fix JAVA-5764

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

@@ -25,6 +25,8 @@
 import org.bson.codecs.pojo.annotations.BsonIgnore;
 import org.bson.codecs.pojo.annotations.BsonProperty;
 import org.bson.codecs.pojo.annotations.BsonRepresentation;
+import org.bson.diagnostics.Logger;
+import org.bson.diagnostics.Loggers;
 
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Constructor;
@@ -41,6 +43,8 @@
 
 final class ConventionAnnotationImpl implements Convention {
 
+    private static final Logger LOGGER = Loggers.getLogger("ConventionAnnotation");
+
     @Override
     public void apply(final ClassModelBuilder<?> classModelBuilder) {
         for (final Annotation annotation : classModelBuilder.getAnnotations()) {
@@ -240,6 +244,15 @@ private void cleanPropertyBuilders(final ClassModelBuilder<?> classModelBuilder)
             if (!propertyModelBuilder.isReadable() && !propertyModelBuilder.isWritable()) {
                 propertiesToRemove.add(propertyModelBuilder.getName());
             }
+            if (classModelBuilder.useDiscriminator() && propertyModelBuilder.getReadName().equals(classModelBuilder.getDiscriminatorKey())) {
+                propertiesToRemove.add(propertyModelBuilder.getName());
+                LOGGER.warn(
+                        format(
+                                "Removed the property '%s' from the model because the discriminator has the same key",
+                                classModelBuilder.getDiscriminatorKey()
+                        )
+                );
+            }
         }
         for (String propertyName : propertiesToRemove) {
             classModelBuilder.removeProperty(propertyName);

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

@@ -76,13 +76,10 @@ public void encode(final BsonWriter writer, final T value, final EncoderContext
             writer.writeStartDocument();
 
             encodeIdProperty(writer, value, encoderContext, classModel.getIdPropertyModelHolder());
-
-            if (classModel.useDiscriminator()) {
-                writer.writeString(classModel.getDiscriminatorKey(), classModel.getDiscriminator());
-            }
+            encodeDiscriminatorProperty(writer);
 
             for (PropertyModel<?> propertyModel : classModel.getPropertyModels()) {
-                if (propertyModel.equals(classModel.getIdPropertyModel())) {
+                if (idProperty(propertyModel)) {
                     continue;
                 }
                 encodeProperty(writer, value, encoderContext, propertyModel);
@@ -140,6 +137,16 @@ private <S> void encodeIdProperty(final BsonWriter writer, final T instance, fin
         }
     }
 
+    private boolean idProperty(final PropertyModel<?> propertyModel) {
+        return propertyModel.equals(classModel.getIdPropertyModel());
+    }
+
+    private void encodeDiscriminatorProperty(final BsonWriter writer) {
+        if (classModel.useDiscriminator()) {
+            writer.writeString(classModel.getDiscriminatorKey(), classModel.getDiscriminator());
+        }
+    }
+
     private <S> void encodeProperty(final BsonWriter writer, final T instance, final EncoderContext encoderContext,
                                     final PropertyModel<S> propertyModel) {
         if (propertyModel != null && propertyModel.isReadable()) {

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

@@ -80,7 +80,7 @@ private <T> PojoCodec<T> createCodec(final Class<T> clazz, final CodecRegistry r
         } else if (automatic || (clazz.getPackage() != null && packages.contains(clazz.getPackage().getName()))) {
             try {
                 classModel = createClassModel(clazz, conventions);
-                if (clazz.isInterface() || !classModel.getPropertyModels().isEmpty()) {
+                if (clazz.isInterface() || !classModel.getPropertyModels().isEmpty() || classModel.useDiscriminator()) {
                     discriminatorLookup.addClassModel(classModel);
                     return new AutomaticPojoCodec<>(createCodec(classModel, registry, propertyCodecProviders,
                             discriminatorLookup));

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

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2008-present 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.pojo.entities.DiscriminatorModel;
+import org.bson.codecs.pojo.entities.DiscriminatorWithGetterModel;
+import org.bson.codecs.pojo.entities.DiscriminatorWithProperty;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+
+public final class PojoCodecDiscriminatorTest extends PojoTestCase {
+
+    @Test
+    public void testDiscriminatorEncodedOnceWhenItIsAlsoAGetter() {
+        byte[] encodedDiscriminatorModel = encode(
+                getCodec(DiscriminatorModel.class),
+                new DiscriminatorModel(),
+                false
+        ).toByteArray();
+        byte[] encodedDiscriminatorWithGetter = encode(
+                getCodec(DiscriminatorWithGetterModel.class),
+                new DiscriminatorWithGetterModel(),
+                false
+        ).toByteArray();
+        assertArrayEquals(encodedDiscriminatorModel, encodedDiscriminatorWithGetter);
+    }
+
+    @Test
+    public void testDiscriminatorRoundTripWhenItIsAlsoAGetter() {
+        roundTrip(
+                new DiscriminatorWithGetterModel(),
+                "{discriminatorKey:'discriminatorValue'}"
+        );
+    }
+
+    @Test
+    public void testDiscriminatorEncodedOnceWhenItIsAlsoAProperty() {
+        byte[] encodedDiscriminatorModel = encode(
+                getCodec(DiscriminatorModel.class),
+                new DiscriminatorModel(),
+                false
+        ).toByteArray();
+        byte[] encodedDiscriminatorWithProperty = encode(
+                getCodec(DiscriminatorWithProperty.class),
+                new DiscriminatorWithProperty(),
+                false
+        ).toByteArray();
+        assertArrayEquals(encodedDiscriminatorModel, encodedDiscriminatorWithProperty);
+    }
+
+    @Test
+    public void testDiscriminatorRoundTripWhenItIsAlsoAProperty() {
+        roundTrip(
+                new DiscriminatorWithProperty(),
+                "{discriminatorKey:'discriminatorValue'}"
+        );
+    }
+}

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

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2008-present 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 org.bson.codecs.pojo.annotations.BsonDiscriminator;
+
+@BsonDiscriminator(key = "discriminatorKey", value = "discriminatorValue")
+public class DiscriminatorModel {
+
+    public DiscriminatorModel() {
+    }
+}

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

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2008-present 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 org.bson.codecs.pojo.annotations.BsonDiscriminator;
+
+import java.util.Objects;
+
+@BsonDiscriminator(key = "discriminatorKey", value = "discriminatorValue")
+public class DiscriminatorWithGetterModel {
+
+    public DiscriminatorWithGetterModel() {
+    }
+
+    public String getDiscriminatorKey() {
+        return "discriminatorValue";
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (o == null || getClass() != o.getClass()) return false;
+        final DiscriminatorWithGetterModel that = (DiscriminatorWithGetterModel) o;
+        return Objects.equals(getDiscriminatorKey(), that.getDiscriminatorKey());
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(getDiscriminatorKey());
+    }
+
+    @Override
+    public String toString() {
+        return "DiscriminatorWithGetterModel{}";
+    }
+}

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

@@ -0,0 +1,51 @@
+/*
+ * Copyright 2008-present 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 org.bson.codecs.pojo.annotations.BsonDiscriminator;
+import org.bson.codecs.pojo.annotations.BsonProperty;
+
+import java.util.Objects;
+
+@BsonDiscriminator(key = "discriminatorKey", value = "discriminatorValue")
+public class DiscriminatorWithProperty {
+
+    public DiscriminatorWithProperty() {
+    }
+
+    @BsonProperty("discriminatorKey")
+    public String getDiscriminator() {
+        return "discriminatorValue";
+    }
+
+    @Override
+    public boolean equals(final Object o) {
+        if (o == null || getClass() != o.getClass()) return false;
+        final DiscriminatorWithProperty that = (DiscriminatorWithProperty) o;
+        return Objects.equals(getDiscriminator(), that.getDiscriminator());
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(getDiscriminator());
+    }
+
+    @Override
+    public String toString() {
+        return "DiscriminatorWithProperty{}";
+    }
+}