使用SpringMVC框架、HTTP協議實現JSON報文的發送、接收與響應

案例簡介：

前端請求對外接口，傳入用戶姓名，查詢該用戶的年齡

一、實現思路

1、首先編寫對外接口，使用Postman發送JSON報文

2、該對外接口請求下游接口

3、獲取下游接口的響應，並相應給上層調用者

二、代碼實現

1、Postman請求URL為：http://localhost:8080/testInterfaces2.htm
2、請求方式：POST請求

3、請求報文：{"name":"張三"}或者{"name":"李四"}（注意：代碼固定寫死，無需請求數據庫查詢，簡化處理）

4、對外接口代碼：

@RequestMapping(value="testInterfaces2.htm", method={RequestMethod.GET, RequestMethod.POST})
    @ResponseBody
    public JSONObject testInterfaces2(HttpServletRequest request) throws Exception{
        //獲取請求報文
        JSONObject json = GetRequestJsonUtils.getRequestJsonObject(request);
        String username = json.getString("name");
        //定義響應報文
        String respMsg = null;
        //定義JSON類型響應報文
        JSONObject jsStr = null;
        //封裝請求報文
        JSONObject obj = new JSONObject();
        obj.put("name", username);
        String reqMsg = obj.toString();
        System.out.println("前端請求報文為：" + reqMsg);
        try {
            //請求下游URL
            URL url = new URL("http://localhost:8080/test.htm");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoInput(true);
            connection.setDoOutput(true);
            connection.setRequestMethod("POST");
            connection.setUseCaches(false);
            connection.setInstanceFollowRedirects(true);
            connection.setRequestProperty("Content-Type", "application/json");
            //開啟連接
            connection.connect();
            //發送請求報文
            OutputStream os = connection.getOutputStream();
            os.write(reqMsg.getBytes("UTF-8"));
            //獲取下游接口響應報文
            BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String lines;
            StringBuffer sbf = new StringBuffer();
            while ((lines = reader.readLine()) != null) {
                lines = new String(lines.getBytes(), "utf-8");
                sbf.append(lines);
            }
            respMsg = sbf.toString();
            System.out.println("下游接口響應報文：" + respMsg);
            jsStr = JSONObject.fromObject(respMsg);
            //斷開連接
            connection.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
        }
        //返回下游接口的響應報文給前端
        return jsStr;
    }

5、下游接口代碼

@RequestMapping(value = "test.htm", method = { RequestMethod.GET,RequestMethod.POST })
    @ResponseBody
    public JSONObject test(HttpServletRequest request)throws Exception {
        //獲取請求報文
        JSONObject json = GetRequestJsonUtils.getRequestJsonObject(request);
        String username = json.getString("name");
        String age = null;
        if (username.equals("張三")){
            age = "30";
        } else if(username.equals("李四")){
            age = "40";
        }
        //封裝響應報文
        JSONObject jsonObj = new JSONObject();
        Map<String,Object> map = new HashMap<>();
        map.put("age", age);
        jsonObj.putAll(map);
        return jsonObj;
    }

6、其中的工具類來自（感謝）：

https://blog.csdn.net/weixin_34405925/article/details/89557851

7、主體代碼來自：

https://www.cnblogs.com/xiaoyue1606bj/p/11577266.html