为什么要用DataSource代替DriverManager

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这个问题本来是SO上的一个问答:http://stackoverflow.com/questions/15198319/why-do-we-use-a-datasource-instead-of-a-drivermanager

大致意思是使用DataSource有更好的可扩展性并且更易于维护。
使用DataSource你不需要每次连接都要配置一大段的用户名密码端口，然后才能获得连接去使用数据库。DS方式的话只需要初始化的时候配置一次，每次使用直接拿出连接用就好了。
关于可扩展性，就是DataSource提供连接池，而DM不提供。

JDK8里的描述:

A factory for connections to the physical data source that this DataSource object represents. An alternative to the DriverManager facility, a DataSource object is the preferred means of getting a connection. An object that implements the DataSource interface will typically be registered with a naming service based on the Java™ Naming and Directory (JNDI) API.

先看下原来DM的用法(找了个实习生写的代码，顺便帮他review):

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public void addMonitorLog(MonitorLog ml) throws IOException, ClassNotFoundException, SQLException{
    Connection conn;
    Statement st;
    ManipuData md = new ManipuData();
 
    Class.forName("com.mysql.jdbc.Driver");
    conn = DriverManager.getConnection(md.readProp());
    String sql =
            "insert into MSM_MonitorLog"
            + "(db_id,msg,check_time,need_warn)values("
            + ml.getDb_id()+",'"+ml.getMsg()+"',NOW(),"
            +ml.getNeed_warn()+")";
 
    st = conn.prepareStatement(sql,Statement.RETURN_GENERATED_KEYS);
    st.executeUpdate(sql);
    st.close();
    conn.close();
}

使用DataSource的版本:

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public void addMonitorLog(MonitorLog ml) throws IOException, ClassNotFoundException, SQLException{
    PreparedStatement stmt = null;
    DataSource ds = null; //fake ds
    Connection conn = ds.getConnection();
    final String sql = "insert into MSM_MonitorLog(db_id,msg,check_time,need_warn) values(?,?,?,?)";
    String[] params = {ml.getDb_id(),ml.getMsg(),NOW(),ml.getNeed_warn()};
    try {
        stmt = conn.prepareStatement(sql, Statement.RETURN_GENERATED_KEYS);
        this.fillStatement(stmt, params);
        stmt.executeUpdate();
    } catch (SQLException e) {
        this.rethrow(e, sql, params);
    } finally {
        close(stmt);
        if (closeConn) {
            close(conn);
        }
    }
}

最后推荐使用dbutil封装jdbc的用法:

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public void addMonitorLog(MonitorLog ml) throws IOException, ClassNotFoundException, SQLException{
    final QueryRunner qr = MySQLHelper.getQueryRunner();
    final String sql = "insert into MSM_MonitorLog(db_id,msg,check_time,need_warn) values(?,?,?,?)";
    final String[] params = {ml.getDb_id(),ml.getMsg(),NOW(),ml.getNeed_warn()};
    qr.batch(sql,params);
}