Added a SET_PRIVATE_FIELDS_CONVENTION

Some existing JSON libraries set field values directly.

While we respect field access modifiers by default, this commit adds a
`SET_PRIVATE_FIELDS_CONVENTION` that can be used to directly set
private fields, thus mimicing other libraries.

This convention is not part of the default conventions and must be explicitly set.

JAVA-2648

Author: rozza

bson/src/main/org/bson/codecs/pojo/ConventionSetPrivateFieldImpl.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2017 MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.bson.codecs.pojo;
+
+import org.bson.codecs.configuration.CodecConfigurationException;
+
+import java.lang.reflect.Field;
+
+import static java.lang.String.format;
+import static java.lang.reflect.Modifier.isPrivate;
+
+final class ConventionSetPrivateFieldImpl implements Convention {
+
+    @Override
+    public void apply(final ClassModelBuilder<?> classModelBuilder) {
+        for (PropertyModelBuilder<?> propertyModelBuilder : classModelBuilder.getPropertyModelBuilders()) {
+            if (propertyModelBuilder.getPropertyAccessor() instanceof PropertyAccessorImpl) {
+                PropertyAccessorImpl<?> defaultAccessor = (PropertyAccessorImpl<?>) propertyModelBuilder.getPropertyAccessor();
+                PropertyMetadata<?> propertyMetaData = defaultAccessor.getPropertyMetadata();
+                if (!propertyMetaData.isDeserializable() && isPrivate(propertyMetaData.getField().getModifiers())) {
+                    setPropertyAccessor(propertyModelBuilder);
+                }
+            }
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    private <T> void setPropertyAccessor(final PropertyModelBuilder<T> propertyModelBuilder) {
+        propertyModelBuilder.propertyAccessor(new PrivateProperyAccessor<T>(
+                (PropertyAccessorImpl<T>) propertyModelBuilder.getPropertyAccessor()));
+    }
+
+    private static final class PrivateProperyAccessor<T> implements PropertyAccessor<T> {
+        private final PropertyAccessorImpl<T> wrapped;
+
+        private PrivateProperyAccessor(final PropertyAccessorImpl<T> wrapped) {
+            this.wrapped = wrapped;
+        }
+
+        @Override
+        public <S> T get(final S instance) {
+            return wrapped.get(instance);
+        }
+
+        @Override
+        public <S> void set(final S instance, final T value) {
+            try {
+                Field field = wrapped.getPropertyMetadata().getField();
+                field.setAccessible(true);
+                field.set(instance, value);
+            } catch (Exception e) {
+                throw new CodecConfigurationException(format("Unable to set value for property '%s' in %s",
+                        wrapped.getPropertyMetadata().getName(),
+                        wrapped.getPropertyMetadata().getDeclaringClassName()), e);
+            }
+        }
+    }
+}

bson/src/main/org/bson/codecs/pojo/Conventions.java

@@ -49,6 +49,16 @@ public final class Conventions {
      */
     public static final Convention ANNOTATION_CONVENTION = new ConventionAnnotationImpl();
 
+    /**
+     * A convention that enables private fields to be set using reflection.
+     *
+     * <p>This convention, mimics how some other JSON libraries directly set a private field when there is no setter.</p>
+     * <p>Note: This convention is not part of the {@code DEFAULT_CONVENTIONS} list and must explicitly be set.</p>
+     *
+     * @since 3.6
+     */
+    public static final Convention SET_PRIVATE_FIELDS_CONVENTION = new ConventionSetPrivateFieldImpl();
+
     /**
      * The default conventions list
      */

bson/src/main/org/bson/codecs/pojo/PropertyAccessorImpl.java

@@ -61,6 +61,10 @@ public <S> void set(final S instance, final T value) {
         }
     }
 
+    PropertyMetadata<T> getPropertyMetadata() {
+        return propertyMetadata;
+    }
+
     private CodecConfigurationException getError(final Exception cause) {
         return new CodecConfigurationException(format("Unable to get value for property '%s' in %s", propertyMetadata.getName(),
                 propertyMetadata.getDeclaringClassName()), cause);

bson/src/test/unit/org/bson/codecs/pojo/PojoCustomTest.java

@@ -36,6 +36,7 @@
 import org.bson.codecs.pojo.entities.Optional;
 import org.bson.codecs.pojo.entities.OptionalPropertyCodecProvider;
 import org.bson.codecs.pojo.entities.PrimitivesModel;
+import org.bson.codecs.pojo.entities.PrivateSetterFieldModel;
 import org.bson.codecs.pojo.entities.SimpleEnum;
 import org.bson.codecs.pojo.entities.SimpleEnumModel;
 import org.bson.codecs.pojo.entities.SimpleModel;
@@ -48,6 +49,7 @@
 import org.bson.types.ObjectId;
 import org.junit.Test;
 
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
@@ -58,7 +60,9 @@
 import static org.bson.codecs.configuration.CodecRegistries.fromCodecs;
 import static org.bson.codecs.configuration.CodecRegistries.fromProviders;
 import static org.bson.codecs.configuration.CodecRegistries.fromRegistries;
+import static org.bson.codecs.pojo.Conventions.DEFAULT_CONVENTIONS;
 import static org.bson.codecs.pojo.Conventions.NO_CONVENTIONS;
+import static org.bson.codecs.pojo.Conventions.SET_PRIVATE_FIELDS_CONVENTION;
 
 public final class PojoCustomTest extends PojoTestCase {
 
@@ -153,6 +157,17 @@ public void apply(final ClassModelBuilder<?> classModelBuilder) {
                         + "           'simple_model': {'integer_field': 42, 'string_field': 'myString' } } }");
     }
 
+    @Test
+    public void testSetPrivateFieldConvention() {
+        PojoCodecProvider.Builder builder = getPojoCodecProviderBuilder(PrivateSetterFieldModel.class);
+        ArrayList<Convention> conventions = new ArrayList<Convention>(DEFAULT_CONVENTIONS);
+        conventions.add(SET_PRIVATE_FIELDS_CONVENTION);
+        builder.conventions(conventions);
+
+        roundTrip(builder, new PrivateSetterFieldModel(1, "2", asList("a", "b")),
+                "{'integerField': 1, 'stringField': '2', listField: ['a', 'b']}");
+    }
+
     @Test
     public void testEnumSupport() {
         roundTrip(getPojoCodecProviderBuilder(SimpleEnumModel.class), new SimpleEnumModel(SimpleEnum.BRAVO), "{ 'myEnum': 'BRAVO' }");

bson/src/test/unit/org/bson/codecs/pojo/entities/PrivateSetterFieldModel.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright 2017 MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.bson.codecs.pojo.entities;
+
+import java.util.List;
+
+public final class PrivateSetterFieldModel {
+
+    private Integer integerField;
+    private String stringField;
+    private List<String> listField;
+
+    public PrivateSetterFieldModel(){
+    }
+
+    public PrivateSetterFieldModel(final Integer integerField, final String stringField, final List<String> listField) {
+        this.integerField = integerField;
+        this.stringField = stringField;
+        this.listField = listField;
+    }
+
+    public Integer getIntegerField() {
+        return integerField;
+    }
+
+    public String getStringField() {
+        return stringField;
+    }
+
+    public List<String> getListField() {
+        return listField;
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+
+        PrivateSetterFieldModel that = (PrivateSetterFieldModel) o;
+
+        if (getIntegerField() != null ? !getIntegerField().equals(that.getIntegerField()) : that.getIntegerField() != null) {
+            return false;
+        }
+        if (getStringField() != null ? !getStringField().equals(that.getStringField()) : that.getStringField() != null) {
+            return false;
+        }
+        return getListField() != null ? getListField().equals(that.getListField()) : that.getListField() == null;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = getIntegerField() != null ? getIntegerField().hashCode() : 0;
+        result = 31 * result + (getStringField() != null ? getStringField().hashCode() : 0);
+        result = 31 * result + (getListField() != null ? getListField().hashCode() : 0);
+        return result;
+    }
+}