提问人:vicki 提问时间:9/30/2020 更新时间:10/2/2020 访问量:580
如何在异步 httpclient java 11 中将多个异步 get 请求的响应写入单个文件?
How to write responses of multiple asynchronous get requests to a single file in asynchronous httpclient java 11?
问:
我可以像这样在 java 11 中使用 httpclient 下载单个媒体文件
public class Httptest {
private static HttpClient client = HttpClient.newBuilder().build();
public static void main(String[] args) throws Exception {
File fts = new File("P:/sample.ts"); //Destination of downloaded file
fts.createNewFile();
URI url = new URI("File url here"); //File Url
HttpRequest request = HttpRequest.newBuilder() //Creating HttpRequest using Builder class
.GET()
.uri(url)
.build();
Path file = Path.of("P:/samp.ts");
//BodyHandlers class has methods to handle the response body
// In this case, save it as a file (BodyHandlers.ofFile())
HttpResponse<Path> response = client.send(request,BodyHandlers.ofFile(file));
}
}
上面的代码片段从 url 下载.ts文件。并且它被正确下载。
现在,我有 url 列表,.我对 url 列表进行了异步调用,并通过添加 .
我卡住的地方是,如何将响应列表写入单个文件。List<URI> urls
Executor service
到目前为止我写的代码:
public class httptest{
// Concurrent requests are made in 4 threads
private static ExecutorService executorService = Executors.newFixedThreadPool(4);
//HttpClient built along with executorservice
private static HttpClient client = HttpClient.newBuilder()
.executor(executorService)
.build();
public static void main(String[] args) throws Exception{
File fts = new File("P:/Spyder_directory/sample.ts");
fts.createNewFile();
List<URI> urls = Arrays.asList(
new URI("Url of file 1"),
new URI("Url of file 2"),
new URI("Url of file 3"),
new URI("Url of file 4"),
new URI("Url of file 5"));
List<HttpRequest> requests = urls.stream()
.map(HttpRequest::newBuilder)
.map(requestBuilder -> requestBuilder.build())
.collect(toList());
Path file = Path.of("P:/Spyder_directory/sample.ts");
List<CompletableFuture<HttpResponse<Path>>> results = requests.stream()
.map(individual_req -> client.sendAsync(individual_req,BodyHandlers.ofFile(file)))
.collect(Collectors.toList());
}
}
在执行结束时创建的文件没有所发出请求的响应。
如果您了解我问题的要点,任何人都可以为此问题提出替代解决方案。sample.ts
答:
1赞
daniel
10/2/2020
#1
一种可能性是将 HttpResponse.BodyHandlers.ofByteArrayConsumer 与将字节写入文件的 a 一起使用。这样可以控制文件的打开方式,从而可以追加到现有文件,而不是每次都创建新文件。Consumer<Optional<byte[]>>
请注意,如果这样做,则不应使用,因为请求将同时发送,因此响应也将同时接收。如果您仍想同时发送请求,则需要缓冲响应,并在将它们写入文件时强制进行一些同步。sendAsync
评论
0赞
vicki
10/3/2020
是的。感谢您的回答,我在异步和并发方面犯了一些小错误。 修复了此问题。Consumer
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