Create HashMap<String,Map> from List < Map<String,Object>> gives java.lang.ClassCastException

Question

Below is my code.Any help is appreciated. I am simply not able to read list and create a Map. I am passing a List<Map<String, Object>> as a function parameter till the Rest layer.In Rest Proxy call its a plain List. In my service layer I need to use Map values stored in the List.

My List has values as mentioned

[{ID=56, VALUE=CPR,DESCRIPTOR=HEAD}, 
{ID=68,VALUE=RegFinance,DESCRIPTOR=FINANCE}]

I want a create Map<String,Map> using List<Map<String, Object>> in below format

{56={ID=56, VALUE=CPR,DESCRIPTOR=HEAD}, 
68={ID=68,VALUE=RegFinance,DESCRIPTOR=FINANCE}}

Below code works before rest call is made i.e in Controller layer but does not work in Service layer after rest call.

    Map<String, Object> userRoleMap = new HashMap<>();
                for (int count = 0; count < allRolesDetails.size(); count++) {
                    //Map<String, Object> mapp=allRolesDetails.get(count);
                   //Above line Gives Exception

                    String[] singleColumn = allRolesDetails.get(count).toString().split(",");
                   //Above line Gives Exception

                    for(String pair : singleColumn)  
                    {
                        String[] entry = pair.split("=");   
                        userRoleMap.put(entry[1].trim(),allRolesDetails.get(count)); 
                        break;//add them to the hashmap and trim whitespaces
                    }
                }

Tried all other options on StackoverFlow

Iterator<Map<String, Object>> it = allRolesDetails.iterator();
            while (it.hasNext()) {
                Map<String, Object> map = it.next(); //so here you don't need a potentially unsafe cast
                for (Map.Entry<String, Object> entry : map.entrySet()) {
                    System.out.println(entry.getKey() + " = " + entry.getValue());
                }
            }

And

for(Map<String, Object> map:allRolesDetails){
                for(Map.Entry<String, Object>entry : map.entrySet()){
                    String Key=entry.getKey();
                    Object Value=entry.getValue();
                }
            }

In all the cases I am getting the below exception whenever I am using allRolesDetails.get(count) or trying to user Iterator or Map.Entry.

java.lang.ClassCastException: java.lang.String cannot be cast to java.util.Map

Welcome to Stack Overflow! Please take the tour to see how the site works and what questions are on topic here, and edit your question accordingly. See also: How to create a Minimal, Complete, and Verifiable example — Joe C
– Joe C, Commented Sep 16, 2017 at 18:49
Yes one is Empty Map userRoleMap<String,Map> in which I want to fill values from List<Map<String,Object>> — Sagarmatha
– Sagarmatha, Commented Sep 17, 2017 at 3:36

Leo Aso · Accepted Answer · 2017-09-16 22:24:49Z

1

You are typing a LOT of code here, when you could just do this

Map<String, Map<String, Object>> userRoleMap = new HashMap<>();
for (Map<String, Object> m : allRolesDetails) {
    userRoleMap.put(m.get("ID"), m);
}

answered Sep 16, 2017 at 22:24

Leo Aso

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2 Comments

Sagarmatha Over a year ago

Still gives me below exception at for (Map<String, Object> m : allRolesDetails) { java.lang.ClassCastException: java.lang.String cannot be cast to java.util.Map at com.apple.sfo.workflow.service.InventoryServiceImpl.fetchCenterForDetails(InventoryServiceImpl.java:4649) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

Sagarmatha Over a year ago

After I figured out the problem used above few lines of code instead of a LOT of code which I was using.Thanks for the inputs.

Sagarmatha · Accepted Answer · 2017-09-17 17:26:51Z

0

I found out the solution. As I mentioned

Below code works before rest call is made i.e in Controller layer but does not work in Service layer after rest call.

There was an Issue with type of parameter I was passing in RestProxy Call I was passing @QueryParam(value = "allRolesDetails") List allRolesDetails instead of final List<Map<String, Object>> allRolesDetails .After this change proper Map was getting retrieved while iterating List. This post helped me find my problem. sending List/Map as POST parameter jersey

answered Sep 17, 2017 at 17:26

Sagarmatha

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