[JSTL](Error) Don't know how to iterate over supplied "items"

forEach문에 넣어준 데이터가 리스트타입이 아니라서 발생 해당 데이터가 리스트 형식인지 확인 필요

javax.servlet.jsp.JspTagException: Don't know how to iterate over supplied "items" in <forEach>

at org.apache.taglibs.standard.tag.common.core.ForEachSupport.toForEachIterator(ForEachSupport.java:274)

at org.apache.taglibs.standard.tag.common.core.ForEachSupport.supportedTypeForEachIterator(ForEachSupport.java:238)

at org.apache.taglibs.standard.tag.common.core.ForEachSupport.prepare(ForEachSupport.java:155)

at javax.servlet.jsp.jstl.core.LoopTagSupport.doStartTag(LoopTagSupport.java:256)