Use legacy page serialization mode if no SpringDataWebSettings are present.

Fixes GH-3101.

Author: odrotbohm

src/main/java/org/springframework/data/web/config/SpringDataJacksonConfiguration.java

@@ -17,7 +17,6 @@
 
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
-
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.context.annotation.Bean;
 import org.springframework.data.domain.Page;
@@ -40,8 +39,7 @@
  */
 public class SpringDataJacksonConfiguration implements SpringDataJacksonModules {
 
-	@Nullable
-	@Autowired(required = false) SpringDataWebSettings settings;
+	@Nullable @Autowired(required = false) SpringDataWebSettings settings;
 
 	@Bean
 	public GeoModule jacksonGeoModule() {
@@ -84,7 +82,7 @@ public PageModule(@Nullable SpringDataWebSettings settings) {
 
 			addSerializer(UNPAGED_TYPE, new UnpagedAsInstanceSerializer());
 
-			if (settings != null && settings.pageSerializationMode() == PageSerializationMode.DIRECT) {
+			if (settings == null || settings.pageSerializationMode() == PageSerializationMode.DIRECT) {
 				setMixInAnnotation(PageImpl.class, WarningMixing.class);
 			} else {
 				setMixInAnnotation(PageImpl.class, WrappingMixing.class);

src/test/java/org/springframework/data/web/config/SpringDataJacksonConfigurationUnitTests.java

@@ -0,0 +1,42 @@
+/*
+ * 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 org.springframework.data.web.config;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.data.domain.PageImpl;
+import org.springframework.data.web.config.SpringDataJacksonConfiguration.PageModule;
+import org.springframework.data.web.config.SpringDataJacksonConfiguration.PageModule.WarningMixing;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+/**
+ * Unit tests for {@link SpringDataJacksonConfiguration}.
+ *
+ * @author Oliver Drotbohm
+ */
+class SpringDataJacksonConfigurationUnitTests {
+
+	@Test // GH-3101
+	void usesDirectRenderingIfNoSpringDataWebSettingsArePresent() {
+
+		ObjectMapper mapper = new ObjectMapper();
+		mapper.registerModule(new PageModule(null));
+
+		assertThat(mapper.getSerializationConfig().findMixInClassFor(PageImpl.class)).isEqualTo(WarningMixing.class);
+	}
+}