Jdbc连接数据库基本步骤详解

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();
    }
  }
}