我在druiddatasource.getconnectioninternal（druiddatasource。java:1704)?
下面是完整的堆栈跟踪。你能帮我理解这个问题吗？

Caused by: org.apache.ibatis.exceptions.PersistenceException:

### Error updating database.  Cause: java.lang.NullPointerException

### The error may exist in com/byai/line/dal/mapper/RegistrantMapper.xml

### The error may involve com.byai.line.dal.mapper.RegistrantMapper.deleteByCallerAccountId

### The error occurred while executing an update

### Cause: java.lang.NullPointerException

    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:199)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.delete(DefaultSqlSession.java:212)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:433)
    ... 100 common frames omitted
Caused by: java.lang.NullPointerException: null
    at com.alibaba.druid.pool.DruidDataSource.getConnectionInternal(DruidDataSource.java:1704)
    at com.alibaba.druid.pool.DruidDataSource.getConnectionDirect(DruidDataSource.java:1402)
    at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.java:5059)
    at com.alibaba.druid.filter.logging.LogFilter.dataSource_getConnection(LogFilter.java:886)
    at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.java:5055)
    at com.alibaba.druid.filter.stat.StatFilter.dataSource_getConnection(StatFilter.java:680)
    at com.alibaba.druid.filter.FilterChainImpl.dataSource_connect(FilterChainImpl.java:5055)
    at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1380)
    at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:1372)
    at com.alibaba.druid.pool.DruidDataSource.getConnection(DruidDataSource.java:109)
    at com.baomidou.dynamic.datasource.AbstractRoutingDataSource.getConnection(AbstractRoutingDataSource.java:42)
    at org.springframework.jdbc.datasource.DataSourceUtils.fetchConnection(DataSourceUtils.java:157)
    at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:115)
    at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:78)
    at org.mybatis.spring.transaction.SpringManagedTransaction.openConnection(SpringManagedTransaction.java:82)
    at org.mybatis.spring.transaction.SpringManagedTransaction.getConnection(SpringManagedTransaction.java:68)
    at org.apache.ibatis.executor.BaseExecutor.getConnection(BaseExecutor.java:336)
    at com.baomidou.mybatisplus.core.executor.MybatisSimpleExecutor.prepareStatement(MybatisSimpleExecutor.java:93)
    at com.baomidou.mybatisplus.core.executor.MybatisSimpleExecutor.doUpdate(MybatisSimpleExecutor.java:53)
    at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:117)
    at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:76)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:197)
    ... 106 common frames omitted