Retrieving JSON Object Literal from HttpServletRequest

Question

I am writing code that needs to extract an object literal posted to a servlet. I have studied the API for the HttpServletRequest object, but it is not clear to me how to get the JSON object out of the request since it is not posted from a form element on a web page.

Any insight is appreciated.

Thanks.

Answer 1

are you looking for this ?

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    StringBuilder sb = new StringBuilder();
    BufferedReader reader = request.getReader();
    try {
        String line;
        while ((line = reader.readLine()) != null) {
            sb.append(line).append('\n');
        }
    } finally {
        reader.close();
    }
    System.out.println(sb.toString());
}

Answer 2

This is simple method to get request data from HttpServletRequest using Java 8 Stream API:

String requestData = request.getReader().lines().collect(Collectors.joining());

Answer 3

make use of the jackson JSON processor

 ObjectMapper mapper = new ObjectMapper();
  Book book = mapper.readValue(request.getInputStream(),Book.class);

Answer 4

The easiest way is to populate your bean would be from a Reader object, this can be done in a single call:

BufferedReader reader = request.getReader();
Gson gson = new Gson();

MyBean myBean = gson.fromJson(reader, MyBean.class);

Answer 5

There is another way to do it, using org.apache.commons.io.IOUtils to extract the String from the request

String jsonString = IOUtils.toString(request.getInputStream());

Then you can do whatever you want, convert it to JSON or other object with Gson, etc.

JSONObject json = new JSONObject(jsonString);
MyObject myObject = new Gson().fromJson(jsonString, MyObject.class);

Answer 6

If you're trying to get data out of the request body, the code above works. But, I think you are having the same problem I was..

If the data in the body is in JSON form, and you want it as a Java object, you'll need to parse it yourself, or use a library like google-gson to handle it for you. You should look at the docs and examples at the project's website to know how to use it. It's fairly simple.

Answer 7

Converting the retreived data from the request object to json object is as below using google-gson

Gson gson = new Gson();
ABCClass c1 = gson.fromJson(data, ABCClass.class);

//ABC class is a class whose strcuture matches to the data variable retrieved

Answer 8

Use following dependencies

<dependency>
   <groupId>com.google.code.gson</groupId>
   <artifactId>gson</artifactId>
   <version>2.10.1</version>
</dependency>

Version can be any latest version

We can process Json input with following line of code

BufferedReader reader = request.getReader();
Gson gson = new Gson();
MyBean myBean = gson.fromJson(reader, MyBean.class);