Support JsonSerializer/JsonDeserializer Beans

Add a `@JsonComponent` annotation that can be used to indicate that a
Bean is a JsonSerializer and/or JsonDeserializer that should be
registered with Jackson.

Support is provide via a new `JsonComponentModule` which is
auto-configured in `JacksonAutoConfiguration`.

Also add `JsonObjectSerializer` and `JsonObjectDeserializer` classes
which provided as a convenient base for serializers that work with
Objects.

Fixes gh-3898

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jackson/JacksonAutoConfiguration.java

@@ -46,6 +46,7 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnJava;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnJava.JavaVersion;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.context.properties.EnableConfigurationProperties;
+import org.springframework.boot.jackson.JsonComponentModule;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -75,6 +76,11 @@ import org.springframework.util.ReflectionUtils;
 @ConditionalOnClass(ObjectMapper.class)
 public class JacksonAutoConfiguration {
 
+	@Bean
+	public JsonComponentModule jsonComponentModule() {
+		return new JsonComponentModule();
+	}
+
 	@Configuration
 	@ConditionalOnClass({ ObjectMapper.class, Jackson2ObjectMapperBuilder.class })
 	static class JacksonObjectMapperConfiguration {

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jackson/JacksonAutoConfigurationTests.java

@@ -50,10 +50,13 @@ import org.junit.Before;
 import org.junit.Test;
 
 import org.springframework.boot.autoconfigure.web.HttpMessageConvertersAutoConfiguration;
+import org.springframework.boot.jackson.JsonComponent;
+import org.springframework.boot.jackson.JsonObjectSerializer;
 import org.springframework.boot.test.EnvironmentTestUtils;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
 import org.springframework.context.annotation.Primary;
 import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
 
@@ -347,6 +350,7 @@ public class JacksonAutoConfigurationTests {
 		assertThat(this.context.getBean(CustomModule.class).getOwners())
 				.contains((ObjectCodec) objectMapper);
 		assertThat(objectMapper.canSerialize(LocalDateTime.class)).isTrue();
+		assertThat(objectMapper.canSerialize(Baz.class)).isTrue();
 	}
 
 	@Test
@@ -456,12 +460,14 @@ public class JacksonAutoConfigurationTests {
 	}
 
 	@Configuration
+	@Import(BazSerializer.class)
 	protected static class ModuleConfig {
 
 		@Bean
 		public CustomModule jacksonModule() {
 			return new CustomModule();
 		}
+
 	}
 
 	@Configuration
@@ -538,6 +544,20 @@ public class JacksonAutoConfigurationTests {
 		}
 	}
 
+	@JsonComponent
+	private static class BazSerializer extends JsonObjectSerializer<Baz> {
+
+		@Override
+		protected void serializeObject(Baz value, JsonGenerator jgen,
+				SerializerProvider provider) throws IOException {
+		}
+
+	}
+
+	private static class Baz {
+
+	}
+
 	private static class CustomModule extends SimpleModule {
 
 		private Set<ObjectCodec> owners = new HashSet<ObjectCodec>();
@@ -552,4 +572,5 @@ public class JacksonAutoConfigurationTests {
 		}
 
 	}
+
 }

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -1470,6 +1470,51 @@ converters. You can also override default converters that way.
 
 
 
+[[boot-features-json-components]]
+==== Custom JSON Serializers and Deserializers
+If you're using Jackson to serialize and deserialize JSON data, you might want to write
+your own `JsonSerializer` and `JsonDeserializer` classes. Custom serializers are usually
+http://wiki.fasterxml.com/JacksonHowToCustomDeserializers[registered with Jackson via a Module],
+but Spring Boot provides an alternative `@JsonComponent` annotation which makes it easier
+to directly register Spring Beans.
+
+You can use `@JsonComponent` directly on `JsonSerializer` or `JsonDeserializer`
+implementations. You can also use it on classes that contains serializers/deserializers as
+inner-classes. For example:
+
+[source,java,indent=0]
+----
+	import java.io.*;
+	import com.fasterxml.jackson.core.*;
+	import com.fasterxml.jackson.databind.*;
+	import org.springframework.boot.jackson.*;
+
+	@JsonComponent
+	public class Example {
+
+		public static class Serializer extends JsonSerializer<SomeObject> {
+			// ...
+		}
+
+		public static class Deserializer extends JsonDeserializer<SomeObject> {
+			// ...
+		}
+
+	}
+----
+
+All `@JsonComponent` beans in the `ApplicationContext` will be automatically registered with
+Jackson, and since `@JsonComponent` is meta-annotated with `@Component`, the usual
+component-scanning rules apply.
+
+Spring Boot also provides
+{sc-spring-boot}/jackson/JsonObjectSerializer.{sc-ext}[`JsonObjectSerializer`] and
+{sc-spring-boot}/jackson/JsonObjectDeserializer.{sc-ext}[`JsonObjectDeserializer`] base
+classes which provide useful alternatives to the standard Jackson versions when
+serializing Objects. See the Javadoc for details.
+
+
+
 [[boot-features-spring-message-codes]]
 ==== MessageCodesResolver
 Spring MVC has a strategy for generating error codes for rendering error messages

spring-boot/src/main/java/org/springframework/boot/jackson/JsonComponent.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2012-2016 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.
+ * 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.jackson;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import com.fasterxml.jackson.databind.JsonSerializer;
+
+import org.springframework.stereotype.Component;
+
+/**
+ * {@link Component} that provides {@link JsonSerializer} and/or {@link JsonDeserializer}
+ * implementations to be registered with Jackson when {@link JsonComponentModule} is in
+ * use. Can be used to annotate {@link JsonSerializer} or {@link JsonDeserializer}
+ * implementations directly or a class that contains them as inner-classes. For example:
+ * <pre class="code">
+ * &#064;JsonComponent
+ * public class CustomerJsonComponent {
+ *
+ *     public static class Serializer extends JsonSerializer&lt;Customer&gt; {
+ *
+ *         // ...
+ *
+ *     }
+ *
+ *     public static class Deserializer extends JsonDeserializer&lt;Customer&gt; {
+ *
+ *         // ...
+ *
+ *     }
+ *
+ * }
+ *
+ * </pre>
+ *
+ * @see JsonComponentModule
+ * @since 1.4.0
+ * @author Phillip Webb
+ */
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+@Component
+public @interface JsonComponent {
+
+	/**
+	 * The value may indicate a suggestion for a logical component name, to be turned into
+	 * a Spring bean in case of an autodetected component.
+	 */
+	String value() default "";
+
+}

spring-boot/src/main/java/org/springframework/boot/jackson/JsonComponentModule.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright 2012-2016 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.
+ * 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.jackson;
+
+import java.util.Map;
+
+import javax.annotation.PostConstruct;
+
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.Module;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+
+import org.springframework.beans.BeansException;
+import org.springframework.beans.factory.BeanFactory;
+import org.springframework.beans.factory.BeanFactoryAware;
+import org.springframework.beans.factory.HierarchicalBeanFactory;
+import org.springframework.beans.factory.ListableBeanFactory;
+import org.springframework.core.ResolvableType;
+
+/**
+ * Spring Bean and Jackson {@link Module} to register {@link JsonComponent} annotated
+ * beans.
+ *
+ * @author Phillip Webb
+ * @since 1.4.0
+ * @see JsonComponent
+ */
+public class JsonComponentModule extends SimpleModule implements BeanFactoryAware {
+
+	private BeanFactory beanFactory;
+
+	@Override
+	public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
+		this.beanFactory = beanFactory;
+	}
+
+	@PostConstruct
+	public void registerJsonComponents() {
+		BeanFactory beanFactory = this.beanFactory;
+		while (beanFactory != null) {
+			if (beanFactory instanceof ListableBeanFactory) {
+				addJsonBeans((ListableBeanFactory) beanFactory);
+			}
+			beanFactory = (beanFactory instanceof HierarchicalBeanFactory
+					? ((HierarchicalBeanFactory) beanFactory).getParentBeanFactory()
+					: null);
+		}
+	}
+
+	private void addJsonBeans(ListableBeanFactory beanFactory) {
+		Map<String, Object> beans = beanFactory
+				.getBeansWithAnnotation(JsonComponent.class);
+		for (Object bean : beans.values()) {
+			addJsonBean(bean);
+		}
+	}
+
+	private void addJsonBean(Object bean) {
+		if (bean instanceof JsonSerializer) {
+			addSerializerWithDeducedType((JsonSerializer<?>) bean);
+		}
+		if (bean instanceof JsonDeserializer) {
+			addDeserializerWithDeducedType((JsonDeserializer<?>) bean);
+		}
+		for (Class<?> innerClass : bean.getClass().getDeclaredClasses()) {
+			if (JsonSerializer.class.isAssignableFrom(innerClass)
+					|| JsonDeserializer.class.isAssignableFrom(innerClass)) {
+				try {
+					addJsonBean(innerClass.newInstance());
+				}
+				catch (Exception ex) {
+					throw new IllegalStateException(ex);
+				}
+			}
+		}
+	}
+
+	@SuppressWarnings({ "unchecked" })
+	private <T> void addSerializerWithDeducedType(JsonSerializer<T> serializer) {
+		ResolvableType type = ResolvableType.forClass(JsonSerializer.class,
+				serializer.getClass());
+		addSerializer((Class<T>) type.resolveGeneric(), serializer);
+	}
+
+	@SuppressWarnings({ "unchecked" })
+	private <T> void addDeserializerWithDeducedType(JsonDeserializer<T> deserializer) {
+		ResolvableType type = ResolvableType.forClass(JsonDeserializer.class,
+				deserializer.getClass());
+		addDeserializer((Class<T>) type.resolveGeneric(), deserializer);
+	}
+
+}

spring-boot/src/main/java/org/springframework/boot/jackson/JsonObjectDeserializer.java

@@ -0,0 +1,138 @@
+/*
+ * Copyright 2012-2016 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.
+ * 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.jackson;
+
+import java.io.IOException;
+import java.math.BigDecimal;
+import java.math.BigInteger;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.ObjectCodec;
+import com.fasterxml.jackson.core.TreeNode;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonDeserializer;
+import com.fasterxml.jackson.databind.JsonMappingException;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.node.NullNode;
+
+import org.springframework.util.Assert;
+
+/**
+ * Helper base class for {@link JsonDeserializer} implementations that deserialize
+ * objects.
+ *
+ * @param <T> The supported object type
+ * @author Phillip Webb
+ * @since 1.4.0
+ * @see JsonObjectSerializer
+ */
+public abstract class JsonObjectDeserializer<T>
+		extends com.fasterxml.jackson.databind.JsonDeserializer<T> {
+
+	@Override
+	public final T deserialize(JsonParser jp, DeserializationContext ctxt)
+			throws IOException {
+		try {
+			ObjectCodec codec = jp.getCodec();
+			JsonNode tree = codec.readTree(jp);
+			return deserializeObject(jp, ctxt, codec, tree);
+		}
+		catch (Exception ex) {
+			if (ex instanceof IOException) {
+				throw (IOException) ex;
+			}
+			throw new JsonMappingException(jp, "Object deserialize error", ex);
+		}
+	}
+
+	/**
+	 * Deserialize JSON content into the value type this serializer handles.
+	 * @param jasonParser the source parser used for reading JSON content
+	 * @param context Context that can be used to access information about this
+	 * deserialization activity
+	 * @param codec the {@link ObjectCodec} associated with the parser
+	 * @param tree deserialized JSON content as tree expressed using set of
+	 * {@link TreeNode} instances
+	 * @return the dserialized object
+	 * @throws IOException on error
+	 * @see #deserialize(JsonParser, DeserializationContext)
+	 */
+	protected abstract T deserializeObject(JsonParser jasonParser,
+			DeserializationContext context, ObjectCodec codec, JsonNode tree)
+					throws IOException;
+
+	/**
+	 * Helper method to extract a value from the given jsonNode or return {@code null}
+	 * when the node itself is {@code null}.
+	 * @param jsonNode the source node (may be {@code null}
+	 * @param type the data type. May be {@link String}, {@link Boolean}, {@link Long},
+	 * {@link Integer}, {@link Short}, {@link Double}, {@link Float}, {@link BigDecimal}
+	 * or {@link BigInteger}.
+	 * @param <D> the data type requested
+	 * @return the node value or {@code null}
+	 */
+	@SuppressWarnings({ "unchecked" })
+	protected final <D> D nullSafeValue(JsonNode jsonNode, Class<D> type) {
+		Assert.notNull(type, "Type must not be null");
+		if (jsonNode == null) {
+			return null;
+		}
+		if (type == String.class) {
+			return (D) jsonNode.textValue();
+		}
+		if (type == Boolean.class) {
+			return (D) Boolean.valueOf(jsonNode.booleanValue());
+		}
+		if (type == Long.class) {
+			return (D) Long.valueOf(jsonNode.longValue());
+		}
+		if (type == Integer.class) {
+			return (D) Integer.valueOf(jsonNode.intValue());
+		}
+		if (type == Short.class) {
+			return (D) Short.valueOf(jsonNode.shortValue());
+		}
+		if (type == Double.class) {
+			return (D) Double.valueOf(jsonNode.doubleValue());
+		}
+		if (type == Float.class) {
+			return (D) Float.valueOf(jsonNode.floatValue());
+		}
+		if (type == BigDecimal.class) {
+			return (D) jsonNode.decimalValue();
+		}
+		if (type == BigInteger.class) {
+			return (D) jsonNode.bigIntegerValue();
+		}
+		throw new IllegalArgumentException("Unsupported value type " + type.getName());
+	}
+
+	/**
+	 * Helper method to return a {@link JsonNode} from the tree.
+	 * @param tree the source tree
+	 * @param fieldName the field name to extract
+	 * @return the {@link JsonNode}
+	 */
+	protected final JsonNode getRequiredNode(JsonNode tree, String fieldName) {
+		Assert.notNull(tree, "Tree must not be null");
+		JsonNode node = tree.get(fieldName);
+		Assert.state(node != null && !(node instanceof NullNode),
+				"Missing JSON field '" + fieldName + "'");
+		return node;
+	}
+
+}

spring-boot/src/main/java/org/springframework/boot/jackson/JsonObjectSerializer.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2012-2016 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.
+ * 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.jackson;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.databind.JsonMappingException;
+import com.fasterxml.jackson.databind.JsonSerializer;
+import com.fasterxml.jackson.databind.SerializerProvider;
+
+/**
+ * Helper base class for {@link JsonSerializer} implementations that serialize objects.
+ *
+ * @param <T> the supported object type
+ * @author Phillip Webb
+ * @since 1.4.0
+ * @see JsonObjectDeserializer
+ */
+public abstract class JsonObjectSerializer<T> extends JsonSerializer<T> {
+
+	@Override
+	public final void serialize(T value, JsonGenerator jgen, SerializerProvider provider)
+			throws IOException {
+		try {
+			jgen.writeStartObject();
+			serializeObject(value, jgen, provider);
+			jgen.writeEndObject();
+		}
+		catch (Exception ex) {
+			if (ex instanceof IOException) {
+				throw (IOException) ex;
+			}
+			throw new JsonMappingException(jgen, "Object serialize error", ex);
+		}
+	}
+
+	/**
+	 * Serialize JSON content into the value type this serializer handles.
+	 * @param value the source value
+	 * @param jgen the JSON generator
+	 * @param provider the serializer provider
+	 * @throws IOException on error
+	 */
+	protected abstract void serializeObject(T value, JsonGenerator jgen,
+			SerializerProvider provider) throws IOException;
+
+}

spring-boot/src/main/java/org/springframework/boot/jackson/package-info.java

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2012-2016 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.
+ * 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.
+ */
+
+/**
+ * Custom enhancements and support for the Jackson Project.
+ */
+package org.springframework.boot.jackson;

spring-boot/src/test/java/org/springframework/boot/jackson/JsonComponentModuleTests.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright 2012-2016 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.
+ * 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.jackson;
+
+import com.fasterxml.jackson.databind.Module;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.junit.Test;
+
+import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link JsonComponentModule}.
+ *
+ * @author Phillip Webb
+ */
+public class JsonComponentModuleTests {
+
+	@Test
+	public void moduleShouldRegisterSerializers() throws Exception {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(
+				JsonComponentModule.class, OnlySerializer.class);
+		JsonComponentModule module = context.getBean(JsonComponentModule.class);
+		assertSerialize(module);
+		context.close();
+	}
+
+	@Test
+	public void moduleShouldRegisterDeserializers() throws Exception {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(
+				JsonComponentModule.class, OnlyDeserializer.class);
+		JsonComponentModule module = context.getBean(JsonComponentModule.class);
+		assertDeserialize(module);
+		context.close();
+	}
+
+	@Test
+	public void moduleShouldRegisterInnerClasses() throws Exception {
+		AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(
+				JsonComponentModule.class, NameAndAgeJsonComponent.class);
+		JsonComponentModule module = context.getBean(JsonComponentModule.class);
+		assertSerialize(module);
+		assertDeserialize(module);
+		context.close();
+	}
+
+	private void assertSerialize(Module module) throws Exception {
+		ObjectMapper mapper = new ObjectMapper();
+		mapper.registerModule(module);
+		String json = mapper.writeValueAsString(new NameAndAge("spring", 100));
+		assertThat(json).isEqualToIgnoringWhitespace("{\"name\":\"spring\",\"age\":100}");
+	}
+
+	private void assertDeserialize(Module module) throws Exception {
+		ObjectMapper mapper = new ObjectMapper();
+		mapper.registerModule(module);
+		NameAndAge nameAndAge = mapper.readValue("{\"name\":\"spring\",\"age\":100}",
+				NameAndAge.class);
+		assertThat(nameAndAge.getName()).isEqualTo("spring");
+		assertThat(nameAndAge.getAge()).isEqualTo(100);
+	}
+
+	@JsonComponent
+	static class OnlySerializer extends NameAndAgeJsonComponent.Serializer {
+
+	}
+
+	@JsonComponent
+	static class OnlyDeserializer extends NameAndAgeJsonComponent.Deserializer {
+
+	}
+
+}

spring-boot/src/test/java/org/springframework/boot/jackson/JsonObjectDeserializerTests.java

@@ -0,0 +1,216 @@
+/*
+ * Copyright 2012-2016 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.
+ * 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.jackson;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.math.BigDecimal;
+import java.math.BigInteger;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.ObjectCodec;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import com.fasterxml.jackson.databind.node.NullNode;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import org.springframework.boot.jackson.NameAndAgeJsonComponent.Deserializer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.BDDMockito.given;
+import static org.mockito.Mockito.mock;
+
+/**
+ * Tests for {@link JsonObjectDeserializer}.
+ *
+ * @author Phillip Webb
+ */
+public class JsonObjectDeserializerTests {
+
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
+	private TestJsonObjectDeserializer<Object> testDeserializer = new TestJsonObjectDeserializer<Object>();
+
+	@Test
+	public void deserializeObjectShouldReadJson() throws Exception {
+		Deserializer deserializer = new NameAndAgeJsonComponent.Deserializer();
+		SimpleModule module = new SimpleModule();
+		module.addDeserializer(NameAndAge.class, deserializer);
+		ObjectMapper mapper = new ObjectMapper();
+		mapper.registerModule(module);
+		NameAndAge nameAndAge = mapper.readValue("{\"name\":\"spring\",\"age\":100}",
+				NameAndAge.class);
+		assertThat(nameAndAge.getName()).isEqualTo("spring");
+		assertThat(nameAndAge.getAge()).isEqualTo(100);
+	}
+
+	@Test
+	public void nullSafeValueWhenValueIsNullShouldReturnNull() throws Exception {
+		String value = this.testDeserializer.testNullSafeValue(null, String.class);
+		assertThat(value).isNull();
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsNullShouldThrowException() throws Exception {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("Type must not be null");
+		this.testDeserializer.testNullSafeValue(mock(JsonNode.class), null);
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsStringShouldReturnString() throws Exception {
+		JsonNode node = mock(JsonNode.class);
+		given(node.textValue()).willReturn("abc");
+		String value = this.testDeserializer.testNullSafeValue(node, String.class);
+		assertThat(value).isEqualTo("abc");
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsBooleanShouldReturnBoolean() throws Exception {
+		JsonNode node = mock(JsonNode.class);
+		given(node.booleanValue()).willReturn(true);
+		Boolean value = this.testDeserializer.testNullSafeValue(node, Boolean.class);
+		assertThat(value).isTrue();
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsLongShouldReturnLong() throws Exception {
+		JsonNode node = mock(JsonNode.class);
+		given(node.longValue()).willReturn(10L);
+		Long value = this.testDeserializer.testNullSafeValue(node, Long.class);
+		assertThat(value).isEqualTo(10L);
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsIntegerShouldReturnInteger() throws Exception {
+		JsonNode node = mock(JsonNode.class);
+		given(node.intValue()).willReturn(10);
+		Integer value = this.testDeserializer.testNullSafeValue(node, Integer.class);
+		assertThat(value).isEqualTo(10);
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsShortShouldReturnShort() throws Exception {
+		JsonNode node = mock(JsonNode.class);
+		given(node.shortValue()).willReturn((short) 10);
+		Short value = this.testDeserializer.testNullSafeValue(node, Short.class);
+		assertThat(value).isEqualTo((short) 10);
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsDoubleShouldReturnDouble() throws Exception {
+		JsonNode node = mock(JsonNode.class);
+		given(node.doubleValue()).willReturn(1.1D);
+		Double value = this.testDeserializer.testNullSafeValue(node, Double.class);
+		assertThat(value).isEqualTo(1.1D);
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsFloatShouldReturnFloat() throws Exception {
+		JsonNode node = mock(JsonNode.class);
+		given(node.floatValue()).willReturn(1.1F);
+		Float value = this.testDeserializer.testNullSafeValue(node, Float.class);
+		assertThat(value).isEqualTo(1.1F);
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsShouldBigDecimalReturnBigDecimal()
+			throws Exception {
+		JsonNode node = mock(JsonNode.class);
+		given(node.decimalValue()).willReturn(BigDecimal.TEN);
+		BigDecimal value = this.testDeserializer.testNullSafeValue(node,
+				BigDecimal.class);
+		assertThat(value).isEqualTo(BigDecimal.TEN);
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsBigIntegerShouldReturnBigInteger()
+			throws Exception {
+		JsonNode node = mock(JsonNode.class);
+		given(node.bigIntegerValue()).willReturn(BigInteger.TEN);
+		BigInteger value = this.testDeserializer.testNullSafeValue(node,
+				BigInteger.class);
+		assertThat(value).isEqualTo(BigInteger.TEN);
+	}
+
+	@Test
+	public void nullSafeValueWhenClassIsUnknownShouldThrowException() throws Exception {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("Unsupported value type java.io.InputStream");
+		this.testDeserializer.testNullSafeValue(mock(JsonNode.class), InputStream.class);
+
+	}
+
+	@Test
+	public void getRequiredNodeWhenTreeIsNullShouldThrowException() throws Exception {
+		this.thrown.expect(IllegalArgumentException.class);
+		this.thrown.expectMessage("Tree must not be null");
+		this.testDeserializer.testGetRequiredNode(null, "test");
+	}
+
+	@Test
+	public void getRequiredNodeWhenNodeIsNullShouldThrowException() throws Exception {
+		JsonNode tree = mock(JsonNode.class);
+		given(tree.get("test")).willReturn(null);
+		this.thrown.expect(IllegalStateException.class);
+		this.thrown.expectMessage("Missing JSON field 'test'");
+		this.testDeserializer.testGetRequiredNode(tree, "test");
+	}
+
+	@Test
+	public void getRequiredNodeWhenNodeIsNullNodeShouldThrowException() throws Exception {
+		JsonNode tree = mock(JsonNode.class);
+		given(tree.get("test")).willReturn(NullNode.instance);
+		this.thrown.expect(IllegalStateException.class);
+		this.thrown.expectMessage("Missing JSON field 'test'");
+		this.testDeserializer.testGetRequiredNode(tree, "test");
+	}
+
+	@Test
+	public void getRequiredNodeWhenNodeIsFoundShouldReturnNode() throws Exception {
+		JsonNode node = mock(JsonNode.class);
+		JsonNode tree = node;
+		given(tree.get("test")).willReturn(node);
+		assertThat(this.testDeserializer.testGetRequiredNode(tree, "test"))
+				.isEqualTo(node);
+	}
+
+	static class TestJsonObjectDeserializer<T> extends JsonObjectDeserializer<T> {
+
+		@Override
+		protected T deserializeObject(JsonParser jasonParser,
+				DeserializationContext context, ObjectCodec codec, JsonNode tree)
+						throws IOException {
+			return null;
+		}
+
+		public <D> D testNullSafeValue(JsonNode jsonNode, Class<D> type) {
+			return nullSafeValue(jsonNode, type);
+		}
+
+		public JsonNode testGetRequiredNode(JsonNode tree, String fieldName) {
+			return getRequiredNode(tree, fieldName);
+		}
+
+	}
+
+}

spring-boot/src/test/java/org/springframework/boot/jackson/JsonObjectSerializerTests.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2012-2016 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.
+ * 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.jackson;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.module.SimpleModule;
+import org.junit.Test;
+
+import org.springframework.boot.jackson.NameAndAgeJsonComponent.Serializer;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link JsonObjectSerializer}.
+ *
+ * @author Phillip Webb
+ */
+public class JsonObjectSerializerTests {
+
+	@Test
+	public void serializeObjectShouldWriteJson() throws Exception {
+		Serializer serializer = new NameAndAgeJsonComponent.Serializer();
+		SimpleModule module = new SimpleModule();
+		module.addSerializer(NameAndAge.class, serializer);
+		ObjectMapper mapper = new ObjectMapper();
+		mapper.registerModule(module);
+		String json = mapper.writeValueAsString(new NameAndAge("spring", 100));
+		assertThat(json).isEqualToIgnoringWhitespace("{\"name\":\"spring\",\"age\":100}");
+	}
+
+}

spring-boot/src/test/java/org/springframework/boot/jackson/NameAndAge.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2012-2016 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.
+ * 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.jackson;
+
+/**
+ * Sample object used for tests.
+ *
+ * @author Phillip Webb
+ */
+public final class NameAndAge {
+
+	private final String name;
+
+	private final int age;
+
+	public NameAndAge(String name, int age) {
+		this.name = name;
+		this.age = age;
+	}
+
+	public String getName() {
+		return this.name;
+	}
+
+	public int getAge() {
+		return this.age;
+	}
+
+}

spring-boot/src/test/java/org/springframework/boot/jackson/NameAndAgeJsonComponent.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright 2012-2016 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.
+ * 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.jackson;
+
+import java.io.IOException;
+
+import com.fasterxml.jackson.core.JsonGenerator;
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.ObjectCodec;
+import com.fasterxml.jackson.databind.DeserializationContext;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.SerializerProvider;
+
+/**
+ * Sample {@link JsonComponent} used for tests.
+ *
+ * @author Phillip Webb
+ */
+@JsonComponent
+public class NameAndAgeJsonComponent {
+
+	public static class Serializer extends JsonObjectSerializer<NameAndAge> {
+
+		@Override
+		protected void serializeObject(NameAndAge value, JsonGenerator jgen,
+				SerializerProvider provider) throws IOException {
+			jgen.writeStringField("name", value.getName());
+			jgen.writeNumberField("age", value.getAge());
+		}
+
+	}
+
+	public static class Deserializer extends JsonObjectDeserializer<NameAndAge> {
+
+		@Override
+		protected NameAndAge deserializeObject(JsonParser jasonParser,
+				DeserializationContext context, ObjectCodec codec, JsonNode tree)
+						throws IOException {
+			String name = nullSafeValue(tree.get("name"), String.class);
+			Integer age = nullSafeValue(tree.get("age"), Integer.class);
+			return new NameAndAge(name, age);
+		}
+
+	}
+
+}