jsp - Retrieve the data sent as JSON from JavaScript, inside a servlet

Question

I have a query on retrieving data sent as JSON from a JavaScript, inside a Java servlet. Following is what I am doing...

This is the part of the code inside JavaScript making a request to a servlet

type : "POST",
url: 'getInitialData',
datatype: 'json',
data : ({items :[{ name: "John", time: "2pm" },{name: "Sam", time: "1pm" }]}),
success: function(data) {
    try{
          ////Code to be handeled where response is recieved
       }catch(e){
        alert(e);
    }
}

On making this request I try to retrieve the parameters sent from JavaScript in a Servlet, but while doing so I was firstly confused on how to retrieve the dat from the request

I used the following in my servlet:

NOTE : the content Type in my Servlet is set to : apllication/json

 response.setContentType("application/json");

 request.getParameterMap();

the above showed me the data as below, but I was not able figure out how to work and get the actual data

{items[1][name]=[Ljava.lang.String;@1930089, items[0][time]=[Ljava.lang.String;@860ba, items[1][time]=[Ljava.lang.String;@664ca, items[0][name]=[Ljava.lang.String;@1c334de}

while the following code gave me Exception of null which was expected.

request.getParametervalues("items");

Among the others i tried where request.getParameter(); request.getParameterNames(); but in vain...

Am I in a wrong direction? Please guide me! Please let me know how to retieve these value.

Thank You for reading this long post...

Sangeet

Answer 1

The request parameter map is a Map<String, String[]> where the map key is the parameter name and map value are the parameter values --HTTP allows more than one value on the same name.

Given the printout of your map, the following should work:

String item0Name = request.getParameter("items[0][name]");
String item0Time = request.getParameter("items[0][time]");
String item1Name = request.getParameter("items[1][name]");
String item1Time = request.getParameter("items[1][time]");

If you want a bit more dynamics, use the following:

for (int i = 0; i < Integer.MAX_VALUE; i++) {
    String itemName = request.getParameter("items[" + i + "][name]");
    String itemTime = request.getParameter("items[" + i + "][time]");

    if (itemName == null) {
        break;
    }

    // Collect name and time in some bean and add to list yourself.
}

Note that setting the response content type is irrelevant when it comes to gathering the request parameters.