java-使用GZIPOutputStream将文件发布到servlet时文件损坏
作者：互联网
我试图修改@BalusC优秀教程here以发送gzip压缩文件.这是一个有效的java类：
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.zip.GZIPOutputStream;
public final class NetworkService {
// *** EDIT THOSE AS APROPRIATE
private static final String FILENAME = "C:/Dropbox/TMP.txt";
private static final String URL =
"http://192.168.1.64:8080/DataCollectionServlet/";
// *** END EDIT
private static final CharSequence CRLF = "\r\n";
private static boolean isServerGzip = true; // ***
private static String charsetForMultipartHeaders = "UTF-8";
public static void main(String[] args) {
HttpURLConnection connection = null;
OutputStream serverOutputStream = null;
try {
File file = new File(FILENAME);
final String boundary = Long
.toHexString(System.currentTimeMillis());
connection = connection(true, boundary);
serverOutputStream = connection.getOutputStream();
try {
flushMultiPartData(file, serverOutputStream, boundary);
} catch (IOException e) {}
System.out.println(connection.getResponseCode()); // 200
} catch (IOException e) {
// Network unreachable : not connected
// No route to host : probably on an encrypted network
// Connection timed out : Server DOWN
} finally {
if (connection != null) connection.disconnect();
}
}
private static HttpURLConnection connection(boolean isMultiPart,
String boundary) throws MalformedURLException, IOException {
HttpURLConnection connection = (HttpURLConnection) new URL(URL)
.openConnection();
connection.setDoOutput(true); // triggers POST
connection.setUseCaches(false); // *** no difference
connection.setRequestProperty("Connection", "Keep-Alive");
connection.setRequestProperty("User-Agent",
"Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.3) "
+ "Gecko/20100401"); // *** tried others no difference
connection.setChunkedStreamingMode(1024); // *** no difference
if (isMultiPart) {
if (boundary == null || "".equals(boundary.trim()))
throw new IllegalArgumentException("Boundary can't be "
+ ((boundary == null) ? "null" : "empty"));
connection.setRequestProperty("Content-Type",
"multipart/form-data; boundary=" + boundary);
}
return connection;
}
// =========================================================================
// Multipart
// =========================================================================
private static void flushMultiPartData(File file,
OutputStream serverOutputStream, String boundary)
throws IOException {
PrintWriter writer = null;
try {
// true = autoFlush, important!
writer = new PrintWriter(new OutputStreamWriter(serverOutputStream,
charsetForMultipartHeaders), true);
appendBinary(file, boundary, writer, serverOutputStream);
// End of multipart/form-data.
writer.append("--" + boundary + "--").append(CRLF);
} finally {
if (writer != null) writer.close();
}
}
private static void appendBinary(File file, String boundary,
PrintWriter writer, OutputStream output)
throws FileNotFoundException, IOException {
// Send binary file.
writer.append("--" + boundary).append(CRLF);
writer.append(
"Content-Disposition: form-data; name=\"binaryFile\"; filename=\""
+ file.getName() + "\"").append(CRLF);
writer.append(
"Content-Type: " // ***
+ ((isServerGzip) ? "application/gzip" : URLConnection
.guessContentTypeFromName(file.getName())))
.append(CRLF);
writer.append("Content-Transfer-Encoding: binary").append(CRLF);
writer.append(CRLF).flush();
InputStream input = null;
OutputStream output2 = output;
if (isServerGzip) {
output2 = new GZIPOutputStream(output);
}
try {
input = new FileInputStream(file);
byte[] buffer = new byte[1024]; // *** tweaked, no difference
for (int length = 0; (length = input.read(buffer)) > 0;) {
output2.write(buffer, 0, length);
}
output2.flush(); // Important! Output cannot be closed. Close of
// writer will close output as well.
} finally {
if (input != null) try {
input.close();
} catch (IOException logOrIgnore) {}
}
writer.append(CRLF).flush(); // CRLF is important! It indicates end of
// binary boundary.
}
}
您必须编辑FILENAME和URL字段并在URL中设置一个servlet-其doPost()方法为：
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
Collection<Part> parts = req.getParts();
for (Part part : parts) {
File save = new File(uploadsDirName, getFilename(part) + "_"
+ System.currentTimeMillis() + ".zip");
final String absolutePath = save.getAbsolutePath();
log.debug(absolutePath);
part.write(absolutePath);
sc.getRequestDispatcher(DATA_COLLECTION_JSP).forward(req, resp);
}
}
现在,当isServerGzip字段设置为true时,FILENAME被压缩并发送到服务器,但是当我尝试提取它时,它已损坏(我在Windows上使用7z,它将打开gzip文件作为存档,但是当我尝试提取其中的文件时,表示已损坏的gzip存档-尽管确实提取了(确实损坏的)文件).尝试了各种文件-较大的文件最终在某个点被破坏,较小的文件最终提取为空-档案中较大文件的报告大小比真实文件大得多,而较小文件为0.我标记了需要注意// ***.我可能会错过一些连接配置,或者我用gzip压缩流的方式可能是完全错误或…？
尝试调整连接属性,缓冲区,缓存等无济于事
解决方法:
你需要打电话
((GZIPOutputStream)output2).finish();
冲洗前.参见javadochere.它指出
Finishes writing compressed data to the output stream without closing
the underlying stream. Use this method when applying multiple filters
in succession to the same output stream.
你在做什么所以
for (int length = 0; (length = input.read(buffer)) > 0;)
output2.write(buffer, 0, length);
}
((GZIPOutputStream)output2).finish(); //Write the compressed parts
// obviously make sure output2 is truly GZIPOutputStream
output2.flush(); //
关于将多个过滤器连续应用于同一输出流的问题,这就是我的理解：
您有一个到HTTP服务器的OutputStream,即套接字连接. HttpUrlConnection编写标头,然后直接编写正文.在这种情况下(多部分),您将边界和标头发送为未压缩的字节,已压缩的文件内容,然后再次发送边界.因此,流最终看起来像这样：
start writing with GZIPOutputStream
v
|---boundary---|---the part headers---|---gzip encoded file content bytes---|---boundary---|
^ ^
write directly with PrintWriter use PrintWriter again
因此,您可以看到如何用不同的过滤器依次编写不同的部分.将PrintWriter视为未过滤的过滤器,您提供的任何内容都可以直接编写. GZIPOutputStream是一个gzip过滤器,它对给定的字节进行编码(gzip).
至于源代码,请在Java JDK安装中查看,您应该有一个src.zip文件,其中包含公共源代码,java.lang *,java.util.*,java.io.*,javax.*等. .
标签：servlet-3-0,gzipoutputstream,java,servlets,multipartform-data 来源： https://codeday.me/bug/20191012/1902920.html