2, 30);                         //设定第2个参数
				prest.setString(3, "男");                    //设定第3个参数
				prest.setDate(4,                             //设定第4个参数
						new Date(System.currentTimeMillis()));
				prest.setString(5, "PreparedStatement 批量插入"); //设定第5个参数
				prest.addBatch();                            //添加SQL语句
			}
			int[] result = prest.executeBatch();             //执行批量插入，返回结果集
		 } catch (SQLException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}catch (ClassNotFoundException e) {
    
    
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
    
    
			//记住关闭连接
			try {
    
    
				prest.close();
				con.close();
			} catch (SQLException e) {
    
    
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		} 
    }
}

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带条件的查询：

<%@ page language="java" contentType="text/html; charset=UTF-8"%>
<%@ page import="java.sql.*" %>
<!DOCTYPE HTML >
<HTML>
	<HEAD>
		<TITLE>查询人员信息列表</TITLE>
		<script type="text/javascript" src="${pageContext.request.contextPath}/js/jquery-1.8.1.js"></script>
	    <!-- 调用日期控件的js -->  
    <script language="javascript" type="text/javascript" src="${pageContext.request.contextPath}/My97DatePicker/WdatePicker.js"></script>
	</HEAD>
	<BODY>
	    <%--<user>
	         <name>张三</name>
	         <english-name>zhangsan</english-name>
	         <age>20</age>
	         <sex>男</sex>
	         <address>广东省广州市</address>
	         <description>他是一个工程师</description>
	    </user>--%>
	    <user>
	         <property name="name" value="张三"/>
	         <property name="english-name" value="zhangsan"/>
	         <property name="age" value="20"/>
	         <property name="sex" value="男"/>
	         <property name="address" value="广东省广州市"/>
	         <property name="description" value="他是一个工程师"/>
	    </user>
			<h4 style="text-align: center;">人员信息列表</h4>
		<% 
		    //获取页面查询条件
		    request.setCharacterEncoding("UTF-8");
		    String name = request.getParameter("name");
		    String sex = request.getParameter("sex");
		    String age = request.getParameter("age");
		    String description = request.getParameter("description");
		    String startTime = request.getParameter("startTime");
		    String endTime = request.getParameter("endTime");
		    Connection con = null;
	        PreparedStatement st = null;
	        ResultSet rs = null;
	        //组合SQL的where条件
	        String sql = "select * from person where 1=1 ";
	        if(name!=null&&!"".equals(name)){
	        	sql+="and name like '%"+name+"%'";
	        }
	        if(sex!=null&&!"".equals(sex)){
	        	sql+="and sex ='"+sex+"'";
	        }
	        if(age!=null&&!"".equals(age)){
	        	sql+="and age ='%"+age+"'";
	        }
	        if(description!=null&&!"".equals(description)){
	        	sql+="and description like '%"+description+"%'";
	        }
	        if(startTime!=null&&!"".equals(startTime)){
	        	sql+="and birthday >= '"+startTime+"'";
	        }
	        if(endTime!=null&&!"".equals(endTime)){
	        	sql+="and birthday <= '%"+endTime+"'";
	        }
	        try {
				Class.forName("com.mysql.cj.jdbc.Driver");     //注册数据库
				con = DriverManager.getConnection(          //获取数据库连接
						"jdbc:mysql://localhost:3306/mydb","root","1234");
				st = con.prepareStatement(sql);             //获取Statement
				rs = st.executeQuery(sql);                  //执行查询，返回结果集
		 %>
		 <form action="searchPerson.jsp" method="post">
			 <table>
			     <tr>
			         <td>姓名：</td>
			         <td><input name="name"/></td>
			         <td>性别：</td>
			         <td><select name="sex" style="width:100">
			                <option value="">无限制</option>
			                <option value="男">男</option>
			                <option value="女">女</option>
			           </select></td>
			     </tr>
			     <tr>
			         <td>年龄：</td>
			         <td><input name="age"/></td>
			         <td>备注：</td>
			         <td><input name="description"/></td>
			     </tr>
			     <td colspan="4">出生日期： 
	              <label> 从：</label><input class="Wdate"  name="startTime" id="startBeginTime" onFocus="WdatePicker({dateFmt:'yyyyMMdd HH:mm:ss',minDate:'1900-01-01'})"/>
			          到
			     <input   class="Wdate" name="endTime" id="endBeginTime" onFocus="WdatePicker({dateFmt:'yyyyMMdd HH:mm:ss',minDate:'1900-01-01'})"/></td>
			     </tr>
			     <tr>
			         <td>
			             <input type="submit" value="提交">
			             <input type="reset" value="重置">
			         </td>
			     </tr>
			 </table>
		 </form>
		 <br/>
		 <br/>
		<table border="1" width="100%" cellpadding="2" cellspacing="1">
			<tr>
				<td>选择</td>
				<td>姓名</td>
				<td>年龄</td>
				<td>性别</td>
				<td>生日</td>
				<td>备注</td>
				<td>操作</td>
			</tr>
		    <%
		        //遍历结果集ResultSet
				while(rs.next()){
					int id = rs.getInt("id");              //获取ID
					String name2  = rs.getString("name");  //获取姓名
					int age2 = rs.getInt("age");           //获取年龄
					String sex2  = rs.getString("sex");    //获取性别
					Date birthday = rs.getDate("birthday"); //获取出生日期
					String description2 = rs.getString("description"); //获取备注
					out.println("<tr>");
					out.println("<td><input type=\"checkbox\" name=\"checkPerson\" value=\""+id+"\"></td>");
					out.println("<td >"+name2+"</td>");
					out.println("<td >"+age2+"</td>");	 
					out.println("<td >"+sex2+"</td>");
					out.println("<td >"+birthday+"</td>");
					out.println("<td >"+description2+"</td>");
					out.println("<td><a href=\"modify.jsp?id="+id+"\">修改</a>&nbsp;&nbsp;"+
					"<a href=\"delete.jsp?id="+id+"\" οnclick=\"return confirm('确定删除该记录？')\">删除</a></td>");
				    out.println("</tr>");
				}
		     %>
		</table>
		<table>
		     <tr>
		        <td>
		                              全选<input type="checkbox" onclick="selectPerson(this);"/>
		        </td>
		     </tr>
		</table>
		<%
		     } catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}finally{
				//记住关闭连接
				try {
					rs.close();
					st.close();
					con.close();
				} catch (SQLException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		 %>
	</BODY>
	<script type="text/javascript">
         function selectPerson(obj){
      
      
              $('input[name="checkPerson"]').attr("checked",obj.checked);  
         }
	</script>
</HTML>

在这里插入图片描述
通过ResultSetMetaData可以获得元数据内容，通过它可以直接得知列名，可以动态的显示查询各列内容:

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<%@ page language="java" contentType="text/html; charset=UTF-8"%>
<%@ page import="java.sql.*" %>
<!DOCTYPE HTML >
<HTML>
	<HEAD>
		<TITLE>人员信息列表</TITLE>
	</HEAD>
	<BODY>
	<div style="text-align: center;">
			<h4>人员信息列表</h4>
		</div>
		<%
		    Connection con = null;
	        Statement st = null;
	        ResultSet rs = null;
	        try {
	        	Class.forName("com.mysql.cj.jdbc.Driver");       //注册数据库
				con = DriverManager.getConnection(            //获取数据库连接
						"jdbc:mysql://localhost:3306/mydb","root","1234");
				st = con.createStatement();                  //获取Statement
				rs = st.executeQuery("select * from person");//执行查询，返回结果集;
		        ResultSetMetaData rsmd = rs.getMetaData();
		        int columnCount= rsmd.getColumnCount();       //获取列数
		        String[] columnNames = new String[columnCount];
		        for(int i=0;i<columnCount;i++){               //获取列对应的列名
		        	columnNames[i] = rsmd.getColumnName(i+1);
		        }
		        out.println("<table border=\"1\" width=\"100%\" cellpadding=\"2\" cellspacing=\"1\"><tr>");
		        for(int i=0;i<columnCount;i++){               //输出列名
		            out.println("<td>"+columnNames[i]+"</td>");
		        }
		        out.println("</tr>");
		        //遍历结果集ResultSet
				while(rs.next()){
					out.println("</tr>");
					//根据列名取得对应列的值
					for(int i=0;i<columnCount;i++){
     
     
			            out.println("<td>"+rs.getString(columnNames[i])+"</td>");
			        }
			        out.println("</tr>");
				}
				out.println("</table>");
		     } catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}finally{
				//记住关闭连接
				try {
					rs.close();
					st.close();
					con.close();
				} catch (SQLException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		 %>
	</BODY>
</HTML>

在这里插入图片描述
在这里插入图片描述

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