How to POST and GET JSON between EXTJS and SpringMVC3

After one month of evaluation of frameworks and tools, I choose ExtJS for UI and Spring/SpringMVC for the business layer for my pet project.

By using ExtJS we can send data to server by form submits or as request parameters, or in JSON format through Ajax requests. ExtJS uses JSON format in many situations to hold data. So I thought using JSON as data exchange format between EXTJS and Spring would be consistent.

The following code snippets explain how we can use ExtJS and SpringMVC3 to exchange data in JSON format.

1. Register MappingJacksonHttpMessageConverter in dispatcher-servlet.xml
  

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

Ext.Ajax.request({
  url : 'doSomething.htm',
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },                        
  params : { "test" : "testParam" },
  jsonData: {
                   "username" : "admin",
                    "emailId" : "admin@sivalabs.com"
                 },
  success: function (response) {
                      var jsonResp = Ext.util.JSON.decode(response.responseText);
                      Ext.Msg.alert("Info","UserName from Server : "+jsonResp.username);
              },
  failure: function (response) {
                  var jsonResp = Ext.util.JSON.decode(response.responseText);
                  Ext.Msg.alert("Error",jsonResp.error);
            }
});

@Controller
public class DataController
{
    @RequestMapping(value = "/doSomething", method = RequestMethod.POST)
    @ResponseBody
    public User handle(@RequestBody User user) throws IOException
    {
        System.out.println("Username From Client : "+user.getUsername());
        System.out.println("EmailId from Client : "+user.getEmailId());
        user.setUsername("SivaPrasadReddy");
        user.setEmailId("siva@sivalabs.com");        
        return user;
    }
}