java-design-patterns/caching/src/main/java/com/iluwatar/caching/DbManager.java

/**
 * The MIT License
 * Copyright (c) 2014 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package com.iluwatar.caching;

import java.text.ParseException;
import java.util.HashMap;
import java.util.Map;

import org.bson.Document;

import com.mongodb.MongoClient;
import com.mongodb.client.FindIterable;
import com.mongodb.client.MongoDatabase;
import com.mongodb.client.model.UpdateOptions;

/**
 *
 * <p>DBManager handles the communication with the underlying data store i.e. Database. It contains the
 * implemented methods for querying, inserting, and updating data. MongoDB was used as the database
 * for the application.</p>
 * 
 * <p>Developer/Tester is able to choose whether the application should use MongoDB as its underlying
 * data storage (connect()) or a simple Java data structure to (temporarily) store the data/objects
 * during runtime (createVirtualDB()).</p>
 * 
 */
public final class DbManager {

  private static MongoClient mongoClient;
  private static MongoDatabase db;
  private static boolean useMongoDB;

  private static Map<String, UserAccount> virtualDB;

  private DbManager() {
  }

  /**
   * Create DB
   */
  public static void createVirtualDb() {
    useMongoDB = false;
    virtualDB = new HashMap<>();
  }

  /**
   * Connect to DB
   */
  public static void connect() throws ParseException {
    useMongoDB = true;
    mongoClient = new MongoClient();
    db = mongoClient.getDatabase("test");
  }

  /**
   * Read user account from DB
   */
  public static UserAccount readFromDb(String userId) {
    if (!useMongoDB) {
      if (virtualDB.containsKey(userId)) {
        return virtualDB.get(userId);
      }
      return null;
    }
    if (null == db) {
      try {
        connect();
      } catch (ParseException e) {
        e.printStackTrace();
      }
    }
    FindIterable<Document> iterable =
        db.getCollection("user_accounts").find(new Document("userID", userId));
    if (iterable == null) {
      return null;
    }
    Document doc = iterable.first();
    return new UserAccount(userId, doc.getString("userName"), doc.getString("additionalInfo"));
  }

  /**
   * Write user account to DB
   */
  public static void writeToDb(UserAccount userAccount) {
    if (!useMongoDB) {
      virtualDB.put(userAccount.getUserId(), userAccount);
      return;
    }
    if (null == db) {
      try {
        connect();
      } catch (ParseException e) {
        e.printStackTrace();
      }
    }
    db.getCollection("user_accounts").insertOne(
        new Document("userID", userAccount.getUserId()).append("userName",
            userAccount.getUserName()).append("additionalInfo", userAccount.getAdditionalInfo()));
  }

  /**
   * Update DB
   */
  public static void updateDb(UserAccount userAccount) {
    if (!useMongoDB) {
      virtualDB.put(userAccount.getUserId(), userAccount);
      return;
    }
    if (null == db) {
      try {
        connect();
      } catch (ParseException e) {
        e.printStackTrace();
      }
    }
    db.getCollection("user_accounts").updateOne(
        new Document("userID", userAccount.getUserId()),
        new Document("$set", new Document("userName", userAccount.getUserName()).append(
            "additionalInfo", userAccount.getAdditionalInfo())));
  }

  /**
   *
   * Insert data into DB if it does not exist. Else, update it.
   */
  public static void upsertDb(UserAccount userAccount) {
    if (!useMongoDB) {
      virtualDB.put(userAccount.getUserId(), userAccount);
      return;
    }
    if (null == db) {
      try {
        connect();
      } catch (ParseException e) {
        e.printStackTrace();
      }
    }
    db.getCollection("user_accounts").updateOne(
        new Document("userID", userAccount.getUserId()),
        new Document("$set", new Document("userID", userAccount.getUserId()).append("userName",
            userAccount.getUserName()).append("additionalInfo", userAccount.getAdditionalInfo())),
        new UpdateOptions().upsert(true));
  }
}