@Override
public void evicted(WindowItem item) {
if (item.getEvent().get(operatedField) != null) {
try {
evict((F) item.getEvent().get(operatedField).getValue());
} catch (ClassCastException e) {
throw new FlowmixException(
"Problem converting value " + item.getEvent().get(operatedField).getValue(), e);
}
}
}
/**
* 假设根据year,age统计count:select year,age,count(*) from table group by year,age
* 则groupByFields=[year,age], operateField=?
*
* @param item
*/
@Override
public void added(WindowItem item) {
// 第一个窗口项(事件)进来时满足条件.后面的窗口项因为groupedValues!=null,不满足条件.
if (groupedValues == null && groupByFields != null) {
groupedValues = new HashMap<String, Collection<Tuple>>();
for (String group : groupByFields) {
groupedValues.put(group, item.getEvent().getAll(group));
}
}
if (item.getEvent().get(operatedField) != null) {
try {
// 参数是事件记录中操作字段的值. 而不是事件记录本身.比如要聚合sum(key3),则我们要把key3的值取出来,作为sum的参数
add(((F) item.getEvent().get(operatedField).getValue()));
} catch (ClassCastException e) {
throw new FlowmixException(
"Problem converting value " + item.getEvent().get(operatedField).getValue(), e);
}
}
// TODO: 关联字段
if (assocField != null) {
try {
// 如果关联的两个字段类型不同呢, 所以最好自定义的Aggregator的F为Object类型.
add(
((F) item.getEvent().get(assocField[0]).getValue()),
((F) item.getEvent().get(assocField[1]).getValue()));
} catch (ClassCastException e) {
throw new FlowmixException(
"Problem converting value " + item.getEvent().get(assocField[0]).getValue(), e);
}
}
}