JsonBuilder.java

package org.fenixedu.bennu.core.json;

import java.util.Collection;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.stream.Stream;

import org.fenixedu.commons.stream.StreamUtils;

import com.google.gson.JsonArray;
import com.google.gson.JsonElement;

@SuppressWarnings({ "rawtypes", "unchecked" })
public class JsonBuilder {
    private final Map<Class<?>, Object> adapters = new ConcurrentHashMap<>();
    private final TableRegistry<JsonCreator> creators = new TableRegistry<>(adapters);
    private final TableRegistry<JsonUpdater> updaters = new TableRegistry<>(adapters);
    private final TableRegistry<JsonViewer> viewers = new TableRegistry<>(adapters);

    public void setDefault(Class<?> objectClass, Class<?> registeeClass) {
        if (JsonCreator.class.isAssignableFrom(registeeClass)) {
            creators.setDefault(objectClass, (Class<? extends JsonCreator>) registeeClass);
        }
        if (JsonViewer.class.isAssignableFrom(registeeClass)) {
            viewers.setDefault(objectClass, (Class<? extends JsonViewer>) registeeClass);
        }
        if (JsonUpdater.class.isAssignableFrom(registeeClass)) {
            updaters.setDefault(objectClass, (Class<? extends JsonUpdater>) registeeClass);
        }
    }

    public JsonElement view(Object obj) {
        return view(obj, null);
    }

    public JsonElement view(Object obj, Class<? extends JsonViewer> jsonViewerClass) {
        return view(obj, obj == null ? null : obj.getClass(), jsonViewerClass);
    }

    public JsonElement view(Object obj, Class<?> objectClass, Class<? extends JsonViewer> jsonViewerClass) {
        if (objectClass == null) {
            return null;
        }

        if (Collection.class.isAssignableFrom(objectClass) && obj != null) {
            return views((Collection) obj, jsonViewerClass);
        }

        if (Stream.class.isAssignableFrom(objectClass) && obj != null) {
            return viewStream((Stream) obj, jsonViewerClass);
        }

        return viewers.get(objectClass, jsonViewerClass).view(obj, this);
    }

    private JsonArray viewStream(Stream<?> stream, Class<? extends JsonViewer> jsonViewerClass) {
        return stream.map(obj -> view(obj, jsonViewerClass)).collect(StreamUtils.toJsonArray());
    }

    private JsonArray views(Collection coll, Class<? extends JsonViewer> jsonViewerClass) {
        JsonArray json = new JsonArray();
        for (final Object el : coll) {
            json.add(view(el, jsonViewerClass));
        }
        return json;
    }

    public <T> T create(JsonElement json, Class<T> clazz) {
        return create(json, clazz, null);
    }

    public <T> T create(JsonElement json, Class<T> clazz, Class<? extends JsonCreator> jsonCreatorClass) {
        final JsonCreator jsonCreator = creators.get(clazz, jsonCreatorClass);
        return (T) jsonCreator.create(json, this);
    }

    public <T> T update(JsonElement json, T object) {
        return update(json, object, null);
    }

    public <T> T update(JsonElement json, T object, Class<? extends JsonUpdater> jsonUpdaterClass) {
        final JsonUpdater jsonUpdater = updaters.get(object.getClass(), jsonUpdaterClass);
        return (T) jsonUpdater.update(json, object, this);
    }
}