mybatis foreach遍历问题：Error evaluating expression 'XXX'. Return value ('xxxx') was not iterable.

mybatis foreach多次遍历问题:

org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.builder.BuilderException: Error evaluating expression 'payMethod'.  Return value ({payMethodName=现金, payMethodValue=10, payMethodKey=payMethod10}) was not iterable.
	at org.mybatis.spring.MyBatisExceptionTranslator.translateExceptionIfPossible(MyBatisExceptionTranslator.java:73)
	at org.mybatis.spring.SqlSessionTemplate$SqlSessionInterceptor.invoke(SqlSessionTemplate.java:364)
	at com.sun.proxy.$Proxy17.selectList(Unknown Source)
	at org.mybatis.spring.SqlSessionTemplate.selectList(SqlSessionTemplate.java:201)
	at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:118)
	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:90)
	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:40)
	at com.sun.proxy.$Proxy67.selectPayMethodStatistics(Unknown Source)
	at com.segi.uhomecp.report.bill.report.service.impl.ReceiptsServiceImpl.selectPayMethodStatistics(ReceiptsServiceImpl.java:280)
	at com.segi.uhomecp.report.bill.report.controller.ReceiptsController.payMethodStatistics(ReceiptsController.java:800)
	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.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:215)
...

sql执行报错，根据错误定位，查询得知原因是：中的item和collection变量名起重复了，修改变量名就好

 

sql:

		...
		
			SUM(IF(t.pay_method = #{payMethod.payMethodValue}, t.paid_fee, 0)) as ${payMethod.payMethodKey}_paidFee,
			
			SUM(IF(t.pay_method = #{payMethod.payMethodValue}, t.refund_fee, 0)) as ${payMethod.payMethodKey}_refundFee,
			
			SUM(IF(t.pay_method = #{payMethod.payMethodValue}, t.paid_fee, 0)) + SUM(IF(t.PAY_METHOD = #{payMethod.payMethodValue}, t.refund_fee, 0)) as ${payMethod.payMethodKey},
		
        ...

但是sql中 中的item和collection变量名是不一样的，那么就不是item和collection变量名起重复导致的。

后面发现我sql入参传递的是一个封装的对象，会不会是对象中的成员变量跟item变量名重复了

parameterType="xxx.CycleStatisticsReq"

对比发现确实是变量名重复导致sql运行时异常（payMethod重复）

解决办法就是item 换一个变量名  ，尽量不要和collection 变量名和对象中的成员变量重复就行了