JavaWeb之BaseDao的写法

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package com.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;/** * 用来做数据的基础连接和相关操作的关闭 * @author Lulu * */public class BaseDAO {    public BaseDAO() {        try {            Class.forName("com.mysql.jdbc.Driver");        } catch (ClassNotFoundException e) {            e.printStackTrace();        }    }    // 属性 --------------------------    private Connection conn;    private Statement stm;    private PreparedStatement pstm;    private ResultSet rs;    // 获得连接--------------------------    public Connection getConn() {        try {            if (conn == null || conn.isClosed()) {                conn = DriverManager.getConnection(                        "jdbc:mysql://localhost:3306/bbs",                        "root", "");            }        } catch (SQLException e) {            e.printStackTrace();            System.out.println("getConnection（）错误");        }        return conn;    }    // 执行增、删、改SQL语句--------------------    /**     *      * @param sql     * @return int表示影响的行数     * @throws SQLException     */    public int executeUpdate(String sql) throws SQLException {        if (getConn() == null) {            System.out.println("与数据库连接失败!");            return -1;        }        stm = conn.createStatement();        return stm.executeUpdate(sql);    }    // 重载执行增、删、改SQL语句--------------------    public int executeUpdate(String sql, Object[] obj) throws SQLException {        if (getConn() == null) {            System.out.println("与数据库连接失败!");            return -1;        }        pstm = conn.prepareStatement(sql);        if (obj != null) {            for (int i = 0; i < obj.length; i++) {                pstm.setObject(i + 1, obj[i]);            }        }        return pstm.executeUpdate();    }    // 执行查询SQL语句----------------------------    public ResultSet executeQuery(String sql) throws SQLException {        if (getConn() == null) {            System.out.println("与数据库连接失败!");            return null;        }        stm = conn.createStatement();        rs = stm.executeQuery(sql);        return rs;    }    // 重载执行查询SQL语句----------------------------    public ResultSet executeQuery(String sql, Object[] obj) throws SQLException {        //第一步获取链接        if (getConn() == null) {//该步骤完成了与数据库的链接操作            System.out.println("与数据库连接失败!");            return null;        }        //将数据准备一下        pstm = conn.prepareStatement(sql);        if (obj != null) {            for (int i = 0; i < obj.length; i++) {                pstm.setObject(i + 1, obj[i]);            }        }        //执行完整sql语句        rs = pstm.executeQuery();        return rs;    }    // 关闭ResultSet    public void closeResultSet() {        if (rs != null) {            try {                rs.close();            } catch (SQLException e) {                // TODO Auto-generated catch block                e.printStackTrace();            }        }    }    // 关闭Connection    public void closeConnection() {        if (conn != null) {            try {                conn.close();            } catch (SQLException e) {                e.printStackTrace();            }        }    }    // 关闭Statement和PreparedStatement    public void closeStatement() {        if (stm != null) {            try {                stm.close();            } catch (SQLException e) {                e.printStackTrace();            }        }        if (pstm != null) {            try {                pstm.close();            } catch (SQLException e) {                e.printStackTrace();            }        }    }}
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