使用 Java 中的附加参数将文件上传到 HTTP 服务器
将文件上传到 HTTP 服务器是许多应用程序的常见需求。但是,有时还需要随文件一起传递附加参数。这是一个允许您在不使用外部库的情况下发送文件和参数的解决方案:
java.net.URLConnection 和 Multipart/Form-Data
发送文件和参数,您将利用 java.net.URLConnection 并采用 multipart/form-data 编码。 Multipart/form-data 允许您在单个 HTTP 请求中混合二进制数据(文件)和字符数据(参数)。
示例代码:
<code class="java">String url = "http://example.com/upload"; String charset = "UTF-8"; String param = "value"; File textFile = new File("/path/to/file.txt"); File binaryFile = new File("/path/to/file.bin"); String boundary = Long.toHexString(System.currentTimeMillis()); String CRLF = "\r\n"; URLConnection connection = new URL(url).openConnection(); connection.setDoOutput(true); connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary); try ( OutputStream output = connection.getOutputStream(); PrintWriter writer = new PrintWriter(new OutputStreamWriter(output, charset), true); ) { // Send normal param. writer.append("--" + boundary).append(CRLF); writer.append("Content-Disposition: form-data; name=\"param\"").append(CRLF); writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF); writer.append(CRLF).append(param).append(CRLF).flush(); // Send text file. writer.append("--" + boundary).append(CRLF); writer.append("Content-Disposition: form-data; name=\"textFile\"; filename=\"" + textFile.getName() + "\"").append(CRLF); writer.append("Content-Type: text/plain; charset=" + charset).append(CRLF); writer.append(CRLF).flush(); Files.copy(textFile.toPath(), output); output.flush(); writer.append(CRLF).flush(); // Send binary file. writer.append("--" + boundary).append(CRLF); writer.append("Content-Disposition: form-data; name=\"binaryFile\"; filename=\"" + binaryFile.getName() + "\"").append(CRLF); writer.append("Content-Type: " + URLConnection.guessContentTypeFromName(binaryFile.getName())).append(CRLF); writer.append("Content-Transfer-Encoding: binary").append(CRLF); writer.append(CRLF).flush(); Files.copy(binaryFile.toPath(), output); output.flush(); writer.append(CRLF).flush(); // End of multipart/form-data. writer.append("--" + boundary + "--").append(CRLF).flush(); } // Request is lazily fired whenever you need to obtain information about response. int responseCode = ((HttpURLConnection) connection).getResponseCode(); System.out.println(responseCode); </code>
附加说明:
参考:
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