java - Spring-MVC 406 Not Acceptable instead of JSON Response

Question

I'm trying to return a JSON response with Spring 3.0.6, but I get a 406 response "Not Acceptable", with the description: "The resource identified by this request is only capable of generating responses with characteristics not acceptable according to the request "accept" headers ()."

I know that a very similar question has been asked before, but I can't make it work for my project, despite many tests and I don't understand what I'm doing wrong.

In my Maven pom.xml I've the following:

<dependency>
  <groupId>org.codehaus.jackson</groupId>
  <artifactId>jackson-mapper-asl</artifactId>
  <version>1.8.5</version>
  <scope>compile</scope>
</dependency>
<dependency>
  <groupId>org.codehaus.jackson</groupId>
  <artifactId>jackson-core-asl</artifactId>
  <version>1.8.5</version>
  <scope>compile</scope>
</dependency>

In web.xml I reference webmvc-config.xml, and the log confirms that is loaded.

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

In webmvc-config.xml I've the following:

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

My Controller is:

@Controller
public class ClassifiedController {

    @RequestMapping(value = "/classified/{idClassified}", headers = "Accept=*/*",
                    method = RequestMethod.GET)
    @ResponseBody
    public final Classified getClassified(@PathVariable final int idClassified) {
        ...

I tried with or without the headers parameter with the same results. If I call the URL directly with Firefox the Request Headers contain the following (checked with firebug):

Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

If I use the following JQuery:

$.ajax({
        url: '/classified/38001',
        type: 'GET',
        dataType: 'json'
});

The following headers are sent:

Accept: application/json, text/javascript, */*; q=0.01

In both cases the result is a 406 error. I don't know what else should I check to make it work.

---

UPDATE: I decided to debug through Spring and I found out that Jackson was called correctly and in org.codehaus.jackson.map.ser.StdSerializerProvider the method _findExplicitUntypedSerializer contains the following code:

try {
    return _createAndCacheUntypedSerializer(runtimeType, property);
} catch (Exception e) {
    return null;
}

This is unfortunate because hides the source of the problem. With the debugger I found out that that exception contained a very descriptive error message:

Conflicting getter definitions for property "reminded": 
ClassifiedImpl#isReminded(0 params) vs
ClassifiedImpl#getReminded(0 params)

Now that I see the error message is a silly mistake and easy to fix, but without that it wasn't that obvious. In fact, fixing the problem, leaded to a working serialization.

Answer 1

Add the following in DispatcherServlet-servlet.xml.

<bean id="jacksonMessageConverter" class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"></bean>
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="messageConverters">
        <list>
            <ref bean="jacksonMessageConverter"/>
        </list>
    </property>
</bean>