POST请求

public static String post(String url,Map<String, Object> param) {
    StringBuilder builder=new StringBuilder();
    try {
        StringBuilder params=new StringBuilder();
        for(Map.Entry<String, Object> entry:param.entrySet()){
            params.append(entry.getKey());
            params.append("=");
            params.append(entry.getValue().toString());
            params.append("&");
        }
        if(params.length()>0){
            params.deleteCharAt(params.lastIndexOf("&"));
        }
        URL restServiceURL = new URL(url+(params.length()>0 ? "?"+params.toString() : ""));
        HttpURLConnection httpConnection = (HttpURLConnection) restServiceURL.openConnection();
        httpConnection.setRequestMethod("POST");
        httpConnection.setRequestProperty("Accept", "application/json");
        // 设置是否从httpUrlConnection读入，默认情况下是true;
        httpConnection.setDoInput(true);
        // Post 请求不能使用缓存
        httpConnection.setUseCaches(false);
        if (httpConnection.getResponseCode() != 200) {
            throw new RuntimeException("HTTP POST Request Failed with Error code : "
                    + httpConnection.getResponseCode());
        }
        InputStream inStrm = httpConnection.getInputStream();
        byte []b=new byte[1024*512];
        int length=-1;
        while((length=inStrm.read(b))!=-1){
            builder.append(new String(b,0,length));
        }
    } catch (MalformedURLException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return builder.toString();
}