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 Trying to use Apache Gobblin to read Salesforce data using SOAP API(s) instead of REST API ), 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? Converting Java objects to JSON with Jackson

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