一、简单说明

本以为mybatis的example可以搞定group by，后面看到说不行

于是曲线救国，直接查出一个list，然后再用java对数据进行操作

不过话说回来，这样写是比写sql麻烦一点，但是个人感觉这样效率会高一点(未做对比测试)

二、需求说明

查出数据库中，过去30天，每个用户(merId)每天的发送条数

改进版，在1的基础上，加上所有日期的统计信息，对应日期没记录也加上

三、所用技术概要

jodatime：方便对时间进行操作，转换等

stream：对java进行操作，很是方便，此处只是stream用法的冰山一角

四、代码实现

省略了生成的实体类、mapper、example等

需求1实现

public Map coountDays(String merId){

SmsCustomerSendDetailExample example = new SmsCustomerSendDetailExample();

// 查询条件

DateTime dt = new DateTime();

// 当天00:00:00往前推30天

DateTime days = dt.withTimeAtStartOfDay().minusDays(30);

Criteria criteria = example.createCriteria();

criteria.andCustomerIdEqualTo(merId);

criteria.andCreateTimeBetween(days.toDate(),dt.toDate());

List details = sendDetailMapper.selectByExample(example);

// 对时间进行更改，清洗为yyyyMMdd(后面按天分组用)

for (SmsCustomerSendDetail detail : details) {

DateTime dateTime = new DateTime(detail.getCreateTime().getTime()).withTimeAtStartOfDay();

detail.setCreateTime(dateTime.toDate());

}

//根据日期分组

Map> dateListMap = details.stream()

.collect(Collectors.groupingBy(SmsCustomerSendDetail::getCreateTime));

// 遍历map,求出当天记录的条数

HashMap resMap = new HashMap<>(128);

for (Entry> detailEntry:dateListMap.entrySet()){

String day = new DateTime(detailEntry.getKey().getTime()).toString("yyyyMMdd");

int daySize = detailEntry.getValue().size();

resMap.put(Integer.valueOf(day),daySize);

}

// 排序

Stream> st = resMap.entrySet().stream();

Map result = new LinkedHashMap<>(32);

st.sorted(Comparator.comparing(e -> e.getKey())).forEach(e -> result.put(e.getKey(), e.getValue()));

return result;

}

结果：{20180306:44,20180307:14,20180308:9}

需求2实现

public Map coountDays(String merId){

SmsCustomerSendDetailExample example = new SmsCustomerSendDetailExample();

// 查询条件

DateTime dt = new DateTime();

// 当天00:00:00往前推30天

DateTime days = dt.withTimeAtStartOfDay().minusDays(30);

Criteria criteria = example.createCriteria();

criteria.andCustomerIdEqualTo(merId);

criteria.andCreateTimeBetween(days.toDate(),dt.toDate());

List details = sendDetailMapper.selectByExample(example);

// 对时间进行更改，清洗为yyyyMMdd(后面按天分组用)

for (SmsCustomerSendDetail detail : details) {

DateTime dateTime = new DateTime(detail.getCreateTime().getTime()).withTimeAtStartOfDay();

detail.setCreateTime(dateTime.toDate());

}

//根据日期分组

Map> dateListMap = details.stream()

.collect(Collectors.groupingBy(SmsCustomerSendDetail::getCreateTime));

// 遍历map,求出当天记录的条数

HashMap resMap = new HashMap<>(128);

for (Entry> detailEntry:dateListMap.entrySet()){

String day = new DateTime(detailEntry.getKey().getTime()).toString("yyyyMMdd");

int daySize = detailEntry.getValue().size();

resMap.put(Integer.valueOf(day),daySize);

}

// 添加过去30天所有天为key,从resMap中取出有数据的，否则为0

Map result = new LinkedHashMap<>(32);

for (int i = 0; i < 30; i++) {

String yyyyMMdd = days.plusDays(i).toString("yyyyMMdd");

Integer day = Integer.valueOf(yyyyMMdd);

int value = 0;

if (resMap.containsKey(day)){

value = resMap.get(day);

}

result.put(Integer.valueOf(yyyyMMdd),value);

}

return result;

}

结果：{20180213:0,20180214:0,20180215:0,20180216:0,20180217:0,20180218:0,20180219:0,20180220:0,20180221:0,20180222:0,20180223:0,20180224:0,20180225:0,20180226:0,20180227:0,20180228:0,20180301:0,20180302:0,20180303:0,20180304:0,20180305:0,20180306:44,20180307:14,20180308:9,20180309:0,20180310:0,20180311:0,20180312:0,20180313:0,20180314:0}