正确使用ResourceBundle

Question

我以前从未使用过ResourceBundle。

我有一个简单的Google刮取器(使用Jsoup库)，我想定制并介绍多语言支持。

我有些课。首先，您必须让html文档稍后进行解析。

GooglePlayConnection类(提供连接，然后只需调用方法get())：

public class GooglePlayConnection {

    /**
     * Typical base part of URL for all apps.
     */
    private static final String BASE_URL = "https://play.google.com/store/apps/details?";

    private final String language;

    private final String country;

    public GooglePlayConnection(String language, String country) {
        this.language = language;
        this.country = country;
    }

    /**
     * Tries to connect to provided URL. Uses localized version of URL that retrieves from {@link #getLocalized(Map, String, String)}.
     * Also checks if URL applies to APPS category to prevent from parsing books/music/movies.
     */
    public Connection connect(String URL) throws InvalidGooglePlayUrlException, MalformedURLException, URISyntaxException {
        final java.net.URL url= new URL(URL);
        if (GooglePlayCorrectURL.isUrlValid(url)) {
            if (!url.getPath().contains("apps")) {
                throw new InvalidGooglePlayUrlException("Wrong Google Play category");
            }
            Map params = getParameters(URL);
            URL = getLocalized(params, language, country).toString();
            return Jsoup.connect(URL);
        }
        else {
            throw new InvalidGooglePlayUrlException("Not Google Play URL");
        }
    }

    /**
     * Gets localized version of provided URL.
     */
    private URL getLocalized(Map params, String language, String country) throws MalformedURLException, URISyntaxException {
        URIBuilder uriBuilder = new URIBuilder(BASE_URL)
                .addParameter("id", params.get("id"))
                .addParameter("hl", language)
                .addParameter("gl", country);
        return uriBuilder.build().toURL();
    }

    private Map getParameters(String url) throws MalformedURLException {
        return Arrays.stream(new URL(url).getQuery().split("&"))
                .map(s -> s.split("="))
                .collect(Collectors.toMap(k -> k[0], v -> v.length > 1 ? v[1] : ""));
    }

刮刀：

public class GooglePlayAppsScraper {

    /**
     * Default language system settings to determine in which language to analyze HTML document.
     */
    private static final ResourceBundle resourceBundle = ResourceBundle.getBundle("patterns", Locale.getDefault());

    /**
     * CSS-like element selectors that find elements matching a query.
     */
    private static final String CURRENT_VERSION = resourceBundle.getString("game.currentVersion");

    private static final String REQUIREMENTS = resourceBundle.getString("game.requirements");

    public String getCurrentVersion(Document htmlDocument) {
        return getIfAttributePresent(CURRENT_VERSION, htmlDocument);
    }

    public String getRequirements(Document htmlDocument) {
        return getIfAttributePresent(REQUIREMENTS, htmlDocument);
    }
    ...

我有一些不同语言的包，像这样：

//en
game.currentVersion = div:matchesOwn(^Current Version$)
game.lastUpdate = div:matchesOwn(^Updated$)
game.installs = div:matchesOwn(^Installs$)
game.requirements = div:matchesOwn(^Requires Android$)
...

//ru
game.currentVersion = div:matchesOwn(^Текущая версия$)
game.lastUpdate = div:matchesOwn(^Обновлено$)
game.installs = div:matchesOwn(^Количество установок$)
game.requirements = div:matchesOwn(^Требуемая версия Android$)
...

重要的是什么？我需要把关于语言的信息“传送”到我的刮刀上。要搜索元素，文档中的语言必须与刮板将使用的语言匹配。

我不想把这些参数传递给每个刮板方法。它看起来将是：

public String getRequirements(Document htmlDocument, String language) {
        ResourceBundle resourceBundle = ResourceBundle.getBundle("patterns", Locale.forLanguageTag(language));
        String requirements = resourceBundle.getString("game.requirements");
        return getIfAttributePresent(requirements, htmlDocument);
    }

我创建了LanguageSettings：

public class LanguageSettings {

    private static Map settings = new HashMap<>();

    public static Map getSettings() {
        return settings;
    }

    public static void setSettings(Map settings) {
        LanguageSettings.settings = settings;
    }
}

然后更新连接：

    private final String language;

    private final String country;

    public GooglePlayConnection(String language, String country) {
        this.language = language;
        this.country = country;
        LanguageSettings.getSettings().put("language", language);
    }

然后更新刮板：

private static final ResourceBundle resourceBundle = ResourceBundle.getBundle("patterns", Locale.forLanguageTag(LanguageSettings.getSettings().get("language")));

简单用法：

String url = "https://play.google.com/store/apps/details?id=com.playdigious.cultist";
Document document = new GooglePlayConnection("en", "US").connect(url).get();
GooglePlayAppsScraper scraper = new GooglePlayAppsScraper();
System.out.println(scraper.getPrice(document));

如果按正确的顺序执行(如示例中的那样)，这将有效，但我确信会有更好的解决方案。

我应该如何连接我的刮刀和连接到一个ResourceBundle以适当的方式？

Answer 1

我在这里看到的一个问题是:您的代码应该按正确的顺序调用才能正常工作。

这意味着您的组件有一个共享状态，它们没有预先状态( ResourceBundle和LanguageSettings)，而且GooglePlayAppsScraper甚至是以这样的方式构建的，即以前的所有操作都必须在这个类加载之前消失--因为它静态地访问LanguageSettings并保存一个static final字段，当类从磁盘加载时，它的初始化将在应用程序生命周期中完成一次(不完全，但接近)。如果没有正确初始化，那么至少在NullPointerException中它会很快失败，但是我们可以做得更好。

我认为更好的方法是摆脱那里的静态状态。我建议让LanguageSettings成为整个系统的一个更明显的部分。

首先，让它成为一个对象：

public class LanguageSettings {
    private String languageTag;
    private String country;

     public LanguageSettings(String language, String country) {
         this.languageTag = Objects.requireNonNull(language, "languageTag");
         this.country = Objects.requireNonNull(country, "country");
     }

     public String getLanguageTag() {
         return languageTag;
     }

     public String getCountry() {
         return country;
     }
}

然后，让GoogleConnection依赖它：

public class GoogleConnection {
    private LanguageSettings settings;

    public GoogleConnection(LanguageSettings settings) {
        this.settings = Objects.requireNonNull(settings);
    }
    <...snip...>
    private URL getLocalized(Map params) throws MalformedURLException, URISyntaxException {
        URIBuilder uriBuilder = new URIBuilder(BASE_URL)
            .addParameter("id", params.get("id"))
            .addParameter("hl", settings.getLanguageTag())
            .addParameter("gl", settings.getCountry());
        return uriBuilder.build().toURL();
    }
}

同时，使GooglePlayAppsScraper依赖于同一个LanguageSettings对象进行初始化：

public class GooglePlayAppsScraper {
    private ResourceBundle bundle;

    /*
     *  Notice here: I am not reading from bundle, these are now simple constants
     */
    private static final String CURRENT_VERSION = "game.currentVersion";

    private static final String REQUIREMENTS = "game.requirements";

    public GooglePlayAppsScraper(LanguageSettings settings) {
        this.bundle = initBundle(settings);
    }

    private ResourceBundle initBundle(LanguageSettings settings) {
        Objects.requireNonNull(settings);
        return ResourceBundle.getBundle("patterns", Locale.forLanguageTag(settings.getLanguageTag());
    }

    public String getRequirements(Document htmlDocument) {
        return getIfAttributePresent(bundle.getString(REQUIREMENTS), htmlDocument);
    }
}

这样做的好处--调用代码的“正确方式”现在基本上是唯一的方法--除非您已经有了LanguageSettings对象，否则就不能初始化GooglePlayAppsScraper或GoogleConnection。当您这样做时(假设您为两者提供了相同的对象)，它将始终正确地初始化，因此很难交换两行代码并获得异常。您的应用程序现在还将支持并行运行多个连接和刮板(假设这是您想要的东西，外部服务允许它)-而且刮板程序甚至可以有不同的语言设置(因为Settings是每个应用程序的状态)。