java - 用于获取插入值的 Cassandra 示例触发代码

Question

我需要你的帮助来提取触发器扩充方法中的列名称和值。

表定义:

           create table dy_data (
                                     id timeuuid,
                                     data_key text,
                                     time timestamp,
                                    data text,primary key((id,data_key),time)
                                    ) with clustering order by (time desc);

触发代码:

public class ArchiveTrigger implements ITrigger {
  public Collection<RowMutation> augment(ByteBuffer key, ColumnFamily cf) {
        try {
            // Below loop only has 2 columns ( one is "data" and another one may be "time" but i am not sure, because i cannot get value.           
            for (Column cell : cf) {
                //Got Exception if I try to get column name
                String name = ByteBufferUtil.string(cell.name());
                //Got only "data" column value and empty value for another column may be "time". If I try ByteBufferUtil.toLong(cell.value()) it throws exception
                String value = ByteBufferUtil.string(cell.value());
                log(" name = " + name);
                log(" value = " + value);
            }
        } catch (Exception e) {
            logger.warn("Exception ", e);
        }
        return null;
    }
}

我尽力在谷歌搜索示例代码。但是失败了。请帮我提供示例代码。提前致谢。

Answer 1

感谢 iamaleksey 的帮助。你的回复对我帮助很大。

下面是对触发器用户有用的代码片段，

public Collection<RowMutation> augment(ByteBuffer key, ColumnFamily cf) {
        try {
            ByteBuffer id_bb = CompositeType.extractComponent(key, 0);
            UUID id=TimeUUIDType.instance.compose(id_bb);

            ByteBuffer data_key_bb = CompositeType.extractComponent(key, 1);
            String data_key=UTF8Type.instance.compose(data_key_bb);


            Iterator col_itr=cf.iterator();

            Column ts_col=(Column)col_itr.next();
            ByteBuffer time_bb=CompositeType.extractComponent(ts_col.name(),0);
            long time=(TimestampType.instance.compose(time_bb)).getTime();


            Column data_bb=(Column)col_itr.next();
            String data=UTF8Type.instance.compose(data_bb.value());

            log(" id --> "+id.toString());
            log(" data_key-->"+data_key);
            log(" time == "+time);
            log(" data == "+data);
        } catch (Exception e) {
            logger.warn("Exception ", e);
        }
        return null;
    }

PS:因为我知道我的表格格式，所以我硬编码了列比较器类型。如果我们想编写通用的触发代码，我们可以使用 cf.getComponentComparator()/getKeyValidator()。