Turn (Jackson|Gson)AutoConfiguration into true auto-configuration

Previously JacksonAutoConfiguration and GsonAutoConfiguration were
not actually auto-configuration classes. They were only processed
due to being imported by HttpMessageConvertersAutoConfiguration.
In addition to being misleadingly named, this meant that they could
not be included or excluded individually and were also tightly coupled
to HTTP message conversion.

This commit updates spring.factories to make both
JacksonAutoConfiguration and GsonAutoConfiguration actual
auto-configuration classes. As a result, they can now be enabled or
disabled individually and are no longer coupled to HTTP message
conversion.

Closes gh-1562

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/web/HttpMessageConvertersAutoConfiguration.java

@@ -21,14 +21,12 @@ import java.util.List;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
-import org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration;
-import org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
-import org.springframework.context.annotation.Import;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.http.converter.json.GsonHttpMessageConverter;
 import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
@@ -44,10 +42,10 @@ import com.google.gson.Gson;
  * @author Piotr Maj
  * @author Oliver Gierke
  * @author David Liu
+ * @author Andy Wilkinson
  */
 @Configuration
 @ConditionalOnClass(HttpMessageConverter.class)
-@Import({ JacksonAutoConfiguration.class, GsonAutoConfiguration.class })
 public class HttpMessageConvertersAutoConfiguration {
 
 	@Autowired(required = false)
@@ -61,8 +59,9 @@ public class HttpMessageConvertersAutoConfiguration {
 
 	@Configuration
 	@ConditionalOnClass(ObjectMapper.class)
+	@ConditionalOnBean(ObjectMapper.class)
 	@EnableConfigurationProperties(HttpMapperProperties.class)
-	protected static class ObjectMappers {
+	protected static class MappingJackson2HttpMessageConverterConfiguration {
 
 		@Autowired
 		private HttpMapperProperties properties = new HttpMapperProperties();
@@ -81,7 +80,8 @@ public class HttpMessageConvertersAutoConfiguration {
 
 	@Configuration
 	@ConditionalOnClass(Gson.class)
-	protected static class GsonConfiguration {
+	@ConditionalOnBean(Gson.class)
+	protected static class GsonHttpMessageConverterConfiguration {
 
 		@Bean
 		@ConditionalOnMissingBean

spring-boot-autoconfigure/src/main/resources/META-INF/spring.factories

@@ -16,8 +16,10 @@ org.springframework.boot.autoconfigure.data.mongo.MongoRepositoriesAutoConfigura
 org.springframework.boot.autoconfigure.data.solr.SolrRepositoriesAutoConfiguration,\
 org.springframework.boot.autoconfigure.data.rest.RepositoryRestMvcAutoConfiguration,\
 org.springframework.boot.autoconfigure.freemarker.FreeMarkerAutoConfiguration,\
+org.springframework.boot.autoconfigure.gson.GsonAutoConfiguration,\
 org.springframework.boot.autoconfigure.hateoas.HypermediaAutoConfiguration,\
 org.springframework.boot.autoconfigure.integration.IntegrationAutoConfiguration,\
+org.springframework.boot.autoconfigure.jackson.JacksonAutoConfiguration,\
 org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration,\
 org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration,\
 org.springframework.boot.autoconfigure.jdbc.XADataSourceAutoConfiguration,\

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/web/HttpMessageConvertersAutoConfigurationTests.java

@@ -16,6 +16,9 @@
 
 package org.springframework.boot.autoconfigure.web;
 
+import java.util.Arrays;
+import java.util.List;
+
 import org.junit.After;
 import org.junit.Test;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
@@ -36,6 +39,7 @@ import static org.junit.Assert.assertTrue;
  * @author Dave Syer
  * @author Oliver Gierke
  * @author David Liu
+ * @author Andy Wilkinson
  */
 public class HttpMessageConvertersAutoConfigurationTests {
 
@@ -49,14 +53,75 @@ public class HttpMessageConvertersAutoConfigurationTests {
 	}
 
 	@Test
-	public void customJacksonConverter() throws Exception {
+	public void noObjectMapperMeansNoConverter() throws Exception {
+		this.context.register(HttpMessageConvertersAutoConfiguration.class);
+		this.context.refresh();
+		assertTrue(this.context.getBeansOfType(ObjectMapper.class).isEmpty());
+		assertTrue(this.context.getBeansOfType(MappingJackson2HttpMessageConverter.class)
+				.isEmpty());
+	}
+
+	@Test
+	public void defaultJacksonConverter() throws Exception {
 		this.context.register(JacksonConfig.class,
 				HttpMessageConvertersAutoConfiguration.class);
 		this.context.refresh();
-		MappingJackson2HttpMessageConverter converter = this.context
-				.getBean(MappingJackson2HttpMessageConverter.class);
-		assertEquals(this.context.getBean(ObjectMapper.class),
-				converter.getObjectMapper());
+
+		assertConverterBeanExists(MappingJackson2HttpMessageConverter.class,
+				"mappingJackson2HttpMessageConverter");
+
+		assertConverterBeanRegisteredWithHttpMessageConverters(MappingJackson2HttpMessageConverter.class);
+	}
+
+	@Test
+	public void customJacksonConverter() throws Exception {
+		this.context.register(JacksonConfig.class, JacksonConverterConfig.class,
+				HttpMessageConvertersAutoConfiguration.class);
+		this.context.refresh();
+
+		assertConverterBeanExists(MappingJackson2HttpMessageConverter.class,
+				"customJacksonMessageConverter");
+	}
+
+	@Test
+	public void noGson() throws Exception {
+		this.context.register(HttpMessageConvertersAutoConfiguration.class);
+		this.context.refresh();
+		assertTrue(this.context.getBeansOfType(Gson.class).isEmpty());
+		assertTrue(this.context.getBeansOfType(GsonHttpMessageConverter.class).isEmpty());
+	}
+
+	@Test
+	public void defaultGsonConverter() throws Exception {
+		this.context.register(GsonConfig.class,
+				HttpMessageConvertersAutoConfiguration.class);
+		this.context.refresh();
+		assertConverterBeanExists(GsonHttpMessageConverter.class,
+				"gsonHttpMessageConverter");
+
+		assertConverterBeanRegisteredWithHttpMessageConverters(GsonHttpMessageConverter.class);
+	}
+
+	@Test
+	public void customGsonConverter() throws Exception {
+		this.context.register(GsonConfig.class, GsonConverterConfig.class,
+				HttpMessageConvertersAutoConfiguration.class);
+		this.context.refresh();
+		assertConverterBeanExists(GsonHttpMessageConverter.class,
+				"customGsonMessageConverter");
+
+		assertConverterBeanRegisteredWithHttpMessageConverters(GsonHttpMessageConverter.class);
+	}
+
+	private void assertConverterBeanExists(Class<?> type, String beanName) {
+		assertEquals(1, this.context.getBeansOfType(type).size());
+		List<String> beanNames = Arrays.asList(this.context.getBeanDefinitionNames());
+		assertTrue(beanName + " not found in " + beanNames, beanNames.contains(beanName));
+	}
+
+	private void assertConverterBeanRegisteredWithHttpMessageConverters(Class<?> type) {
+
+		Object converter = this.context.getBean(type);
 		HttpMessageConverters converters = this.context
 				.getBean(HttpMessageConverters.class);
 		assertTrue(converters.getConverters().contains(converter));
@@ -64,48 +129,42 @@ public class HttpMessageConvertersAutoConfigurationTests {
 
 	@Configuration
 	protected static class JacksonConfig {
-
-		@Bean
-		public MappingJackson2HttpMessageConverter jacksonMessageConverter() {
-			MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
-			converter.setObjectMapper(objectMapper());
-			return converter;
-		}
-
 		@Bean
 		public ObjectMapper objectMapper() {
 			return new ObjectMapper();
 		}
-
 	}
 
-	@Test
-	public void customGsonConverter() throws Exception {
-		this.context.register(GsonConfig.class,
-				HttpMessageConvertersAutoConfiguration.class);
-		this.context.refresh();
-		GsonHttpMessageConverter converter = this.context
-				.getBean(GsonHttpMessageConverter.class);
-		assertEquals(this.context.getBean(Gson.class), converter.getGson());
-		HttpMessageConverters converters = this.context
-				.getBean(HttpMessageConverters.class);
-		assertTrue(converters.getConverters().contains(converter));
+	@Configuration
+	protected static class JacksonConverterConfig {
+
+		@Bean
+		public MappingJackson2HttpMessageConverter customJacksonMessageConverter(
+				ObjectMapper objectMapper) {
+			MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
+			converter.setObjectMapper(objectMapper);
+			return converter;
+		}
 	}
 
 	@Configuration
 	protected static class GsonConfig {
 
-		@Bean
-		public GsonHttpMessageConverter gsonMessageConverter() {
-			GsonHttpMessageConverter converter = new GsonHttpMessageConverter();
-			converter.setGson(gson());
-			return converter;
-		}
-
 		@Bean
 		public Gson gson() {
 			return new Gson();
 		}
 	}
 
+	@Configuration
+	protected static class GsonConverterConfig {
+
+		@Bean
+		public GsonHttpMessageConverter customGsonMessageConverter(Gson gson) {
+			GsonHttpMessageConverter converter = new GsonHttpMessageConverter();
+			converter.setGson(gson);
+			return converter;
+		}
+	}
+
 }