Order jacksonCodecCustomizer so user-provided customizer can go after it

Closes gh-15167

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/http/codec/CodecsAutoConfiguration.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -26,6 +26,7 @@ import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
 import org.springframework.boot.web.codec.CodecCustomizer;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.core.annotation.Order;
 import org.springframework.http.codec.CodecConfigurer;
 import org.springframework.http.codec.json.Jackson2JsonDecoder;
 import org.springframework.http.codec.json.Jackson2JsonEncoder;
@@ -51,6 +52,7 @@ public class CodecsAutoConfiguration {
 	static class JacksonCodecConfiguration {
 
 		@Bean
+		@Order(0)
 		@ConditionalOnBean(ObjectMapper.class)
 		public CodecCustomizer jacksonCodecCustomizer(ObjectMapper objectMapper) {
 			return (configurer) -> {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/http/codec/CodecsAutoConfigurationTests.java

+/*
+ * Copyright 2012-2018 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
+ *
+ *      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.springframework.boot.autoconfigure.http.codec;
+
+import java.util.List;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.Test;
+
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+import org.springframework.boot.web.codec.CodecCustomizer;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.http.codec.CodecConfigurer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link CodecsAutoConfiguration}.
+ *
+ * @author Andy Wilkinson
+ */
+public class CodecsAutoConfigurationTests {
+
+	private ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(CodecsAutoConfiguration.class));
+
+	@Test
+	public void jacksonCodecCustomizerBacksOffWhenThereIsNoObjectMapper() {
+		this.contextRunner.run(
+				(context) -> assertThat(context).doesNotHaveBean(CodecCustomizer.class));
+	}
+
+	@Test
+	public void jacksonCodecCustomizerIsAutoConfiguredWhenObjectMapperIsPresent() {
+		this.contextRunner.withUserConfiguration(ObjectMapperConfiguration.class).run(
+				(context) -> assertThat(context).hasSingleBean(CodecCustomizer.class));
+	}
+
+	@Test
+	public void userProvidedCustomizerCanOverrideJacksonCodecCustomizer() {
+		this.contextRunner.withUserConfiguration(ObjectMapperConfiguration.class,
+				CodecCustomizerConfiguration.class).run((context) -> {
+					List<CodecCustomizer> codecCustomizers = context
+							.getBean(CodecCustomizers.class).codecCustomizers;
+					assertThat(codecCustomizers).hasSize(2);
+					assertThat(codecCustomizers.get(1))
+							.isInstanceOf(TestCodecCustomizer.class);
+				});
+	}
+
+	@Configuration
+	static class ObjectMapperConfiguration {
+
+		@Bean
+		ObjectMapper objectMapper() {
+			return new ObjectMapper();
+		}
+
+	}
+
+	@Configuration
+	static class CodecCustomizerConfiguration {
+
+		@Bean
+		CodecCustomizer codecCustomizer() {
+			return new TestCodecCustomizer();
+		}
+
+		@Bean
+		CodecCustomizers codecCustomizers(List<CodecCustomizer> customizers) {
+			return new CodecCustomizers(customizers);
+		}
+
+	}
+
+	private static final class TestCodecCustomizer implements CodecCustomizer {
+
+		@Override
+		public void customize(CodecConfigurer configurer) {
+		}
+
+	}
+
+	private static final class CodecCustomizers {
+
+		private final List<CodecCustomizer> codecCustomizers;
+
+		private CodecCustomizers(List<CodecCustomizer> codecCustomizers) {
+			this.codecCustomizers = codecCustomizers;
+		}
+
+	}
+
+}