Restructure sortColumn in Pagination

components/device-mgt/org.wso2.carbon.device.mgt.common/src/main/java/org/wso2/carbon/device/mgt/common/PaginationRequest.java

@@ -44,7 +44,7 @@ public class PaginationRequest {
     private Map<String, Object> property = new HashMap<>();
     private List<String> statusList = new ArrayList<>();
     private OperationLogFilters operationLogFilters = new OperationLogFilters();
-    private List<String> sortColumns;
+    private List<SortColumn> sortColumns = new ArrayList<>();
     public OperationLogFilters getOperationLogFilters() {
         return operationLogFilters;
     }
@@ -173,27 +173,31 @@ public class PaginationRequest {
         this.filter = filter;
     }
 
-    public void setSortColumns(List<String> sortColumns) { this.sortColumns = sortColumns; }
+    public void setSortColumns(List<SortColumn> sortColumns) { this.sortColumns = sortColumns; }
 
-    public List<String> getSortColumns() { return sortColumns; }
+    public List<SortColumn> getSortColumns() { return sortColumns; }
 
     /**
      * Convert SortColumns field parameter and splitting string into columnName and sortType
      *
-     * @param sortColumns which is separated by a colon(:) and first will be the columnNane and the second will be type ASC or DESC
+     * @param sortColumns which is separated by a colon(:) and first will be the columnNane and the second will be type ASC or DESC,
+     *                    if there is no colon(:) detected, ASC will be default
+     *                    (Ex: sort=col1:ASC&sort=col2:DESC, sort=col1&sort=col2:DESC)
      * @return sortColumnList as a list of sortColumn
      */
-    public static List<SortColumn> addSortColumn(List<String> sortColumns) {
+    public void addSortColumn(List<String> sortColumns) {
         List<SortColumn> sortColumnList = new ArrayList<>();
+        SortColumn sortColumn;
+        String[] sorting;
         for (String sortBy: sortColumns) {
-            SortColumn sortColumn = new SortColumn();
-            String[] sorting = sortBy.split(":");
+            sortColumn = new SortColumn();
+            sorting = sortBy.split(":");
             sortColumn.setName(sorting[0]);
             sortColumn.setType(sorting.length >= 2 && (sorting[1].equalsIgnoreCase("desc"))
                     ? SortColumn.types.DESC : SortColumn.types.ASC);
             sortColumnList.add(sortColumn);
         }
-        return sortColumnList;
+        setSortColumns(sortColumnList);
     }
 
     @Override