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) 數據庫連接，有以下幾個步驟：
 *1.加載驅動程序  Class.forName(driver);
 *2.創建連接對象 Connection con = DriverManager.getConnection(url,username,password);
 *3.創建sql語句的執行對象 
 *4.執行sql語句
 *5.對執行結果進行處理
 *6.關閉相關連接對象 （順序跟聲明的順序相反）。
 */
  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("找不到驅動");
      e.printStackTrace();
    }
    Connection conn = null;
    try {
      conn = DriverManager.getConnection(oracleUrl, userName,passWord );
    } catch (SQLException e) {
      System.out.println("數據庫連接錯誤");
      e.printStackTrace();
    }
    Statement st = null;
    try {
      st = conn.createStatement();
    } catch (SQLException e) {
      System.out.println("創建數據庫聲明類錯誤");
      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()){
        //通過列的標號來查詢數據；
        String name =rs.getString(1);
        //通過列名來查詢數據
        String name2 = rs.getString("ename");
        System.out.println(name);
      }
    } catch (SQLException e) {
      System.out.println("測試--");
      e.printStackTrace();
    }
    //關閉數據連接對象
    try {
      if(rs!= null){
        rs.close();
      }
      if(st!= null){
        st.close();
      }
      if(conn!=null){
        conn.close();
      }
    } catch (SQLException e) {
      e.printStackTrace();
    }
  }
}