JDBC

Posted 2020-11-03 star521

增删改查

  1 package test03;
  2 
  3 import java.sql.Connection;
  4 import java.sql.DriverManager;
  5 import java.sql.ResultSet;
  6 import java.sql.Statement;
  7 /**
  8  * JDBC 增  
  9  *      删
 10  *      改
 11  *      查
 12  * @author star
 13  *
 14  */
 15 public class CURDTest {
 16     public static void main(String[] args) throws Exception {
 17         //insertTest();
 18         //deleteTest();
 19         //updateTest();
 20         selectTest();
 21     }
 22     //查
 23     private static void selectTest() throws Exception {
 24         // TODO Auto-generated method stub
 25         //注册驱动
 26         Class.forName("com.mysql.jdbc.Driver");
 27         //创建连接
 28         Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/day01", "root", "root");
 29         //创建Statement对象
 30         Statement st = conn.createStatement();
 31         //sql查询
 32         String sql = "select * from stu where math<80";
 33         ResultSet rs = st.executeQuery(sql);//结果集
 34         //显示
 35         while(rs.next()) {
 36             int id = rs.getInt(1);
 37             String name =rs.getString(2);
 38             int age = rs.getInt(3);
 39             int math = rs.getInt(4);
 40             int english = rs.getInt(5);
 41             System.out.println(id+" "+name+" "+age+" "+math+" "+english);
 42             
 43         }
 44         rs.close();
 45         st.close();
 46         conn.close();
 47         
 48         
 49     }
 50 
 51     //改
 52     private static void updateTest() throws Exception {
 53         // TODO Auto-generated method stub
 54         //注册驱动
 55         
 56         Class.forName("com.mysql.jdbc.Driver");
 57         //建立连接
 58         Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/day01", "root", "root");
 59         //创建statement对象
 60         Statement st = conn.createStatement();
 61         //执行sql语句
 62         String sql = "update stu set name = \'小马哥\' where id =1";
 63         int i = st.executeUpdate(sql);
 64         //判断是否修改
 65         if(i!=0) {
 66              System.out.println("修改成功");
 67         }
 68         //关闭资源
 69         st.close();
 70         conn.close();
 71         
 72     }
 73 
 74     //删除
 75     private static void deleteTest() throws Exception {
 76         // TODO Auto-generated method stub
 77         //注册驱动
 78         Class.forName("com.mysql.jdbc.Driver");
 79         //创建连接
 80         Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/day01", "root", "root");
 81         //创建Statement对象
 82         Statement st = conn.createStatement();
 83         //  sql注入的问题
 84         //     在SQL语句中使用了系统自带的关键字 or and ,让where条件判断失效
 85         //String sql = "delete from stu where id= 1 or 1=1";//SQL注入问题，会把整张表的内容删除
 86         String sql = "delete from stu where id= 1";
 87         int i = st.executeUpdate(sql);
 88         if (i!=0) {
 89             System.out.println("删除成功");
 90         }
 91         st.close();
 92         conn.close();
 93     }
 94     //增
 95     private static void insertTest() throws Exception {
 96         // TODO Auto-generated method stub
 97         //注册驱动
 98         Class.forName("com.mysql.jdbc.Driver");
 99         //创建连接
100         Connection conn = DriverManager.getConnection("jdbc:mysql:///day01", "root", "root");
101         //创建Statement对象
102         Statement st = conn.createStatement();
103         //执行语句
104         String sql = "insert into stu values(null,\'pp\',\'50\',70,50)";
105         int i = st.executeUpdate(sql);
106         //判断插入是否正确
107         if (i!=0) {
108             System.out.println("插入成功");
109         }
110         st.close();
111         conn.close();
112         
113     }
114 }

增删改查

 

jar包导入

包： java.sql

　　javax.sql

1.加载驱动

//DriverManager.registerDriver(new Driver());

//通过源码发现Driver 类有一个静态代码块，自己创建一个对象添加进registerDriver()，我们自己又创建一个对象，造成两次注册
  //com.mysql.jdbc.Driver
  Class.forName("com.mysql.jdbc.Driver");

//获取连接对象

Connection coon = DriverManager.getConnection("jdbc:mysql://localhost:3306/day01","root","root");

//获取statement对象

Statement  st = coon.createStatement();

//执行查询

String sql = "select * from emp";

ResultSet rs = st.executeQuery(sql);

//获取结果集中的数据

while(res.next()) {
   int id = res.getInt(1);
   String name = res.getString(2);
   String age = res.getString(3);
   int math = res.getInt(4);
   int english = res.getInt(5);
   System.out.println(id+" "+name +" "+age+" "+math+" "+english);
   
  }

 

//释放资源

rs.close();

st.close();

coon.close();

 1 package day28_test;
 2 
 3 
 4 import java.sql.Connection;
 5 import java.sql.DriverManager;
 6 import java.sql.ResultSet;
 7 import java.sql.SQLException;
 8 import java.sql.Statement;
 9 
10 import com.mysql.jdbc.Driver;
11 
12 public class JDBC_Demo {
13     public static void main(String[] args) throws Exception {
14         //加载驱动
15         DriverManager.registerDriver(new Driver());
16         //获取连接对象
17         Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/day01", "root", "root");
18         //获取Statement
19         Statement st = conn.createStatement();
20         //执行查询
21         String sql = "select * from stu";
22         ResultSet res = st.executeQuery(sql);
23         //获取结果集中的数据
24         while(res.next()) {
25             int id = res.getInt(1);
26             String name = res.getString(2);
27             String age = res.getString(3);
28             int math = res.getInt(4);
29             int english = res.getInt(5);
30             System.out.println(id+" "+name +" "+age+" "+math+" "+english);
31             
32         }
33         //释放资源
34         res.close();
35         st.close();
36         conn.close();
37     }
38 }

JDBC