使用HttpURLConnection访问接口进行数据处理

        项目中有这样一个场景：web工程接收到外部数据后，需要转发给biz工程进行处理，然后biz将处理结果数据返回给web工程。为什么要这么做呢？是因为蛋疼的网络权限控制，只有web工程能够跟外部打交道，那么问题来了，这种交互模式如何处理？

         这里就使用到了HttpURLConnection对象，直接看如下方法吧，在web工程中使用如下：

public static String getResponseMessage(String resMsgUrl, String requestXmlData) throws IOException
    {
        // 向biz的接口发用户的上行消息，把requestXmlData发给biz工程的接口，这里的resMsgUrl就是biz工程提供的url
        URL url = new URL(resMsgUrl);

        //建立连接
        HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();

        //设置是否向HttpURLConnection输出，因为这个是post请求，参数放在http正文内，因此需要设置为true，默认为false
        httpURLConnection.setDoOutput(true);

        //设置是否从HttpURLConnection读入，默认为true
        httpURLConnection.setDoInput(true);

        //设置请求方法
        httpURLConnection.setRequestMethod("POST");

        //设置连接超时时间
        httpURLConnection.setConnectTimeout(5000);

        //设置读取超时时间
        httpURLConnection.setReadTimeout(5000);

        //对请求的正文使用urlencode进行编码
        httpURLConnection.setRequestProperty("content-type", "application/x-www-form-urlencoded");

        //一定是上面的参数设置完了之后才进行connection连接
        httpURLConnection.connect();

        //使用BufferedWriter对象进行参数写入到正文
        BufferedWriter out = new BufferedWriter(new OutputStreamWriter(httpURLConnection.getOutputStream(), "UTF-8"));
        if(StringUtils.isNotEmpty(requestXmlData)){
            out.write(requestXmlData);
        }
        out.flush();
        out.close();
        int code = httpURLConnection.getResponseCode();
        String message = httpURLConnection.getResponseMessage();
        logger.info("%%%name:" + httpURLConnection.getHeaderField("name"));


        // 连接成功后，从biz的接口读取返回的message
        if (code == 200 || message.equalsIgnoreCase("ok"))
        {
            InputStream inputStream = httpURLConnection.getInputStream();
            String resonpseMessage = readBytesFromStream(inputStream);
            inputStream.close();
            httpURLConnection.disconnect();
            return resonpseMessage;
        }
        httpURLConnection.disconnect();
        return "";
    }

   biz提供接口，先从request对象中读出web的请求参数，然后根据参数在数据库中找到欲返回的信息，然后通过BufferedWriter对象写入到response中，代码如下：

@RequestMapping(value="res_message.xhtml",method = RequestMethod.POST)
    public void resMessage(HttpServletRequest request, HttpServletResponse response) throws IOException{
        String requestXmlData = Util.getRequestXmlData(request);
        String resopnseXmlData =  messageService.getResponseXml(requestXmlData);
        response.setCharacterEncoding("UTF-8");
        logger.info("&&&&&&&resopnseXmlData:"+resopnseXmlData);
        BufferedWriter out = new BufferedWriter(new OutputStreamWriter(response.getOutputStream(), "UTF-8"));
        out.write(resopnseXmlData);
        out.flush();
        out.close();
    }

二者的交互就完成了，值得注意的是，上述两个方法中都涉及到了从request或InputStream中读取数据，这里有两种模式：

1、按行读取，例如：

public static String getRequestXmlData(HttpServletRequest request) throws IOException
    {
        request.setCharacterEncoding("UTF-8");
        BufferedReader br = new BufferedReader(new InputStreamReader((ServletInputStream) request.getInputStream(), "UTF-8"));
        String line;
        StringBuilder sb = new StringBuilder();
        while ((line = br.readLine()) != null)
        {
            sb.append(line);
        }
        String recievestr = sb.toString();
        return recievestr;
    }

public static String readBytesFromStream(InputStream inputStream) throws IOException
    {
        String responseStr = "";
        String totalResponseStr = "";
        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"));
        while ((responseStr = reader.readLine()) != null)
        {
            totalResponseStr += responseStr + "\n";
        }
        return totalResponseStr;
    }

2、按规定字符串长度读取

逐字节读取：

public static String getRequestXmlData(HttpServletRequest request) throws IOException {
        ServletInputStream sis = request.getInputStream();
        int size = request.getContentLength()==-1?0:request.getContentLength();
        byte[] buffer = new byte[size];
        byte[] xmldataByte = new byte[size];
        int count = 0;
        int rbyte = 0;
        while (count < size) {
            rbyte = sis.read(buffer);
            for (int i = 0; i < rbyte; i++) {
                xmldataByte[count + i] = buffer[i];
            }
            count += rbyte;
        }
        return new String(xmldataByte, "UTF-8");
    }

这里很容易出现乱码，因为每次按长度进行读取，如果刚好一个汉字被截断，就会出现乱码，因此不建议这么使用。

public static String readBytesFromInputStream(InputStream inputStream) throws IOException
    {
        byte[] b = new byte[1024];
        String res = "";
        int bytesRead = 0;
        while (true) {
            bytesRead = inputStream.read(b, 0, 1024);
            if (bytesRead == -1) {
                return res;
            }
            res += new String(b, 0, bytesRead, "UTF-8");
         }
    }