此段代码导出excel功能在swagger里调试可以下载正常打开excel，从前台页面调用接口时确无法打开文件报错信息如下，打开之后也是一堆乱码
一开始以为时用流传输，转化的流出现了问题，可是swagg能打开说明流没有问题，于是猜测是和前台进行交互的过程中出现问题，仔细排查后发现前端传参用的是Post而后端用的是Get，统一Get传参后问题解决
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在编写过程中经常遇到的报错：
NullPointerException: null 空指针
ERROR o.a.c.c.C.[.[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root cause java.lang.NullPointerException: null
总结了一下这个报错我遇到的原因有以下几点：
1、字符串变量未初始化
2、接口类型的对象没有用具体的类初始化
3、当一个对象的值为空时，没有判空
Unparseable date: "XXXX"
ERROR o.a.c.c.C.[.[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.text.ParseException: Unparseable date: "202004"] with root cause java.text.ParseException: Unparseable date: "202004"
原因：数据库存储的字段数据类型与传过来的数据类型不一样
Parameter 'XXXX' not found. Available parameters are [XXX, param1]
ERROR o.a.c.c.C.[.[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.binding.BindingException: Parameter 'job_id' not found. Available parameters are [userinformation, param1]] with root cause org.apache.ibatis.binding.BindingException: Parameter 'job_id' not found. Available parameters are [userinformation, param1]
参数传递错误，出现的原因：接口方法没用@Param注解
For input string: "XXX"
ERROR o.a.c.c.C.[.[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is java.lang.NumberFormatException: For input string: "string"] with root cause java.lang.NumberFormatException: For input string: "string"
参数类型转换时报错：把不符合数字格式的字符串转换为数字时抛出的格式化异常；
Expected one result (or null) to be returned by selectOne(), but found: XX
ERROR o.a.c.c.C.[.[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 12] with root cause org.apache.ibatis.exceptions.TooManyResultsException: Expected one result (or null) to be returned by selectOne(), but found: 12
实际的返回数据条数超出设定的返回条数
Invalid bound statement (not found)
ERROR o.a.c.c.C.[.[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.httech.hrms.mapper.cdp.PromotionInfoMapper.getAllInformationWithErr] with root cause org.apache.ibatis.binding.BindingException: Invalid bound statement (not found): com.httech.hrms.mapper.cdp.PromotionInfoMapper.getAllInformationWithErr
原因：xml里面的namespace不对 或者id和mapper里面的方法名不一样，或者parameterType对应不上
