Message Converters

See equivalent in the Reactive stack

You can set the HttpMessageConverter instances to use in Java configuration, replacing the ones used by default, by overriding configureMessageConverters(). You can also customize the list of configured message converters at the end by overriding extendMessageConverters().

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 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

  • Kotlin

@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()));
	}
}
@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, 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-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:

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

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

Other interesting Jackson modules are available:

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"/>