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();    }  }}