Add support for Jackson 2.7

AbstractJackson2HttpMessageConverter now implements its own
TypeVariable resolution algorithm since in Jackson 2.7 it is now
deprecated and has not the same behavior .
See https://github.com/FasterXML/jackson-databind/issues/1087
for more details.

The dependency on jackson-datatype-jdk7 has been removed since
it is now provided by default in the jackson-databind module.

Issues: SPR-13483, SPR-13728

build.gradle

@@ -49,7 +49,7 @@ configure(allprojects) { project ->
 	ext.htmlunitVersion      = "2.19"
 	ext.httpasyncVersion     = "4.1.1"
 	ext.httpclientVersion    = "4.5.1"
-	ext.jackson2Version      = "2.6.4"
+	ext.jackson2Version      = "2.7.0"
 	ext.jasperreportsVersion = "6.2.0"
 	ext.javamailVersion      = "1.5.5"
 	ext.jettyVersion         = "9.3.6.v20151106"
@@ -735,7 +735,6 @@ project("spring-web") {
 			exclude group: "org.apache.taglibs", module: "taglibs-standard-spec"
 		}
 		testCompile("com.fasterxml.jackson.datatype:jackson-datatype-joda:${jackson2Version}")
-		testCompile("com.fasterxml.jackson.datatype:jackson-datatype-jdk7:${jackson2Version}")
 		testCompile("com.fasterxml.jackson.datatype:jackson-datatype-jdk8:${jackson2Version}")
 		testRuntime("com.sun.mail:javax.mail:${javamailVersion}")
 	}

spring-web/src/main/java/org/springframework/http/converter/json/AbstractJackson2HttpMessageConverter.java

 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -18,6 +18,7 @@ package org.springframework.http.converter.json;
 
 import java.io.IOException;
 import java.lang.reflect.Type;
+import java.lang.reflect.TypeVariable;
 import java.nio.charset.Charset;
 import java.util.concurrent.atomic.AtomicReference;
 
@@ -30,7 +31,9 @@ import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.ObjectWriter;
 import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.databind.ser.FilterProvider;
+import com.fasterxml.jackson.databind.type.TypeFactory;
 
+import org.springframework.core.ResolvableType;
 import org.springframework.http.HttpInputMessage;
 import org.springframework.http.HttpOutputMessage;
 import org.springframework.http.MediaType;
@@ -296,7 +299,35 @@ public abstract class AbstractJackson2HttpMessageConverter extends AbstractGener
 	 * @return the Jackson JavaType
 	 */
 	protected JavaType getJavaType(Type type, Class<?> contextClass) {
-		return this.objectMapper.getTypeFactory().constructType(type, contextClass);
+		TypeFactory typeFactory = this.objectMapper.getTypeFactory();
+		if (type instanceof TypeVariable && contextClass != null) {
+			ResolvableType resolvedType = resolveVariable((TypeVariable<?>)type, ResolvableType.forClass(contextClass));
+			if (resolvedType != ResolvableType.NONE) {
+				return typeFactory.constructType(resolvedType.resolve());
+			}
+		}
+		return typeFactory.constructType(type);
+	}
+
+	private ResolvableType resolveVariable(TypeVariable<?> typeVariable, ResolvableType contextType) {
+		ResolvableType resolvedType;
+		if (contextType.hasGenerics()) {
+			resolvedType = ResolvableType.forType(typeVariable, contextType);
+			if (resolvedType.resolve() != null) {
+				return resolvedType;
+			}
+		}
+		resolvedType = resolveVariable(typeVariable, contextType.getSuperType());
+		if (resolvedType.resolve() != null) {
+			return resolvedType;
+		}
+		for (ResolvableType i : contextType.getInterfaces()) {
+			resolvedType = resolveVariable(typeVariable, i);
+			if (resolvedType.resolve() != null) {
+				return resolvedType;
+			}
+		}
+		return ResolvableType.NONE;
 	}
 
 	/**

spring-web/src/test/java/org/springframework/http/converter/json/SpringHandlerInstantiatorTests.java

 /*
- * Copyright 2002-2015 the original author or authors.
+ * Copyright 2002-2016 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.
@@ -218,10 +218,15 @@ public class SpringHandlerInstantiatorTests {
 			return null;
 		}
 
-		// New in Jackson 2.5
+		@Override
 		public JavaType typeFromId(DatabindContext context, String id) {
 			return null;
 		}
+
+		// New in Jackson 2.7
+		public String getDescForKnownTypeIds() {
+			return null;
+		}
 	}