how to return multiple json objects from java servlet using one ajax request

Question

I am building web application using jsp and servlet, I send ajax request from jsp and I want to return two json objects from servlet. I tried to do the following but the code did not work.

// in jquery I wrote this code

        var id = $(this).attr('id');

        var paramenters = {"param":id};

        $.getJSON("MyServlet", paramenters, function (data1,data2){

            $("h3#name").text(data1["name"]);

            $("span#level").text(data1["level"]);

            $("span#college").text(data2["college"]);

            $("span#department").text(data2["department"]);

        });

// in the servlet I wrote this code

    String json1 = new Gson().toJson(object1);

    String json2 = new Gson().toJson(object2);

    response.setContentType("application/json");

    response.setCharacterEncoding("utf-8");

    response.getWriter().write(json1);

    response.getWriter().write(json2);

can someone help me???

Edgar Villegas Alvarado · Accepted Answer · 2011-05-07 20:02:05Z

23

You should do it like this:

Server side:

String json1 = new Gson().toJson(object1); 
String json2 = new Gson().toJson(object2); 
response.setContentType("application/json"); 
response.setCharacterEncoding("utf-8"); 
String bothJson = "["+json1+","+json2+"]"; //Put both objects in an array of 2 elements
response.getWriter().write(bothJson);

Client side:

$.getJSON("MyServlet", paramenters, function (data){ 
   var data1=data[0], data2=data[1]; //We get both data1 and data2 from the array
   $("h3#name").text(data1["name"]); 
   $("span#level").text(data1["level"]); 
   $("span#college").text(data2["college"]); 
   $("span#department").text(data2["department"]);
});

Hope this helps. Cheers

answered May 7, 2011 at 20:02

Edgar Villegas Alvarado

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Comments

Peter Knego · Accepted Answer · 2011-05-07 19:57:24Z

2

Wrap them in JSON array:

[ {..}, {..}, {..}]

or, wrap them in another object:

{ "result1":{..}, "result2":{..} }

answered May 7, 2011 at 19:57

Peter Knego

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Chris Cherry · Accepted Answer · 2011-05-07 20:00:31Z

1

You could return a JSON array with both objects as elements of the array. Have your servlet return JSON that has a structure like this one:

[{"name": "object1"}, {"name": "object2"}]

Then your javascript code can be something like this:

$.getJSON("MyServlet", paramenters, function (data){
        var data1 = data[0];
        var data2 = data[1];

        $("h3#name").text(data1["name"]);

        $("span#level").text(data1["level"]);

        $("span#college").text(data2["college"]);

        $("span#department").text(data2["department"]);

    });

answered May 7, 2011 at 20:00

Chris Cherry

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Comments

ratchet freak · Accepted Answer · 2011-05-07 20:01:43Z

1

you're going to need to put both into a single json string like so

response.getWriter().write("[");
response.getWriter().write(json1);
response.getWriter().write(",");
response.getWriter().write(json2);
response.getWriter().write("]");

this puts them in a json array

you could also put them in a json object

response.getWriter().write("{\"object1\":");
response.getWriter().write(json1);
response.getWriter().write(",\"object2\":");
response.getWriter().write(json2);
response.getWriter().write("}");

answered May 7, 2011 at 20:01

ratchet freak

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Comments

Charlotte · Accepted Answer · 2017-03-22 00:45:45Z

@Edgar 's answer works for me. But I think we should avoid to form the array by ourselves, so I suggest to use a list. The codes will be something like this:

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    ...
    resp.setContentType("application/json");
    resp.setCharacterEncoding("utf-8");
    ArrayList<Object> obj_arr = new ArrayList<Object>();
    obj_arr.add(obj1);
    obj_arr.add(obj2);
    Gson gson = new Gson();
    String tmp = gson.toJson(obj_arr);
    resp.getWriter().write(tmp);
}

And in the front end, for the data we get, we can use data[0] to retrive obj1 and data[1] to retrive obj2. The codes will be something like this (I am using ajax here):

$('#facts_form').submit(function (e) {
    e.preventDefault();
    var data = new FormData(this);
    var url = 'import';
    $.ajax({
        url: url,
        type: "POST",
        data: data,
        processData: false,  
        contentType: false,   
        async: false,
        cache: false,
        success: function (data) {                
            for (var i = 1; i < data.length; i++){
               //do whatever 
            }
        },
        error: function (xhr, status, error) {
            alert(status + "\n" + error);
        }
    });
});

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