Add supports for sets to pagination along with lists

Previously only lists were supported. Sets support was added by converting to a naturally sorted set and then converting to a list for ease of use.

core/src/main/java/org/eclipsefoundation/core/response/PaginatedResultsFilter.java

@@ -2,6 +2,9 @@ package org.eclipsefoundation.core.response;
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Set;
+import java.util.TreeSet;
+import java.util.stream.Collectors;
 
 import javax.annotation.Priority;
 import javax.enterprise.inject.Instance;
@@ -60,33 +63,39 @@ public class PaginatedResultsFilter implements ContainerResponseFilter {
     public void filter(ContainerRequestContext requestContext, ContainerResponseContext responseContext)
             throws IOException {
         if (enablePagination.get()) {
-            int pageSize = getCurrentLimit(responseContext);
             Object entity = responseContext.getEntity();
             // only try and paginate if there are multiple entities
-            if (entity instanceof List) {
-                List<?> listEntity = (List<?>) entity;
-                // if available, use max results header value
-                String rawMaxSize = (String) getResponseHeader(responseContext, MAX_RESULTS_SIZE_HEADER);
-                int maxSize = listEntity.size();
-                if (StringUtils.isNumeric(rawMaxSize)) {
-                    maxSize = Integer.valueOf(rawMaxSize);
-                }
-                int page = getRequestedPage(maxSize, pageSize);
-
-                int lastPage = (int) Math.ceil((double) maxSize / pageSize);
-                // slice if the results set is larger than page size
-                if (listEntity.size() > pageSize) {
-                    // set the sliced array as the entity
-                    responseContext.setEntity(
-                            listEntity.subList(getArrayLimitedNumber(listEntity, Math.max(0, page - 1) * pageSize),
-                                    getArrayLimitedNumber(listEntity, pageSize * page)));
-                }
-                // set the link header to the response
-                responseContext.getHeaders().add("Link", createLinkHeader(page, lastPage));
+            if (entity instanceof Set) {
+                paginateResults(responseContext,
+                        (new TreeSet<>((Set<?>) entity)).stream().collect(Collectors.toList()));
+            } else if (entity instanceof List) {
+                paginateResults(responseContext, (List<?>) entity);
             }
         }
     }
 
+    private void paginateResults(ContainerResponseContext responseContext, List<?> listEntity) {
+        int pageSize = getCurrentLimit(responseContext);
+        // if available, use max results header value
+        String rawMaxSize = (String) getResponseHeader(responseContext, MAX_RESULTS_SIZE_HEADER);
+        int maxSize = listEntity.size();
+        if (StringUtils.isNumeric(rawMaxSize)) {
+            maxSize = Integer.valueOf(rawMaxSize);
+        }
+        int page = getRequestedPage(maxSize, pageSize);
+
+        int lastPage = (int) Math.ceil((double) maxSize / pageSize);
+        // slice if the results set is larger than page size
+        if (listEntity.size() > pageSize) {
+            // set the sliced array as the entity
+            responseContext
+                    .setEntity(listEntity.subList(getArrayLimitedNumber(listEntity, Math.max(0, page - 1) * pageSize),
+                            getArrayLimitedNumber(listEntity, pageSize * page)));
+        }
+        // set the link header to the response
+        responseContext.getHeaders().add("Link", createLinkHeader(page, lastPage));
+    }
+
     /**
      * Gets a header value if available, checking first the servlet response then the mutable response wrapper.
      *