Java 中HttpURLConnection附件上传的实例详解

Java 中HttpURLConnection附件上传的实例详解

整合了一个自己写的采用Http做附件上传的工具，分享一下！

示例代码：

/**
 * 以Http协议传输文件
 *
 * @author mingxue.zhang@163.com
 *
 */
public class HttpPostUtil { 

  private final static char[] MULTIPART_CHARS = "-_1234567890abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
      .toCharArray(); 

  private URL url;
  private HttpURLConnection conn;
  private String boundary = null;
  private Map<String, String> textParams = new HashMap<String, String>();
  private Map<String, File> fileparams = new HashMap<String, File>(); 

  public HttpPostUtil(String url) throws Exception {
    this.url = new URL(url);
  } 

  // 重新设置要请求的服务器地址，即上传文件的地址。
  public void setUrl(String url) throws Exception {
    this.url = new URL(url);
  } 

  // 增加一个普通字符串数据到form表单数据中
  public void addTextParameter(String name, String value) {
    textParams.put(name, value);
  } 

  // 增加一个文件到form表单数据中
  public void addFileParameter(String name, File value) {
    fileparams.put(name, value);
  } 

  // 清空所有已添加的form表单数据
  public void clearAllParameters() {
    textParams.clear();
    fileparams.clear();
  } 

  /**
   * 发送数据到服务器
   *
   * @return 一个字节包含服务器的返回结果的数组
   * @throws Exception
   */
  public byte[] send() throws Exception {
    initConnection();
    try {
      conn.connect();
    } catch (SocketTimeoutException e) {
      throw new Exception(e);
    } 

    OutputStream connOutStream = new DataOutputStream(
        conn.getOutputStream()); 

    writeFileParams(connOutStream);
    writeStringParams(connOutStream);
    writesEnd(connOutStream); 

    InputStream responseInStream = conn.getInputStream();
    ByteArrayOutputStream responseOutStream = new ByteArrayOutputStream();
    int len;
    byte[] bufferByte = new byte[1024];
    while ((len = responseInStream.read(bufferByte)) != -1) {
      responseOutStream.write(bufferByte, 0, len);
    }
    responseInStream.close();
    connOutStream.close(); 

    conn.disconnect();
    byte[] resultByte = responseOutStream.toByteArray();
    responseOutStream.close();
    return resultByte;
  } 

  // 文件上传的connection的一些必须设置
  private void initConnection() throws Exception {
    StringBuffer buf = new StringBuffer("----");
    Random rand = new Random();
    for (int i = 0; i < 15; i++) {
      buf.append(MULTIPART_CHARS[rand.nextInt(MULTIPART_CHARS.length)]);
    }
    this.boundary = buf.toString(); 

    conn = (HttpURLConnection) this.url.openConnection();
    conn.setDoOutput(true);
    conn.setUseCaches(false);
    conn.setConnectTimeout(3 * 60 * 1000); // 连接超时为10秒
    conn.setRequestMethod("POST");
    conn.setRequestProperty("Content-Type",
        "multipart/form-data; boundary=" + boundary);
  } 

  // 普通字符串数据
  private void writeStringParams(OutputStream out) throws Exception {
    Set<String> keySet = textParams.keySet();
    for (Iterator<String> it = keySet.iterator(); it.hasNext();) {
      String name = it.next();
      String value = textParams.get(name); 

      out.write(("--" + boundary + "\r\n").getBytes());
      out.write(("Content-Disposition: form-data; name=\"" + name + "\"\r\n")
          .getBytes());
      out.write(("\r\n").getBytes());
      out.write((encode(value) + "\r\n").getBytes());
    }
  } 

  // 文件数据
  private void writeFileParams(OutputStream out) throws Exception {
    Set<String> keySet = fileparams.keySet();
    for (Iterator<String> it = keySet.iterator(); it.hasNext();) {
      String name = it.next();
      File value = fileparams.get(name); 

      out.write(("--" + boundary + "\r\n").getBytes());
      out.write(("Content-Disposition: form-data; name=\"" + name
          + "\"; filename=\"" + encode(value.getName()) + "\"\r\n")
          .getBytes());
      out.write(("Content-Type: " + getContentType(value) + "\r\n")
          .getBytes());
      out.write(("Content-Transfer-Encoding: " + "binary" + "\r\n")
          .getBytes()); 

      out.write(("\r\n").getBytes()); 

      FileInputStream inStream = new FileInputStream(value);
      int bytes = 0;
      byte[] bufferByte = new byte[1024];
      while ((bytes = inStream.read(bufferByte)) != -1) {
        out.write(bufferByte, 0, bytes);
      }
      inStream.close(); 

      out.write(("\r\n").getBytes());
    }
  } 

  // 添加结尾数据
  private void writesEnd(OutputStream out) throws Exception {
    out.write(("--" + boundary + "--" + "\r\n").getBytes());
    out.write(("\r\n").getBytes());
  } 

  // 获取文件的上传类型，图片格式为image/png,image/jpg等。非图片为application/octet-stream
  private String getContentType(File f) throws Exception {
    String fileName = f.getName();
    if (fileName.endsWith(".jpg")) {
      return "image/jpeg";
    } else if (fileName.endsWith(".png")) {
      return "image/png";
    }
    return "application/octet-stream";
  } 

  // 对包含中文的字符串进行转码，此为UTF-8。服务器那边要进行一次解码
  private String encode(String value) throws Exception {
    return URLEncoder.encode(value, "UTF-8");
  } 

}

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