Add support for parameterized classes that contain generic arrays. (#118

)

Co-authored-by: Tim Johnson <[email protected]>

core/src/main/java/com/backblaze/b2/json/B2JsonHandlerMap.java

@@ -8,6 +8,7 @@
 import com.backblaze.b2.util.B2Preconditions;
 
 import java.lang.reflect.Field;
+import java.lang.reflect.GenericArrayType;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 import java.lang.reflect.Modifier;
@@ -258,6 +259,10 @@ public synchronized <T> B2JsonTypeHandler<T> getHandler(Type type) throws B2Json
             //noinspection unchecked
             handler = getUninitializedHandlerForParameterizedType(parameterizedType);
 
+        } else if (type instanceof GenericArrayType) {
+            final GenericArrayType genericArrayType = (GenericArrayType) type;
+            handler = getUninitializedHandlerForGenericArrayType(genericArrayType);
+
         } else {
             throw new B2JsonException("do not know how to get handler for type " + type.getTypeName());
         }
@@ -344,6 +349,17 @@ private synchronized B2JsonTypeHandler getUninitializedHandlerForParameterizedTy
         return new B2JsonObjectHandler(resolvedRawTypeClass, parameterizedType.getActualTypeArguments());
     }
 
+    private synchronized B2JsonTypeHandler getUninitializedHandlerForGenericArrayType(
+            GenericArrayType genericArrayType) throws B2JsonException {
+
+        // Java does not allow the component type to be a parameterized type. Therefore,
+        // we can get the Class of the generic component Type without losing information.
+        return new B2JsonObjectArrayHandler(
+                genericArrayType.getClass(),
+                genericArrayType.getGenericComponentType().getClass(),
+                getUninitializedHandler(genericArrayType.getGenericComponentType()));
+    }
+
     /**
      * Returns a list of all of the fields in a class that should be included in JSON.
      */

core/src/test/java/com/backblaze/b2/json/B2JsonTest.java

@@ -2517,6 +2517,34 @@ public void testGenerics() throws B2JsonException {
 
     }
 
+    @Test
+    public void testGenericArraySupport() throws B2JsonException {
+        final ClassWithGenericArrays objectWithGenericArrays =
+                new ClassWithGenericArrays(
+                        new ItemArray<>(new Integer[] {0, 1, 2, 3}),
+                        new ItemArray<>(new String[] {"a", "b"}));
+        final String expected = "" +
+                "{\n" +
+                "  \"intArray\": {\n" +
+                "    \"values\": [\n" +
+                "      0,\n" +
+                "      1,\n" +
+                "      2,\n" +
+                "      3\n" +
+                "    ]\n" +
+                "  },\n" +
+                "  \"stringArray\": {\n" +
+                "    \"values\": [\n" +
+                "      \"a\",\n" +
+                "      \"b\"\n" +
+                "    ]\n" +
+                "  }\n" +
+                "}";
+
+        assertEquals(expected, b2Json.toJson(objectWithGenericArrays));
+    }
+
+
     private static class ClassThatUsesGenerics {
 
         @B2Json.required
@@ -2559,4 +2587,30 @@ public T getValue() {
             return value;
         }
     }
+
+    private static class ClassWithGenericArrays {
+        @B2Json.required
+        private final ItemArray<Integer> intArray;
+
+        @B2Json.required
+        private final ItemArray<String> stringArray;
+
+
+        @B2Json.constructor(params = "intArray, stringArray")
+        public ClassWithGenericArrays(ItemArray<Integer> intArray, ItemArray<String> stringArray) {
+            this.intArray = intArray;
+            this.stringArray = stringArray;
+        }
+    }
+
+    private static class ItemArray<T> {
+
+        @B2Json.required
+        private final T[] values;
+
+        @B2Json.constructor(params = "values")
+        public ItemArray(T[] values) {
+            this.values = values;
+        }
+    }
 }