openstack: adjusting deserialization to treat {} as null if (and ONLY if) a null pointer is thrown when attempting to construct an object from the empty json object ({})

core/src/main/java/org/jclouds/json/internal/DeserializationConstructorAndReflectiveTypeAdapterFactory.java

@@ -52,6 +52,9 @@ import com.google.gson.stream.JsonWriter;
  * If there's an annotation designating a parameterized constructor, invoke that for fields
  * correlating to named parameter annotations. Otherwise, use {@link ConstructorConstructor}, and
  * set fields via reflection.
+ * <p/>
+ * Notes: primitive constructor params are set to the Java defaults (0 or false) if not present; and
+ *  the empty object ({}) is treated as a null if the constructor for the object throws an NPE.
  * <li>Serialization</li>
  * Serialize based on reflective access to fields, delegating to ReflectiveTypeAdaptor.
  * </ul>
@@ -155,8 +158,9 @@ public final class DeserializationConstructorAndReflectiveTypeAdapterFactory imp
 
          Class<?>[] paramTypes = parameterizedCtor.getParameterTypes();
          Object[] ctorParams = new Object[paramTypes.length];
+         boolean empty = true;
 
-         // TODO determine if we can drop this
+         // Set all primitive constructor params to defaults
          for (int i = 0; i < paramTypes.length; i++) {
             if (paramTypes[i] == boolean.class) {
                ctorParams[i] = Boolean.FALSE;
@@ -168,6 +172,7 @@ public final class DeserializationConstructorAndReflectiveTypeAdapterFactory imp
          try {
             in.beginObject();
             while (in.hasNext()) {
+               empty = false;
                String name = in.nextName();
                ParameterReader parameter = parameterReaders.get(name);
                if (parameter == null) {
@@ -183,12 +188,21 @@ public final class DeserializationConstructorAndReflectiveTypeAdapterFactory imp
 
          for (int i = 0; i < paramTypes.length; i++) {
             if (paramTypes[i].isPrimitive()) {
-               checkArgument(ctorParams[i] != null, "Primative param[" + i + "] in constructor " + parameterizedCtor
+               checkArgument(ctorParams[i] != null, "Primitive param[" + i + "] in constructor " + parameterizedCtor
                      + " cannot be absent!");
             }
          }
          in.endObject();
+
+         try {
             return newInstance(ctorParams);
+         } catch (NullPointerException ex) {
+            // If {} was found and constructor threw NPE, we treat the field as null
+            if (empty && paramTypes.length > 0) {
+               return null;
+            }
+            throw ex;
+         }
       }
 
       /**

core/src/test/java/org/jclouds/json/internal/DeserializationConstructorAndReflectiveTypeAdapterFactoryTest.java

@@ -18,6 +18,7 @@ package org.jclouds.json.internal;
  * under the License.
  */
 
+import static com.google.common.base.Preconditions.checkNotNull;
 import static org.testng.Assert.assertEquals;
 import static org.testng.Assert.assertNotSame;
 import static org.testng.Assert.assertNull;
@@ -38,6 +39,7 @@ import org.jclouds.json.internal.NamingStrategies.ExtractNamed;
 import org.jclouds.json.internal.NamingStrategies.ExtractSerializedName;
 import org.testng.annotations.Test;
 
+import com.google.common.base.Objects;
 import com.google.common.collect.ImmutableSet;
 import com.google.gson.FieldNamingStrategy;
 import com.google.gson.Gson;
@@ -164,6 +166,8 @@ public final class DeserializationConstructorAndReflectiveTypeAdapterFactoryTest
          return true;
       }
 
+      @Override
+      public String toString() { return "ValidatedConstructor[foo=" + foo + ",bar=" + bar + "]"; }
    }
 
    public void testValidatedConstructor() throws IOException {
@@ -227,7 +231,6 @@ public final class DeserializationConstructorAndReflectiveTypeAdapterFactoryTest
             return false;
          return true;
       }
-
    }
 
    public void testRenamedFields() throws IOException {
@@ -236,6 +239,44 @@ public final class DeserializationConstructorAndReflectiveTypeAdapterFactoryTest
       assertEquals(adapter.toJson(new RenamedFields(0, 1)), "{\"foo\":0,\"_bar\":1}");
    }
 
+   private static class ComposedObjects {
+      final ValidatedConstructor x;
+      final ValidatedConstructor y;
+
+      @ConstructorProperties({"x", "y"})
+      ComposedObjects(ValidatedConstructor x, ValidatedConstructor y) {
+         this.x = checkNotNull(x);
+         this.y = checkNotNull(y);
+      }
+
+      @Override
+      public boolean equals(Object obj) {
+         ComposedObjects other = ComposedObjects.class.cast(obj);
+         return other != null && Objects.equal(x, other.x) && Objects.equal(y, other.y);
+      }
+      
+      @Override
+      public String toString() { return "ComposedObjects[x=" + x.toString() + ";y=" + y.toString() + "]"; }
+   }
+   
+   public void checkSimpleComposedObject() throws IOException  {
+      ValidatedConstructor x = new ValidatedConstructor(0,1);
+      ValidatedConstructor y = new ValidatedConstructor(1,2);
+      TypeAdapter<ComposedObjects> adapter = parameterizedCtorFactory.create(gson, TypeToken.get(ComposedObjects.class));
+      assertEquals(new ComposedObjects(x, y), adapter.fromJson("{\"x\":{\"foo\":0,\"bar\":1},\"y\":{\"foo\":1,\"bar\":2}}"));
+   }
+
+   public void testEmptyObjectIsNull() throws IOException {
+      TypeAdapter<ComposedObjects> adapter = parameterizedCtorFactory.create(gson, TypeToken.get(ComposedObjects.class));
+      assertNull(adapter.fromJson("{}"));
+   }
+
+   @Test(expectedExceptions = NullPointerException.class)
+   public void testPartialObjectStillThrows() throws IOException {
+      TypeAdapter<ComposedObjects> adapter = parameterizedCtorFactory.create(gson, TypeToken.get(ComposedObjects.class));
+      assertNull(adapter.fromJson("{\"x\":{\"foo\":0,\"bar\":1}}"));
+   }
+
    public void testCanOverrideDefault() throws IOException {
       Gson gson = new GsonBuilder().registerTypeAdapterFactory(parameterizedCtorFactory).create();