com.images3.data.impl.MongoDBAccess.java Source code

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Here is the source code for com.images3.data.impl.MongoDBAccess.java

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/*******************************************************************************
 * Copyright 2014 Rui Sun
 *
 * 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.images3.data.impl;

import java.util.Date;
import java.util.List;

import org.gogoup.dddutils.pagination.PaginatedResult;

import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.MongoClient;
import com.mongodb.WriteResult;

public abstract class MongoDBAccess<T> {

    private MongoClient mongoClient;
    private String dbname;
    private MongoDBObjectMapper objectMapper;
    private int pageSize;

    public MongoDBAccess(MongoClient mongoClient, String dbname, MongoDBObjectMapper objectMapper, int pageSize) {
        this.mongoClient = mongoClient;
        this.dbname = dbname;
        this.objectMapper = objectMapper;
        this.pageSize = pageSize;
    }

    protected DB getDatabase() {
        return mongoClient.getDB(dbname);
    }

    protected MongoDBObjectMapper getObjectMapper() {
        return objectMapper;
    }

    protected int getPageSize() {
        return pageSize;
    }

    protected void checkForAffectedDocuments(WriteResult result, int expectedAffectedNumber) {
        if (result.getN() != expectedAffectedNumber) {
            throw new RuntimeException("Unexpected affected number of documents," + "" + result.getN() + " != "
                    + expectedAffectedNumber);
        }
    }

    protected Object nextPageCursorId(String tag, Object[] arguments, Object pageCursor, List<T> result) {
        if (foundTheLastRecord(result)) {
            return PaginatedResult.NONE_PAGE_CURSOR;
        }
        return nextPageCursor((String) pageCursor).getId();
    }

    protected Object previousPageCursorId(String tag, Object[] arguments, Object pageCursor, List<T> result) {
        PageCursor cursor = selectPageCursorById((String) pageCursor);
        return cursor.getPreviousPageCursorId();
    }

    protected PageCursor nextPageCursor(String pageCursorId) {
        PageCursor cursor = null;
        if (null != pageCursorId) {

            //try to find exsiting next page cursor.
            cursor = selectPageCursorByPreviousId(pageCursorId);
            if (null != cursor) {
                return cursor;
            }
            cursor = selectPageCursorById(pageCursorId);
        }
        Page page = createNextPage(cursor);
        PageCursor nextPageCursor = createPageCursor(page, cursor);
        insertPageCursor(nextPageCursor);
        return nextPageCursor;
    }

    private Page createNextPage(PageCursor cursor) {
        if (null == cursor) {
            return createFirstPage();
        } else {
            return new Page().startAtPage(cursor.getPage().getStart() + 1).withSize(pageSize);
        }
    }

    private Page createFirstPage() {
        return new Page().startAtPage(1).withSize(pageSize); //first page
    }

    private PageCursor createPageCursor(Page page, PageCursor prevPageCursor) {
        String id = ShortUUID.randomUUID();
        Date createdTime = new Date(System.currentTimeMillis());
        return new PageCursor(id, (prevPageCursor == null ? null : prevPageCursor.getId()), page, createdTime);
    }

    private void insertPageCursor(PageCursor cursor) {
        DBCollection coll = getDatabase().getCollection("PageCursor");
        coll.insert(getObjectMapper().mapToBasicDBObject(cursor));
    }

    protected PageCursor selectPageCursorById(String id) {
        DBCollection coll = getDatabase().getCollection("PageCursor");
        BasicDBObject criteria = new BasicDBObject().append("id", id);
        DBCursor cursor = coll.find(criteria);
        if (!cursor.hasNext()) {
            return null;
        }
        return getObjectMapper().mapToPageCursor((BasicDBObject) cursor.next());
    }

    private PageCursor selectPageCursorByPreviousId(String id) {
        DBCollection coll = getDatabase().getCollection("PageCursor");
        BasicDBObject criteria = new BasicDBObject().append("previousPageCursorId", id);
        DBCursor cursor = coll.find(criteria);
        if (!cursor.hasNext()) {
            return null;
        }
        return getObjectMapper().mapToPageCursor((BasicDBObject) cursor.next());
    }

    private boolean foundTheLastRecord(List<T> result) {
        return (null != result && (result.size() == 0 || getPageSize() > result.size()));
    }
}