Converting from DescribeSObjectResult to JsonArray (or to HttpEntity)

A couple of weeks ago, I asked a question about reading Salesforce data using the SOAP API instead of the REST API (see https://stackoverflow.com/questions/63455670/trying-to-use-apache-gobblin-to-read-salesforce-data-using-soap-apis-instead-o ), but unfortunately nobody answered it, and so I am trying to implement the solution (with a little help) directly.

Using the REST API, the existing code that reads in a table's definition (by making a call to the REST API) looks like this:

// the URL starts with the Salesforce REST API endpoint, and ends with "/describe"
public String getSchema(String url, String accessToken, HttpClient httpClient) {
    String jsonStr;
    HttpRequestBase httpRequest = new HttpGet(url);
    if (accessToken != null) {
        httpRequest.addHeader("Authorization", "OAuth " + this.accessToken);
    }
    httpRequest.addHeader("Content-Type", "application/json");
    HttpEntity httpEntity = null;
    HttpResponse httpResponse = null;
    try {
        httpResponse = httpClient.execute(httpRequest);
        StatusLine status = httpResponse.getStatusLine();
        httpEntity = httpResponse.getEntity();

        if (httpEntity != null) {
            jsonStr = EntityUtils.toString(httpEntity);
        }

        if (status.getStatusCode() >= 400) {
            System.out.println("There was an error.  Http Status code of " + status.getStatusCode());
            EntityUtils.consumeEntity(httpEntity);
            return null;
        }
        return jsonStr;
    } catch (Exception e) {
       e.printStackTrace();
       return null;
    }
    return jsonStr;
}

I would like to write a method that uses the Salesforce SOAP API (using the generated "partner.wsdl" file) similar to the following incomplete code:

public String getSchemaViaSoap(String tableName) {
    String jsonStr;
    PartnerConnection partnerConnection = ...;
    try {
        DescribeSObjectResult[] dsrArray = partnerConnection.describeSObjects(new String[] { entity });
        // Since we described only one sObject, we should have only
        // one element in the DescribeSObjectResult array.
        DescribeSObjectResult dsr = dsrArray[0];
        String jsonStr = ...;  /* this is where I need help in converting dsr into a similar JSON string. */
    } catch (ConnectionException e) {
        e.printStackTrace();
        log.error("Error getting connection", e);
        System.out.println("Error getting connection" + e);
        return null;
    }
    return jsonStr;
}

Any sort of help in determining how to convert from the DescribeSObjectResult object to a similar JsonString / HttpEntity / StringEntity object would be greatly appreciated.

You have consumed the WSDL, right? The DescribeSObjectResult is a normal class in your project. So... my Java is rusty but seems the question is simple "how to convert a Java object to JSON"?

There are libraries for this, right? Jackson for example. This helps? https://stackoverflow.com/q/15786129/313628

I'm not sure if you'll end with identical result but should be close enough.