respond to http request with json object in portlet - json

Question

I am a beginner in liferay portlet development and I am developing a portlet that receives a http get request, processes some information and than it has to return a json object. My problem is that my portlet sends a whole html page instead of just the json object.
This is my code:
HttpServletResponse servletResponse = PortalUtil.getHttpServletResponse((renderResponse));
servletResponse.setHeader("Content-type", "application/json");
servletResponse.setCharacterEncoding("application/json");
PrintWriter out = servletResponse.getWriter();
out.write(EntityUtils.toString(responseEntity));
out.flush();
out.close();
I execute this in the doView() method I know that this is not the best practice, but I am not concerned with that at the moment. Can someone explain to me how to return just the json object I read something about serveResponse, but I couldn't figure out how to invoke it.

Answer 1

Well, one thing to notice, that the doView() is mostly responsible for rendering of your portlet. Your requirement can better achieved by
1 - processAction(Portlet Action) or
2 - serveResource(Portlet AJAX service).
To my view, AJAX request-response will be the most suitable case; for that you just need to create a resource URL on your portlet view. Like:
<portlet:resourceURL var="ajaxResourceURL" />
Add a JavaScript method to the page, from where you can generate AJAX request to your portlet. The method will look something like this,
<script type="text/javascript">
function _callAjax(val1, val2){
var url = '<%=ajaxResourceURL %>'; // pass resource URL you created using scriplet / EL.
jQuery.ajax({
type : "POST",
url : url,
cache:false,
dataType: "json",
data: {
value1: val1, // extra parameters if you want to pass
value2: val2
},
success : function(data){
// do whatever you want with your response data
},
error : function(XMLHttpRequest, textStatus, errorThrown){
alert(errorThrown);
alert(textStatus);
}
});
};
</script>
Call that ajax method on a button / link click event:
<input type="button" onclick="_callAjax('val1', 'val2')" value="Send" />
And finally, in your portlet's action listener class add the following serveResource method, responsible for handling AJAX based request(s).
Here you can get your request parameters and generate a response in the sense you want:
#Override
public void serveResource(ResourceRequest request, ResourceResponse response) throws PortletException,IOException {
String value1 = ParamUtil.getString(request , "value1", "default"); // request parameters
String value2 = ParamUtil.getString(request , "value2", "");
PrintWriter writer = response.getWriter();
JSONObject jsonObject = new JSONObject();
jsonObject.put(String key, boolean/long/Collection/double/Map/Object value);
writer.write(jsonObject.toString());
}
Thats it! Hope, this will be helpful for you :)