RestTemplate and <mvc:message-converters> in Spring Framework 4.3

The Spring Framework’s documentation says that RestTemplate instance created by the default constructor gets the default set of HttpMessageConverters.

But what is the default set of HttpMessageConverters? Well, this is defined in the Spring Framework Reference. Unfortunately I’ve missed it somehow and I was believing that the default set of HttpMessageConverters is affected by <mvc:message-converters> Spring XML configuration element, like in the sample below:

    <bean id="customGsonHttpMsgConverter" class="org.springframework.http.converter.json.GsonHttpMessageConverter">
        <property name="gson">
            <bean class="CustomGsonFactoryBean"/>
        </property>
    </bean>
    
    <mvc:annotation-driven>
        <mvc:message-converters>
            <ref bean="customGsonHttpMsgConverter"/>
        </mvc:message-converters>
    </mvc:annotation-driven>

    <bean id="restTemplate" class="org.springframework.web.client.RestTemplate"/>

Actually it’s not true. In the above example the RestTemplate bean will not be using this “customGsonHttpMsgConverter” bean. The default set of HttpMessageConverters for RestTemplate is… hardcoded in RestTemplate class. However one can customize it easily. This is the correct way of configuring HttpMessageConverters to be used by RestTemplate:

    <bean id="customGsonHttpMsgConverter" class="org.springframework.http.converter.json.GsonHttpMessageConverter">
        <property name="gson">
            <bean class="CustomGsonFactoryBean"/>
        </property>
    </bean>
    
    <bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
        <constructor-arg>
            <list>
                <ref bean="customGsonHttpMsgConverter"/>
            </list>
        </constructor-arg>
    </bean>

Lesson learned! RestTemplate has nothing to do with <mvc:message-converters> configuration.