HttpPost java上传文件封装方法

以下是一个简单的封装方法，可以用于上传单个文件：

public static String uploadFile(String url, File file) throws Exception {
    CloseableHttpClient httpClient = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost(url);
    MultipartEntityBuilder builder = MultipartEntityBuilder.create();
    builder.addPart("file", new FileBody(file));
    HttpEntity multipart = builder.build();
    httpPost.setEntity(multipart);
    CloseableHttpResponse response = httpClient.execute(httpPost);
    try {
        HttpEntity responseEntity = response.getEntity();
        return EntityUtils.toString(responseEntity, StandardCharsets.UTF_8);
    } finally {
        response.close();
    }
}

其中，`url` 为上传的目标地址，`file` 为待上传的文件对象。这个方法使用了 Apache HttpClient 和 MultipartEntityBuilder 来构建一个包含文件的 multipart/form-data 请求体，并发送到目标地址。上传成功后，返回服务器的响应内容（假设为字符串类型）。