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Message Converters

You can set the HttpMessageConverter instances to use in Java configuration, replacing the ones used by default, by overriding {spring-framework-api}/web/servlet/config/annotation/WebMvcConfigurer.html#configureMessageConverters-java.util.List-[configureMessageConverters()]. You can also customize the list of configured message converters at the end by overriding {spring-framework-api}/web/servlet/config/annotation/WebMvcConfigurer.html#extendMessageConverters-java.util.List-[extendMessageConverters()].

Tip
 In a Spring Boot application, the WebMvcAutoConfiguration adds any HttpMessageConverter beans it detects, in addition to default converters. Hence, in a Boot application, prefer to use the {spring-boot-docs}/web.html#web.servlet.spring-mvc.message-converters[HttpMessageConverters] mechanism. Or alternatively, use extendMessageConverters to modify message converters at the end.

The following example adds XML and Jackson JSON converters with a customized ObjectMapper instead of the default ones:

Java
@Configuration
@EnableWebMvc
public class WebConfiguration implements WebMvcConfigurer {

	@Override
	public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
		Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder()
				.indentOutput(true)
				.dateFormat(new SimpleDateFormat("yyyy-MM-dd"))
				.modulesToInstall(new ParameterNamesModule());
		converters.add(new MappingJackson2HttpMessageConverter(builder.build()));
		converters.add(new MappingJackson2XmlHttpMessageConverter(builder.createXmlMapper(true).build()));
	}
}
Kotlin
@Configuration
@EnableWebMvc
class WebConfiguration : WebMvcConfigurer {

	override fun configureMessageConverters(converters: MutableList<HttpMessageConverter<*>>) {
		val builder = Jackson2ObjectMapperBuilder()
				.indentOutput(true)
				.dateFormat(SimpleDateFormat("yyyy-MM-dd"))
				.modulesToInstall(ParameterNamesModule())
		converters.add(MappingJackson2HttpMessageConverter(builder.build()))
		converters.add(MappingJackson2XmlHttpMessageConverter(builder.createXmlMapper(true).build()))

In the preceding example, {spring-framework-api}/http/converter/json/Jackson2ObjectMapperBuilder.html[Jackson2ObjectMapperBuilder] is used to create a common configuration for both MappingJackson2HttpMessageConverter and MappingJackson2XmlHttpMessageConverter with indentation enabled, a customized date format, and the registration of {jackson-github-org}/jackson-module-parameter-names[jackson-module-parameter-names], Which adds support for accessing parameter names (a feature added in Java 8).

This builder customizes Jackson’s default properties as follows:

  • {jackson-docs}/jackson-databind/javadoc/2.6/com/fasterxml/jackson/databind/DeserializationFeature.html#FAIL_ON_UNKNOWN_PROPERTIES[DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES] is disabled.

  • {jackson-docs}/jackson-databind/javadoc/2.6/com/fasterxml/jackson/databind/MapperFeature.html#DEFAULT_VIEW_INCLUSION[MapperFeature.DEFAULT_VIEW_INCLUSION] is disabled.

It also automatically registers the following well-known modules if they are detected on the classpath:

  • {jackson-github-org}/jackson-datatype-joda[jackson-datatype-joda]: Support for Joda-Time types.

  • {jackson-github-org}/jackson-datatype-jsr310[jackson-datatype-jsr310]: Support for Java 8 Date and Time API types.

  • {jackson-github-org}/jackson-datatype-jdk8[jackson-datatype-jdk8]: Support for other Java 8 types, such as Optional.

  • {jackson-github-org}/jackson-module-kotlin[jackson-module-kotlin]: Support for Kotlin classes and data classes.

Note
 Enabling indentation with Jackson XML support requires woodstox-core-asl dependency in addition to jackson-dataformat-xml one.

Other interesting Jackson modules are available:

  • jackson-datatype-money: Support for javax.money types (unofficial module).

  • {jackson-github-org}/jackson-datatype-hibernate[jackson-datatype-hibernate]: Support for Hibernate-specific types and properties (including lazy-loading aspects).

The following example shows how to achieve the same configuration in XML:

<mvc:annotation-driven>
	<mvc:message-converters>
		<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
			<property name="objectMapper" ref="objectMapper"/>
		</bean>
		<bean class="org.springframework.http.converter.xml.MappingJackson2XmlHttpMessageConverter">
			<property name="objectMapper" ref="xmlMapper"/>
		</bean>
	</mvc:message-converters>
</mvc:annotation-driven>

<bean id="objectMapper" class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean"
	  p:indentOutput="true"
	  p:simpleDateFormat="yyyy-MM-dd"
	  p:modulesToInstall="com.fasterxml.jackson.module.paramnames.ParameterNamesModule"/>

<bean id="xmlMapper" parent="objectMapper" p:createXmlMapper="true"/>