在JSF中的国际化与从数据库加载的ResourceBundle条目 [英] internationalization in JSF with ResourceBundle entries which are loaded from database

问题描述

我正在使用JPA / EJB / JSF开发一个Java EE6项目，我在为实体设计多语言支持时遇到了一些麻烦。有三个相关实体：

I'm working on a Java EE6 project using JPA/EJB/JSF and I'm having some trouble designing multiple language support for entities. There are three relevant entities:

语言（有id）

能力（有id）

CompetenceName ，语言引用和一个字符串）

Language (has id)
Competence (has id)
CompetenceName (has Competence reference, Language reference and a String)

Competence有一个对一个地图实现的CompetenceName的一对多引用，每个语言包含一个对象，能力。注意，能力是动态创建的，因此他们的名称不能存在于资源包中。

Competence has a one-to-many reference to CompetenceName implemented with a Map, containing one object for every Language that there exists a name for a Competence. Note that competences are created dynamically and their names can thus not exist in a resource bundle.

当在网页上列出竞争力希望他们用当前登录的用户的语言显示，这是存储在会话范围的托管Bean。

When listing the Competences on a web page, I want them to show with the language of the currently logged in user, this is stored in a Session Scoped Managed Bean.

有没有什么好的方法来完成这个而不打破好MVC设计？我的第一个想法是通过FacesContext直接从Competence实体的getName方法获取会话作用域bean，并在CompetenceNames的地图中查找它如下：

Is there any good way to accomplish this without breaking good MVC design? My first idea was to get the session scoped bean directly from a "getName" method in the Competence entity via FacesContext, and look in the map of CompetenceNames for it as following:

public class Competence
{
...
@MapKey(name="language")
@OneToMany(mappedBy="competence", cascade=CascadeType.ALL, orphanRemoval=true)
private Map<Language, CompetenceName> competenceNames;

public String getName(String controller){
    FacesContext context = FacesContext.getCurrentInstance();
    ELResolver resolver = context.getApplication().getELResolver();
    SessionController sc = (SessionController)resolver.getValue(context.getELContext(), null, "sessionController");
    Language language = sc.getLoggedInUser().getLanguage();
    if(competenceNames.get(language) != null)
        return competenceNames.get(language).getName();
    else
        return "resource missing";
}

这个解决方案非常原始，因为实体依赖于Controller层，每次我想要它的名称时提取一个会话控制器。更多的符合MVC的解决方案是使用一个Language参数，但是这意味着从JSF的每一个单独的调用将必须包括从会话作用域管理bean获取的语言，也不觉得像一个好的解决方案。

This solution feels extremly crude since the entity relies on the Controller layer, and have to fetch a session controller every time I want its name. A more MVC compliant solution would be to take a Language parameter, but this means that every single call from JSF will have to include the language fetched from the session scoped managed bean which does not feel like a good solution either.

这个问题有没有任何想法或设计模式？

Does anyone have any thoughts or design patterns for this issue?

推荐答案

国际化/应当优选地在视图侧完全完成。该模型不应该知道这一点。

Internationalization/localization should preferably be entirely done in the view side. The model shouldn't be aware of this.

在JSF中，< resource-bundle> faces-config.xml 和XHTML中的< f：loadBundle> 也可以指向一个完整的 ResourceBundle 类，而不是 .properties 文件的basename。在Java SE 6中有一个新的 ResourceBundle.Control API可以完全控制加载和填充包。

In JSF, the <resource-bundle> entry in faces-config.xml and the <f:loadBundle> in XHTML can also point to a fullworthy ResourceBundle class instead of basename of .properties files. In Java SE 6 there's a new ResourceBundle.Control API available which allows full control over loading and filling the bundle.

知道这些事实，可以使用自定义 ResourceBundle 和控制从数据库加载包消息。这是一个启动示例：

Knowing those facts, it should be possible to load the bundle messages from the DB with a custom ResourceBundle and Control. Here's a kickoff example:

public class CompetenceBundle extends ResourceBundle {

    protected static final String BASE_NAME = "Competence.messages"; // Can be name of @NamedQuery
    protected static final Control DB_CONTROL = new DBControl();

    private Map<String, String> messages;

    public CompetenceBundle() {
        setParent(ResourceBundle.getBundle(BASE_NAME, 
            FacesContext.getCurrentInstance().getViewRoot().getLocale(), DB_CONTROL));
    }

    protected CompetenceBundle(Map<String, String> messages) {
        this.messages = messages;
    }

    @Override
    protected Object handleGetObject(String key) {
        return messages != null ? messages.get(key) : parent.getObject(key);
    }

    @Override
    public Enumeration<String> getKeys() {
        return messages != null ? Collections.enumeration(messages.keySet()) : parent.getKeys();
    }

    protected static class DBControl extends Control {

        @Override
        public ResourceBundle newBundle
            (String baseName, Locale locale, String format, ClassLoader loader, boolean reload)
                throws IllegalAccessException, InstantiationException, IOException
        {
            String language = locale.getLanguage();
            Map<String, String> messages = getItSomehow(baseName, language); // Do your JPA thing. The baseName can be used as @NamedQuery name.
            return new CompetenceBundle(messages);
        }

    }

}

这样你可以在 faces-config.xml 中声明如下：

This way you can declare it as follows in faces-config.xml:

<resource-bundle>
    <base-name>com.example.i18n.CompetenceBundle</base-name>
    <var>competenceBundle</var>
</resource-bundle>

或在Facelet中执行以下操作：

Or as follows in the Facelet:

<f:loadBundle basename="com.example.i18n.CompetenceBundle" var="competenceBundle" />

无论哪种方式，您都可以使用通常的方式：

Either way, you can use it the usual way:

<h:outputText value="#{competenceBundle.name}" />

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