如何摆脱不必要的（？）代码——适应 DRY 原则
How to get rid of unnecessary(?) code - adjusting to DRY principle
前段时间我也在讨论类似的话题。我正在查看我的应用程序，我认为它有很多不必要的代码。我的意思是我有服务负责从两家书店的不同类别的书籍中抓取数据。现在我有 5 个类别，所以我有 5 个方法，但如果我要添加一些新类别怎么办？我将不得不添加更多方法......我认为这不是一个好的选择。现在看起来像这样：
控制器
@GetMapping("/romances")
public Map<Bookstore, List<Book>> get15RomanticBooks() {
return categorizedBookService.get15BooksFromRomanceCategory();
}
@GetMapping("/biographies")
public Map<Bookstore, List<Book>> get15BiographiesBooks() {
return categorizedBookService.get15BooksFromBiographiesCategory();
}
@GetMapping("/guides")
public Map<Bookstore, List<Book>> get15GuidesBooks() {
return categorizedBookService.get15BooksFromGuidesCategory();
}
@GetMapping("/fantasy")
public Map<Bookstore, List<Book>> get15FantasyBooks() {
return categorizedBookService.get15BooksFromFantasyCategory();
}
我在想
@GetMapping("/{category}")
public Map<......> get 15BooksFromCategory(@PathVariable CategoryType category)
{...}
我认为这是最好的方法，但是服务比较难。
它的服务是这样的：
package bookstore.scraper.book.scrapingtypeservice;
import bookstore.scraper.enums.Bookstore;
import bookstore.scraper.book.Book;
import bookstore.scraper.fetcher.empik.EmpikFetchingBookService;
import bookstore.scraper.fetcher.merlin.MerlinFetchingBookService;
import bookstore.scraper.urlproperties.EmpikUrlProperties;
import bookstore.scraper.urlproperties.MerlinUrlProperties;
import bookstore.scraper.utilities.JSoupConnector;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.EnumMap;
import java.util.List;
import java.util.Map;
@Service
@Slf4j
public class CategorizedBookService {
private final EmpikFetchingBookService empikBookService;
private final MerlinFetchingBookService merlinFetchingBookService;
private final EmpikUrlProperties empikUrlProperties;
private final MerlinUrlProperties merlinUrlProperties;
private final JSoupConnector jSoupConnector;
@Autowired
public CategorizedBookService(EmpikFetchingBookService empikBookService, MerlinFetchingBookService merlinFetchingBookService, EmpikUrlProperties empikUrlProperties, MerlinUrlProperties merlinUrlProperties, JSoupConnector jSoupConnector) {
this.empikBookService = empikBookService;
this.merlinFetchingBookService = merlinFetchingBookService;
this.empikUrlProperties = empikUrlProperties;
this.merlinUrlProperties = merlinUrlProperties;
this.jSoupConnector = jSoupConnector;
}
public Map<Bookstore, List<Book>> get15BooksFromRomanceCategory() {
return get15BooksFrom(empikUrlProperties.getEmpik().getRomances(), merlinUrlProperties.getMerlin().getRomances());
}
public Map<Bookstore, List<Book>> get15BooksFromFantasyCategory() {
return get15BooksFrom(empikUrlProperties.getEmpik().getFantasy(), merlinUrlProperties.getMerlin().getFantasy());
}
public Map<Bookstore, List<Book>> get15BooksFromCrimeCategory() {
return get15BooksFrom(empikUrlProperties.getEmpik().getCrime(), merlinUrlProperties.getMerlin().getCrime());
}
public Map<Bookstore, List<Book>> get15BooksFromGuidesCategory() {
return get15BooksFrom(empikUrlProperties.getEmpik().getGuides(), merlinUrlProperties.getMerlin().getGuides());
}
public Map<Bookstore, List<Book>> get15BooksFromBiographiesCategory() {
return get15BooksFrom(empikUrlProperties.getEmpik().getBiographies(), merlinUrlProperties.getMerlin().getBiographies());
}
private Map<Bookstore, List<Book>> get15BooksFrom(String bookStoreEmpikURL, String bookStoreMerlinURL) {
Map<Bookstore, List<Book>> bookstoreWith15CategorizedBooks = new EnumMap<>(Bookstore.class);
bookstoreWith15CategorizedBooks.put(Bookstore.EMPIK, empikBookService
.get15BooksFromCategory(jSoupConnector.connect(bookStoreEmpikURL)));
bookstoreWith15CategorizedBooks.put(Bookstore.MERLIN, merlinFetchingBookService
.get15BooksFromCategory(jSoupConnector.connect(bookStoreMerlinURL)));
return bookstoreWith15CategorizedBooks;
}
}
我必须传递 2 个不同的链接，具体取决于调用的是哪个类别。有什么办法吗？
EmpikBookService/merlinFetchingBookService 是使用 Jsoup 来 抓取 数据的服务。
package bookstore.scraper.fetcher.empik;
import bookstore.scraper.book.Book;
import bookstore.scraper.urlproperties.EmpikUrlProperties;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;
@Service
public class EmpikFetchingBookService {
private static final int FIRST_PART_PRICE = 0;
private static final int SECOND_PART_PRICE = 1;
private static final int BESTSELLERS_NUMBER_TO_FETCH = 5;
private static final int CATEGORIZED_BOOKS_NUMBER_TO_FETCH = 15;
private static final String DIV_PRODUCT_WRAPPER = "div.productWrapper";
private static final String DATA_PRODUCT_ID = "data-product-id";
private final EmpikUrlProperties empikUrlProperties;
@Autowired
public EmpikFetchingBookService(EmpikUrlProperties empikUrlProperties) {
this.empikUrlProperties = empikUrlProperties;
}
public Book getMostPreciseEmpikBook(Document document) {
String author = document.select("div.smartAuthorWrapper.ta-product-smartauthor").select("a").first().text();
String price = convertEmpikPriceWithPossibleDiscountToActualPrice(document.select("div.price.ta-price-tile").first().text());
String title = document.select(DIV_PRODUCT_WRAPPER).select("strong").first().text();
String productID = document.select(DIV_PRODUCT_WRAPPER).select("a").first().attr(DATA_PRODUCT_ID);
String bookUrl = createBookURL(title, productID);
return Book.builder()
.author(author)
.price(price)
.title(title)
.productID(productID)
.bookURL(bookUrl).build();
}
public List<Book> get5BestSellersEmpik(Document document) {
List<Element> siteElements = document.select(DIV_PRODUCT_WRAPPER);
List<Book> empikBestSellers = new ArrayList<>();
IntStream.range(0, BESTSELLERS_NUMBER_TO_FETCH)
.forEach(iteratedElement -> {
String author = siteElements.get(iteratedElement).select("div.smartAuthorWrapper.ta-product-smartauthor").select("a").first().text();
String price = convertEmpikPriceWithPossibleDiscountToActualPrice(siteElements.get(iteratedElement).select("div.price.ta-price-tile").first().text());
String title = siteElements.get(iteratedElement).select("strong").first().ownText();
String productID = siteElements.get(iteratedElement).select(DIV_PRODUCT_WRAPPER).select("a").first().attr(DATA_PRODUCT_ID);
String bookUrl = createBookURL(title, productID);
empikBestSellers.add(Book.builder()
.author(author)
.price(price)
.title(title)
.productID(productID)
.bookURL(bookUrl)
.build());
});
return empikBestSellers;
}
public List<Book> get15BooksFromCategory(Document document) {
List<Book> books = new ArrayList<>();
List<Element> siteElements = document.select("div.productBox__info");
IntStream.range(0, CATEGORIZED_BOOKS_NUMBER_TO_FETCH)
.forEach(iteratedElement -> {
String author = executeFetchingAuthorProcess(siteElements, iteratedElement);
String price = convertEmpikPriceWithPossibleDiscountToActualPrice(siteElements.get(iteratedElement).select("div.productBox__price").first().text());
String title = siteElements.get(iteratedElement).select("span").first().ownText();
String productID = siteElements.get(iteratedElement).select("a").first().attr(DATA_PRODUCT_ID);
String bookUrl = createBookURL(title, productID);
books.add(Book.builder()
.author(author)
.price(price)
.title(title)
.productID(productID)
.bookURL(bookUrl)
.build());
});
return books;
}
private String convertEmpikPriceWithPossibleDiscountToActualPrice(String price) {
String[] splittedElements = price.split("\s+");
return splittedElements[FIRST_PART_PRICE] + splittedElements[SECOND_PART_PRICE];
}
private String createBookURL(String title, String productID) {
return String.format(empikUrlProperties.getEmpik().getConcreteBook(), title, productID);
}
//method is required as on empik site, sometimes occurs null for author and we need to change code for fetching
private static String executeFetchingAuthorProcess(List<Element> siteElements, int i) {
String author;
Element authorElements = siteElements.get(i).select("span > a").first();
if (authorElements != null)
author = authorElements.ownText();
else
author = siteElements.get(i).select("> span > span").first().text();
return author;
}
}
实施 Chain Of Responsibility 模式并允许服务获取结果并将结果放入结果 Map 对象。还让 Spring 通过提供一些通用接口
来使用自动装配服务创造一些魔力
public interface FetchingService {
public Map<Bookstore, List<Book>> fetchAndAddToResult(Map<Bookstore, List<Book>> result, CategoryType category);
}
@Service
public class EmpikFetchingBookService implements FetchingService {
// ...
@Override
public Map<Bookstore, List<Book>> fetchAndAddToResult(Map<Bookstore, List<Book>> result, CategoryType category) {
result.put(Bookstore.EMPIK, getListOfBooks(category));
return result;
}
}
@Service
public class MerlinFetchingBookService implements FetchingService {
// ...
@Override
public Map<Bookstore, List<Book>> fetchAndAddToResult(Map<Bookstore, List<Book>> result, CategoryType category) {
result.put(Bookstore.MERLIN, getListOfBooks(category));
return result;
}
}
@Service
@Slf4j
public class CategorizedBookService {
private final List<FetchingService> services;
//JSoup connector and Properties move to FetchingServices because it is part of those services implementation
@Autowired
public CategorizedBookService(List<FetchingService> services) {
this.services = services;
}
public Map<Bookstore, List<Book>> get15BooksByCategory(CategoryType category) {
Map<Bookstore, List<Book>> result = new HashMap<>();
for(FetchingService service : services) {
result = service.fetchAndAddToResult(result, category);
}
return result;
}
}
(1) 名称 get15BooksFromCategory(CategoryType) 不正确：您将要 returned 的许多书籍硬编码到方法名称中。
今天你return15，明天你需要return20，周日你可能需要return5，安卓你可能需要return 50. 你明白了。
考虑这些签名。
getAllBooksFromCategory(CategoryType);
getNBooksFromCategory(CategoryType, Integer);
(2)去掉服务中的这些字段。
private final EmpikUrlProperties empikUrlProperties;
private final MerlinUrlProperties merlinUrlProperties;
private final JSoupConnector jSoupConnector;
前两个分别是EmpikFetchingBookService和MerlinFetchingBookService的一部分。 JSoupConnector 是一个更底层的抽象，它不应该出现在这个级别。它可能驻留在这些图书服务的共同父项中，或者是共同父项所依赖的单独 JSoupService。
(3) 理想情况下，您最终应该得到一个非常简单的服务，该服务具有单一职责 - 从其来源收集书籍。
class BookService {
private List<BookServiceSource> sources;
public Map<String, List<Book>> getBooksByCategory(Category category) {
return sources.stream()
.collect(Collectors.toMap(BookServiceSource::getName,
source -> source.getBooksByCategory(category)));
}
}
BookServiceSource 具有与 BookService 相似的界面。但是，MerlinSource 作为 BookServiceSource 的子类，不会将工作委托给其他人。相反，它准备一个 URL 并将其提供给 JSoupService。
BookServiceSource 的职责是准备请求参数并将结果 return 从 JSoupService 转换为 List<Book>。由于每个书店都有不同的 DOM，您需要知道如何将特定的 DOM 映射到您的结构中。
interface BookServiceSource {
String getName();
List<Book> getBooksByCategory(Category category);
}
class MerlinSource implements BookServiceSource {
private JSoupService service;
private MerlinUrlProperties properties;
@Override
public String getName() {
return "merlin";
}
@Override
public List<Book> getBooksByCategory(Category category) {
// at this point, we have both
// JSoupService (to make a real request) and
// MerlinUrlProperties (to prepare everything for that request)
}
}
将 MerlinUrlProperties 视为一种实用程序，可以在类别和 URL 之间为该类别的书籍提供映射。
MerlinUrlProperties 可以是一个 Map 本身，如果它只包含一堆 return URL 的方法。重点是您不必为新类别定义新方法并强制使用您的 API 的每个人都改变自己以包含 API 的新部分。使用 Map 或枚举，界面会更稳定。
Map<String, String> categoryToMarlinURL = new HashMap<>();
categoryToMarlinURL.put("horror", "marlin.com/horror");
categoryToMarlinURL.put("drama", "marlin.com/drama");
您拥有所需的一切：
- 类别（
category），
- URL 属于该类别 (
categoryToMarlinURL.get(category))，
- 发出请求的服务 (
jSoupService.connect(categoryToMarlinURL.get(category)))。
1) 分成两个不同的服务。
2) 我认为使用分页代替 get15 方法是值得的。
3) 除了 getRomantic ， getCrime 你还可以：
class Service {
private final Map<String,String> categoryToUrl = new HashMap<>();
public Service(){
categoryToUrl.put("crime","http://....");
}
... fetchBook(String category) {
String url = categoryToUrl.get(category);
return fetchUsingJsoap(url);
}
}
前段时间我也在讨论类似的话题。我正在查看我的应用程序，我认为它有很多不必要的代码。我的意思是我有服务负责从两家书店的不同类别的书籍中抓取数据。现在我有 5 个类别，所以我有 5 个方法，但如果我要添加一些新类别怎么办？我将不得不添加更多方法......我认为这不是一个好的选择。现在看起来像这样：
控制器
@GetMapping("/romances")
public Map<Bookstore, List<Book>> get15RomanticBooks() {
return categorizedBookService.get15BooksFromRomanceCategory();
}
@GetMapping("/biographies")
public Map<Bookstore, List<Book>> get15BiographiesBooks() {
return categorizedBookService.get15BooksFromBiographiesCategory();
}
@GetMapping("/guides")
public Map<Bookstore, List<Book>> get15GuidesBooks() {
return categorizedBookService.get15BooksFromGuidesCategory();
}
@GetMapping("/fantasy")
public Map<Bookstore, List<Book>> get15FantasyBooks() {
return categorizedBookService.get15BooksFromFantasyCategory();
}
我在想
@GetMapping("/{category}")
public Map<......> get 15BooksFromCategory(@PathVariable CategoryType category)
{...}
我认为这是最好的方法，但是服务比较难。
它的服务是这样的：
package bookstore.scraper.book.scrapingtypeservice;
import bookstore.scraper.enums.Bookstore;
import bookstore.scraper.book.Book;
import bookstore.scraper.fetcher.empik.EmpikFetchingBookService;
import bookstore.scraper.fetcher.merlin.MerlinFetchingBookService;
import bookstore.scraper.urlproperties.EmpikUrlProperties;
import bookstore.scraper.urlproperties.MerlinUrlProperties;
import bookstore.scraper.utilities.JSoupConnector;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.EnumMap;
import java.util.List;
import java.util.Map;
@Service
@Slf4j
public class CategorizedBookService {
private final EmpikFetchingBookService empikBookService;
private final MerlinFetchingBookService merlinFetchingBookService;
private final EmpikUrlProperties empikUrlProperties;
private final MerlinUrlProperties merlinUrlProperties;
private final JSoupConnector jSoupConnector;
@Autowired
public CategorizedBookService(EmpikFetchingBookService empikBookService, MerlinFetchingBookService merlinFetchingBookService, EmpikUrlProperties empikUrlProperties, MerlinUrlProperties merlinUrlProperties, JSoupConnector jSoupConnector) {
this.empikBookService = empikBookService;
this.merlinFetchingBookService = merlinFetchingBookService;
this.empikUrlProperties = empikUrlProperties;
this.merlinUrlProperties = merlinUrlProperties;
this.jSoupConnector = jSoupConnector;
}
public Map<Bookstore, List<Book>> get15BooksFromRomanceCategory() {
return get15BooksFrom(empikUrlProperties.getEmpik().getRomances(), merlinUrlProperties.getMerlin().getRomances());
}
public Map<Bookstore, List<Book>> get15BooksFromFantasyCategory() {
return get15BooksFrom(empikUrlProperties.getEmpik().getFantasy(), merlinUrlProperties.getMerlin().getFantasy());
}
public Map<Bookstore, List<Book>> get15BooksFromCrimeCategory() {
return get15BooksFrom(empikUrlProperties.getEmpik().getCrime(), merlinUrlProperties.getMerlin().getCrime());
}
public Map<Bookstore, List<Book>> get15BooksFromGuidesCategory() {
return get15BooksFrom(empikUrlProperties.getEmpik().getGuides(), merlinUrlProperties.getMerlin().getGuides());
}
public Map<Bookstore, List<Book>> get15BooksFromBiographiesCategory() {
return get15BooksFrom(empikUrlProperties.getEmpik().getBiographies(), merlinUrlProperties.getMerlin().getBiographies());
}
private Map<Bookstore, List<Book>> get15BooksFrom(String bookStoreEmpikURL, String bookStoreMerlinURL) {
Map<Bookstore, List<Book>> bookstoreWith15CategorizedBooks = new EnumMap<>(Bookstore.class);
bookstoreWith15CategorizedBooks.put(Bookstore.EMPIK, empikBookService
.get15BooksFromCategory(jSoupConnector.connect(bookStoreEmpikURL)));
bookstoreWith15CategorizedBooks.put(Bookstore.MERLIN, merlinFetchingBookService
.get15BooksFromCategory(jSoupConnector.connect(bookStoreMerlinURL)));
return bookstoreWith15CategorizedBooks;
}
}
我必须传递 2 个不同的链接，具体取决于调用的是哪个类别。有什么办法吗？
EmpikBookService/merlinFetchingBookService 是使用 Jsoup 来 抓取 数据的服务。
package bookstore.scraper.fetcher.empik;
import bookstore.scraper.book.Book;
import bookstore.scraper.urlproperties.EmpikUrlProperties;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;
@Service
public class EmpikFetchingBookService {
private static final int FIRST_PART_PRICE = 0;
private static final int SECOND_PART_PRICE = 1;
private static final int BESTSELLERS_NUMBER_TO_FETCH = 5;
private static final int CATEGORIZED_BOOKS_NUMBER_TO_FETCH = 15;
private static final String DIV_PRODUCT_WRAPPER = "div.productWrapper";
private static final String DATA_PRODUCT_ID = "data-product-id";
private final EmpikUrlProperties empikUrlProperties;
@Autowired
public EmpikFetchingBookService(EmpikUrlProperties empikUrlProperties) {
this.empikUrlProperties = empikUrlProperties;
}
public Book getMostPreciseEmpikBook(Document document) {
String author = document.select("div.smartAuthorWrapper.ta-product-smartauthor").select("a").first().text();
String price = convertEmpikPriceWithPossibleDiscountToActualPrice(document.select("div.price.ta-price-tile").first().text());
String title = document.select(DIV_PRODUCT_WRAPPER).select("strong").first().text();
String productID = document.select(DIV_PRODUCT_WRAPPER).select("a").first().attr(DATA_PRODUCT_ID);
String bookUrl = createBookURL(title, productID);
return Book.builder()
.author(author)
.price(price)
.title(title)
.productID(productID)
.bookURL(bookUrl).build();
}
public List<Book> get5BestSellersEmpik(Document document) {
List<Element> siteElements = document.select(DIV_PRODUCT_WRAPPER);
List<Book> empikBestSellers = new ArrayList<>();
IntStream.range(0, BESTSELLERS_NUMBER_TO_FETCH)
.forEach(iteratedElement -> {
String author = siteElements.get(iteratedElement).select("div.smartAuthorWrapper.ta-product-smartauthor").select("a").first().text();
String price = convertEmpikPriceWithPossibleDiscountToActualPrice(siteElements.get(iteratedElement).select("div.price.ta-price-tile").first().text());
String title = siteElements.get(iteratedElement).select("strong").first().ownText();
String productID = siteElements.get(iteratedElement).select(DIV_PRODUCT_WRAPPER).select("a").first().attr(DATA_PRODUCT_ID);
String bookUrl = createBookURL(title, productID);
empikBestSellers.add(Book.builder()
.author(author)
.price(price)
.title(title)
.productID(productID)
.bookURL(bookUrl)
.build());
});
return empikBestSellers;
}
public List<Book> get15BooksFromCategory(Document document) {
List<Book> books = new ArrayList<>();
List<Element> siteElements = document.select("div.productBox__info");
IntStream.range(0, CATEGORIZED_BOOKS_NUMBER_TO_FETCH)
.forEach(iteratedElement -> {
String author = executeFetchingAuthorProcess(siteElements, iteratedElement);
String price = convertEmpikPriceWithPossibleDiscountToActualPrice(siteElements.get(iteratedElement).select("div.productBox__price").first().text());
String title = siteElements.get(iteratedElement).select("span").first().ownText();
String productID = siteElements.get(iteratedElement).select("a").first().attr(DATA_PRODUCT_ID);
String bookUrl = createBookURL(title, productID);
books.add(Book.builder()
.author(author)
.price(price)
.title(title)
.productID(productID)
.bookURL(bookUrl)
.build());
});
return books;
}
private String convertEmpikPriceWithPossibleDiscountToActualPrice(String price) {
String[] splittedElements = price.split("\s+");
return splittedElements[FIRST_PART_PRICE] + splittedElements[SECOND_PART_PRICE];
}
private String createBookURL(String title, String productID) {
return String.format(empikUrlProperties.getEmpik().getConcreteBook(), title, productID);
}
//method is required as on empik site, sometimes occurs null for author and we need to change code for fetching
private static String executeFetchingAuthorProcess(List<Element> siteElements, int i) {
String author;
Element authorElements = siteElements.get(i).select("span > a").first();
if (authorElements != null)
author = authorElements.ownText();
else
author = siteElements.get(i).select("> span > span").first().text();
return author;
}
}
实施 Chain Of Responsibility 模式并允许服务获取结果并将结果放入结果 Map 对象。还让 Spring 通过提供一些通用接口
public interface FetchingService {
public Map<Bookstore, List<Book>> fetchAndAddToResult(Map<Bookstore, List<Book>> result, CategoryType category);
}
@Service
public class EmpikFetchingBookService implements FetchingService {
// ...
@Override
public Map<Bookstore, List<Book>> fetchAndAddToResult(Map<Bookstore, List<Book>> result, CategoryType category) {
result.put(Bookstore.EMPIK, getListOfBooks(category));
return result;
}
}
@Service
public class MerlinFetchingBookService implements FetchingService {
// ...
@Override
public Map<Bookstore, List<Book>> fetchAndAddToResult(Map<Bookstore, List<Book>> result, CategoryType category) {
result.put(Bookstore.MERLIN, getListOfBooks(category));
return result;
}
}
@Service
@Slf4j
public class CategorizedBookService {
private final List<FetchingService> services;
//JSoup connector and Properties move to FetchingServices because it is part of those services implementation
@Autowired
public CategorizedBookService(List<FetchingService> services) {
this.services = services;
}
public Map<Bookstore, List<Book>> get15BooksByCategory(CategoryType category) {
Map<Bookstore, List<Book>> result = new HashMap<>();
for(FetchingService service : services) {
result = service.fetchAndAddToResult(result, category);
}
return result;
}
}
(1) 名称 get15BooksFromCategory(CategoryType) 不正确：您将要 returned 的许多书籍硬编码到方法名称中。
今天你return15，明天你需要return20，周日你可能需要return5，安卓你可能需要return 50. 你明白了。
考虑这些签名。
getAllBooksFromCategory(CategoryType);
getNBooksFromCategory(CategoryType, Integer);
(2)去掉服务中的这些字段。
private final EmpikUrlProperties empikUrlProperties;
private final MerlinUrlProperties merlinUrlProperties;
private final JSoupConnector jSoupConnector;
前两个分别是EmpikFetchingBookService和MerlinFetchingBookService的一部分。 JSoupConnector 是一个更底层的抽象，它不应该出现在这个级别。它可能驻留在这些图书服务的共同父项中，或者是共同父项所依赖的单独 JSoupService。
(3) 理想情况下，您最终应该得到一个非常简单的服务，该服务具有单一职责 - 从其来源收集书籍。
class BookService {
private List<BookServiceSource> sources;
public Map<String, List<Book>> getBooksByCategory(Category category) {
return sources.stream()
.collect(Collectors.toMap(BookServiceSource::getName,
source -> source.getBooksByCategory(category)));
}
}
BookServiceSource 具有与 BookService 相似的界面。但是，MerlinSource 作为 BookServiceSource 的子类，不会将工作委托给其他人。相反，它准备一个 URL 并将其提供给 JSoupService。
BookServiceSource 的职责是准备请求参数并将结果 return 从 JSoupService 转换为 List<Book>。由于每个书店都有不同的 DOM，您需要知道如何将特定的 DOM 映射到您的结构中。
interface BookServiceSource {
String getName();
List<Book> getBooksByCategory(Category category);
}
class MerlinSource implements BookServiceSource {
private JSoupService service;
private MerlinUrlProperties properties;
@Override
public String getName() {
return "merlin";
}
@Override
public List<Book> getBooksByCategory(Category category) {
// at this point, we have both
// JSoupService (to make a real request) and
// MerlinUrlProperties (to prepare everything for that request)
}
}
将 MerlinUrlProperties 视为一种实用程序，可以在类别和 URL 之间为该类别的书籍提供映射。
MerlinUrlProperties 可以是一个 Map 本身，如果它只包含一堆 return URL 的方法。重点是您不必为新类别定义新方法并强制使用您的 API 的每个人都改变自己以包含 API 的新部分。使用 Map 或枚举，界面会更稳定。
Map<String, String> categoryToMarlinURL = new HashMap<>();
categoryToMarlinURL.put("horror", "marlin.com/horror");
categoryToMarlinURL.put("drama", "marlin.com/drama");
您拥有所需的一切：
- 类别（
category）， - URL 属于该类别 (
categoryToMarlinURL.get(category))， - 发出请求的服务 (
jSoupService.connect(categoryToMarlinURL.get(category)))。
1) 分成两个不同的服务。
2) 我认为使用分页代替 get15 方法是值得的。
3) 除了 getRomantic ， getCrime 你还可以：
class Service {
private final Map<String,String> categoryToUrl = new HashMap<>();
public Service(){
categoryToUrl.put("crime","http://....");
}
... fetchBook(String category) {
String url = categoryToUrl.get(category);
return fetchUsingJsoap(url);
}
}