Introduce ObjectCodec to support bindNull(Object.class)

[resolves #664]

src/main/java/io/r2dbc/postgresql/codec/DefaultCodecs.java

@@ -268,7 +268,7 @@ EncodedParameter encodeParameterValue(Object value, @Nullable PostgresTypeIdenti
         if (dataType == null) {
 
             if (parameterValue == null) {
-                throw new IllegalArgumentException(String.format("Cannot encode null value %s using type inference", value));
+                return ObjectCodec.INSTANCE.encodeNull();
             }
 
             Codec<?> codec = this.codecLookup.findEncodeCodec(parameterValue);
@@ -294,6 +294,10 @@ EncodedParameter encodeParameterValue(Object value, @Nullable PostgresTypeIdenti
     public EncodedParameter encodeNull(Class<?> type) {
         Assert.requireNonNull(type, "type must not be null");
 
+        if (type == Object.class) {
+            return ObjectCodec.INSTANCE.encodeNull();
+        }
+
         Codec<?> codec = this.codecLookup.findEncodeNullCodec(type);
         if (codec != null) {
             return codec.encodeNull();

src/main/java/io/r2dbc/postgresql/codec/ObjectCodec.java

@@ -0,0 +1,72 @@
+/*
+ * Copyright 2024 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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 io.r2dbc.postgresql.codec;
+
+import io.netty.buffer.ByteBuf;
+import io.r2dbc.postgresql.client.EncodedParameter;
+import io.r2dbc.postgresql.message.Format;
+
+import static io.r2dbc.postgresql.codec.PostgresqlObjectId.UNSPECIFIED;
+import static io.r2dbc.postgresql.message.Format.FORMAT_TEXT;
+
+final class ObjectCodec implements Codec<Object> {
+
+    static final ObjectCodec INSTANCE = new ObjectCodec();
+
+    private ObjectCodec() {
+    }
+
+    @Override
+    public EncodedParameter encodeNull() {
+        return AbstractCodec.createNull(FORMAT_TEXT, UNSPECIFIED);
+    }
+
+    public EncodedParameter encodeNull(int dataType) {
+        return new EncodedParameter(FORMAT_TEXT, dataType, EncodedParameter.NULL_VALUE);
+    }
+
+    @Override
+    public boolean canDecode(int dataType, Format format, Class<?> type) {
+        return false;
+    }
+
+    @Override
+    public boolean canEncode(Object value) {
+        return false;
+    }
+
+    @Override
+    public boolean canEncodeNull(Class<?> type) {
+        return Object.class.equals(type);
+    }
+
+    @Override
+    public Object decode(ByteBuf buffer, int dataType, Format format, Class<?> type) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public EncodedParameter encode(Object value) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public EncodedParameter encode(Object value, int dataType) {
+        throw new UnsupportedOperationException();
+    }
+
+}

src/test/java/io/r2dbc/postgresql/codec/ObjectCodecIntegrationTests.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2024 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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 io.r2dbc.postgresql.codec;
+
+import io.r2dbc.postgresql.AbstractIntegrationTests;
+import org.junit.jupiter.api.Test;
+import reactor.test.StepVerifier;
+
+/**
+ * Integration tests for {@link ObjectCodec} usage.
+ */
+class ObjectCodecIntegrationTests extends AbstractIntegrationTests {
+
+    @Test
+    void shouldEncodeNull() {
+
+        SERVER.getJdbcOperations().execute("DROP TABLE IF EXISTS test");
+        SERVER.getJdbcOperations().execute("CREATE TABLE test (ci INT4, cs VARCHAR)");
+
+        this.connection.createStatement("INSERT INTO test VALUES($1, $2)")
+            .bindNull("$1", Object.class)
+            .bindNull("$2", Object.class)
+            .execute()
+            .flatMap(it -> it.getRowsUpdated())
+            .as(StepVerifier::create)
+            .expectNext(1L)
+            .verifyComplete();
+
+        SERVER.getJdbcOperations().execute("DROP TABLE test");
+    }
+
+}