JavaWeb基础工具类——BaseDao

 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();
         }
     }
 }