Serializer

package org.example.query;

import java.io.UnsupportedEncodingException;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;

public class Serializer {
    public static String urlEncode(String text) {
        try {
            return URLEncoder.encode(text, StandardCharsets.UTF_8.toString());
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException("Should never happen", e);
        }
    }

    public static String buildQuery(Object obj) throws SerializerException {
        StringBuilder result = new StringBuilder();

        for (java.lang.reflect.Field fld : obj.getClass().getFields()) {
            QueryField annot = fld.getAnnotation(QueryField.class);
            if (annot == null) {
                // This field has no "Field" annotation, ignore it.
                continue;
            }

            Object fldVal;
            try {
                fldVal = fld.get(obj);
            } catch (IllegalArgumentException e) {
                throw new RuntimeException("Should never happen", e);
            } catch (IllegalAccessException e) {
                // TODO Auto-generated catch block
                throw new SerializerException("Failed to access field "+fld.getName(), e);
            }

            if (fldVal == null) {
                if (annot.required()) {
                    throw new SerializerException("Required field is null");
                } else {
                    // Ignore optional fields
                    continue;
                }
            }

            String valText = urlEncode(fldVal.toString());

            String valName = annot.name();
            if (valName.length() == 0) {
                // No custom name, use field name instead
                valName = fld.getName();
            }
            valName = urlEncode(valName);

            result.append('&').append(valName).append('=').append(valText);
        }
        return result.substring(1);
    }
}