How to convert object to query string in Java?

Why convert to Map then MultiValueMap, instead of just building it directly?

DateFormat dateFmt = new SimpleDateFormat("whatever date format you want");
URIComponentsBuilder.fromHttpUrl("httpL//example.com")
                    .queryParam("prop1", a.prop1)
                    .queryParam("prop2", a.prop2)
                    .queryParam("date1", dateFmt.format(a.date1))
                    .queryParam("date2", dateFmt.format(a.date2))
                    .queryParam("prop3", a.objB.prop3)
                    .queryParam("prop4", a.objB.prop4)
                    .build();

You could write your own method that uses java.lang.reflect. Here's an example

public static String getRequestString(String urlString, Class clazz, Object o){
    String queryString = "?";

    try {
        for (Field f : clazz.getDeclaredFields()) {
            f.setAccessible(true);
            queryString += queryString.concat(f.getName() + "=" + String.valueOf(f.get(o)) + "&");
        }
    }catch (Exception e){
        e.printStackTrace();
    }

    return urlString + queryString.substring(0,queryString.length()-1);
}