com.ikanow.infinit.e.data_model.index.BaseIndexPojo.java Source code

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Here is the source code for com.ikanow.infinit.e.data_model.index.BaseIndexPojo.java

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/*******************************************************************************
 * Copyright 2012 The Infinit.e Open Source Project
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/
package com.ikanow.infinit.e.data_model.index;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.Collection;
import java.util.Date;

import org.bson.types.ObjectId;

import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;
import com.google.gson.reflect.TypeToken;

public class BaseIndexPojo {
    // Override this function to perform custom serialization (see BasePojoIndexMap)
    public GsonBuilder extendBuilder(GsonBuilder gp) {
        return extendBuilder_internal(gp);
    }

    // Allows Index owner to enforce some custom serializations
    final public static GsonBuilder getDefaultBuilder() {
        return new GsonBuilder().registerTypeAdapter(ObjectId.class, new ObjectIdSerializer())
                .registerTypeAdapter(Date.class, new DateSerializer());
    }

    private static GsonBuilder extendBuilder_internal(GsonBuilder gp) {
        return gp;
    }
    //________________________________________________________________________________________________

    // Won't normally override these (but can)
    // DB format conversion

    // For BaseIndexPojos
    // 2 versions, 1 where you need dynamic mapping (eg runtime-specific)
    // (in both cases for single objects, you can use the nicer class<X> or 
    //  the nastier Google TypeToken, the latter has 2 advantages:
    //  a. consisntency with list types, where you have to use the TypeToken
    //  b. the class<X> doesn't work where X is generic)
    //
    // Note - the code is a bit unpleastant in places....

    /////////////////////////////////////////////////////////////////////////////////////
    // To the Index JSON From a single Object
    public static <S extends BaseIndexPojo> String toIndex(S s) {
        return toIndex(s, null);
    }

    // (Nicer version of the static "toIndex")   
    public String toIndex() {
        return toIndex(this);
    }

    public static <S extends BaseIndexPojo> String toIndex(S s, BasePojoIndexMap<S> dynamicMap) {
        GsonBuilder gb = s.extendBuilder(BaseIndexPojo.getDefaultBuilder());
        if (null != dynamicMap) {
            gb = dynamicMap.extendBuilder(gb);
        }
        return gb.create().toJson(s);
    }

    /////////////////////////////////////////////////////////////////////////////////////
    // From the Index JSON To a single Object
    public static <S extends BaseIndexPojo> S fromIndex(String s, Class<S> type) {
        return fromIndex(s, type, null);
    }

    public static <S extends BaseIndexPojo> S fromIndex(String s, TypeToken<S> type) {
        return fromIndex(s, type, null);
    }

    public static <S extends BaseIndexPojo> S fromIndex(String s, Class<S> type, BasePojoIndexMap<S> dynamicMap) {
        // Create a new instance of the class in order to override it
        GsonBuilder gb = null;
        try {
            gb = type.newInstance().extendBuilder(BaseIndexPojo.getDefaultBuilder());
        } catch (Exception e) {
            return null;
        }
        if (null != dynamicMap) {
            gb = dynamicMap.extendBuilder(gb);
        }
        return gb.create().fromJson(s.toString(), type);
    }

    @SuppressWarnings("unchecked")
    public static <S extends BaseIndexPojo> S fromIndex(String s, TypeToken<S> type,
            BasePojoIndexMap<S> dynamicMap) {
        GsonBuilder gb = null;
        try {
            Class<S> clazz = (Class<S>) type.getType();
            gb = ((S) clazz.newInstance()).extendBuilder(BaseIndexPojo.getDefaultBuilder());
        } catch (Exception e) {
            return null;
        }
        if (null != dynamicMap) {
            gb = dynamicMap.extendBuilder(gb);
        }
        return (S) gb.create().fromJson(s.toString(), type.getType());
    }

    /////////////////////////////////////////////////////////////////////////////////////
    // To the Index JSON From a list of objects
    public static <S extends BaseIndexPojo> String listToIndex(Collection<S> list,
            TypeToken<? extends Collection<S>> listType) {
        return listToIndex(list, listType, null);
    }

    public static <S extends BaseIndexPojo> String listToIndex(Collection<S> list,
            TypeToken<? extends Collection<S>> listType, BasePojoIndexMap<S> dynamicMap) {
        GsonBuilder gb = null;
        try {
            if (!list.isEmpty()) {
                gb = list.iterator().next().extendBuilder(BaseIndexPojo.getDefaultBuilder());
            }
        } catch (Exception e) {
            return null;
        }
        return gb.create().toJson(list, listType.getType());
    }

    /////////////////////////////////////////////////////////////////////////////////////
    // From the Index JSON to a list of objects
    public static <S extends BaseIndexPojo, L extends Collection<S>> L listFromIndex(String bson,
            TypeToken<? extends L> listType) {
        return listFromIndex(bson, listType, null);
    }

    @SuppressWarnings("unchecked")
    public static <S extends BaseIndexPojo, L extends Collection<S>> L listFromIndex(String bson,
            TypeToken<? extends L> listType, BasePojoIndexMap<S> dynamicMap) {
        GsonBuilder gb = null;
        try {
            Class<S> clazz = (Class<S>) ((ParameterizedType) listType.getType()).getActualTypeArguments()[0];
            // (know this works because of construction of listType)
            gb = (clazz.newInstance()).extendBuilder(BaseIndexPojo.getDefaultBuilder());
        } catch (Exception e) {
            return null;
        }
        if (null != dynamicMap) {
            gb = dynamicMap.extendBuilder(gb);
        }
        return (L) gb.create().fromJson(bson, listType.getType());
    }
    //___________________________________________________________________

    // Default MongoDB serialization rule:   
    // 1. Object Ids
    protected static class ObjectIdSerializer implements JsonSerializer<ObjectId> {
        @Override
        public JsonElement serialize(ObjectId id, Type typeOfT, JsonSerializationContext context) {
            return new JsonPrimitive(id.toStringMongod());
        }
    }

    // 2. Dates
    protected static class DateSerializer implements JsonSerializer<Date> {
        @Override
        public JsonElement serialize(Date date, Type typeOfT, JsonSerializationContext context) {
            return new JsonPrimitive(date.getTime());
        }
    }
}