java spring mvc @service方法:nullpointerexception新手和翻译 [英] java spring mvc @service method: nullpointerexception | newbie and translation

问题描述

我正在尝试设置将使用gnu gettext的翻译服务.基本想法来自: https://thedarkgod. wordpress.com/2009/01/18/java-webapp-localization-through-gettext/

I am trying to set up a translation service which will use gnu gettext. The basic idea is from: https://thedarkgod.wordpress.com/2009/01/18/java-webapp-localization-through-gettext/

但是我希望将其作为服务来实现.由于某些奇怪的原因，我想上这个课:

But I would like it to be implemented as a service. For some odd reasons, I would like to have this class:

import webapp.service.TranslationService;
import org.springframework.context.i18n.LocaleContextHolder;

/**
 * AppStrings<p>
 * <p/>
 * DOC-TODO:
 */
@Service("applicationStrings")
public class ApplicationStrings {

    @Autowired private TranslationService translationService;

    public String CART_SUBTYPE = "Cart";

    public ApplicationStrings(){
    Locale locale = LocaleContextHolder.getLocale();        
    //translationService.initLocale();
    this.updateLocale();
    }

    public void updateLocale(){
    Locale locale = LocaleContextHolder.getLocale();        
    translationService.updateLocale(locale);
    this.setLocale(locale);
    }

    public void setLocale(Locale locale){
    //this.CART_SUBTYPE = translationService._("Cart");
    this.CART_SUBTYPE = "CART_DEF - Check ApplicationStrings";
    }
}

部分代码被注释了，因为它实际上并不起作用...但是它可能揭示了我的目标.确实有问题的服务类如下所示:

Part of the code is commented as it doesn't really work... but it might reveal my target. The indeed problematic service class looks like this:

package webapp.service;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import gnu.gettext.GettextResource;
import java.util.ResourceBundle;
import java.util.Locale;
import java.text.MessageFormat;
import java.util.Hashtable;

import org.springframework.context.i18n.LocaleContextHolder;
import org.springframework.stereotype.Service;

/**
 * From: https://thedarkgod.wordpress.com/2009/01/18/java-webapp-localization-through-gettext/
 *
 */

@Service("translationService")
public class TranslationService {

    private final Logger logger = LoggerFactory.getLogger(getClass());

    private static Hashtable<Locale, ResourceBundle> trht = new Hashtable<Locale, ResourceBundle> ();

    private ResourceBundle myResources = null;

    public TranslationService () {

    Locale locale = LocaleContextHolder.getLocale();
    if ( locale == null){
        logger.warn("Setting a default locale!");
        locale = Locale.ENGLISH;
    }
    this.updateLocale(locale);

    }

    public TranslationService (Locale locale) {
    this.updateLocale(locale);
    }

    public void initLocale () {

        Locale locale = LocaleContextHolder.getLocale();
        this.updateLocale(locale);
    }

    public void updateLocale(Locale locale)
    {
    synchronized (trht)
        {
        if (!trht.contains (locale))
            {
            try
                {
                myResources = GettextResource.getBundle("translation", locale);
                }
            catch (Exception e)
                {
                logger.error("UPDATE: Exception.");
                e.printStackTrace();
                }

            trht.put ((Locale) locale.clone(), myResources);
            }
        else
            myResources = trht.get (locale);
        }
    }

    public String _(String s)
    {
    if (myResources == null) return s;
    return GettextResource.gettext (myResources, s);
    }

    public String N_(String singular, String plural, long n)
    {
    if (myResources == null) return (n == 1 ? singular : plural);
    return GettextResource.ngettext (myResources, singular,
                     plural,      n);
    }

    public String format (String s, Object ... args)
    {
    return MessageFormat.format (_(s), args);
    }

    public String formatN (String singular, String plural, 
               long n, Object ... args)
    {
    return MessageFormat.format (N_(singular, plural, n), args);
    }

}

这些类在我的应用程序中甚至没有使用，但是spring会实例化它们，并且错误看起来像这样:

These classes are not even a bit used in my application, but of course spring will instantiate them and the error looks like this:

java.lang.NullPointerException
    at webapp.constant.ApplicationStrings.updateLocale(ApplicationStrings.java:34)
    at webapp.constant.ApplicationStrings.<init>(ApplicationStrings.java:29)

请注意，所有其他@service都在工作，因此我认为这不是某些xml配置的问题，为此我发现了关于stackoverflow的几个问题(和答案)，其他服务也都在工作，因此配置应该可以.

Please note that all other @service are working so I assume it is not a problem of some xml configuration, for which I found few questions (and answers) on stackoverflow, again other services are working so the configuration should be fine.

我认为这是我的新手方法，可能会错过一些简单的关键字.甚至是概念.

I assume it is my newbie approach which might miss some simple keyword.. or even concept..

感谢和欢呼

与答案一起使用，因为这可能是获取文本的通用方法，并且确实与问题有关，所以我希望对实际方法提出一些意见.

Together with the answers, as this might be a general approach to gettext and indeed related to the question, I would appreciate a couple of comments on the actual approach.

我也完全不确定同步"部分:这可能是问题所在吗?

Also I am totally not sure about the "sychronized" part: can this be the problem?

推荐答案

您正在构造函数中调用依赖项. Spring在构造对象之后连接了bean依赖项，因此在这里您尝试过早调用这些方法，Spring当时没有机会连接您的bean.要解决此问题，您可以使用@PostConstruct批注.在构造并连接一个bean之后，Spring总是会调用带有此标记的方法.

You are calling dependencies in your constructor. Spring wires the bean dependencies after constructing the object so here you are trying to call those methods a bit too early, Spring had no chance to wire your bean at that moment. To solve the issue you could make use of the @PostConstruct annotation. A method marked with this is always called by Spring after constructing and wiring up a bean.

例如

public ApplicationStrings() {
}

@PostConstruct
public void init() {
    //translationService.initLocale();
    this.updateLocale();
}

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