Java连接数据库取数据简例

• 数据库连接

public class DBhelper{
    //数据库驱动
    public static final String driver_class = "org.netezza.Deiver";
    //数据库位置
    public static final String driver_url = "jdbc:netezza://10.16.1.56:5480/wml";
    //用户名
    public static final String user = "***";
    //密码
    public static final String password = "***";
    private static Connection connection = null;
    private PreparedStatement preparedStatement = null;
    private ResultSet resultSet = null;//查询结果集

    //构造函数
    public DBhelper(){
        try{
        connection = DBhelper.getConnInstance();
        }catch (Exception e){
            e.printStackTrace();
        }
    }

    //线程同步
    private static synchronized Connection getConnInstance(){
        if(connection = null){
            try{
                Class.forName(driver_class);
                connection = DriverManager.getConnection(driver_url, user, password);
            }catch (ClassNotFoundException e){
                e.printStackTrace();
            }catch (SQLException e){
                e.printStackTrace();
            }
            System.out.println("连接数据库成功");
        }
        return connection;
    }

    //关闭数据库连接
    public void close(){
        try{
            if(resultSet != null){
                this.resultSet.close();
            }
            if(preparedStatement != null){
                this.preparedStatement.close();
            }
            if(connection != null){
                DBhelper.connection.close();
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }

    //执行SQL语句查询结果
    public ResultSet executeQuery(String sql){
        try{
            preparedStatement = connection.prepareStatement(sql);
            resultSet = preparedStatement.executeQuery();
        }catch (SQLException e){
            e.printStackTrace();
        }
        return resultSet;
    }
}

• 查询调用类

public class ZDao{
    private ResultSet resultSet;
    private DBhelper DBhelper;
    private String sql = "select aa, bb, cc, dd from abcd";

    public ZDao(){
        DBhelper = new DBhelper();
        resultSet = DBhelper.executeQuery(sql);
    }
    public void close(){
        DBhelper.close();
    }
    public ResultSet getResultSet(){
        return resultSet;
    }
}

• 测试类

public class Test{
    public static void main(String args[]){
        //简单测试一下就用数组接收了，更好的选择是用List或者实体类接收
        String[][] abcdTest = new String[1000][4];
        ZDao ZDao = new ZDao();
        ResultSet rs = ZDao.getResultSet();
        int i = 0;
        try{
            while(rs.next()){
                abcdTest[i][0] = rs.getString("aa");
                abcdTest[i][1] = rs.getString("bb");
                abcdTest[i][2] = rs.getString("cc");
                abcdTest[i++][3] = rs.getString("dd");
            }
        }catch (SQLException e){
            e.printStackTrace();
        }
        ZDao.close();
        //随便打印几个看看成功没
        System.out.println(abcdTest[4][0]+'\t'+abcdTest[4][1]+'\t'+abcdTest[4][2]+'\t'+abcdTest[4][3]);
    }
}

需要导的包没写进去，eclipse自动导一下就好^_^