java form-data

发送请求的方式有哪些？如何设置Content-Type为multipart/form-data？

Java发送form-data请求的方式有多种，其中常用的有使用HttpURLConnection和HttpClient两种方式。使用HttpURLConnection发送form-data请求的示例代码如下：

    URL url = new URL("http://example.com/upload");
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod("POST");
    connection.setDoOutput(true);
    connection.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + boundary);
    OutputStream outputStream = connection.getOutputStream();
    // 将form-data数据写入outputStream
    outputStream.close();
    // 处理响应数据

使用HttpClient发送form-data请求的示例代码如下：

    CloseableHttpClient httpClient = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://example.com/upload");
    MultipartEntityBuilder builder = MultipartEntityBuilder.create();
    builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);
    // 添加form-data数据
    HttpEntity entity = builder.build();
    httpPost.setEntity(entity);
    CloseableHttpResponse response = httpClient.execute(httpPost);
    // 处理响应数据

要设置Content-Type为multipart/form-data，需要在请求头中添加"Content-Type"字段，值为"multipart/form-data; boundary=" + boundary，其中boundary为分隔符，用于分隔不同的form-data数据。