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();
        }
    }
}