JSON转换的实现

String转成JSON
这个依赖很重要，我们将围绕fastjson中的JSONObject这个类来谈转换

 <dependency>
 <groupId>com.alibaba</groupId>
 <artifactId>fastjson</artifactId>
 <version>1.2.15</version>
 </dependency>

String转成JSON

 String json = "{"abc":"1","hahah":"2"}";
 JSONObject jsonObject = JSONObject.parseObject(content);

一句话就能解决，非常便捷。
想要取出值，可以对`jsonObject`进行操作：
jsonObject.getString("abc");
结果为：`1`

将String转为list后转为JSON

 List<String> list = new ArrayList<String>();
 list.add("username");
 list.add("age");
 list.add("sex");
 JSONArray array = new JSONArray();
 array.add(list);

将String转为map后转为JSON

 Map<String, String> map = new HashMap<String, String>();
 map.put("abc", "abc");
 map.put("def", "efg");
 JSONArray array_test = new JSONArray();
 array_test.add(map);
 JSONObject jsonObject = JSONObject.fromObject(map);

特别注意:从JSONObject中取值，碰到了数字为key的时候，如

{
"userAnswer": {
"28568": {
"28552": {
"qId": "28552",
"order": "1",
"userScore": {
"score": 100
},
"answer": {
"28554": "28554"
},
"qScore": "100.0",
"qtype": "SingleChoice",
"sId": "28568"
}
}
},
"paperType": "1",
"paperOid": "28567",
"instanceId": 30823,
"remainingTime": -1,
"examOid": "28570"
}

获取“userAnswer”的value,再转成JSON,可仿照如下形式：
JSONObject userJson = JSONObject.parseObject(jsonObject.getString("userAnswer"));
但是想获取key"28568"就没这么容易了。直接像上述的写法，会报错。
我们浏览fastjson中的源码，总结下，应该如下写：
JSONObject question = (JSONObject) JSONObject.parseObject(section.getString("28568"), Object.class);
整体代码：

dao代码很容易，就不贴出来了。

 package com.xiamenair.training.business.service;
 import com.alibaba.fastjson.JSONObject;
 import com.xiamenair.training.business.dao.elearningdao.ELearningExamInstanceDao;
 import com.xiamenair.training.business.dao.masterdao.ELearningChoiceRecordDao;
 import com.xiamenair.training.business.model.LasChoiceRecord;
 import com.xiamenair.training.business.model.entity.elearning.LasExamInstance;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.scheduling.annotation.Scheduled;
 import org.springframework.stereotype.Service;
 import java.math.BigDecimal;
 import java.sql.Blob;
 import java.sql.SQLException;
 import java.text.SimpleDateFormat;
 import java.util.*;
 @Service
 public class ChoiceRecordService {
 //查询数据Dao
 @Autowired
 private ELearningChoiceRecordDao eLearningChoiceRecordDao;
 //转储数据Dao
 @Autowired
 private ELearningExamInstanceDao eLearningExamInstanceDao;
 private ChoiceRecordService() {
 }
 private static class SingletonRecordInstance {
 private static final LasChoiceRecord choiceRecord = new LasChoiceRecord();
 }
 public static LasChoiceRecord getMapInstance() {
 return SingletonRecordInstance.choiceRecord;
 }
 private static SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
 /**
 * 定时任务，每天定时将E学网考试数据分析并转储
 *
 * @param : instanceIdList
 * @return : void
 * @author : 28370·皮育才
 * @date : 2018/11/20
 **/
 @Scheduled(cron = "00 00 01 * * ?")
 public void analysisChoiceRecord() {
 //获取前一天的时间
 Date date = new Date();
 Calendar calendar = Calendar.getInstance();
 calendar.setTime(date);
 calendar.add(calendar.DATE, -1);
 date = calendar.getTime();
 String dateString = simpleDateFormat.format(date);
 List<BigDecimal> instanceIdList = eLearningExamInstanceDao.findInstanceIdByFinishTime(dateString);
 if(0 != instanceIdList.size()){
 LasChoiceRecord lasChoiceRecord = getMapInstance();
 instanceIdList.stream().forEach(instanceId -> {
 Blob answerBlob = eLearningExamInstanceDao.findUserAnswer(instanceId);
 Long userId = eLearningExamInstanceDao.findUserId(instanceId);
 String content = null;
 try {
 content = new String(answerBlob.getBytes((long) 1, (int) answerBlob.length()));
 } catch (SQLException e) {
 e.printStackTrace();
 System.out.println("SQLEXCEPTION:" + e);
 }
 JSONObject jsonObject = JSONObject.parseObject(content);
 //针对本section的"公共"属性直接设置
 lasChoiceRecord.setUserId(userId);
 lasChoiceRecord.setPaperType(jsonObject.getString("paperType"));
 lasChoiceRecord.setPaperId(jsonObject.getString("paperOid"));
 lasChoiceRecord.setExamInstanceId(jsonObject.getString("instanceId"));
 lasChoiceRecord.setRemainingTime(jsonObject.getString("remainingTime"));
 lasChoiceRecord.setExamId(jsonObject.getString("examOid"));
 //针对section中的题目进行细化循环拆分
 JSONObject userJson = JSONObject.parseObject(jsonObject.getString("userAnswer"));
 Set sectionSet = userJson.keySet();
 Iterator<String> setIt = sectionSet.iterator();
 analyzeAnswer(lasChoiceRecord, userJson, setIt);
 });
 }
 }
 private void analyzeAnswer(LasChoiceRecord lasChoiceRecord, JSONObject userJson, Iterator<String> setIt) {
 while (setIt.hasNext()) {
 //对每个question进行再次拆分出题目
 JSONObject section = (JSONObject) JSONObject.parseObject(userJson.getString(setIt.next()), Object.class);
 Set questionSet = section.keySet();
 Iterator<String> queIt = questionSet.iterator();
 while (queIt.hasNext()) {
 JSONObject question = (JSONObject) JSONObject.parseObject(section.getString(queIt.next()), Object.class);
 String userAnswer = question.getString("answer");
 String userScore = question.getString("userScore");
 lasChoiceRecord.setQuestionId(question.getString("qId"));
 lasChoiceRecord.setRecordId(UUID.randomUUID().toString());
 eLearningChoiceRecordDao.save(lasChoiceRecord);
 }
 }
 }
 }