gson.java

package com.wescon.cv.utilities;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

import org.nutz.castor.Castors;

import com.google.common.base.Supplier;
import com.google.common.collect.BiMap;
import com.google.common.collect.HashBasedTable;
import com.google.common.collect.HashBiMap;
import com.google.common.collect.Multimap;
import com.google.common.collect.Multimaps;
import com.google.common.collect.SetMultimap;
import com.google.common.collect.Sets;
import com.google.common.collect.Table;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonArray;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;

@SuppressWarnings("rawtypes")
public class Gsons {
    static Gson gson;
    static {
        gson = new GsonBuilder().registerTypeAdapter(Multimap.class,
                                                     new JsonSerializer<Multimap>() {
                                                         public JsonElement serialize(Multimap multimap,
                                                                                      Type type,
                                                                                      JsonSerializationContext jsonSerializationContext) {
                                                             return jsonSerializationContext.serialize(multimap.asMap());
                                                         }
                                                     })
                                .registerTypeAdapter(Multimap.class,
                                                     new JsonDeserializer<Multimap>() {
                                                         public Multimap deserialize(JsonElement jsonElement,
                                                                                     Type type,
                                                                                     JsonDeserializationContext jsonDeserializationContext)
                                                                 throws JsonParseException {
                                                             final SetMultimap<String, String> map = Multimaps.newSetMultimap(new HashMap<String, Collection<String>>(),
                                                                                                                              new Supplier<Set<String>>() {
                                                                                                                                  public Set<String> get() {
                                                                                                                                      return Sets.newHashSet();
                                                                                                                                  }
                                                                                                                              });
                                                             for (Map.Entry<String, JsonElement> entry : ((JsonObject) jsonElement).entrySet()) {
                                                                 for (JsonElement element : (JsonArray) entry.getValue()) {
                                                                     map.get(entry.getKey())
                                                                        .add(element.getAsString());
                                                                 }
                                                             }
                                                             return map;
                                                         }
                                                     })
                                .registerTypeAdapter(Table.class, new JsonDeserializer<Table>() {

                                    @SuppressWarnings("unchecked")
                                    @Override
                                    public Table deserialize(JsonElement json,
                                                             Type type,
                                                             JsonDeserializationContext context)
                                            throws JsonParseException {
                                        Table table = HashBasedTable.create();
                                        JsonObject object = (JsonObject) json;
                                        JsonElement element = object.get("backingMap");
                                        for (Map.Entry<String, JsonElement> entry : ((JsonObject) element).entrySet()) {
                                            String row = entry.getKey();
                                            for (Map.Entry<String, JsonElement> column : ((JsonObject) entry.getValue()).entrySet()) {
                                                table.put(row, column.getKey(), column.getValue());
                                            }
                                        }
                                        return table;
                                    }
                                })
                                .registerTypeAdapter(BiMap.class, new JsonDeserializer<BiMap>() {

                                    @SuppressWarnings("unchecked")
                                    @Override
                                    public BiMap deserialize(JsonElement json,
                                                             Type type,
                                                             JsonDeserializationContext context)
                                            throws JsonParseException {
                                        BiMap mapping = HashBiMap.create();
                                        Type[] typeParameters = ((ParameterizedType) type).getActualTypeArguments();
                                        JsonObject object = (JsonObject) json;
                                        for (Map.Entry<String, JsonElement> entry : object.entrySet()) {
                                            String value = entry.getValue().getAsString();
                                            mapping.put(entry.getKey(),
                                                        Castors.me()
                                                               .castTo(value,
                                                                       (Class) typeParameters[1]));
                                        }
                                        return mapping;
                                    }
                                })
                                .setPrettyPrinting()
                                .create();
    }

    public static final Gson gson() {
        return gson;
    }

    private Gsons() {}
}