DATACMNS-1386 - Avoid strong type dependency to Jackson in SpringDataWebConfiguration.

We now avoid using a Lambda to provide a default ObjectMapper instance in the code that's reflectively guarded against Jackson not being present. The lambda causes a method to be generated for the class that will require ObjectMapper to be present on reflection inspection of that method. Switching to a method reference to ObjectMapper's constructor resolves that problem as the indirection via the additional, offending method is not needed.

Further reading: https://www.javabullets.com/how-lambdas-and-anonymous-inner-classesaic-work/

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

@@ -158,7 +158,7 @@ public class SpringDataWebConfiguration implements WebMvcConfigurer, BeanClassLo
 		if (ClassUtils.isPresent("com.jayway.jsonpath.DocumentContext", context.getClassLoader())
 				&& ClassUtils.isPresent("com.fasterxml.jackson.databind.ObjectMapper", context.getClassLoader())) {
 
-			ObjectMapper mapper = getUniqueBean(ObjectMapper.class, context, () -> new ObjectMapper());
+			ObjectMapper mapper = getUniqueBean(ObjectMapper.class, context, ObjectMapper::new);
 
 			ProjectingJackson2HttpMessageConverter converter = new ProjectingJackson2HttpMessageConverter(mapper);
 			converter.setBeanFactory(context);

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

@@ -28,10 +28,12 @@ import org.springframework.context.annotation.AnnotationConfigApplicationContext
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.data.classloadersupport.HidingClassLoader;
+import org.springframework.data.classloadersupport.ShadowingClassLoader;
 import org.springframework.data.web.ProjectingJackson2HttpMessageConverter;
 import org.springframework.data.web.XmlBeamHttpMessageConverter;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.test.util.ReflectionTestUtils;
+import org.springframework.util.ReflectionUtils;
 import org.xmlbeam.XBProjector;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
@@ -108,8 +110,13 @@ public class SpringDataWebConfigurationIntegrationTests {
 		}, SomeConfiguration.class);
 	}
 
-	private void createConfigWithClassLoader(ClassLoader classLoader, Consumer<SpringDataWebConfiguration> callback,
-			Class<?>... additionalConfigurationClasses) {
+	@Test // DATACMNS-1386
+	public void doesNotFailWithJacksonMissing() throws Exception {
+		ReflectionUtils.getUniqueDeclaredMethods(loadWithout(SpringDataWebConfiguration.class, ObjectMapper.class));
+	}
+
+	private static void createConfigWithClassLoader(ClassLoader classLoader,
+			Consumer<SpringDataWebConfiguration> callback, Class<?>... additionalConfigurationClasses) {
 
 		List<Class<?>> configClasses = new ArrayList<>(Arrays.asList(additionalConfigurationClasses));
 		configClasses.add(SpringDataWebConfiguration.class);
@@ -122,6 +129,16 @@ public class SpringDataWebConfigurationIntegrationTests {
 		}
 	}
 
+	private static Class<?> loadWithout(Class<?> configurationClass, Class<?>... typesOfPackagesToExclude)
+			throws ClassNotFoundException {
+
+		HidingClassLoader hidingClassLoader = HidingClassLoader.hide(typesOfPackagesToExclude);
+		ShadowingClassLoader loader = new ShadowingClassLoader(hidingClassLoader);
+		loader.excludeClass(configurationClass.getName());
+
+		return loader.loadClass(configurationClass.getName());
+	}
+
 	/**
 	 * Creates a {@link Condition} that checks if an object is an instance of a class with the same name as the provided
 	 * class. This is necessary since we are dealing with multiple classloaders which would make a simple instanceof fail