Java中使用httputil如何发送form-data请求

Java中的`httputil`没有原生的实现，但是可以使用`Apache HttpClient`库来发送`form-data`请求。以下是一个示例代码：

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.HttpMultipartMode;
import org.apache.http.entity.mime.MultipartEntityBuilder;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import java.io.File;
import java.io.IOException;

public class HttpUtil {

    public static CloseableHttpResponse sendFormData(String url, String fieldName, String fileName) throws IOException {
        CloseableHttpClient client = HttpClients.createDefault();
        HttpPost httpPost = new HttpPost(url);

        // 创建 multipart 请求体
        MultipartEntityBuilder builder = MultipartEntityBuilder.create();
        builder.setMode(HttpMultipartMode.BROWSER_COMPATIBLE);
        builder.addBinaryBody(fieldName, new File(fileName), ContentType.DEFAULT_BINARY, fileName);

        HttpEntity entity = builder.build();
        httpPost.setEntity(entity);

        // 发送请求
        CloseableHttpResponse response = client.execute(httpPost);

        // 处理响应
        System.out.println(response.getStatusLine());
        return response;
    }
}

在调用此函数时，您需要提供目标URL，表单字段名称和文件名。例如：

try {
    CloseableHttpResponse response = HttpUtil.sendFormData("http://example.com/upload", "file", "/path/to/file");
    // 处理响应
} catch (IOException e) {
    e.printStackTrace();
}

请注意，您需要在代码中处理任何可能的异常，例如在发送请求或处理响应时发生的错误。