java httpurlconnection 文件_Java-HttpURLConnection上传文件

Java中使用HttpURLConnection上传文件需要以下步骤：

1. 创建URL对象

URL url = new URL(uploadUrl);

2. 创建HttpURLConnection对象

HttpURLConnection conn = (HttpURLConnection) url.openConnection();

3. 设置请求方式为POST，设置其他请求头参数

conn.setRequestMethod("POST");
conn.setDoOutput(true);
conn.setDoInput(true);
conn.setUseCaches(false);
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("Connection", "Keep-Alive");
conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + BOUNDARY);

4. 创建输出流并将数据写入输出流

DataOutputStream outputStream = new DataOutputStream(conn.getOutputStream());
outputStream.writeBytes("--" + BOUNDARY + "\r\n");
outputStream.writeBytes("Content-Disposition: form-data; name=\"file\"; filename=\"" + file.getName() + "\"\r\n");
outputStream.writeBytes("\r\n");

FileInputStream fileInputStream = new FileInputStream(file);
byte[] buffer = new byte[1024];
int len;
while ((len = fileInputStream.read(buffer)) != -1) {
    outputStream.write(buffer, 0, len);
}

outputStream.writeBytes("\r\n--" + BOUNDARY + "--\r\n");

5. 获取响应结果

InputStream inputStream = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
String line;
StringBuilder result = new StringBuilder();
while ((line = reader.readLine()) != null) {
    result.append(line);
}

完整的代码示例：

public static void uploadFile(File file, String uploadUrl) throws Exception {
    String BOUNDARY = "---------------------------123821742118716";

    URL url = new URL(uploadUrl);
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();

    conn.setRequestMethod("POST");
    conn.setDoOutput(true);
    conn.setDoInput(true);
    conn.setUseCaches(false);
    conn.setRequestProperty("Charset", "UTF-8");
    conn.setRequestProperty("Connection", "Keep-Alive");
    conn.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + BOUNDARY);

    DataOutputStream outputStream = new DataOutputStream(conn.getOutputStream());
    outputStream.writeBytes("--" + BOUNDARY + "\r\n");
    outputStream.writeBytes("Content-Disposition: form-data; name=\"file\"; filename=\"" + file.getName() + "\"\r\n");
    outputStream.writeBytes("\r\n");

    FileInputStream fileInputStream = new FileInputStream(file);
    byte[] buffer = new byte[1024];
    int len;
    while ((len = fileInputStream.read(buffer)) != -1) {
        outputStream.write(buffer, 0, len);
    }

    outputStream.writeBytes("\r\n--" + BOUNDARY + "--\r\n");

    InputStream inputStream = conn.getInputStream();
    BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
    String line;
    StringBuilder result = new StringBuilder();
    while ((line = reader.readLine()) != null) {
        result.append(line);
    }

    outputStream.close();
    fileInputStream.close();
    inputStream.close();
    conn.disconnect();
}