将json写入csv文件

          反正最近就一直在处理流。。。这次写的是给一个url，跳到一个json串页面。。。然后·，将这个json串数据写入csv文件。。。具体要求就是，把符合条件的"features" 下的"attributes"写入csv文件。

  

      public static void jsonWrite(String urlString, String filePath) {
            BufferedWriter writer = null;
            InputStreamReader isr = null;
            BufferedReader br = null;
            HttpURLConnection conn = null;
            StringBuffer json = new StringBuffer();
            try {
                writer = new BufferedWriter(new FileWriter(new File(filePath)));
                URL url = new URL(urlString);
                conn = (HttpURLConnection) url.openConnection();
                isr = new InputStreamReader(conn.getInputStream());
                br = new BufferedReader(isr);
                String line;
                if ((line = br.readLine()) != null) {
                    json.append(line);       //将json数据获取下来
                }
                JSONObject data = JSONObject.fromObject(json.toString());  //将json整个数据转换成JSONObject 格式
                JSONArray features = data.getJSONArray("features"); //获取json这个JSONObject中的features，features是个JSONArray

                JSONArray selectedArray = new JSONArray();
                int countHead = 0;
                StringBuffer head = new StringBuffer();
                if (features.size() > 0) {
                    for(int j = 0;j<features.size();j++){
                        JSONObject feature1 = features.getJSONObject(j);
                        JSONObject attribute1 = feature1==null?null:feature1.getJSONObject("attributes");
                        String majorStatusValue = attribute1==null?"":attribute1.get("MAJOR_STATUS").toString();
          //读取配置文件，获取需要的majorStatus                                                                                                            List<String> majorStatusList = readProperties("major_status.properties", "MAJOR_STATUS");                    
                        for(String majorStatus:majorStatusList){                                                                                                                                      //从全部的features中筛选符合条件的features，放到新的JSONArray中
                            if(majorStatusValue.equals(majorStatus)){
                                selectedArray.add(feature1);
                                break;
                            }
                        }
                    }
                    
                    for (int i = 0; i < selectedArray.size(); i++) {
                        LinkedHashMap<String, Object> map = new LinkedHashMap<String, Object>();
                        JSONObject feature = selectedArray.getJSONObject(i);
                        JSONObject attributesObj = feature.getJSONObject("attributes");
                        System.out.println(attributesObj.toString());
                        Iterator it = attributesObj.keys();
                        while (it.hasNext()) {
                            
                            String key = (String) it.next();
                            Object value = attributesObj.get(key);
                           if (key.equals("last_edited_date")  || key.equals("created_date")) { //需要把long型的时间转换成date类型
                               Object valueObj = attributesObj.get(key);  //因为value的类型不确定
                           if (valueObj instanceof Long) { // valueObj 类型是Long，就转换成date类型，如果为null，就直接放进去                                            
                                    Long time = Long.parseLong(dealWithData(valueObj.toString()));
                                    Date date = new Date(time);
                                    SimpleDateFormat sd = new SimpleDateFormat(
                                            "yyyy-MM-dd HH:mm:ss");
                                    value = sd.format(date);
                                }
                            }
                            map.put(key, value); //一个 attributes数据以key-value形式放入map
                        }                  

                        for (String key : map.keySet()) {
                            countHead++;         //写入表头，也就是写入前25个（25列）
                            if (countHead > 25)   
                                break;           
                            head.append(dealWithData(key)).append(",");
                        }
                        if (countHead == 25) {   //写完第一行表头，换行，只有第一个map的key写进去，其他map的key不写进去
                            writer.write(head.toString());
                            writer.newLine();
                        }
                        int countValue = 0;
                        for (Object value : map.values()) {
                            StringBuffer values = new StringBuffer();//这里values是一个map的value拼在一起 

                            values.append(dealWithData(value.toString())).append(
                                    ",");
                            countValue++;
                            writer.write(values.toString());//将一个map的数据写入BufferedWriter ，也就是一个 attributes数据
                            if (countValue % 25 == 0) {   //写完一个map都要换行
                                writer.newLine();
                            }
                        }
                    }

                }

                writer.close(); //不要忘记

            } catch (Exception e) {
                e.printStackTrace();
            }
        }