JDBC连接Oracle数据库

List<Map> result = new ArrayList<Map>();
Connection conn = null;
PreparedStatement pstmt;
ResultSet rs;
try {
    Class.forName("oracle.jdbc.driver.OracleDriver");
} catch (ClassNotFoundException e){
    System.out.println("驱动出错");
    e.printStackTrace();
}
try {
    conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:HelloWorld", "root", "root");
    pstmt = conn.prepareStatement("select * from HelloWorld");
    rs = pstmt.executeQuery();
    ResultSetMetaData md = rs.getMetaData();
    int columnCount = md.getColumnCount();
    while (rs.next()) {
        Map map = new HashMap();
        for (int i = 1; i <= columnCount; i++) {
            map.put(md.getColumnName(i), rs.getObject(i));
        }
        result.add(map);
    }
} catch (SQLException e) {
    e.printStackTrace();
} finally {
    if (connection != null) {
        try {
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
    //pstmt.close();
    //rs.close();
}

finally中，conn的关闭必须放在第一个，而pstmt和rs是否有必要close()视具体情况而定。