webQQ jsp项目

package db; // 1导包 import java.sql.*; public class DB { private Connection con = null; private Statement st = null; private ResultSet rs = null; private PreparedStatement pstmt = null; public DB() { try { // 2加载驱动 Class.forName(DBConfig.JDBC_DRIVER); // 3建立连接 con = DriverManager.getConnection(DBConfig.JDBC_URL, DBConfig.JDBC_USRE, DBConfig.JDBC_PASSWORD); // 4创建执行sql语句对象 st = con.createStatement(); System.out.println("DB int OK!"); } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (SQLException e) { e.printStackTrace(); } } /** * 增删改处理 * * @param sql：增删改sql语句 * @return 操作影响行数 */ public int update(String sql) { int res = 0; System.out.println(sql); try { res = st.executeUpdate(sql); } catch (SQLException e) { e.printStackTrace(); } finally { this.close(); // 释放资源 } return res; } /** * 查询 * * @param sql * @return */ public ResultSet query(String sql) { System.out.println(sql); try { rs = st.executeQuery(sql); } catch (SQLException e) { e.printStackTrace(); } return rs; } public ResultSet executeQuery(String preparedSql) { System.out.println(preparedSql); try { pstmt = con.prepareStatement(preparedSql); // 得到PreparedStatement对象 rs = pstmt.executeQuery(); } catch (SQLException e) { e.printStackTrace(); } return rs; } /** *执行增删改处理 * @param preparedSql：预编译的sql语句，里面可能包含? * @param param：给预编译的sql语句中的？赋值， * 并且数量位置一一对应，如过预编译的sql语句中没有？则param应该为null * @return */ public int executeUpdate(String preparedSql, String[] param) { int num = 0; /* 处理SQL,执行SQL */ try { // 得到数据库连接 pstmt = con.prepareStatement(preparedSql); // 得到PreparedStatement对象 if (param != null) { for (int i = 0; i < param.length; i++) { pstmt.setString(i + 1, param[i]); // 为预编译sql设置参数 } } num = pstmt.executeUpdate(); // 执行SQL语句 } catch (SQLException e) { e.printStackTrace(); // 处理SQLException异常 } finally { this.close(); // 释放资源 } return num; } public int getCount(String tableName) { int res = 0; String sql = "select count(*) as c from " + tableName; rs = this.query(sql); try { rs.next(); // res=rs.getInt("c"); res = rs.getInt(1); } catch (SQLException e) { e.printStackTrace(); } finally { this.close(); // 释放资源 } return res; } /** * 关闭 */ public void close() { try { if (rs != null) { rs.close(); rs = null; } if (st != null) { st.close(); st = null; } if (con != null && !con.isClosed()) { con.close(); con = null; } } catch (SQLException e) { e.printStackTrace(); } } public Connection getCon() { return con; } public static void main(String[] args) { new DB(); } }