使用HttpURLConnection 上传大文件,会出现内存溢出问题:
观察HttpURLConnection 源码:
@Overridepublic synchronized OutputStream getOutputStream() throws IOException {
connecting = true;
SocketPermission p = URLtoSocketPermission(this.url);
if (p != null) {
try {
return AccessController.doPrivilegedWithCombiner(
new PrivilegedExceptionAction<>() {
public OutputStream run() throws IOException {
return getOutputStream0();
}
}, null, p );
} catch (PrivilegedActionException e) {
throw (IOException) e.getException();
}
} else {
return getOutputStream0();
}
}
private synchronized OutputStream getOutputStream0() throws IOException {
try {
if (!doOutput) {
throw new ProtocolException("cannot write to a URLConnection" + " if doOutput=false - call setDoOutput(true)");
}
if (method.equals("GET")) {
method = "POST"; // Backward compatibility }
if ("TRACE".equals(method) && "http".equals(url.getProtocol())) {
throw new ProtocolException("HTTP method TRACE" +
" doesn't support output");
}
// if there's already an input stream open, throw an exception if (inputStream != null) {
throw new ProtocolException("Cannot write output after reading input.");
}
if (!checkReuseConnection())
connect();
boolean expectContinue = false;
String expects = requests.findValue("Expect");
if ("100-Continue".equalsIgnoreCase(expects) && streaming()) {
http.setIgnoreContinue(false);
expectContinue = true;
}
if (streaming() && strOutputStream == null) {
writeRequests();
}
if (expectContinue) {
expect100Continue();
}
ps = (PrintStream)http.getOutputStream();
if (streaming()) {
if (strOutputStream == null) {
if (chunkLength != -1) { /* chunked */ strOutputStream = new StreamingOutputStream(
new ChunkedOutputStream(ps, chunkLength), -1L);
} else { /* must be fixed content length */ long length = 0L;
if (fixedContentLengthLong != -1) {
length = fixedContentLengthLong;
} else if (fixedContentLength != -1) {
length = fixedContentLength;
}
strOutputStream = new StreamingOutputStream(ps, length);
}
}
return strOutputStream;
} else {
if (poster == null) {
poster = new PosterOutputStream();
}
return poster;
}
} catch (RuntimeException e) {
disconnectInternal();
throw e;
} catch (ProtocolException e) {
// Save the response code which may have been set while enforcing // the 100-continue. disconnectInternal() forces it to -1 int i = responseCode;
disconnectInternal();
responseCode = i;
throw e;
} catch (IOException e) {
disconnectInternal();
throw e;
}
}
public boolean streaming () {
return (fixedContentLength != -1) || (fixedContentLengthLong != -1) ||
(chunkLength != -1);
}
如上, 默认设置情况下streaming () 为false。
package sun.net.www.http
public class PosterOutputStream extends ByteArrayOutputStream {
}
PosterOutputStream 默认为 ByteArrayOutputStream 子类
解决办法:
目标服务支持情况下,可以不使用HttpURLConnection的ByteArrayOutputStream缓存机制,直接将流提交到服务器上。如下函数设置:
httpConnection.setChunkedStreamingMode(0); // 或者设置自定义大小,0默认大小
public void setChunkedStreamingMode (int chunklen) { if (connected) { throw new IllegalStateException ("Can't set streaming mode: already connected"); } if (fixedContentLength != -1 || fixedContentLengthLong != -1) { throw new IllegalStateException ("Fixed length streaming mode set"); } chunkLength = chunklen <=0? DEFAULT_CHUNK_SIZE : chunklen; }
遗憾的是,我上传的服务不支持这种模式。因此采用固定大小。
HttpURLConnection con = (HttpURLConnection)new URL("url").openConnection();
con.setFixedLengthStreamingMode(输出流的固定长度);
/** * This method is used to enable streaming of a HTTP request body * without internal buffering, when the content length is known in * advance. *
* An exception will be thrown if the application * attempts to write more data than the indicated * content-length, or if the application closes the OutputStream * before writing the indicated amount. *
* When output streaming is enabled, authentication * and redirection cannot be handled automatically. * A HttpRetryException will be thrown when reading * the response if authentication or redirection are required. * This exception can be queried for the details of the error. *
* This method must be called before the URLConnection is connected. *
* NOTE: {@link #setFixedLengthStreamingMode(long)} is recommended * instead of this method as it allows larger content lengths to be set. * * @param contentLength The number of bytes which will be written * to the OutputStream. * * @throws IllegalStateException if URLConnection is already connected * or if a different streaming mode is already enabled. * * @throws IllegalArgumentException if a content length less than * zero is specified. * * @see #setChunkedStreamingMode(int) * @since 1.5 */ public void setFixedLengthStreamingMode (int contentLength) { if (connected) { throw new IllegalStateException ("Already connected"); } if (chunkLength != -1) { throw new IllegalStateException ("Chunked encoding streaming mode set"); } if (contentLength < 0) { throw new IllegalArgumentException ("invalid content length"); } fixedContentLength = contentLength; }
我是上传文件场景: 使用文件的大小作为长度
FileInputStream fileInputStream = new FileInputStream(uploadFileName);
long totalLength= fileInputStream.getChannel().size();
var boundary = "someboundary";
var temUploadUrl = "url path";
//
var url = new URL(temUploadUrl);
var connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("PUT");
connection.setRequestProperty("Content-Type", MediaType.MULTIPART_FORM_DATA_VALUE + "; boundary=" + boundary);
connection.setDoOutput(true);
// 设置 Content-Length
connection.setRequestProperty("Content-Length", String.valueOf(totalLength));
connection.setFixedLengthStreamingMode(totalLength);