Jdbc连接数据库基本步骤

Jdbc连接数据库的基本步骤：

 package demo.jdbc;

 import java.sql.Connection;
 import java.sql.DriverManager;
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.Statement;

 public class JdbcConn {
 /**
  *JDBC (Java Data Base Connectivity) 数据库连接，有以下几个步骤：
  *1.加载驱动程序   Class.forName(driver);
  *2.创建连接对象  Connection con = DriverManager.getConnection(url,username,password);
  *3.创建sql语句的执行对象
  *4.执行sql语句
  *5.对执行结果进行处理
  *6.关闭相关连接对象 （顺序跟声明的顺序相反）。
  */
     public static void main(String[] args) {
         String mysqlDriver = "com.mysql.jdbc.Driver";
         String mysqlUrl = "jdbc:mysql://localhost:3306/mybase";
         String mysqlUser = "root";
         String mysqlPass = "111";

         String oracleDriver = "oracle.jdbc.driver.OracleDriver";
         String oracleUrl = "jdbc:oracle:thin:@localhost:1521:XE";
         String userName = "zl";
         String passWord = "444";
         String sql = "select ename from emp";

         try {
             Class.forName(oracleDriver);
         } catch (ClassNotFoundException e) {
             System.out.println("找不到驱动");
             e.printStackTrace();
         }
         Connection conn = null;
         try {
             conn = DriverManager.getConnection(oracleUrl, userName,passWord );
         } catch (SQLException e) {
             System.out.println("数据库连接错误");
             e.printStackTrace();
         }
         Statement st = null;
         try {
             st = conn.createStatement();
         } catch (SQLException e) {
             System.out.println("创建数据库声明类错误");
             e.printStackTrace();
         }
         boolean flag = false;
         int rows = 0;
         ResultSet rs = null;
         try {
             flag = st.execute(sql);
             rows = st.executeUpdate(sql);
             rs   = st.executeQuery(sql);
             while(rs.next()){
                 //通过列的标号来查询数据；
                 String name =rs.getString(1);
                 //通过列名来查询数据
                 String name2 = rs.getString("ename");
                 System.out.println(name);
             }
         } catch (SQLException e) {
             System.out.println("测试--");
             e.printStackTrace();
         }
         //关闭数据连接对象
         try {
             if(rs!= null){
                 rs.close();
             }
             if(st!= null){
                 st.close();
             }
             if(conn!=null){
                 conn.close();
             }
         } catch (SQLException e) {
             e.printStackTrace();
         }
     }
 }