This took me a lot of effort to figure out so I'm going to answer the question below. This answer doesn't use annotations and does not require creating additional classes.
You put this in your spring xml context configuration:
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:jaxrs="http://cxf.apache.org/jaxrs" xmlns:mvc="http://www.springframework.org/schema/mvc"
xmlns:p="http://www.springframework.org/schema/p"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans.xsd
http://cxf.apache.org/jaxrs
http://cxf.apache.org/schemas/jaxrs.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">
...
<bean id="jacksonMapper" class="com.fasterxml.jackson.databind.ObjectMapper">
<property name="dateFormat">
<bean class="java.text.SimpleDateFormat">
<constructor-arg type="java.lang.String" value="yyyyMMdd'T'HHmmss.SSSZ"/>
</bean>
</property>
</bean>
<bean id="jsonProvider" class="com.fasterxml.jackson.jaxrs.json.JacksonJsonProvider"
p:mapper-ref="jacksonMapper"/>
...
<jaxrs:providers>
<ref bean="jsonProvider"></ref>
</jaxrs:providers>
</jaxrs:server>