Minor refactoring wrt #4149

Author: cowtowncoder

src/test/java/com/fasterxml/jackson/databind/deser/TestMixedCollections.java

@@ -27,7 +27,7 @@ public XBean() { }
     /**********************************************************************
      */
 
-    private final static ObjectMapper MAPPER = new ObjectMapper();
+    private final static ObjectMapper MAPPER = newJsonMapper();
 
     // And then a round-trip test for singleton collections
     public void testSingletonCollections() throws Exception
@@ -60,15 +60,8 @@ public void testUnmodifiableSet() throws Exception
 
         assertEquals("[\"java.util.Collections$UnmodifiableSet\",[\"a\"]]", json);
 
-        // 04-Jan-2018, tatu: Alas, no way to make this actually work well, at this point.
-         //   In theory could jiggle things back on deser, using one of two ways:
-         //
-         //   1) Do mapping to regular Set/List types (abstract type mapping): would work, but get rid of immutability
-         //   2) Have actually separate deserializer OR ValueInstantiator
-        /*
-        Set<String> result = mapper.readValue(json, Set.class);
+        Set<?> result = mapper.readValue(json, Set.class);
         assertNotNull(result);
         assertEquals(1, result.size());
-        */
     }
 }

src/test/java/com/fasterxml/jackson/databind/deser/jdk/JDKCollectionsDeserTest.java

@@ -0,0 +1,40 @@
+package com.fasterxml.jackson.databind.deser.jdk;
+
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import com.fasterxml.jackson.core.type.TypeReference;
+import com.fasterxml.jackson.databind.BaseMapTest;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+public class NestedCollectionsTest extends BaseMapTest
+{
+    private final static ObjectMapper MAPPER = newJsonMapper();
+
+    // Tests from [databind#4149] to show problems wrt [databind#4122]
+
+    public void testMapOfLists() throws Exception
+    {
+        List<Integer> l1 = Arrays.asList(1, 2);
+        List<Integer> l2 = Arrays.asList(3, 4);
+        HashMap<Object, Object> src = new HashMap<>();
+        src.put("key1", l1);
+        src.put("key2", l2);
+        String json = MAPPER.writeValueAsString(src);
+        assertEquals(src, MAPPER.readValue(json,
+                new TypeReference<Map<?, List<?>>>() {}));
+    }
+
+    public void testMapOfMaps() throws Exception
+    {
+        HashMap<Object, Object> src = new HashMap<>();
+        HashMap<Object, Object> innerMap = new HashMap<>();
+        innerMap.put("X", "Y");
+        src.put("1", innerMap);
+        String json = MAPPER.writeValueAsString(src);
+        assertEquals(src, MAPPER.readValue(json, new TypeReference<Map<?, Map<?, ?>>>() {}));
+    }    
+
+}