我想从本地计算机发送到OCR图像，而不是那里有图像的远程URL（这种情况下效果很好）。但是问题是，我不知道如何正确构造多部分实体的有效负载。我的有效负载应如下所述。
这就是documentation of API中描述的内容。解码直接在多部分/相关数据中给出的图像数据。顺序很重要，第一部分应该是JSON，它告诉它使用哪个OCR引擎。 JSON的模式记录在/ocr端点中。在这种情况下，JSON的img_url参数将被忽略。
图片附件应为 second 部分，并且应适用于任何图片内容类型（例如image / png，image / jpg等）。
Request (multipart/related; boundary=---BOUNDARY)
-----BOUNDARY
Content-Type: application/json
{"engine":"tesseract"}
-----BOUNDARY
-----BOUNDARY
Content-Disposition: attachment;
Content-Type: image/png
filename="attachment.txt".
PNGDATA.........
-----BOUNDARY
这就是我尝试过的。要执行多部分/相关请求，我正在使用org.apache.httpcomponents
CloseableHttpClient httpClient = HttpClients.createDefault();
MultipartEntityBuilder multipartEntityBuilder =
MultipartEntityBuilder.create().setBoundary(BOUNDARY).setContentType(ContentType.APPLICATION_JSON).addTextBody("engine", "tesseract")
.setBoundary(BOUNDARY).setBoundary(BOUNDARY);
multipartEntityBuilder.addBinaryBody("file_upload", new File(fileTextPath), ContentType.create(CONTENT_TYPE), fileTextPath).setBoundary(BOUNDARY);
HttpEntity entity = multipartEntityBuilder.build();
HttpPost httpPost = new HttpPost(URL);
httpPost.setHeader(HttpHeaders.CONTENT_TYPE, CONTENT_TYPE_MULTIPART+";boundary="+BOUNDARY);
httpPost.setEntity(entity);
答案 0 :(得分：0)
几周前我解决了这个问题，为方便起见，为这两种情况（远程和文件上传）创建了一个lightweight java web application。
您可以在here以上找到有关该问题的特定答案。多部分请求的源代码如下所示：
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.UUID;
public class MultipartUtility {
private static final Logger logger = LoggerFactory.getLogger(MultipartUtility.class);
private final String boundary = UUID.randomUUID().toString();
private static final String LINE_FEED = "\r\n";
private HttpURLConnection httpConn;
private String charset;
private OutputStream outputStream;
private PrintWriter writer;
/**
* This constructor initializes a new HTTP POST request with content type
* is set to multipart/form-data
*
* @param requestURL
* @param charset
* @throws IOException
*/
public MultipartUtility(String requestURL, String charset) {
this.charset = charset;
try {
URL url = new URL(requestURL);
httpConn = (HttpURLConnection) url.openConnection();
httpConn.setUseCaches(false);
httpConn.setDoOutput(true); // indicates POST method
httpConn.setDoInput(true);
httpConn.setRequestProperty("Content-Type", "multipart/related; boundary=\"" + boundary + "\"");
httpConn.setRequestProperty("Accept-Encoding", "gzip");
outputStream = httpConn.getOutputStream();
//outputStream = System.out;
writer = new PrintWriter(new OutputStreamWriter(outputStream, charset), true);
} catch (IOException ex) {
logger.error("Error during creation of MultiPart: ", ex);
}
}
/**
* Adds a form field to the request
*/
public void addFormField(String jsonBody) {
writer.append("--").append(boundary).append(LINE_FEED);
writer.append("Content-Type: application/json;").append(LINE_FEED);
writer.append(LINE_FEED);
writer.append(jsonBody).append(LINE_FEED);
writer.flush();
}
/**
* Adds a upload file section to the request
*
* @param uploadFile a File to be uploaded
* @throws IOException
*/
public void addFilePart(File uploadFile) {
String fileName = uploadFile.getName();
writer.append("--").append(boundary).append(LINE_FEED);
writer.append("Content-Disposition: attachment;");
writer.append(" filename=\"" + fileName + "\".").append(LINE_FEED);
writer.append("Content-Type: image/*").append(LINE_FEED);
writer.append(LINE_FEED);
writer.flush();
try {
FileInputStream inputStream = new FileInputStream(uploadFile);
//byte[] buffer = new byte[(int) uploadFile.length()];
byte[] buffer = Files.readAllBytes(Paths.get(uploadFile.getPath()));
int bytesRead = -1;
while ((bytesRead = inputStream.read(buffer)) != -1) {
outputStream.write(buffer, 0, bytesRead);
}
outputStream.flush();
inputStream.close();
} catch (IOException ex) {
logger.error("File transformation to bytes went wrong: {}", ex);
}
writer.append(LINE_FEED);
writer.flush();
}
/**
* Adds a header field to the request.
*
* @param name - name of the header field
* @param value - value of the header field
*/
public void addHeaderField(String name, String value) {
writer.append(name + ": " + value).append(LINE_FEED);
writer.flush();
}
/**
* Completes the request and receives response from the server.
*
* @return a list of Strings as response in case the server returned
* status OK, otherwise an exception is thrown.
* @throws IOException
*/
public String finish() {
String response = "";
int status = 0;
writer.flush();
writer.append("--").append(boundary).append("--").append(LINE_FEED);
writer.println();
writer.close();
try {
// checks server's status code first
status = httpConn.getResponseCode();
if (status == HttpURLConnection.HTTP_OK) {
BufferedReader reader = new BufferedReader(new InputStreamReader(httpConn.getInputStream()));
String line;
while ((line = reader.readLine()) != null) {
response += line;
}
reader.close();
httpConn.disconnect();
} else {
logger.error("OCR API returned error stream: {}", printErrorStream());
throw new IOException("Server returned non-OK status: " + status + " : " + httpConn.getResponseMessage());
//logger.error("Server returned non-OK status: " + status + " : " + httpConn.getResponseMessage());
}
} catch(IOException ex) {
logger.error("Response message in Multipart finish has been received with problems: ", ex);
}
return response;
}
private String printErrorStream() throws IOException {
//System.out.print("DEBUG System out ocr API error stream: ");
InputStream errorStream = httpConn.getErrorStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(errorStream));
String errLine = "", tempLine;
while ((tempLine = reader.readLine()) != null) {
errLine += tempLine;
}
return errLine;
}
private void getRequestHeaders(HttpURLConnection httpURLConnection) {
for (Map.Entry<String, List<String>> entries : httpURLConnection.getRequestProperties().entrySet()) {
String values = "";
for (String value : entries.getValue()) {
values += value + ",";
}
System.out.println("Request" + " " + entries.getKey() + " - " + values );
}
}
}