Merge pull request #1448 from Alfresco/fix/MNT-23094_prevent-error-when-sorting-by-empty-field

[MNT-23094] Prevent ArrayIndexOutOfBoundsException when sorting by empty field

(cherry picked from commit b113a05f6f1e9245a6bb01e4af1a258668aa46ea)

search-services/alfresco-search/src/main/java/org/alfresco/solr/AlfrescoCollatableTextFieldType.java

@@ -162,29 +162,39 @@ public class AlfrescoCollatableTextFieldType extends StrField
             return values[slot];
         }
 
+        /**
+         * Finds the term string value for supplied doc
+         * 
+         * @param doc
+         *            the document id that was hit
+         * @param term
+         *            a {@link BytesRef} object representing an UTF8 encoded term in the index
+         * 
+         * @return the term value in string format
+         */
         private String findBestValue(int doc, BytesRef term)
         {
             if (term.length == 0 && docsWithField != null && docsWithField.get(doc) == false)
             {
                 return null;
             }
-            
+
+            // Converts the stored bytes (as UTF8) to string
             String withLocale = term.utf8ToString();
-            
-            // split strin into MLText object
-            if (withLocale == null)
-            {
-                return withLocale;
-            }
-            else if (withLocale.startsWith("\u0000"))
+
+            if (withLocale != null && withLocale.startsWith("\u0000"))
             {
+                // the array can either be [, locale, term value] or just [, locale] depending whether the term value used
+                // to perform the sort is empty or not
                 String[] parts = withLocale.split("\u0000");
-                return parts[2];
-            }
-            else
-            {
-                return withLocale;
+
+                if (parts != null && parts.length == 3)
+                {
+                    return parts[2];
+                }
             }
+
+            return withLocale;
         }
 
         /* (non-Javadoc)

search-services/alfresco-search/src/test/java/org/alfresco/solr/AlfrescoCollatableTextFieldTypeTest.java

@@ -173,4 +173,17 @@ public class AlfrescoCollatableTextFieldTypeTest
         verify(mockCollator).compare("NotNull1", "NotNull2");
         assertEquals("Expected result to be obtained from collator.", comparisonResult, result);
     }
+
+    @Test
+    public void testMNT23094()
+    {
+        // Set up the document to have an encoded value for the field.
+        when(mockDocTerms.get(DOC)).thenReturn(new BytesRef("\u0000"));
+        when(mockDocsWithField.get(DOC)).thenReturn(false);
+
+        // Call the method under test.
+        textSortFieldComparator.compareBottom(DOC);
+
+        verify(mockCollator).compare(BOTTOM_STRING, "\u0000");
+    }
 }