RestTemplate cannot map a single object to a list

ResponseEntity<String> response = restTemplate.exchange(url, HttpMethod.GET, entity, String.class);

resObject = mapper.readValue(response.getBody(), ResponseObject.class);

The problem is that if ResponseObject in server side has only one item set to a list, by default, JAXB will convert this list to a single json object (not an array contains one object as we expected) so the mapper in client side cannot map correctly.

Solution 1: by code

List converters = restTemplate.getMessageConverters();

              for (Object converter : converters) {

                     if (converter instanceof MappingJacksonHttpMessageConverter) {

                           MappingJacksonHttpMessageConverter jconverter = (MappingJacksonHttpMessageConverter) converter;

                           

                           final ObjectMapper mapper = new ObjectMapper();

                             mapper.configure(

                                     DeserializationConfig.Feature.ACCEPT_SINGLE_VALUE_AS_ARRAY,

                                     true);

                           jconverter.setObjectMapper(mapper);

                          

                     }

              }

Solution 2: by XML configuration:

<!-- Jackson Mapper -->
<bean id="jacksonObjectMapper" class="org.codehaus.jackson.map.ObjectMapper" />
<bean class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
    <property name="targetObject" ref="jacksonObjectMapper" />
    <property name="targetMethod" value="configure" />
    <property name="arguments">
        <list>
            <value type="org.codehaus.jackson.map.DeserializationConfig.Feature">FAIL_ON_UNKNOWN_PROPERTIES</value>
            <value>false</value>
        </list>
    </property>
</bean>

<bean id="restTemplate" class="org.springframework.web.client.RestTemplate">
    <property name="messageConverters">
        <list>
            <bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
                <property name="objectMapper" ref="jacksonObjectMapper" />
            </bean>
        </list>
    </property>
</bean>

Hope that helps.

References:

http://stackoverflow.com/questions/14343477/how-do-you-globally-set-jackson-to-ignore-unknown-properties-within-spring