java post带文件HTTP

/**
* 文件上传到微信服务器
* 
* @param fileType
*            文件类型
* @return JSONObject
* @throws Exception
*/
public static String postMethodWithFile(String url, String filePath)
{
String result = null;
File file = new File(filePath);
if (!file.exists() || !file.isFile())
{
try
{
throw new IOException("文件不存在");
} catch (IOException e)
{
e.printStackTrace();
}
}
/**
* 第一部分
*/
URL urlObj;
try
{
urlObj = new URL(url);
HttpURLConnection con = (HttpURLConnection) urlObj.openConnection();
con.setRequestMethod("POST"); // 以Post方式提交表单，默认get方式
con.setDoInput(true);
con.setDoOutput(true);
con.setUseCaches(false); // post方式不能使用缓存
// 设置请求头信息
con.setRequestProperty("Connection", "Keep-Alive");
con.setRequestProperty("Charset", "UTF-8");
// 设置边界
String BOUNDARY = "----------" + System.currentTimeMillis();
con.setRequestProperty("Content-Type", "multipart/form-data; boundary=" + BOUNDARY);
// 请求正文信息
// 第一部分：
StringBuilder sb = new StringBuilder();
sb.append("--"); // 必须多两道线
sb.append(BOUNDARY);
sb.append("\r\n");
sb.append("Content-Disposition: form-data;name=\"file\";filename=\"" + file.getName() + "\"\r\n");
sb.append("Content-Type:application/octet-stream\r\n\r\n");
byte[] head = sb.toString().getBytes("utf-8");
// 获得输出流
OutputStream out = new DataOutputStream(con.getOutputStream());
// 输出表头
out.write(head);
// 文件正文部分
// 把文件已流文件的方式 推入到url中
DataInputStream in = new DataInputStream(new FileInputStream(file));
int bytes = 0;
byte[] bufferOut = new byte[1024];
while ((bytes = in.read(bufferOut)) != -1)
{
out.write(bufferOut, 0, bytes);
}
in.close();
// 结尾部分
byte[] foot = ("\r\n--" + BOUNDARY + "--\r\n").getBytes("utf-8");// 定义最后数据分隔线
out.write(foot);
out.flush();
out.close();
StringBuffer buffer = new StringBuffer();
BufferedReader reader = null;
try
{
// 定义BufferedReader输入流来读取URL的响应
reader = new BufferedReader(new InputStreamReader(con.getInputStream()));
String line = null;
while ((line = reader.readLine()) != null)
{
// System.out.println(line);
buffer.append(line);
}
if (result == null)
{
result = buffer.toString();
}
} catch (IOException e)
{
System.out.println("发送POST请求出现异常！" + e);
e.printStackTrace();
throw new IOException("数据读取异常");
} finally
{
if (reader != null)
{
reader.close();
}
}
} catch (Exception e1)
{
e1.printStackTrace();
}

return result;
}