How to get JSON data from POST request using Servlet - java

This is my code on the client side:
$.ajax({
type:'POST',
charset:'utf-8',
url:'http://localhost:8180/GisProject/MainService',
data:JSON.stringify(params),
success:function(msg)
{
console.log(msg);
},
error:function(xhr,status)
{
console.log(status);
},
contentType:"application/json"
});
I have previously parsed this data in Node using express.bodyParser but now I have to parse it using the servlet.I have seen people assign variables here without using JSON.stringify and getting that variable using request.getParameter(myData).
What is the standard way of getting the JSON data into the servlet?
And why do people seem to be sending Javascript objects with JSON embedded as a String within like data:{mydata:JSON.stringify(actualData)}?
In case I was not being clear,I want to use the doPost method's request object to get the data I sent from the client side.

On the server side in a servlet you can read POST data payload from request.getReader()
And you can use JSON library like GSON to parse JSON. Something like:
YourClass obj = new Gson().fromJson(request.getReader(), YourClass.class)

Try this:
$.ajax({
type:"POST",
url:'http://localhost:8180/GisProject/MainService',
data:{mydata:JSON.stringify(params)},
datatype:"json",
success:function(msg)
{
console.log(msg);
},
error:function(xhr,status)
{
console.log(status);
},
});

you can send request and response object to doGet method and than get the json in the same way.
Way to send object to doGet
doGet(request, response); call it in to the post method.

Hope this should help for you:
var obj = jQuery.parseJSON( '{ "name": "John" }' );
alert( obj.name === "John" );

Related

JQuery was not Called

I am getting errors on callBacks. I have tried following code in jsfiddle.com . You can also try. Data from servelet is not returning. It's returning same error again and again. Check jquery library when you try in jsfiddle
$.ajax({
url : 'http://192.168.16.111:8081/MiddleWareUsman/androidServlet',
type : "post",
dataType: "jsonp",
data : {
"fname": "chaaaaapiio",
"lname": "gya"
},
success : function(data) {
alert("hello"+data);
},
error : function(xhr, ajaxOptions, thrownError) {
alert(thrownError);
}
});
My server side:
String a=request.getParameter("fname");
String b=request.getParameter("lname");
response.getWriter().write(a+" "+ b);
It appears you have a couple problems.
JSONP requests can't be sent via POST. They are actually sent as <script> tag requests anyway which are GET requests.
Your server isn't doing JSONP. For the server to do JSONP, it must wrap the requested data in a call to a javascript function who's name was passed as an argument to the request and then the actual data is passed as an argument to that function. JSONP is a big hack, but it works by requesting a javascript and that's what the server must return.
you simply can't send a POST request using JSONP
check this link out to see how JSONP works..

display results in jsp by calling a servlet using jquery ajax?

I want to call a servlet. servlet will fetch the data from database and keeps it in request. And the result i need t display in some.jsp using jstl tags.
$('#ownForm #myButton').click(function() {
$.ajax({
type: "GET",
url: "./controller",
success: function(msg) {
//Todo
},
error: function(ob,errStr) {
//Todo
}
});
});
In servlet i have below code:
//keep database returned list in request
request.setAttribute("myresult", result);
request.getRequestDispatcher("/WEB-INF/some.jsp").forward(request, response);
Please help me how can i achieve it?
Ignore the jsp. Use FlexJson to serialize your result directly from the result object to json. Print the serialized result to the out stream in the response.
Something like this:
response.setContentType("application/json");
response.setCharacterEncoding("UTF-8");
JSONSerializer serializer = new JSONSerializer();
serializer.exclude("*.class"); //reduce clutter in your output as you see fit
serializer.serialize(objectToSerialize, response.getWriter());
Using jquery, parse this json and act on the result.

Jquery ajax call returns error when the rest service is returning a string

Trying to send a simple text from my rest service and read it using ajax call. Found many answers about jsonp and cross browser compatibility, tried crossdomain too.
Here is the rest service:
Trimmed everything down to send only a simple string.
#GET
#Path("/getcontents2")
#Produces({MediaType.TEXT_PLAIN})
public String getContents2(#QueryParam("name") String msg) {
return "abc";
}
The ajax call:
$(document).ready(function() {
$.ajax({
type: 'GET',
url: 'http://metrics/getcontents2?name=Work/loc.txt',
crossDomain: true,
async: false,
dataType:'html',
success: function (data) {
console.log(data);
},
error: function (xhr, ajaxOptions, thrownError) {
console.log(xhr.status);
console.log(thrownError);
console.log(xhr.responseText);
console.log(xhr);
},
});
});
The browsers opens up the string as is. I guess something is really wrong in the jquery script.
Error on Firebug:
GET http://metrics/getcontents2?name=Work/loc.txt 200 OK 4ms
0
(an empty string)
(an empty string)
Object { readyState=0, status=0, statusText="error"}
Fixed it!
It was because my server was not supporting cross-domain. Configured it will corsfilter and it worked like a charm!
try setting your datatype to text jsonp
dataType: 'jsonp',
http://api.jquery.com/jQuery.ajax/
You will have to do one of two things to go with this to resolve the error further;
making changes on the server side to pass the data back as json and not as text
retun the string encoded in json return "{"text":"abc"}"; //or something like this
Why?
jquery cross-domain requests are only allowed for dataTypes "script" and "jsonp".
I have updated your fiddle it still throws an error but that is related to a parse json error

How to send an array from Servlet to Java Script with AJAX?

I need send an array to js with ajax, this is my function with ajax in a java script...
$.ajax({
url: "/localizacion/ServletPeticiones",
type:"Post",
data:"accion=LatLong_UR",
dataType: "text",
success: function(results){
console.info(results);
cad=results;
}
});
I've got an array String[][] datos, and I have to send this array from my Servlet to JS with the last function.
How I can do this?
How receive the array from my Servlet with my function of ajax in a js?
The servlet will return a application/json response, and a JSON-encoded array (better, you can use a Map<String, String>). There are libraries, like Gson, to do the conversion:
public void doPost(HttpServletRequest request, HttpServletResponse response) {
response.setContentType("application/json; charset=UTF-8");
Gson gson = new Gson();
Map<String, String> datos = getDatos(); // you have to implement this
response.getWriter().println(gson.toJson(datos));
}
You can try using JSON .. you can use google's GSON library to convert an array into JSON representation and send it to your client
On the client side ... change the $.ajax's dataType to "json"
In the success function you just use the returned data as javascript array
JSON would be the right way to go about it. PHP has json_encode function that very well does it for you from arrays. Another way is to manually create a JSON string although it's not a good idea. On the other hand, just for practice and get familiar with JSON, it's advisable, but you are better of using built-in json generating capabilities of your server side platform.
You might want to send a correct header from the server so browsers are able to receive it as json data: "Content-Type: application/json"

I'm unable to receive the json object sent from my servlet

$(document).ready(function() {
var path = null;
console.log('${pageContext.request.contextPath}/loadfile');
$.ajax({
dataType: "json",
url: '${pageContext.request.contextPath}/loadfile',
success: function(data){
$.each(data,function(index,obj){
console.log(obj.id);
alert('inside');
path = obj.path;
});
}
});
here /loadfile is the url which returns the json object , when I go to this url I am able to see the JSON object printed on the html page , however I dont get the same when I access the page which contains the above javascript code
Often people don't tell their server to the the browser that the JSON string they are sending is to be interpreted as a json object.
Despite the fact that dataType:'json' is supposed to sort it out, it is not always the case.
in PHP
header("Content-type: application/json");
ASP
Response.AddHeader('Content-Type', 'application/json');
Failing that,
success: function(data){
if (typeof data!='object') data=$.parseJSON(data); // make sure it's an object
I can't figure out why jQuery doesn't fix it but the response headers, even with dataType:'json' set can appear as application/x-www-form-urlencoded; charset=UTF-8 and the object doesn't get created.

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