MappingJacksonJsonView return top-level json object - spring-mvc

Question

I converted to controller to use ContentNegotiatingViewResolver instead of MessageConverters to support multiple output types. With json, I am using MappingJacksonJsonView:
<bean
class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
<property name="order" value="1" />
<property name="mediaTypes">
<map>
<entry key="html" value="text/html"/>
<entry key="json" value="application/json" />
<entry key="xml" value="application/xml" />
</map>
</property>
<property name="defaultViews">
<list>
<bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView" />
<bean class="org.springframework.web.servlet.view.xml.MarshallingView">
<constructor-arg>
<bean class="org.springframework.oxm.xstream.XStreamMarshaller" />
</constructor-arg>
</bean>
</list>
</property>
<property name="ignoreAcceptHeader" value="true" />
<property name="defaultContentType" value="application/json" />
</bean>
With the following controller logic:
#RequestMapping(value = "/id/{id}", method = RequestMethod.GET)
public ModelAndView getById(#PathVariable (value="id") String id) {
MyObject ret = doGetById(id);
ModelAndView modelAndView = new ModelAndView("common/single");
modelAndView.addObject("myObject", ret);
return modelAndView;
}
The json return when I access /id/1234.json is something like:
{
myObject: {
field1:"abc",
field2:"efg"
}
}
Is there a way for my to set myObject as the top level node for the result so it look like this instead:
{
field1:"abc",
field2:"efg"
}

Answer 1

What's happening is Spring MVC is taking the ModelAndView and serializing it to JSON. Since a ModelAndView just looks like a map, and in this case, you only have one entry in the map with a key name of myObject, that's what the JSON response looks at. In order to get just your object, you need to return just your object instead of a ModelAndView and let Jackson serialize your object to JSON.
Rather than returning a ModelAndView, return a MyObject and annotate the method with #ResponseBody, so your controller method becomes
#RequestMapping(value="/id/{id}", method=RequestMethod.GET, produces="application/json")
public #ResponeBody MyObject getById(#PathVariable (value="id") String id) {
return doGetById(id);
}

Answer 2

I faced same issue and following solution works for me.
<bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView">
<property name="prefixJson" value="true" />
</bean>

Answer 3

You should be able to remove the outer node by using MappingJacksonJsonView.setExtractValueFromSingleKeyModel(true):
Set whether to serialize models containing a single attribute as a map
or whether to extract the single value from the model and serialize it
directly.
The effect of setting this flag is similar to using
MappingJacksonHttpMessageConverter with an #ResponseBody
request-handling method.
For example:
private final MappingJacksonJsonView view = new MappingJacksonJsonView();
public MyController() {
view.setExtractValueFromSingleKeyModel(true);
}
#RequestMapping(value = "/id/{id}", method = RequestMethod.GET)
public ModelAndView getById(#PathVariable (value="id") String id) {
MyObject ret = doGetById(id);
ModelAndView modelAndView = new ModelAndView();
modelAndView.setView(this.view);
modelAndView.addObject("myObject", ret);
return modelAndView;
}
This should also work if you prefer to do it via configuration:
<bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView">
<property name="extractValueFromSingleKeyModel" value="true" />
</bean>