[英]How to use multiple streams and .map functions in java 8 with lambda expressions
[英]Collection of lambda functions in Java Streams
我有一个流函数KStream<K, V>[] branch(final Predicate<? super K, ? super V>... predicates)
。 我想动态创建一个谓词列表。 那可能吗?
KStream<Long, AccountMigrationEvent>[] branches = stream
.map((key, event) -> enrich(key, event))
.branch(getStrategies());
[...]
private List<org.apache.kafka.streams.kstream.Predicate<Long, AccountMigrationEvent>> getStrategies() {
ArrayList<Predicate<Long, AccountMigrationEvent>> predicates = new ArrayList<>();
for (MigrationStrategy strategy : strategies) {
predicates.add(new org.apache.kafka.streams.kstream.Predicate<Long, AccountMigrationEvent>() {
@Override
public boolean test(Long key, AccountMigrationEvent value) {
return strategy.match(value);
}
});
}
return predicates;
}
我还没有测试过这段代码,但理论上它应该可以工作:
//All the predicates mentioned in here are of type org.apache.kafka.streams.kstream.Predicate
private Predicate<Long, AccountMigrationEvent>>[] getStrategies() {
List<Predicate<Long, AccountMigrationEvent>> predicates = strategies.stream()
.map(strategy -> (Predicate<Long, AccountMigrationEvent>>) (key, value) -> strategy.matches(value))
.collect(toList());
// branch() method on KStream requires an array so we need to transform our list
return predicates.toArray(new Predicate[predicates.size()]);
}
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