java - ReSTLet - 使用 StreamingOutput 的 StreamClosedException

Question

我的 ReSTLet 资源遇到问题。它使用 TrueZip 构建 Zip 存档的子集并允许用户下载它。

// Create a Streaming Response Entity.
    final StreamingOutput stream = new StreamingOutput() {
        @Override
        public void write(final OutputStream output) {
                ZipBrowser.extract(source, path, output);
        }
    };
    LOGGER.debug("Download of Path {} with the length {} initiated", path, length);
    ResponseBuilder rb = Response.ok(stream);
    rb.header(HeaderConstants.HEADER_CONTENT_DISPOSITION, CONDISPOVALUE + fileName);
    rb.header(HeaderConstants.HEADER_CONTENT_LENGTH, length);
    return rb.build();

尽管它有效，但我收到了一个恼人的 StreamClosedException。只有当我尝试下载一个子集而不是整个 Zip 存档时才会出现此错误:

An exception occured writing the responseentity

    sun.net.httpserver.StreamClosedException
    at sun.net.httpserver.ChunkedOutputStream.flush(ChunkedOutputStream.java:156)
    at sun.net.httpserver.PlaceholderOutputStream.flush(ExchangeImpl.java:449)
    at org.restlet.engine.adapter.ServerCall.writeResponseBody(ServerCall.java:511)
    at org.restlet.engine.adapter.ServerCall.sendResponse(ServerCall.java:454)
    at org.restlet.engine.adapter.ServerAdapter.commit(ServerAdapter.java:187)
    at org.restlet.engine.adapter.HttpServerHelper.handle(HttpServerHelper.java:144)
    at org.restlet.engine.connector.HttpServerHelper$1.handle(HttpServerHelper.java:64)
    at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:77)
    at sun.net.httpserver.AuthFilter.doFilter(AuthFilter.java:83)
    at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:80)
    at sun.net.httpserver.ServerImpl$Exchange$LinkHandler.handle(ServerImpl.java:677)
    at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:77)
    at sun.net.httpserver.ServerImpl$Exchange.run(ServerImpl.java:649)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)Unable to send error response

    java.io.IOException: headers already sent

    at sun.net.httpserver.ExchangeImpl.sendResponseHeaders(ExchangeImpl.java:204)
    at sun.net.httpserver.HttpExchangeImpl.sendResponseHeaders(HttpExchangeImpl.java:86)
    at org.restlet.engine.connector.HttpExchangeCall.writeResponseHead(HttpExchangeCall.java:148)
    at org.restlet.engine.adapter.ServerCall.sendResponse(ServerCall.java:450)
    at org.restlet.engine.adapter.ServerAdapter.commit(ServerAdapter.java:205)
    at org.restlet.engine.adapter.HttpServerHelper.handle(HttpServerHelper.java:144)
    at org.restlet.engine.connector.HttpServerHelper$1.handle(HttpServerHelper.java:64)
    at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:77)
    at sun.net.httpserver.AuthFilter.doFilter(AuthFilter.java:83)
    at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:80)
    at sun.net.httpserver.ServerImpl$Exchange$LinkHandler.handle(ServerImpl.java:677)
    at com.sun.net.httpserver.Filter$Chain.doFilter(Filter.java:77)
    at sun.net.httpserver.ServerImpl$Exchange.run(ServerImpl.java:649)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)

Answer 1

这是由 zip 库和 ReSTLet Framework 在完成后试图关闭 OutputStream 引起的。

我过去在其他库中遇到过这种情况，并设法通过包装 OutputStream 来消除异常，我将传递给 zip 库的类覆盖了 close()什么也不做。委托(delegate)所有其他方法。然后这允许 ReSTLet 关闭流。

这样在您的代码中调用 Zip 实用程序的行就变成了:

 ZipBrowser.extract(source, path, new WrappedOutputStream(output));

WrappedOutputStream 类如下所示(需要添加委托(delegate)方法)。

import java.io.IOException;
import java.io.OutputStream;

public class WrappedOutputStream extends OutputStream {

    private final OutputStream delegate;

    public WrappedOutputStream(final OutputStream delegate) {
        this.delegate = delegate;
    }

    public void close() throws IOException {
        // Do Nothing to allow Restlet to close the underlying stream
    }

    // TODO Delegate other Outpt Stream methods.
}