[FIXED] EL1012E: Cannot index into a null value

Issue

I have this piece of code in a Thymeleaf template

var theList = /*[[${route}]]*/

for (i = 0; i < theList.length; i++) {
    var coordinate = [ /*[[${theList[i].longitude}]]*/ , /*[[${theList[i].latitude}]]*/ ];
    coordinates2.push(coordinate);
}
                        

when the object ${route} is not null, but an empty List that I pass through the controller:

List<Coordinate> route = new ArrayList<Coordinate>();
model.addAttribute("route", route);

I get this error:

org.springframework.expression.spel.SpelEvaluationException: EL1012E: Cannot index into a null value
    at org.springframework.expression.spel.ast.Indexer.getValueRef(Indexer.java:132)
    at org.springframework.expression.spel.ast.Indexer.getValueInternal(Indexer.java:89)
    at org.springframework.expression.spel.ast.CompoundExpression.getValueRef(CompoundExpression.java:57)
    at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:87)
    at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:121)
    at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:324)

Solution

You can't mix JavaScript and Thymeleaf variables. The variable i is defined in the JavaScript for loop (for (i = 0; i < theList.length; i++)), but you are trying to use it in a Thymeleaf expression. You need to keep them separate.

var theList = /*[[${route}]]*/ [];

for (i = 0; i < theList.length; i++) {
    var coordinate = [theList[i].longitude, theList[i].latitude];
    coordinates2.push(coordinate);
}

Answered By - Metroids