How to parse JSON data in moqui services without using nay 3rd party library?

Technical Questions
1 
        <in-parameters>
            <parameter name="emojis" type="List">
                <parameter name="emoji">
                    <parameter name="emojiName"/>
                    <parameter name="contentFile" type="org.apache.commons.fileupload.FileItem" />
                </parameter>
            </parameter>
        </in-parameters>

I have created a service in moqui. The service takes an array of emoji files and emoji name. I am using React for frontend. So to pass the data from react I need to use formData and JSON.stringify because I am passing an array of objects. The problem is since I am using JSON.stringyfy how can I parse the data in backend without using any 2rd party packages? or is there any other way to pass the data without using stringify?

here is the frontend code:

    const formData = new FormData();

    const emojis = [
      {
        emojiName: ':ABC:',
        contentFile: file,
      },
    ];


    formData.append('emojis', JSON.stringify(emojis));
    return Api.channels.createChannelSubscription(formData);
2

I would start with getting the raw http response and parsing it from there if there is a problem with encoding: