: EL1008E: Property or field 'LEVEL' cannot be found on object of type 'java.util.ArrayList' - maybe not public or not valid? - spring-boot

Question

please assist with the below. I am trying to display an arraylist returned from the controller and display it to an Html table but I get the above error.
here is my controller code:
#GetMapping(value="/chart" )
public List<List<CanvasjsChartData.DataPointModel>> chart(Model modelMap) {
List<List<CanvasjsChartData.DataPointModel>> dataPointsList = canvasjsChartService.getCanvasjsChartData();
modelMap.addAttribute("dataPointsList", dataPointsList);
System.out.println("dataPointsList");
return dataPointsList;
}
and this is the table I want to display my list in
<table class="table" id="dataTable" style="width:100%">
<thead>
<th>Level</th>
<th>Occurences</th>
</thead>
<tbody>
<tr th:each="item :${dataPointsList}">
<td th:text="${item.LEVEL}"> </td>
<td th:text="${item.OCCURENCES}"> </td>
</tr>
</tr>
</tbody>
I know for sure the ArrayList has the data I require as shown below I dont know why its giving me the error

Answer 1

Your debug shows you have an List<List<CanvasjsChartData.DataPointModel>> (two Lists inside of each other) -- when your HTML is expecting List<CanvasjsChartData.DataPointModel>. You should fix that in your controller/model by only returning a single list.
You could also display your HTML like this (where you loop over the 0th element of the outer array):
<tr th:each="item :${dataPointsList[0]}">
<td th:text="${item.LEVEL}" />
<td th:text="${item.OCCURENCES}" />
</tr>