JDBC连接MySQL并更新、插入、查询数据

package dao; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import org.junit.jupiter.api.Test;  public class JDBC {     @Test     public void fun1() throws Exception {         // 注册驱动         String driverClassName = com.mysql.jdbc.Driver;         Class.forName(driverClassName);         // 获取连接,jdbc协议的格式         String url = jdbc:mysql://localhost:3306/db1;         String username = root;         String password = 747699;         Connection con = DriverManager.getConnection(url, username, password);          // 定义sql语句         String sql1 = update account set money = 2000 where id = 1;         String sql2 = INSERT INTO account VALUES('3','王五',3000);         // 获取SQL对象         Statement stmt = con.createStatement();          // 执行sql语句,返回影响的行数         int count = stmt.executeUpdate(sql1); // executeUpdate是向mysql发送sql语句，不是只能发送update语句          // 打印行数         System.out.println(影响的行数： + count);     }      @Test     public void fun2() throws Exception {         // 驱动名         String driverClassName = com.mysql.jdbc.Driver;         // 注册驱动         Class.forName(driverClassName);         // 连接sql参数         String url = jdbc:mysql://localhost:3306/db1; // mysql格式         String username = root;         String password = 747699;          // 连接sql         Connection con = DriverManager.getConnection(url, username, password);          // sql对象         Statement stmt = con.createStatement();          // 定义sql语句         String sql1 = SELECT * FROM account;          // 发送sql语句,返回一个表格对象         ResultSet re = stmt.executeQuery(sql1);          // ResultSet中有一个行光标         while (re.next()) { // 光标下移(下一行存在)             int id = re.getInt(1); // 通过列编号获取             String name = re.getString(name); // 通过列名称获取             double salary = re.getDouble(3); // 通过列编号获取             System.out.println(id =  + id +  、 name =  + name +  、 salary =  + salary);         }         re.close();         stmt.close();         con.close();     }      /**      * 进行SQL连接的规范(应该尽可能使用try...catch...finally...语句块以保证资源的关闭)      *       * @throws SQLException      */     @Test     public void fun3() throws Exception {         Connection con = null;         Statement st = null;         ResultSet rs = null;         try {             // 四个参数             String driverClassName = com.mysql.jdbc.Driver;             String url = jdbc:mysql://localhost:3306/db1;             String username = root;             String password = 747699;              // 注册驱动             con = DriverManager.getConnection(url, username, password);              // 获取SQL对象             st = con.createStatement();              // 定义SQL语句             String sql1 = SELECT * FROM account;              // 发送SQL语句             rs = st.executeQuery(sql1);              while (rs.next()) {                 int id = rs.getInt(id);                 String name = rs.getString(name);                 double salary = rs.getDouble(money);                 System.out.println(id =  + id +  、 name =  + name +  、 salary =  + salary);             }         } finally {             if (rs != null)                 rs.close();             if (st != null)                 st.close();             if (con != null)                 con.close();         }     } }