使用Ajax发布JSON对象

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.

Answer 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>

Answer 2

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.