mybatis-plus map

mybatis-plus分组求和以及Map与Bean的转换

mybatis-plus、Map转对象

Posted by John Doe on 2021-02-16
Words 308 and Reading Time 1 Minutes
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mybatis-plus分组求和

平常lambdaQuery写习惯了突然发现lambdaQuery好像不能求和，捡一下QueryWrapper写法

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QueryWrapper<Entity> yearQueryWrapper = new QueryWrapper<>();
        yearQueryWrapper.select("bid_year as name,sum(amount) as value");
        yearQueryWrapper.groupBy("bid_year").orderByAsc("bid_year");
        List<Map<String, Object>> yearMapList= bidInforService.listMaps(yearQueryWrapper);

groupby多个字段

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// 源码信息
    default Children groupBy(R... columns) {
        return this.groupBy(true, columns);
    }


QueryWrapper.groupBy("bid_year","bid_month");

map与javaBean对象转换

方法一:用Apache BeanUtils将Map转Bean

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// 用apache的BeanUtils实现Map covert to Bean
Map<String,String> map=new HashMap<>();
        User user=new User();
        map.put("userName","wang shisheng");
        map.put("passWord","xxxxx44333");

        BeanUtils.populate(user,map);

方法二:自封装工具类

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public class MapToObjectUtil {
    public static <T> T map2Object(Map<String, Object> map, Class<T> clazz) {
        if (map == null) {
            return null;
        }
        T obj = null;
        try {
            obj = clazz.newInstance();

            Field[] fields = obj.getClass().getDeclaredFields();
            for (Field field : fields) {
                int mod = field.getModifiers();
                if (Modifier.isStatic(mod) || Modifier.isFinal(mod)) {
                    continue;
                }
                field.setAccessible(true);
                String filedTypeName = field.getType().getName();
                if (filedTypeName.equalsIgnoreCase("java.util.date")) {
                    String datetimestamp = String.valueOf(map.get(field.getName()));
                    if (datetimestamp.equalsIgnoreCase("null")) {
                        field.set(obj, null);
                    } else {
                        field.set(obj, new Date(Long.parseLong(datetimestamp)));
                    }
                } else {
                    field.set(obj, map.get(field.getName()));
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return obj;
    }
}

实战使用:

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List<Entity> yearList = yearMapList.stream().map(item -> MapToObjectUtil.map2Object(item, Entity.class)).collect(Collectors.toList());

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