Java 9 HttpClient 發送多部分/表單數據請求

Question

下面是一個表格：

<form action="/example/html5/demo_form.asp" method="post" 
enctype=”multipart/form-data”>
   <input type="file" name="img" />
   <input type="text" name=username" value="foo"/>
   <input type="submit" />
</form>

何時提交此表單，請求將如下所示：

POST /example/html5/demo_form.asp HTTP/1.1
Host: 10.143.47.59:9093
Connection: keep-alive
Content-Length: 326
Accept: application/json, text/javascript, */*; q=0.01
Origin: http://10.143.47.59:9093
X-Requested-With: XMLHttpRequest
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.90 Safari/537.36
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryEDKBhMZFowP9Leno
Accept-Encoding: gzip, deflate
Accept-Language: en-US,en;q=0.8,zh-CN;q=0.6,zh;q=0.4

Request Payload
------WebKitFormBoundaryEDKBhMZFowP9Leno
Content-Disposition: form-data; name="username"

foo
------WebKitFormBoundaryEDKBhMZFowP9Leno
Content-Disposition: form-data; name="img"; filename="out.txt"
Content-Type: text/plain


------WebKitFormBoundaryEDKBhMZFowP9Leno--

請注意“Request Payload”，在form中可以看到兩個參數，username和img(form-data; name="img"; filename="out.txt")，finename就是文件系統中的真實文件名（或路徑），您將在后端（例如彈簧控制器）中按名稱（而不是文件名）接收文件。
如果我們使用Apache Httpclient來模擬請求，我們會寫這樣的代碼：

MultipartEntity mutiEntity = newMultipartEntity();
File file = new File("/path/to/your/file");
mutiEntity.addPart("username",new StringBody("foo", Charset.forName("utf-8")));
mutiEntity.addPart("img", newFileBody(file)); //img is name, file is path

但是在 java 9 中，我們可以編寫這樣的代碼：

HttpClient client = HttpClient.newHttpClient();
HttpRequest request = HttpRequest.
        newBuilder(new URI("http:///example/html5/demo_form.asp"))
       .method("post",HttpRequest.BodyProcessor.fromString("foo"))
       .method("post", HttpRequest.BodyProcessor.fromFile(Paths.get("/path/to/your/file")))
       .build();
HttpResponse response = client.send(request, HttpResponse.BodyHandler.asString());
System.out.println(response.body());

現在您明白了，我如何設置參數的“名稱”？

Answer 1

我想在不需要引入 Apache 客戶端的情況下為項目執行此操作，因此我編寫了一個MultiPartBodyPublisher （Java 11，僅供參考）：

import java.io.IOException;
import java.io.InputStream;
import java.io.UncheckedIOException;
import java.net.http.HttpRequest;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.*;
import java.util.function.Supplier;

public class MultiPartBodyPublisher {
    private List<PartsSpecification> partsSpecificationList = new ArrayList<>();
    private String boundary = UUID.randomUUID().toString();

    public HttpRequest.BodyPublisher build() {
        if (partsSpecificationList.size() == 0) {
            throw new IllegalStateException("Must have at least one part to build multipart message.");
        }
        addFinalBoundaryPart();
        return HttpRequest.BodyPublishers.ofByteArrays(PartsIterator::new);
    }

    public String getBoundary() {
        return boundary;
    }

    public MultiPartBodyPublisher addPart(String name, String value) {
        PartsSpecification newPart = new PartsSpecification();
        newPart.type = PartsSpecification.TYPE.STRING;
        newPart.name = name;
        newPart.value = value;
        partsSpecificationList.add(newPart);
        return this;
    }

    public MultiPartBodyPublisher addPart(String name, Path value) {
        PartsSpecification newPart = new PartsSpecification();
        newPart.type = PartsSpecification.TYPE.FILE;
        newPart.name = name;
        newPart.path = value;
        partsSpecificationList.add(newPart);
        return this;
    }

    public MultiPartBodyPublisher addPart(String name, Supplier<InputStream> value, String filename, String contentType) {
        PartsSpecification newPart = new PartsSpecification();
        newPart.type = PartsSpecification.TYPE.STREAM;
        newPart.name = name;
        newPart.stream = value;
        newPart.filename = filename;
        newPart.contentType = contentType;
        partsSpecificationList.add(newPart);
        return this;
    }

    private void addFinalBoundaryPart() {
        PartsSpecification newPart = new PartsSpecification();
        newPart.type = PartsSpecification.TYPE.FINAL_BOUNDARY;
        newPart.value = "--" + boundary + "--";
        partsSpecificationList.add(newPart);
    }

    static class PartsSpecification {

        public enum TYPE {
            STRING, FILE, STREAM, FINAL_BOUNDARY
        }

        PartsSpecification.TYPE type;
        String name;
        String value;
        Path path;
        Supplier<InputStream> stream;
        String filename;
        String contentType;

    }

    class PartsIterator implements Iterator<byte[]> {

        private Iterator<PartsSpecification> iter;
        private InputStream currentFileInput;

        private boolean done;
        private byte[] next;

        PartsIterator() {
            iter = partsSpecificationList.iterator();
        }

        @Override
        public boolean hasNext() {
            if (done) return false;
            if (next != null) return true;
            try {
                next = computeNext();
            } catch (IOException e) {
                throw new UncheckedIOException(e);
            }
            if (next == null) {
                done = true;
                return false;
            }
            return true;
        }

        @Override
        public byte[] next() {
            if (!hasNext()) throw new NoSuchElementException();
            byte[] res = next;
            next = null;
            return res;
        }

        private byte[] computeNext() throws IOException {
            if (currentFileInput == null) {
                if (!iter.hasNext()) return null;
                PartsSpecification nextPart = iter.next();
                if (PartsSpecification.TYPE.STRING.equals(nextPart.type)) {
                    String part =
                            "--" + boundary + "\r\n" +
                            "Content-Disposition: form-data; name=" + nextPart.name + "\r\n" +
                            "Content-Type: text/plain; charset=UTF-8\r\n\r\n" +
                            nextPart.value + "\r\n";
                    return part.getBytes(StandardCharsets.UTF_8);
                }
                if (PartsSpecification.TYPE.FINAL_BOUNDARY.equals(nextPart.type)) {
                    return nextPart.value.getBytes(StandardCharsets.UTF_8);
                }
                String filename;
                String contentType;
                if (PartsSpecification.TYPE.FILE.equals(nextPart.type)) {
                    Path path = nextPart.path;
                    filename = path.getFileName().toString();
                    contentType = Files.probeContentType(path);
                    if (contentType == null) contentType = "application/octet-stream";
                    currentFileInput = Files.newInputStream(path);
                } else {
                    filename = nextPart.filename;
                    contentType = nextPart.contentType;
                    if (contentType == null) contentType = "application/octet-stream";
                    currentFileInput = nextPart.stream.get();
                }
                String partHeader =
                        "--" + boundary + "\r\n" +
                        "Content-Disposition: form-data; name=" + nextPart.name + "; filename=" + filename + "\r\n" +
                        "Content-Type: " + contentType + "\r\n\r\n";
                return partHeader.getBytes(StandardCharsets.UTF_8);
            } else {
                byte[] buf = new byte[8192];
                int r = currentFileInput.read(buf);
                if (r > 0) {
                    byte[] actualBytes = new byte[r];
                    System.arraycopy(buf, 0, actualBytes, 0, r);
                    return actualBytes;
                } else {
                    currentFileInput.close();
                    currentFileInput = null;
                    return "\r\n".getBytes(StandardCharsets.UTF_8);
                }
            }
        }
    }
}

您可以像這樣使用它：

MultiPartBodyPublisher publisher = new MultiPartBodyPublisher()
       .addPart("someString", "foo")
       .addPart("someInputStream", () -> this.getClass().getResourceAsStream("test.txt"), "test.txt", "text/plain")
       .addPart("someFile", pathObject);
HttpRequest request = HttpRequest.newBuilder()
       .uri(URI.create("https://www.example.com/dosomething"))
       .header("Content-Type", "multipart/form-data; boundary=" + publisher.getBoundary())
       .timeout(Duration.ofMinutes(1))
       .POST(publisher.build())
       .build();

請注意，輸入流的addPart實際上采用Supplier<InputStream>而不僅僅是InputStream 。

Answer 2

您可以實現多形式數據調用的方向如下：

BodyProcessor可以與它們的默認實現一起使用，或者也可以使用自定義實現。 使用它們的方法很少：

1. 通過字符串讀取處理器為：

    HttpRequest.BodyProcessor dataProcessor = HttpRequest.BodyProcessor.fromString("{\\"username\\":\\"foo\\"}")

2. 使用文件路徑從文件創建處理器

   Path path = Paths.get("/path/to/your/file"); // in your case path to 'img' HttpRequest.BodyProcessor fileProcessor = HttpRequest.BodyProcessor.fromFile(path);

或

3. 您可以使用apache.commons.lang （或您可以提出的自定義方法）將文件輸入轉換為字節數組，以添加一個小工具，如：

    org.apache.commons.fileupload.FileItem file; org.apache.http.HttpEntity multipartEntity = org.apache.http.entity.mime.MultipartEntityBuilder.create() .addPart("username",new StringBody("foo", Charset.forName("utf-8"))) .addPart("img", newFileBody(file)) .build(); multipartEntity.writeTo(byteArrayOutputStream); byte[] bytes = byteArrayOutputStream.toByteArray();

   然后 byte[] 可以與BodyProcessor一起使用：

    HttpRequest.BodyProcessor byteProcessor = HttpRequest.BodyProcessor.fromByteArray();

---

此外，您可以將請求創建為：

HttpRequest request = HttpRequest.newBuilder()
            .uri(new URI("http:///example/html5/demo_form.asp"))
            .headers("Content-Type","multipart/form-data","boundary","boundaryValue") // appropriate boundary values
            .POST(dataProcessor)
            .POST(fileProcessor)
            .POST(byteProcessor) //self-sufficient
            .build();

---

相同的響應可以作為文件處理，並使用新的HttpClient處理

HttpResponse.BodyHandler bodyHandler = HttpResponse.BodyHandler.asFile(Paths.get("/path"));

HttpClient client = HttpClient.newBuilder().build();

如：

HttpResponse response = client.send(request, bodyHandler);
System.out.println(response.body());

Answer 3

您可以使用甲醇。 它包含一個MultipartBodyPublisher和一個方便易用的MultipartBodyPublisher.Builder 。 這是使用它的示例（需要 JDK11 或更高版本）：

var multipartBody = MultipartBodyPublisher.newBuilder()
    .textPart("foo", "foo_text")
    .filePart("bar", Path.of("path/to/file.txt"))
    .formPart("baz", BodyPublishers.ofInputStream(() -> ...))
    .build();
var request = HttpRequest.newBuilder()
    .uri(URI.create("https://example.com/"))
    .POST(multipartBody)
    .build();

請注意，您可以添加任何您想要的BodyPublisher或HttpHeaders 。 查看文檔以獲取更多信息。

Answer 4

可以使用multipart/form-data或任何其他內容類型 - 但您必須自己以正確的格式對正文進行編碼。 客戶端本身不會根據內容類型進行任何編碼。

這意味着您最好的選擇是使用另一個 HTTP 客戶端，例如Apache HttpComponents客戶端，或者只使用另一個庫的編碼器，例如@nullpointer的答案示例。

---

如果您自己對主體進行編碼，請注意您不能多次調用POST等方法。 POST只是設置BodyProcessor並再次調用它只會覆蓋任何先前設置的處理器。 您必須實現一個以正確格式生成整個身體的處理器。

對於multipart/form-data ，這意味着：

1. 將boundary標頭設置為適當的值

2. 編碼每個參數，使其在您的示例中看起來像。 對於文本輸入，基本上是這樣的：

    boundary + "\\nContent-Disposition: form-data; name=\\"" + name + "\\"\\n\\n" + value + "\\n"

   這里，名稱指的是 HTML 表單中的name屬性。 對於問題中的文件輸入，這將是img ，值將是編碼的文件內容。

Answer 5

我在這個問題上掙扎了一段時間，即使在看到和閱讀了這個頁面之后。 但是，使用此頁面上的答案為我指明了正確的方向，閱讀了有關多部分表單和邊界的更多信息，並進行了修補，我能夠創建一個可行的解決方案。

解決方案的要點是使用 Apache 的 MultipartEntityBuilder 創建實體及其邊界（ HttpExceptionBuilder是一個本土類）：

import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.util.Optional;
import java.util.function.Supplier;

import org.apache.commons.lang3.Validate;
import org.apache.http.HttpEntity;
import org.apache.http.entity.BufferedHttpEntity;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.mime.MultipartEntityBuilder;

/**
 * Class containing static helper methods pertaining to HTTP interactions.
 */
public class HttpUtils {
    public static final String MULTIPART_FORM_DATA_BOUNDARY = "ThisIsMyBoundaryThereAreManyLikeItButThisOneIsMine";

    /**
     * Creates an {@link HttpEntity} from a {@link File}, loading it into a {@link BufferedHttpEntity}.
     *
     * @param file     the {@link File} from which to create an {@link HttpEntity}
     * @param partName an {@link Optional} denoting the name of the form data; defaults to {@code data}
     * @return an {@link HttpEntity} containing the contents of the provided {@code file}
     * @throws NullPointerException  if {@code file} or {@code partName} is null
     * @throws IllegalStateException if {@code file} does not exist
     * @throws HttpException         if file cannot be found or {@link FileInputStream} cannot be created
     */
    public static HttpEntity getFileAsBufferedMultipartEntity(final File file, final Optional<String> partName) {
        Validate.notNull(file, "file cannot be null");
        Validate.validState(file.exists(), "file must exist");
        Validate.notNull(partName, "partName cannot be null");

        final HttpEntity entity;
        final BufferedHttpEntity bufferedHttpEntity;

        try (final FileInputStream fis = new FileInputStream(file);
                final BufferedInputStream bis = new BufferedInputStream(fis)) {
            entity = MultipartEntityBuilder.create().setBoundary(MULTIPART_FORM_DATA_BOUNDARY)
                    .addBinaryBody(partName.orElse("data"), bis, ContentType.APPLICATION_OCTET_STREAM, file.getName())
                    .setContentType(ContentType.MULTIPART_FORM_DATA).build();

            try {
                bufferedHttpEntity = new BufferedHttpEntity(entity);
            } catch (final IOException e) {
                throw HttpExceptionBuilder.create().withMessage("Unable to create BufferedHttpEntity").withThrowable(e)
                        .build();
            }
        } catch (final FileNotFoundException e) {
            throw HttpExceptionBuilder.create()
                    .withMessage("File does not exist or is not readable: %s", file.getAbsolutePath()).withThrowable(e)
                    .build();
        } catch (final IOException e) {
            throw HttpExceptionBuilder.create()
                    .withMessage("Unable to create multipart entity from file: %s", file.getAbsolutePath())
                    .withThrowable(e).build();
        }

        return bufferedHttpEntity;
    }

    /**
     * Returns a {@link Supplier} of {@link InputStream} containing the content of the provided {@link HttpEntity}. This
     * method closes the {@code InputStream}.
     *
     * @param entity the {@link HttpEntity} from which to get an {@link InputStream}
     * @return an {@link InputStream} containing the {@link HttpEntity#getContent() content}
     * @throws NullPointerException if {@code entity} is null
     * @throws HttpException        if something goes wrong
     */
    public static Supplier<? extends InputStream> getInputStreamFromHttpEntity(final HttpEntity entity) {
        Validate.notNull(entity, "entity cannot be null");

        return () -> {
            try (final InputStream is = entity.getContent()) {
                return is;
            } catch (final UnsupportedOperationException | IOException e) {
                throw HttpExceptionBuilder.create().withMessage("Unable to get InputStream from HttpEntity")
                        .withThrowable(e).build();
            }
        };
    }
}

然后是使用這些輔助方法的方法：

private String doUpload(final File uploadFile, final String filePostUrl) {
    assert uploadFile != null : "uploadFile cannot be null";
    assert uploadFile.exists() : "uploadFile must exist";
    assert StringUtils.notBlank(filePostUrl, "filePostUrl cannot be blank");

    final URI uri = URI.create(filePostUrl);
    final HttpEntity entity = HttpUtils.getFileAsBufferedMultipartEntity(uploadFile, Optional.of("partName"));
    final String response;

    try {
        final Builder requestBuilder = HttpRequest.newBuilder(uri)
                .POST(BodyPublisher.fromInputStream(HttpUtils.getInputStreamFromHttpEntity(entity)))
                .header("Content-Type", "multipart/form-data; boundary=" + HttpUtils.MULTIPART_FORM_DATA_BOUNDARY);

        response = this.httpClient.send(requestBuilder.build(), BodyHandler.asString());
    } catch (InterruptedException | ExecutionException e) {
        throw HttpExceptionBuilder.create().withMessage("Unable to get InputStream from HttpEntity")
                    .withThrowable(e).build();
    }

    LOGGER.info("Http Response: {}", response);
    return response;
}

Answer 6

雖然正確答案是全面實施並且可能是正確的，但它對我不起作用。

我的解決方案從這里獲得靈感。 我剛剛清理了我的用例不需要的部分。 我個人使用多部分表單僅上傳圖片或 zip 文件（單數）。 代碼：

    public static HttpRequest buildMultiformRequest(byte[] body) {
        String boundary = "-------------" + UUID.randomUUID().toString();
        Map<String, byte[]> data = Map.of("formFile", body);

        return HttpRequest.newBuilder()
                .uri(URI.create(<URL>))
                .POST(HttpRequest.BodyPublishers.ofByteArrays(buildMultipartData(data, boundary, "filename.jpeg", MediaType.IMAGE_JPEG_VALUE)))
                .header("Content-Type", "multipart/form-data; boundary=" + boundary)
                .header("Accept", MediaType.APPLICATION_JSON_VALUE)
                .timeout(Duration.of(5, ChronoUnit.SECONDS))
                .build();
    }

    public static ArrayList<byte[]> buildMultipartData(Map<String, byte[]> data, String boundary, String filename, String mediaType) {
        var byteArrays = new ArrayList<byte[]>();
        var separator = ("--" + boundary + "\r\nContent-Disposition: form-data; name=").getBytes(StandardCharsets.UTF_8);

        for (var entry : data.entrySet()) {
            byteArrays.add(separator);
            byteArrays.add(("\"" + entry.getKey() + "\"; filename=\"" + filename + "\"\r\nContent-Type:" + mediaType + "\r\n\r\n").getBytes(StandardCharsets.UTF_8));
            byteArrays.add(entry.getValue());
            byteArrays.add("\r\n".getBytes(StandardCharsets.UTF_8));
        }

        byteArrays.add(("--" + boundary + "--").getBytes(StandardCharsets.UTF_8));
        return byteArrays;
    }

Answer 7

以下對我BodyPublisher.ofString ，即在內存中創建一個原始 HTTP 正文作為字符串，然后使用標准BodyPublisher.ofString ：

以下鏈接顯示了正文的外觀： https : //developer.mozilla.org/en-US/docs/Web/HTTP/Methods/POST

String data = "--boundary\nContent-Disposition: form-data; name=\"type\"\r\n\r\nserverless";
byte[] fileContents = Files.readAllBytes(f.toPath());
data += "\r\n--boundary\nContent-Disposition: form-data; name=\"filename\"; filename=\""
        + f.getName() + "\"\r\n\r\n" + new String(fileContents, StandardCharsets.ISO_8859_1); // iso-8859-1 is http default
data += "\r\n--boundary--"; // end boundary

HttpRequest.BodyPublisher bodyPublisher = HttpRequest.BodyPublishers.ofString(data, StandardCharsets.ISO_8859_1);

HttpRequest request = HttpRequest.newBuilder()
                    .uri(uri)
                    .setHeader("Content-Type", "multipart/form-data;boundary=\"boundary\"")
                    .POST(bodyPublisher).build();
HttpResponse<String> response = getClient().send(request, HttpResponse.BodyHandlers.ofString());

注意\\r\\n而不是只是說\\n - 我用 Apache Commons File Upload 測試了這個，它期望兩者，可能是因為這是 RFC 所期望的。

另請注意使用 ISO-8859-1 而不是 UTF-8。 我使用它是因為它是標准 - 我沒有用 UTF-8 測試它 - 如果服務器也以這種方式配置，它可能會工作。

getClient大致是這樣做的：

HttpClient.newBuilder()
    .version(HttpClient.Version.HTTP_1_1)
    .connectTimeout(Duration.ofSeconds(20))
    .build()