从 Java 客户端上传文件到 HTTP 服务器

Upload files from Java client to a HTTP server

提问by Marius

I'd like to upload a few files to a HTTP server. Basically what I need is some sort of a POST request to the server with a few parameters and the files. I've seen examples of just uploading files, but didn't find how to also pass additional parameters.

我想将一些文件上传到 HTTP 服务器。基本上我需要的是某种带有一些参数和文件的服务器的 POST 请求。我看过只上传文件的例子，但没有找到如何传递额外的参数。

What's the simplest and free solution of doing this? Does anyone have any file upload examples that I could study? I've been googling for a few hours, but (maybe it's just one of those days) couldn't find exactly what I needed. The best solution would be something that doesn't involve any third party classes or libraries.

这样做的最简单和免费的解决方案是什么？有没有人有任何我可以研究的文件上传示例？我已经用谷歌搜索了几个小时，但是（也许只是那些日子之一）找不到我需要的东西。最好的解决方案是不涉及任何第三方类或库的东西。

采纳答案by BalusC

You'd normally use java.net.URLConnectionto fire HTTP requests. You'd also normally use multipart/form-dataencoding for mixed POST content (binary and character data). Click the link, it contains information and an example how to compose a multipart/form-datarequest body. The specification is in more detail described in RFC2388.

您通常用于java.net.URLConnection触发 HTTP 请求。您通常还会multipart/form-data对混合的 POST 内容（二进制和字符数据）使用编码。单击该链接，它包含有关如何编写multipart/form-data请求正文的信息和示例。该规范在RFC2388中有更详细的描述。

Here's a kickoff example:

这是一个启动示例：

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()); // Just generate some unique random value.
String CRLF = "\r\n"; // Line separator required by multipart/form-data.

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); // Text file itself must be saved in this charset!
    writer.append(CRLF).flush();
    Files.copy(textFile.toPath(), output);
    output.flush(); // Important before continuing with writer!
    writer.append(CRLF).flush(); // CRLF is important! It indicates end of boundary.

    // 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(); // Important before continuing with writer!
    writer.append(CRLF).flush(); // CRLF is important! It indicates end of boundary.

    // 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); // Should be 200

This code is less verbose when you use a 3rd party library like Apache Commons HttpComponents Client.

当您使用 Apache Commons HttpComponents Client等 3rd 方库时，此代码就不那么冗长了。

The Apache Commons FileUploadas some incorrectly suggest here is only of interest in the server side. You can't use and don't need it at the client side.

Apache Commons FileUpload正如某些人在这里错误地建议的那样，只对服务器端感兴趣。您不能在客户端使用也不需要它。

See also

也可以看看

• Using java.net.URLConnection to fire and handle HTTP requests

• 使用 java.net.URLConnection 来触发和处理 HTTP 请求

回答by Karussell

It could depend on your framework. (for each of them could exist an easier solution).

这可能取决于您的框架。（对于它们中的每一个都可能存在一个更简单的解决方案）。

But to answer your question: there are a lot of external librariesfor this functionality. Look herehow to use apache commons fileupload.

但是要回答您的问题：此功能有很多外部库。看看这里如何使用 apache commons fileupload。

回答by Emmanuel Bourg

Here is how you would do it with Apache HttpClient(this solution is for those who don't mind using a 3rd party library):

以下是使用Apache HttpClient 的方法（此解决方案适用于不介意使用 3rd 方库的人）：

    HttpEntity entity = MultipartEntityBuilder.create()
                       .addPart("file", new FileBody(file))
                       .build();

    HttpPost request = new HttpPost(url);
    request.setEntity(entity);

    HttpClient client = HttpClientBuilder.create().build();
    HttpResponse response = client.execute(request);

回答by user1693371

protected void doPost(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {

    boolean isMultipart = ServletFileUpload.isMultipartContent(request);

    if (!isMultipart) {
        return;
    }

    DiskFileItemFactory factory = new DiskFileItemFactory();

    factory.setSizeThreshold(MAX_MEMORY_SIZE);

    factory.setRepository(new File(System.getProperty("java.io.tmpdir")));

    String uploadFolder = getServletContext().getRealPath("")
            + File.separator + DATA_DIRECTORY;//DATA_DIRECTORY is directory where you upload this file on the server

    ServletFileUpload upload = new ServletFileUpload(factory);

    upload.setSizeMax(MAX_REQUEST_SIZE);//MAX_REQUEST_SIZE is the size which size you prefer

And use <form enctype="multipart/form-data">and use <input type="file">in the html

并在html中使用<form enctype="multipart/form-data">和使用<input type="file">

回答by deeplinks

public static String simSearchByImgURL(int  catid ,String imgurl) throws IOException{
    CloseableHttpClient httpClient = HttpClients.createDefault();
    CloseableHttpResponse response = null;
    String result =null;
    try {
        HttpPost httppost = new HttpPost("http://api0.visualsearchapi.com:8084/vsearchtech/api/v1.0/apisim_search");
        StringBody catidBody = new StringBody(catid+"" , ContentType.TEXT_PLAIN);
        StringBody keyBody = new StringBody(APPKEY , ContentType.TEXT_PLAIN);
        StringBody langBody = new StringBody(LANG , ContentType.TEXT_PLAIN);
        StringBody fmtBody = new StringBody(FMT , ContentType.TEXT_PLAIN);
        StringBody imgurlBody = new StringBody(imgurl , ContentType.TEXT_PLAIN);
        MultipartEntityBuilder builder = MultipartEntityBuilder.create();
        builder.addPart("apikey", keyBody).addPart("catid", catidBody)
        .addPart("lang", langBody)
        .addPart("fmt", fmtBody)
        .addPart("imgurl", imgurlBody);
        HttpEntity reqEntity =  builder.build();
        httppost.setEntity(reqEntity);
        response = httpClient.execute(httppost);
        HttpEntity resEntity = response.getEntity();
        if (resEntity != null) {
           // result = ConvertStreamToString(resEntity.getContent(), "UTF-8");
            String charset = "UTF-8";   
          String content=EntityUtils.toString(response.getEntity(), charset);   
            System.out.println(content);
        }
        EntityUtils.consume(resEntity);
    }catch(Exception e){
        e.printStackTrace();
    }finally {
        response.close();
        httpClient.close();
    }
    return result;
}

回答by Prashant

click link get example file upload clint java with apache HttpComponents

单击链接获取示例文件上传 clint java with apache HttpComponents

http://hc.apache.org/httpcomponents-client-ga/httpmime/examples/org/apache/http/examples/entity/mime/ClientMultipartFormPost.java

http://hc.apache.org/httpcomponents-client-ga/httpmime/examples/org/apache/http/examples/entity/mime/ClientMultipartFormPost.java

and library downalod link

和图书馆下载链接

https://hc.apache.org/downloads.cgi

https://hc.apache.org/downloads.cgi

use 4.5.3.zip it's working fine in my code

使用 4.5.3.zip 它在我的代码中工作正常

and my working code..

和我的工作代码..

import java.io.File;
import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.entity.mime.content.FileBody;
import org.apache.http.entity.mime.content.StringBody;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public class ClientMultipartFormPost {

     public static void main(String[] args) throws Exception {

          CloseableHttpClient httpclient = HttpClients.createDefault();
          try {
             HttpPost httppost = new HttpPost("http://localhost:8080/MyWebSite1/UploadDownloadFileServlet");

             FileBody bin = new FileBody(new File("E:\meter.jpg"));
             StringBody comment = new StringBody("A binary file of some kind", ContentType.TEXT_PLAIN);

             HttpEntity reqEntity = MultipartEntityBuilder.create()
                .addPart("bin", bin)
                .addPart("comment", comment)
                .build();


             httppost.setEntity(reqEntity);

             System.out.println("executing request " + httppost.getRequestLine());
             CloseableHttpResponse response = httpclient.execute(httppost);
           try {
                System.out.println("----------------------------------------");
                System.out.println(response.getStatusLine());
                HttpEntity resEntity = response.getEntity();
                if (resEntity != null) {
                     System.out.println("Response content length: " +    resEntity.getContentLength());
                }
              EntityUtils.consume(resEntity);
             } finally {
                 response.close();
            }
       } finally {
          httpclient.close();
      }
   }

}

回答by Nils Samuelsson

Here is how you could do it with Java 11's java.net.http package:

以下是使用 Java 11 的 java.net.http 包的方法：

    var fileA = new File("a.pdf");
    var fileB = new File("b.pdf");

    var mimeMultipartData = MimeMultipartData.newBuilder()
            .withCharset(StandardCharsets.UTF_8)
            .addFile("file1", fileA.toPath(), Files.probeContentType(fileA.toPath()))
            .addFile("file2", fileB.toPath(), Files.probeContentType(fileB.toPath()))
            .build();

    var request = HttpRequest.newBuilder()
            .header("Content-Type", mimeMultipartData.getContentType())
            .POST(mimeMultipartData.getBodyPublisher())
            .uri(URI.create("http://somehost/upload"))
            .build();

    var httpClient = HttpClient.newBuilder().build();
    var response = httpClient.send(request, BodyHandlers.ofString());

With the following MimeMultipartData:

使用以下 MimeMultipartData：

public class MimeMultipartData {

    public static class Builder {

        private String boundary;
        private Charset charset = StandardCharsets.UTF_8;
        private List<MimedFile> files = new ArrayList<MimedFile>();
        private Map<String, String> texts = new LinkedHashMap<>();

        private Builder() {
            this.boundary = new BigInteger(128, new Random()).toString();
        }

        public Builder withCharset(Charset charset) {
            this.charset = charset;
            return this;
        }

        public Builder withBoundary(String boundary) {
            this.boundary = boundary;
            return this;
        }

        public Builder addFile(String name, Path path, String mimeType) {
            this.files.add(new MimedFile(name, path, mimeType));
            return this;
        }

        public Builder addText(String name, String text) {
            texts.put(name, text);
            return this;
        }

        public MimeMultipartData build() throws IOException {
            MimeMultipartData mimeMultipartData = new MimeMultipartData();
            mimeMultipartData.boundary = boundary;

            var newline = "\r\n".getBytes(charset);
            var byteArrayOutputStream = new ByteArrayOutputStream();
            for (var f : files) {
                byteArrayOutputStream.write(("--" + boundary).getBytes(charset)); 
                byteArrayOutputStream.write(newline);
                byteArrayOutputStream.write(("Content-Disposition: form-data; name=\"" + f.name + "\"; filename=\"" + f.path.getFileName() + "\"").getBytes(charset));
                byteArrayOutputStream.write(newline);
                byteArrayOutputStream.write(("Content-Type: " + f.mimeType).getBytes(charset));
                byteArrayOutputStream.write(newline);
                byteArrayOutputStream.write(newline);
                byteArrayOutputStream.write(Files.readAllBytes(f.path));
                byteArrayOutputStream.write(newline);
            }
            for (var entry: texts.entrySet()) {
                byteArrayOutputStream.write(("--" + boundary).getBytes(charset));
                byteArrayOutputStream.write(newline);
                byteArrayOutputStream.write(("Content-Disposition: form-data; name=\"" + entry.getKey() + "\"").getBytes(charset));
                byteArrayOutputStream.write(newline);
                byteArrayOutputStream.write(newline);
                byteArrayOutputStream.write(entry.getValue().getBytes(charset));
                byteArrayOutputStream.write(newline);
            }
            byteArrayOutputStream.write(("--" + boundary + "--").getBytes(charset));

            mimeMultipartData.bodyPublisher = BodyPublishers.ofByteArray(byteArrayOutputStream.toByteArray());
            return mimeMultipartData;
        }

        public class MimedFile {

            public final String name;
            public final Path path;
            public final String mimeType;

            public MimedFile(String name, Path path, String mimeType) {
                this.name = name;
                this.path = path;
                this.mimeType = mimeType;
            }
        }
    }

    private String boundary;
    private BodyPublisher bodyPublisher;

    private MimeMultipartData() {
    }

    public static Builder newBuilder() {
        return new Builder();
    }

    public BodyPublisher getBodyPublisher() throws IOException {
        return bodyPublisher;
    }

    public String getContentType() {
        return "multipart/form-data; boundary=" + boundary;
    }

}