com.iluwatar.event.sourcing.processor.JsonFileJournal.java Source code

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Here is the source code for com.iluwatar.event.sourcing.processor.JsonFileJournal.java

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/**
 * The MIT License
 * Copyright (c) 2014 Ilkka Seppl
 *
 * 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.event.sourcing.processor;

import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonParser;
import com.iluwatar.event.sourcing.event.AccountCreateEvent;
import com.iluwatar.event.sourcing.event.DomainEvent;
import com.iluwatar.event.sourcing.event.MoneyDepositEvent;
import com.iluwatar.event.sourcing.event.MoneyTransferEvent;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.List;

/**
 * This is the implementation of event journal.
 * This implementation serialize/deserialize the events with JSON
 * and writes/reads them on a Journal.json file at the working directory.
 *
 * Created by Serdar Hamzaogullari on 06.08.2017.
 */
public class JsonFileJournal {

    private final File aFile;
    private final List<String> events = new ArrayList<>();
    private int index = 0;

    /**
     * Instantiates a new Json file journal.
     */
    public JsonFileJournal() {
        aFile = new File("Journal.json");
        if (aFile.exists()) {
            try (BufferedReader input = new BufferedReader(
                    new InputStreamReader(new FileInputStream(aFile), "UTF-8"))) {
                String line;
                while ((line = input.readLine()) != null) {
                    events.add(line);
                }
            } catch (IOException e) {
                throw new RuntimeException(e);
            }
        } else {
            reset();
        }
    }

    /**
     * Write.
     *
     * @param domainEvent the domain event
     */
    public void write(DomainEvent domainEvent) {
        Gson gson = new Gson();
        JsonElement jsonElement;
        if (domainEvent instanceof AccountCreateEvent) {
            jsonElement = gson.toJsonTree(domainEvent, AccountCreateEvent.class);
        } else if (domainEvent instanceof MoneyDepositEvent) {
            jsonElement = gson.toJsonTree(domainEvent, MoneyDepositEvent.class);
        } else if (domainEvent instanceof MoneyTransferEvent) {
            jsonElement = gson.toJsonTree(domainEvent, MoneyTransferEvent.class);
        } else {
            throw new RuntimeException("Journal Event not recegnized");
        }

        try (Writer output = new BufferedWriter(
                new OutputStreamWriter(new FileOutputStream(aFile, true), "UTF-8"))) {
            String eventString = jsonElement.toString();
            output.write(eventString + "\r\n");
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    /**
     * Reset.
     */
    public void reset() {
        aFile.delete();
    }

    /**
     * Read next domain event.
     *
     * @return the domain event
     */
    public DomainEvent readNext() {
        if (index >= events.size()) {
            return null;
        }
        String event = events.get(index);
        index++;

        JsonParser parser = new JsonParser();
        JsonElement jsonElement = parser.parse(event);
        String eventClassName = jsonElement.getAsJsonObject().get("eventClassName").getAsString();
        Gson gson = new Gson();
        DomainEvent domainEvent;
        if (eventClassName.equals("AccountCreateEvent")) {
            domainEvent = gson.fromJson(jsonElement, AccountCreateEvent.class);
        } else if (eventClassName.equals("MoneyDepositEvent")) {
            domainEvent = gson.fromJson(jsonElement, MoneyDepositEvent.class);
        } else if (eventClassName.equals("MoneyTransferEvent")) {
            domainEvent = gson.fromJson(jsonElement, MoneyTransferEvent.class);
        } else {
            throw new RuntimeException("Journal Event not recegnized");
        }

        domainEvent.setRealTime(false);
        return domainEvent;
    }
}