package dao;

 import java.sql.Connection;

 import java.sql.DriverManager;

 import java.sql.PreparedStatement;

 import java.sql.ResultSet;

 import java.sql.SQLException;

 import java.sql.Statement;

 public class BaseDao {

     private static String URL = "jdbc:sqlserver://localhost:1433;DatabaseName=StudentManageSys";

     private static String USER = "sa";

     private static String PWD = "sa";

     protected Connection conn = null;

     protected PreparedStatement pstmt = null;

     static {

         try {

             Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");

         } catch (ClassNotFoundException e) {

             e.printStackTrace();

         }

     }

     protected Connection getConnection() {

         try {

             return (conn == null || conn.isClosed()) ? DriverManager.getConnection(URL, USER, PWD) : conn;

         } catch (SQLException e) {

             e.printStackTrace();

             return null;

         }

     }

     protected void closeAll(Connection conn, Statement stmt, ResultSet rs) {

         try {

             if (rs != null)

                 rs.close();

             if (stmt != null)

                 stmt.close();

             if (conn != null)

                 conn.close();

         } catch (SQLException e) {

             e.printStackTrace();

         }

     }

     protected Object execute(String sql, Object... objs) {

         handle(sql, objs);

         try {

             boolean flag = pstmt.execute();

             if (flag) {

                 return pstmt.getResultSet(); // 查询不必先释放资源

             } else {

                 closeAll(conn, pstmt, null);

                 return pstmt.getUpdateCount();

             }

         } catch (SQLException e) {

             e.printStackTrace();

             return null;

         }

     }

     private void handle(String sql, Object[] objs) {

         conn = getConnection();

         try {

             pstmt = conn.prepareStatement(sql);

             if (objs != null) {

                 for (int i = 0; i < objs.length; i++) {

                     pstmt.setObject(i + 1, objs[i]);

                 }

             }

         } catch (SQLException e) {

             e.printStackTrace();

         }

     }

 }