浏览器上传大文件的尴尬
想上传超过1G的文件？
先来解读浏览器上传大文件的实际表现
1. IE 上传 1G 文件时，得到的Conent-Length 是不准确，上传3G，Content-Length 变为负数了。 囧
2. FireFox 添加后，点击提交没有反应。
再来看看标准协议 rfc1867.txt 里面有几点是关键内容
1. 上传的表单编码 必须是 multipart/form-data
2. 上传多个文件时格式有2种，一种是
Content-type: multipart/form-data, boundary=AaB03x
--AaB03x
content-disposition: form-data; name="field1"
Joe Blow
--AaB03x
content-disposition: form-data; name="pics"; filename="file1.txt"
Content-Type: text/plain
... contents of file1.txt ...
--AaB03x--
另一种是
Content-type: multipart/form-data, boundary=AaB03x
--AaB03x
content-disposition: form-data; name="field1"
Joe Blow
--AaB03x
content-disposition: form-data; name="pics"
Content-type: multipart/mixed, boundary=BbC04y
--BbC04y
Content-disposition: attachment; filename="file1.txt"
IE 采用的是第一种，
Java 实现注意的地方
1. Common-FileUpload
是个专门用来处理上传的公共包，里面有个 MultipartStream 可以直接用来解析协议内容。
2. 注意的是，需要要解析大文件流，不能设置Conent-Length，将此值设置为 -1 即可。如
3. 得到上传的文件名如果乱码，是因为设置的编码不对，需要设置为GBK编码。
最后，贴一下 用 JBoss Netty 实现的上传
import java.io.IOException; import java.io.InputStream; import java.util.List; import org.apache.commons.fileupload.FileItem; import org.apache.commons.fileupload.FileItemFactory; import org.apache.commons.fileupload.FileItemIterator; import org.apache.commons.fileupload.FileUpload; import org.apache.commons.fileupload.FileUploadException; import org.jboss.netty.handler.codec.http.HttpMethod; import org.jboss.netty.handler.codec.http.HttpRequest; /** * 用Netty来实现上传 */ public class NettyUploader extends FileUpload { public static final boolean isMultipartContent(HttpRequest request) { if (HttpMethod.POST != request.getMethod()) { return false; } if (request.getHeaders("Content-Type") == null && request.getHeaders("Content-Type").size() == 0) { return false; } String contentType = request.getHeaders("Content-Type").get(0); if (contentType == null) { return false; } if (contentType.toLowerCase().startsWith("multipart/")) { return true; } return false; } /** * 上传的内容流 */ private InputStream inputStream; public NettyUploader(InputStream inputStream) { this.inputStream = inputStream; } public NettyUploader(FileItemFactory fileItemFactory) { super(fileItemFactory); } @SuppressWarnings("unchecked") public List<FileItem> parseRequest(String encoding, String contentType, int contentLength) throws FileUploadException { return parseRequest(new NettyRequestContext(encoding, contentType, contentLength, inputStream)); } public FileItemIterator getItemIterator(String encoding, String contentType, int contentLength) throws FileUploadException, IOException { this.setHeaderEncoding(encoding == null ? "GBK" : encoding); return super.getItemIterator(new NettyRequestContext(encoding, contentType, contentLength, inputStream)); } }
import java.io.IOException; import java.io.InputStream; import org.apache.commons.fileupload.RequestContext; /** * 实现FileUploader */ public class NettyRequestContext implements RequestContext { private String encoding; private String contentType; private long contentLength = -1; /** * 上传的内容流 */ private InputStream inputStream; public NettyRequestContext(String encoding, String contentType, long contentLength, InputStream inputStream) { this.encoding = encoding; this.contentType = contentType; this.contentLength = contentLength; this.inputStream = inputStream; } public String getCharacterEncoding() { return encoding; // return request.getHeader("Character-Encoding"); } public String getContentType() { return contentType; // return request.getHeader("Content-Type"); } public int getContentLength() { return (int) contentLength; // return (int) request.getContentLength(); } public InputStream getInputStream() throws IOException { // return new ChannelBufferInputStream(request.getContent()); // 不能直接用request的流，因为有HttpChunk return inputStream; } public String toString() { return "ContentLength=" + this.getContentLength() + ", ContentType=" + this.getContentType(); } }
NettyUploader uploader = new NettyUploader(uploadStream); // 不能读取头，因为大文件，IE的都不是正确的 FileItemIterator iterator = uploader.getItemIterator(encoding, contentType, -1); int counts = 0; while (iterator.hasNext()) { .............. }