我想并行执行多个数据库查询并将结果存储在 map 中。我正在尝试这样做,但是当我访问 map 时 map 没有完全填充。
我做错了什么吗?
public Map<MapKeyEnums, Set<String>> doDBCalls(String phoneNumber, long timestamp) {
Map<MapKeyEnums, Set<String>> instrumentsEdgesMap = new EnumMap<>(MapKeyEnums.class);
CompletableFuture.supplyAsync(() -> dbReadService.getCall(phoneNumber, PhoneNumber.class, "ABC", timestamp)).
thenApply(x -> instrumentsEdgesMap.put(MapKeyEnums.ABC, x));
CompletableFuture.supplyAsync(() -> dbReadService.getCall(phoneNumber, PhoneNumber.class, "XYZ", timestamp)).
thenApply(x -> instrumentsEdgesMap.put(MapKeyEnums.XYZ, x));
CompletableFuture.supplyAsync(() -> dbReadService.getCall(phoneNumber, PhoneNumber.class, "DEF", timestamp)).
thenApply(x -> instrumentsEdgesMap.put(MapKeyEnums.DEF, x));
return instrumentsEdgesMap;
}
任何帮助将不胜感激,提前致谢。
最佳答案
在上述方法中 supplyAsync
将由 Async
执行来自 ForkJoinPool 的线程,但是 thenApply
方法总是通过调用线程来执行。因此,您的查询将按顺序一个接一个地运行,而不是异步的
All async methods without an explicit Executor argument are performed using the ForkJoinPool.commonPool() (unless it does not support a parallelism level of at least two, in which case, a new Thread is created to run each task).
这是例子
CompletableFuture.supplyAsync(()->{
System.out.println(Thread.currentThread().getName());
return "SupplyAsync";
}).thenAccept(i->{
System.out.println(Thread.currentThread().getName()+"--"+i);
});
输出:
ForkJoinPool.commonPool-worker-3
main--SupplyAsync
因此,如果您希望您的流程是
Async
然后首先使用 supplyAsync
触发所有三个数据库查询并捕获 CompletableFuture
内的输出CompletableFuture<Set<String>> first = CompletableFuture.supplyAsync(() -> dbReadService.getCall(phoneNumber, PhoneNumber.class, "ABC", timestamp));
CompletableFuture<Set<String>> second = CompletableFuture.supplyAsync(() -> dbReadService.getCall(phoneNumber, PhoneNumber.class, "XYZ", timestamp));
CompletableFuture<Set<String>> third = CompletableFuture.supplyAsync(() -> dbReadService.getCall(phoneNumber, PhoneNumber.class, "DEF", timestamp));
然后现在用其中三个创建一个流,然后将它们收集到
Map
Stream.of(new AbstractMap.SimpleEntry<MapKeyEnums, CompletableFuture<Set<String>>>(MapKeyEnums.ABC, first),
new AbstractMap.SimpleEntry<MapKeyEnums, CompletableFuture<Set<String>>>(MapKeyEnums.XYZ, second),
new AbstractMap.SimpleEntry<MapKeyEnums, CompletableFuture<Set<String>>>(MapKeyEnums.DEF, third))
.forEach(entry->{
entry.getValue().thenAccept(val-> instrumentsEdgesMap.put(entry.getKey(), val));
});
关于java - CompletableFuture 异步执行多个数据库查询,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/58866096/