Posting JSON object using Ajax

Question

I wondered if someone could answer a question for me as I dont quite understand why I needed to read a json object from the request input stream when I passed one to a spring controller manually.

Normally I use a json-rpc framework and it handles everything for me so I hadnt actually had to do this manually until now. Everything works ok but what I dont understand is why there was nothing in the request like when you post a form, and instead I had to use this code to map my object to Jackson:

BufferedInputStream bis = new BufferedInputStream(request.getInputStream());
ChartParameters chartParameters = mapper.readValue(bis, ChartParameters.class);

I would just like to understand why I needed to read in the input stream and pass this to jackson instead of being able to get a value as a string which I first thought I would have to do.

Thanks in advance for any helpful answers.

Can you show the relevant parts of your Spring controller where those two lines are being used? A bit of context might clarify... — mthmulders
– mthmulders, Commented Jul 11, 2013 at 7:10
I wasnt really that interested in the Spring side of things unless the reason is purely spring related? I didnt write a plain servlet to test if I still needed to do the same thing. Here is the controller method anyway in case it is: public void handleChartJsonRPC(HttpServletRequest request, HttpServletResponse response) throws Exception { jsonService.getBarChart(request, response); } — berimbolo
– berimbolo, Commented Jul 11, 2013 at 7:26

mthmulders · Accepted Answer · 2013-07-11 07:38:00Z

1

If you're on a recent Spring version, the following should be enough to get things rolling:

@ResponseBody
public Chart handleChartJsonRPC(@RequestBody ChartParameters chartParameters) throws Exception {
    return jsonService.getBarChart(chartParameters);
}

This (obviously) assumes your jsonService returns a Chart object, which should be serialised to JSON before sending it back to the browser.

Make sure you have a MessageConverter that will (de-)serialise your objects to and from JSON, as described by @user2054820.

answered Jul 11, 2013 at 7:38

mthmulders

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3 Comments

berimbolo Over a year ago

Right ok so is the reason that I had to get the stream because I dont have a message converter in the chain?

mthmulders Over a year ago

Most likely that's the reason, but it's a bit hard to say with only two lines of code context.

berimbolo Over a year ago

Ok thanks, for now I will have to assume thats the correct answer, and thanks for the code snippet above. I was planning to convert my chart object that the service returns manually with Jackson and then return this in the response but using a message converter and the annotations method looks a better option.

Jimmy Geers · Accepted Answer · 2013-07-11 07:23:09Z

1

You can post your JSON just as a string and you can configure :

    <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>

answered Jul 11, 2013 at 7:23

Jimmy Geers

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