出现如下问题
java.sql.SQLSyntaxErrorException: Unknown column ‘lastname’ in ‘field list’
; bad SQL grammar []; nested exception is java.sql.SQLSyntaxErrorException: Unknown column ‘lastname’ in ‘field list’
at org.springframework.jdbc.support.SQLErrorCodeSQLExceptionTranslator.doTranslate(SQLErrorCodeSQLExceptionTranslator.java:239)at org.springframework.jdbc.support.AbstractFallbackSQLExceptionTranslator.translate(AbstractFallbackSQLExceptionTranslator.java:70)at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:88)at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:440)at com.sun.proxy.$Proxy54.selectOne(Unknown Source)at org.mybatis.spring.SqlSessionTemplate.selectOne(SqlSessionTemplate.java:159)at com.baomidou.mybatisplus.core.override.MybatisMapperMethod.execute(MybatisMapperMethod.java:90)at com.baomidou.mybatisplus.core.override.MybatisMapperProxy$PlainMethodInvoker.invoke(MybatisMapperProxy.java:148)at com.baomidou.mybatisplus.core.override.MybatisMapperProxy.invoke(MybatisMapperProxy.java:89)at com.sun.proxy.$Proxy60.selectById(Unknown Source)at cn.yswu.test.select(test.java:22)at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
原因分析：
主要是数据库中字段与 Java程序实体pojo或者entity类中定义的字段不匹配.
观察发现 mysql中为last_name字段，经过驼峰转换可为 lastName
而pojo类中则定义了lastname; 粗心导致的错误 改为lastName即可。