Receiving JSON data from POST

[Al Grant]

Hello,

I am having trouble receiving JSON data from an HTML form and mapping it into a Java Object.

The line that is causing me error is:

        Episode episode = mapper.readValue(json , Episode.class);

Which results in: HTTP Status 500 - Unrecognized token 'start_date': was expecting ('true', 'false' or 'null')

Some background about the code:

A snippet of my Episode Class:

package com.fh;

public class Episode {

    private String start_date;
    private String end_date;
    private String report_date;
    private String attend_date;
    private String proximity;...

    public String getProximity() {
        return proximity;
    }

    public void setProximity(String proximity) {
        this.proximity = proximity;

etc.....

And the servlet class:

Enter code here..@WebServlet(name = "newfh", urlPatterns = {"/form"})

public class cmfhapp extends HttpServlet {
   
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        System.out.println("doGet hit");
        request.getRequestDispatcher("/index1.jsp").forward(request, response);
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        //  GET RECEIVED JSON DATA
        BufferedReader br = new BufferedReader((new InputStreamReader(request.getInputStream())));
        String json = "";
        if (br != null) {
            json = br.readLine();
        }

        System.out.println("Print proximity Value " +request.getParameter("proximity"));
        ObjectMapper mapper = new ObjectMapper();
        Episode episode = mapper.readValue(json , Episode.class);
        System.out.println(episode.getProximity());

        System.out.println("doPost hit");
        request.getRequestDispatcher("/login.html").forward(request, response);
    }
}.

The JSON data is being sent from the form with:

$.fn.serializeObject = function()
{
    var o = {};
    var a = this.serializeArray();
    $.each(a, function() {
        if (o[this.name] !== undefined) {
            if (!o[this.name].push) {
                o[this.name] = [o[this.name]];
            }
            o[this.name].push(this.value || '');
        } else {
            o[this.name] = this.value || '';
        }
    });
    return o;
};
 
<script>
    $(document).ready(function() {
        // click on button submit
        $("#submit").on('click', function(e){
        // send ajax
        $.ajax({
            url: "form", // url where to submit the request
            type : "POST", // type of action POST || GET
            dataType : "json", // data type
            data : JSON.stringify($('#formfv').serializeObject()), // post data || get data
            contentType : "application/json",
            success : function(result) {
                console.log(result);
            },
            error: function(xhr, resp, text) {
                console.log(xhr, resp, text);
            }
        })
    });
    });
</script>

I think the JSON data is being received correctly as the value of json when printed in console looks like:

{
    "start_date": "",
    "end_date": "",
    "report_date": "",
    "attend_date": "",
    "proximity": "Nearby",
    "locationtype": "",
    "reported_by": "Family",
    "location": "",

And this validates on JSO linter.

So why am I getting: HTTP Status 500 - Unrecognized token 'start_date': was expecting ('true', 'false' or 'null')

Cheers

Al
 

[Al Grant]

The full error in the browser is :

HTTP Status 500 - Unrecognized token 'start_date': was expecting ('true', 'false' or 'null')

type Exception report

message Unrecognized token 'start_date': was expecting ('true', 'false' or 'null')

description The server encountered an internal error that prevented it from fulfilling this request.

exception

com.fasterxml.jackson.core.JsonParseException: Unrecognized token 'start_date': was expecting ('true', 'false' or 'null')
 at [Source: start_date=28%2F02%2F2017+14%3A01&end_date=01%2F03%2F2017+14%3A03&report_date=01%2F03%2F2017+14%3A03&attend_date=01%2F03%2F2017+14%3A03&proximity=Outside&locationtype=Commercial&reported_by=Neighbour&location=&b_station=Akaroa&a_station=Addington+CCB&weapon=BD&alcohol=&drugs=&firearms=&unborn=&surname=&address=&firstname=&gender=&dob=&ethnicity=&ethnicity=&Supervisor_id=&ethnicity=&ethnicity=; line: 1, column: 11]
	com.fasterxml.jackson.core.JsonParser._constructError(JsonParser.java:1702)
	com.fasterxml.jackson.core.base.ParserMinimalBase._reportError(ParserMinimalBase.java:558)
	com.fasterxml.jackson.core.json.ReaderBasedJsonParser._reportInvalidToken(ReaderBasedJsonParser.java:2835)
	com.fasterxml.jackson.core.json.ReaderBasedJsonParser._handleOddValue(ReaderBasedJsonParser.java:1903)
	com.fasterxml.jackson.core.json.ReaderBasedJsonParser.nextToken(ReaderBasedJsonParser.java:749)
	com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:3834)
	com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3783)
	com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2842)
	com.fh.cmfhapp.doPost(cmfhapp.java:42)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
	javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

note The full stack trace of the root cause is available in the Apache Tomcat/8.5.4 logs.

---

Apache Tomcat/8.5.4

[Tatu Saloranta]

Looking at the exception output, interesting part is this:

at [Source: start_date=28%2F02%2F2017+14%3A01&end_date=01%2F03%2F2017+14%3A03&report_date=01%2F03%

which gets printed because input comes as a String (otherwise wouldn't
print, although Jackson 2.9 does improve on this a bit). So input that
is been given looks like URL query String and NOT as JSON content.

It has been a while since I worked on javascript so I can't offhand
see what would cause this to happen; I think some form submit modes
would just send things as form encoded, and not as specified payload.

-+ Tatu +-

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