87 lines
3.1 KiB
Java
87 lines
3.1 KiB
Java
/*
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* The MIT License
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* Copyright © 2014-2019 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.versionnumber;
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import java.util.HashMap;
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import java.util.Map;
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/**
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* This repository represents simplified database.
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* As a typical database do, repository operates with copies of object.
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* So client and repo has different copies of book, which can lead to concurrency conflicts
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* as much as in real databases.
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*/
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public class BookRepository {
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private final Map<Long, Book> collection = new HashMap<>();
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/**
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* Adds book to collection.
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* Actually we are putting copy of book (saving a book by value, not by reference);
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*/
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public void add(Book book) throws BookDuplicateException {
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if (collection.containsKey(book.getId())) {
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throw new BookDuplicateException("Duplicated book with id: " + book.getId());
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}
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// add copy of the book
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collection.put(book.getId(), new Book(book));
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}
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/**
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* Updates book in collection only if client has modified the latest version of the book.
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*/
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public void update(Book book) throws BookNotFoundException, VersionMismatchException {
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if (!collection.containsKey(book.getId())) {
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throw new BookNotFoundException("Not found book with id: " + book.getId());
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}
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var latestBook = collection.get(book.getId());
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if (book.getVersion() != latestBook.getVersion()) {
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throw new VersionMismatchException(
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"Tried to update stale version " + book.getVersion()
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+ " while actual version is " + latestBook.getVersion()
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);
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}
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// update version, including client representation - modify by reference here
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book.setVersion(book.getVersion() + 1);
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// save book copy to repository
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collection.put(book.getId(), new Book(book));
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}
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/**
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* Returns book representation to the client.
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* Representation means we are returning copy of the book.
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*/
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public Book get(long bookId) throws BookNotFoundException {
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if (!collection.containsKey(bookId)) {
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throw new BookNotFoundException("Not found book with id: " + bookId);
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}
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// return copy of the book
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return new Book(collection.get(bookId));
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}
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}
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