Spring REST service not consuming JSON

Question

I am having some difficulty using Spring's built-in JSON consumption using Jackson with REST web services. If I define the following:

...
@RequestMapping(value="/stub")
public void doSomething(@RequestBody User user) {
    System.err.println("In method");
    ...
}

... it never reaches the method. I have Jackson in the classpath. However, when I manually use Jackson:

@RequestMapping(value="/stub")
public void doSomething(@RequestBody String user) {
    System.err.println("In method");

    User newUser = null;

    try {
        user = URLDecoder.decode(user, "UTF-8");
    } catch (UnsupportedEncodingException e1) {...}

    try {
        newUser = new ObjectMapper().readValue(user, User.class);
    } catch (Exception e) {...}
}

... it works perfectly. The User object gets created correctly with all the correct values, so I know the JSON is correct. Does it have something to do with the decoding? As far as I know from Spring 2.5 the decoding is on by default. Maybe I am missing something else, maybe a configuration step. My web.xml is as follows:

<?xml version="1.0" encoding="UTF-8"?>
<web-app
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    xsi:schemaLocation="
        http://java.sun.com/xml/ns/javaee
        http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
    id="WebApp_ID" version="2.5">

<servlet>
    <servlet-name>DispatcherServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>/WEB-INF/servlet-context.xml</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
    <servlet-name>DispatcherServlet</servlet-name>
    <url-pattern>/*</url-pattern>
</servlet-mapping>

</web-app>

... while my servlet-context.xml defines:

<?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:context="http://www.springframework.org/schema/context"
    xmlns:mvc="http://www.springframework.org/schema/mvc"
    xmlns:util="http://www.springframework.org/schema/util"
    xsi:schemaLocation="
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc.xsd
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/util
        http://www.springframework.org/schema/util/spring-util.xsd">

<import resource="mongo-context.xml"/>

<context:component-scan base-package="com.moonlight42.sampleserver.model" />

<mvc:annotation-driven />

<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/jsp/" />
    <property name="suffix" value=".jsp" />
</bean>

<bean id="jsonHttpMessageConverter" class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
    <property name="prefixJson" value="false"/>
    <property name="supportedMediaTypes" value="application/json"/>
</bean>

<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="messageConverters">
        <util:list id="beanList">
            <ref bean="jsonHttpMessageConverter"/>
        </util:list>
    </property>
</bean>
</beans>

Thanks in advance.

Answer 1

I believe that tag setups Jackson automatically if Jackson is in the classpath. No need for other configuration.

Look at adding the correct consumes and produces with-in the RequestMapping:

@RequestMapping(method = RequestMethod.POST, value = "/stub", consumes = "application/json", produces = "application/json")

These annoatations are pulled from a Spring MVC 3.1 project. You may need to user header="" and then the correct MVC header.

I have found that versions 3+ have some huge improvements in this arena.

You may have one of two problems:

1. Jackson is not being found
2. The mapping to your controller not configured correctly