Java实际场景应用案例

1. 把一个类对象赋给另一个所有属性相同的类对象

工具类：
BeanUtil.copyProperties(period,newPeriod);
谨记：BeanUtils.copyProperties只对bean属性进行复制，这里的复制属于浅复制

把javabean复制到另一个javabean 使用BeanUtils.copyProperties(a,b) 复制。该方法对于两种不同的jar包有两种不同的意义 ，a，b通常是两个结构相似的javabean，注意：a，b里的定义类型名称必须一致才能复制。引用的是org.springframework.beans，则是把a 的内容复制到b

if (period.getEndDate() < curDate) {
  FinancePeriodIncomePeriod newPeriod = financePeriodIncomePeriodService.getFinancePeriodIncomePeriodByDate(curDate, period.getCorpId());
   if(null==newPeriod) {
       BeanUtil.copyProperties(period,newPeriod);
       newPeriod.setId(null);
       newPeriod.setCreateTime(null);
       newPeriod.setStartDate(CalendarUtil.getDateWithInterval(period.getEndDate(), 1));
       newPeriod.setEndDate(CalendarUtil.getDateWithInterval(period.getEndDate(), 12));
       newPeriod.setType(FinanceInventoryContants.INVENTORY_ROYALTY_PERIOD_TYPE_CURRENT);// 当前区间
       newPeriod.setId(iIdService.getId());         // need to check!!!
       financePeriodIncomePeriodService.save(newPeriod);
       }
}

2. 获取时间LocalDateTime类

1. 获取当前时间：LocalDateTime.now()
2. 如何将Date类的对象转化LocalDateTime类的对象

    private LocalDateTime dateToLocalDateTime(Date date){
        Instant instant = date.toInstant();
        ZoneId zoneId = ZoneId.systemDefault();
        LocalDateTime localDateTime = instant.atZone(zoneId).toLocalDateTime();
        return localDateTime;
    }

3. Mybatis-Plus 插入数据函数—save(entity)

曾以为还要写insert的sql语句，save函数可实现插入功能。

4. Sql 查询2个表，只返回一个表的所有属性

1. 可读性高 ：一个个属性列举出来
2. 表的别名.*
   案例如下:

    <select id="getAllCorpYearPoolList" resultType="com.kinglex.executor.entity.FinanceCorpYearPool">
        select corpYearPool.* from finance_corp_pool pool,finance_corp_year_pool corpYearPool
        where corpYearPool.isDel= 0
          and corpYearPool.company=#{arg2}
          and pool.isDel=0
          and pool.company=#{arg2}
          and pool.id = corpYearPool.poolId
          and corpYearPool.state = 1
          and pool.corpId=#{arg0}
          and corpYearPool.periodId=#{arg1}
          order by corpYearPool.createTime
    </select>

5. 关于Sql中IF如何使用？（三种实现方法if）

1 针对单个表可以用wrapper来实现，if判断属性是否为空时或者不为空时，各写一段wrapper。
2 如下案例

	@Override
	public List<FinanceTeamYearPool> getTeamYearPoolList(Long corpId, Long periodId, Integer isFixed, Long company) {
	Map<String,Object> params = new HashMap<String,Object>();

	StringBuffer where = new StringBuffer(" where teamYearPool.isDel="+UserConstant.DELETED_STATE_NO+" and teamYearPool.company=:company");
	where.append(" and pool.isDel="+UserConstant.DELETED_STATE_NO+" and pool.company=:company");
	where.append(" and pool.id = teamYearPool.poolId");
	where.append(" and teamYearPool.state = 1");
	where.append(" and pool.corpId=:corpId and teamYearPool.periodId=:periodId");
//	where.append(" and pool.corpId="+corpId+" and teamYearPool.periodId=:periodId");
	params.put("corpId", corpId);
	params.put("periodId", periodId);
	params.put("company", company);
	if(null!=isFixed) {
		where.append(" and pool.isFixed = :isFixed");
		params.put("isFixed", isFixed);
	}

	String hql = "select teamYearPool from FinanceTeamPool pool,FinanceTeamYearPool teamYearPool "+where.toString()+" order by teamYearPool.createTime ";

	return super.getListData(hql, params);
	}

    <select id="getTeamYearPoolList" resultType="com.kinglex.executor.entity.FinanceTeamYearPool">
        select teamYearPool.* from finance_team_pool pool,finance_team_year_pool teamYearPool
        where teamYearPool.isDel=0
          and teamYearPool.company= #{arg3}
          and pool.isDel= 0
          and pool.company = #{arg3}
          and pool.id = teamYearPool.poolId
          and teamYearPool.state = 1
          and pool.corpId=#{arg0}
          and teamYearPool.periodId=#{arg1}
          and IF (#{arg2} is null, 1 = 1, pool.isFixed = #{arg2})
    </select>

3 面对这种情况，也可以先用String类 sql拼接好字符串，然后在xml中 ￥{sql} ， 就可以实现同样的功能。

6. 日志类

6.1 日志级别

每个Logger都被定义了一个日志级别（log level），用来控制日志信息的输出。日志级别从高到低分为：
A：off 最高等级，用于关闭所有日志记录。
B：fatal 指出每个严重的错误事件将会导致应用程序的退出。
C：error 指出虽然发生错误事件，但仍然不影响系统的继续运行。
D：warm 表明会出现潜在的错误情形。
E：info 一般和在粗粒度级别上，强调应用程序的运行全程。
F：debug 一般用于细粒度级别上，对调试应用程序非常有帮助。
G：all 最低等级，用于打开所有日志记录。
上面这些级别是定义在org.apache.log4j.Level类中。Log4j只建议使用4个级别，优先级从高到低分别是 error,warn,info和debug。通过使用日志级别，可以控制应用程序中相应级别日志信息的输出。例如，如果使用b了info级别，则应用程 序中所有低于info级别的日志信息(如debug)将不会被打印出来

6.2 实例

// log4j 日志记录
    public final Log log = LogFactory.getLog(getClass());
    public synchronized void save(SearchConflictCasesource conflictCasesource) {
        if(Boolean.valueOf(isSyncEs)==false) {
            return;
        }
        String jsonString = "";
        try {
          JSONObject.fromObject(EntityUtils.toString(response.getEntity()));
            if(result.has("error") || !result.has("result")) {
                log.error("ES返回为："+result.toString());
                throw new RuntimeException();
            } else {
              // 变更为已同步至ES
              // updateCasesourceIsSyncEs(conflictCasesource.getId(), 1);   need to add!!!
            }
        } catch (Exception e) {
            e.printStackTrace();
            log.error("ES案源当事人保存失败["+jsonString+"]：",e);
            throw new RuntimeException("ES案源当事人插入异常");
        }
    }

7. 分页查询

1. 定时器

	int pageSize = 500;
    List<EmpInfo> empInfoList = null;
    int page = 1;
    do {
         empInfoList = empInfoService.getEmpListAllWechatLinkByNotification(page, pageSize);
         if (empInfoList != null) {
             for (int i = 0; i < empInfoList.size(); i++) {
                 EmpInfo empInfo = (EmpInfo) empInfoList.get(i);
             }
          }
            page++;
       } while (!empInfoList.isEmpty());               

2. service层

	@Override
    public List<EmpInfo> getEmpListAllWechatLinkByNotification(Integer page, Integer pageSize) {
        
        Page<EmpInfo> page1 = new Page<>();
        page1.setCurrent(page);
        page1.setSize(pageSize);
        IPage<EmpInfo> empListAllWechatLinkByNotification = empInfoMapper.getEmpListAllWechatLinkByNotification(page1);
        List<EmpInfo> empInfoList = empListAllWechatLinkByNotification.getRecords();
        return empInfoList;
    }

3.Mapper

8. 复杂查询—多表，数据库字段与非数据库字段联合查询案例

account.empName中empName是非数据库字段

<select id="getListAllInventoryLawyerAccountByCorpIdPeriod"
            resultType="com.kinglex.executor.entity.InventoryLawyerAccount">
--         select account.*
--         from finance_set_lawyer lawyer,
--              inventory_lawyer_account account
--         where lawyer.isDel = 0
--           and IF(#{arg0} is null, 1 = 2, lawyer.cropId = #{arg0})
--           and IF(#{arg2} is null, 1 = 1, account.empName like "%"#{arg2}"%")
--           and lawyer.periodId = #{arg1}
--           and lawyer.isAllocation = 1
--           and account.isDel = 0
--           and lawyer.empId = account.empId
--         order by account.createTime desc

        select account.*
        from finance_set_lawyer lawyer,
             inventory_lawyer_account account,
             emp_info emp
        where lawyer.isDel = 0
          and emp.isDel = 0
          and emp.empid = account.empId
          and IF(#{arg0} is null, 1 = 2, lawyer.cropId = #{arg0})
          and IF(#{arg2} is null, 1 = 1, emp.empName like "%"#{arg2}"%")
          and lawyer.periodId = #{arg1}
          and lawyer.isAllocation = 1
          and account.isDel = 0
          and lawyer.empId = account.empId
        order by account.createTime desc
    </select>