对接Content-Type="application/json;"的接口示例

url：调用目标接口的路径

headers:请求头属性

params：目标接口需要的入参

public static String sendPostJson(String url, Map<String, String> headers, Map<String, Object> params) {
    String param = JSONUtils.toJSONString(params);
    PrintWriter out = null;
    BufferedReader in = null;
    String result = "";
    try {
        URL realUrl = new URL(url);
        // 打开和URL之间的连接
        URLConnection conn = realUrl.openConnection();
        // 设置通用的请求属性
        conn.setRequestProperty("accept", "*/*");
        conn.setRequestProperty("connection", "Keep-Alive");
        conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
        if (headers != null) {
            List<NameValuePair> nvps = Lists.newArrayList();
            Set<Map.Entry<String, String>> entrySet = headers.entrySet();
            for (Map.Entry<String, String> entry : entrySet) {
                conn.setRequestProperty(entry.getKey(), entry.getValue());
            }
        }
        // 发送POST请求必须设置如下两行
        conn.setDoOutput(true);
        conn.setDoInput(true);
        // 获取URLConnection对象对应的输出流
        out = new PrintWriter(conn.getOutputStream());
        // 发送请求参数
        out.print(param);
        // flush输出流的缓冲
        out.flush();
        // 定义BufferedReader输入流来读取URL的响应
        in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        String line;
        while ((line = in.readLine()) != null) {
            result += line;
        }
    } catch (Exception e) {
        System.out.println("发送 POST 请求出现异常！" + e);
        log.error(e.getMessage());
    }
    //使用finally块来关闭输出流、输入流
    finally {
        try {
            if (out != null) {
                out.close();
            }
            if (in != null) {
                in.close();
            }
        } catch (IOException ex) {
            log.error(ex.getMessage());
        }
    }
    return result;
}