业务层资源国际化处理

用过struts2等mvc框架开发的同学都知道，使用struts2处理国际化的消息非常简单直观，但是mvc框架的定位是在展示层(jsp,action)等，在一个典型的3层结构中，处于最上层的位置，按照分层设计原则，下层组件是不可以调用上层组件的，这样就存在一个问题，我们在业务层中可能也会出现一些需要国际化处理的消息信息，这些信息如何设置呢？

     在这篇文章中，我们将借鉴struts2的国际化处理机制，但是要比struts2简单的多，因为业务层需要国际化处理的消息毕竟是少数，废话不多说，直接上干货

先举个例子-业务层未国际化处理前的代码

  @Override    public ExecuteResult<User> login(String userName, String password) {        ExecuteResult<User> executeResult = new ExecuteResult<User>();        User userInfo = userDAO.getUserByName(userName);        if(userInfo == null){            executeResult.addErrorMessage("不存在的用户名");            return executeResult;        }        if(!userInfo.getPassword().equals(password)){            executeResult.addErrorMessage("密码错误");            return executeResult;        }        executeResult.setResult(userInfo);        return executeResult;    }

设计实现：

1.添加国际化消息拦截器

我们的应用是基于struts2的，struts2默认提供了一个i18n拦截器，这里我们扩展了以下该拦截器的功能，将locale信息保存起来

/** * 扩展struts2默认的i18n拦截器，添加设置local到LocaleContextHolder中的功能 * @author WangXuzheng * @see com.opensymphony.xwork2.interceptor.I18nInterceptor * @see org.springframework.context.i18n.LocaleContextHolder */public class I18nResolverInterceptor extends I18nInterceptor {private static final long serialVersionUID = 5888969294461266478L;@Overrideprotected void saveLocale(ActionInvocation invocation, Locale locale) {super.saveLocale(invocation, locale);LocaleContextHolder.setLocale(locale);}}

2.在struts.xml中替换默认的i18n拦截器

<interceptor name="i18n" class="com.haier.openplatform.i18n.interceptor.I18nResolverInterceptor"/>

3.设计业务层国际化资源解析器接口

/** * 国际化资源处理器 * @author WangXuzheng * */public interface I18nResolver {/** * 设置要进行资源处理的目标类 * @param clazz */@SuppressWarnings("rawtypes")public void setClass(Class clazz);/** * 解析国际化资源文件，如果找不到该code，返回默认的消息 * @param code i18n资源的key值 * @return 如果找到返回具体的消息值，如果不存在返回默认消息 * @see java.text.MessageFormat */String getMessage(String code);/** * 解析国际化资源文件，如果找不到该code，返回默认的消息 * @param code i18n资源的key值 * @return 如果找到返回具体的消息值，如果不存在返回默认消息 * @see java.text.MessageFormat */String getMessage(String code,String arg);/** * 解析国际化资源文件，如果找不到该code，返回默认的消息 * @param code i18n资源的key值 * @param args 资源中的变量值 * @param defaultMessage 默认消息 * @return 如果找到返回具体的消息值，如果不存在返回默认消息 * @see java.text.MessageFormat */String getMessage(String code, Object[] args, String defaultMessage);/** * 解析国际化资源文件查找指定code对应的消息，如果不存在，抛出异常 * @param code * @param args * @return * @throws MessageNotFoundException * @see java.text.MessageFormat * @throws MessageNotFoundException */String getMessage(String code, Object[] args);}

默认的实现类-这里我们的资源配置文件放在和待处理的类同文件下同名的.properties文件中

例如：java类

com.haier.openplatform.showcase.security.service.impl.UserServiceImpl

 对应的资源文件为

com/haier/openplatform/showcase/security/service/impl/UserServiceImpl_zh_CN.properties

com/haier/openplatform/showcase/security/service/impl/UserServiceImpl_en_US.properties

/** * 默认的资源文件解析器，该类读取<code>org.springframework.context.i18n.LocaleContextHolder</code>中保存的Local信息解析资源文件 * @author WangXuzheng * @see org.springframework.context.i18n.LocaleContextHolder */public class DefaultI18nResolver extends MessageSourceSupport implements I18nResolver {private static final ConcurrentMap<String, ResourceBundle> BUNDLE_MAP = new ConcurrentHashMap<String, ResourceBundle>();private static final List<String> DEFAULT_RESOURCE_BUNDLES = new CopyOnWriteArrayList<String>();private static final Log LOG = LogFactory.getLog(DefaultI18nResolver.class);@SuppressWarnings("rawtypes")protected Class clazz;/** * 添加全局资源配置信息 * * @param resourceBundleName the name of the bundle to add. */public static void addDefaultResourceBundle(String resourceBundleName) {//make sure this doesn't get added more than oncesynchronized (DEFAULT_RESOURCE_BUNDLES) {DEFAULT_RESOURCE_BUNDLES.remove(resourceBundleName);DEFAULT_RESOURCE_BUNDLES.add(0, resourceBundleName);}if (LOG.isDebugEnabled()) {LOG.debug("Added default resource bundle '" + resourceBundleName + "' to default resource bundles = "+ DEFAULT_RESOURCE_BUNDLES);}}/** * Creates a key to used for lookup/storing in the bundle misses cache. * * @param aBundleName the name of the bundle (usually it's FQN classname). * @param locale      the locale. * @return the key to use for lookup/storing in the bundle misses cache. */private String createMissesKey(String aBundleName, Locale locale) {return aBundleName + "_" + locale.toString();}/** * 从全局资源文件中读取文案信息 * * @param aTextName 文案 key * @param locale    the locale the message should be for * @return  */private String findDefaultText(String aTextName, Locale locale) {List<String> localList = DEFAULT_RESOURCE_BUNDLES;for (String bundleName : localList) {ResourceBundle bundle = findResourceBundle(bundleName, locale);if (bundle != null) {try {return bundle.getString(aTextName);} catch (MissingResourceException e) {// ignore and try others}}}return null;}/** * 根据资源名称和locale信息查找资源信息 * @param aBundleName the name of the bundle (usually it's FQN classname). * @param locale      the locale. * @return the bundle, <tt>null</tt> if not found. */protected ResourceBundle findResourceBundle(String aBundleName, Locale locale) {String key = createMissesKey(aBundleName, locale);ResourceBundle bundle = BUNDLE_MAP.get(key);if (bundle == null) {bundle = ResourceBundle.getBundle(aBundleName, locale, Thread.currentThread().getContextClassLoader());BUNDLE_MAP.put(key, bundle);}return bundle;}private Locale getLocale() {return LocaleContextHolder.getLocale();}@Overridepublic String getMessage(String code) {return getMessage(code, new Object[] {});}/** * 获取资源消息对应的值,先从指定的bundleName的资源中获取文案，如果找不到，从globalResources中读取 * @param bundleName * @param locale * @param key * @param args * @return * @see #findResourceBundle */private String getMessage(String bundleName, Locale locale, String key, Object[] args) {ResourceBundle bundle = findResourceBundle(bundleName, locale);if (bundle == null) {return null;}String orginalMessage = null;try {orginalMessage = bundle.getString(key);} catch (MissingResourceException e) {// read text from global resourcesorginalMessage = findDefaultText(bundleName, locale);}return this.formatMessage(orginalMessage, args, locale);}@Overridepublic String getMessage(String code, Object[] args) {return getMessage(resolveBunFile(), getLocale(), code, args);}@Overridepublic String getMessage(String code, Object[] args, String defaultMessage) {return StringUtils.defaultIfBlank(getMessage(code, args), defaultMessage);}@Overridepublic String getMessage(String code, String arg) {String[] args = new String[] { arg };return getMessage(code, args);}protected String resolveBunFile() {String pack = this.clazz.getName();return pack.replaceAll("[.]", "/");}@SuppressWarnings("rawtypes")public void setClass(Class clazz) {this.clazz = clazz;}}

加一个静态工厂类来获取解析器

/** * 资源解析器工厂类 * @author WangXuzheng * */public final class I18nResolverFactory {@SuppressWarnings("rawtypes")private static final ConcurrentMap<Class, I18nResolver> I18N_RESOVER_MAP = new ConcurrentHashMap<Class, I18nResolver>();private I18nResolverFactory(){}@SuppressWarnings("rawtypes")public static I18nResolver getDefaultI18nResolver(Class clazz){I18nResolver resolver = I18N_RESOVER_MAP.get(clazz);if(resolver == null){resolver = new DefaultI18nResolver();resolver.setClass(clazz);I18N_RESOVER_MAP.put(clazz, resolver);}return resolver;}}

4.调用实现-非常类似log4j的调用方式

public class UserServiceImpl implements UserService {    private static final I18nResolver I18N_RESOLVER = I18nResolverFactory.getDefaultI18nResolver(UserServiceImpl.class);    private UserDAO userDAO;    private RoleDAO roleDAO;@Override    public ExecuteResult<User> login(String userName, String password) {        ExecuteResult<User> executeResult = new ExecuteResult<User>();        User userInfo = userDAO.getUserByName(userName);        if(userInfo == null){            executeResult.addErrorMessage( I18N_RESOLVER.getMessage("user.notexisted"));            return executeResult;        }        if(!userInfo.getPassword().equals(password)){            executeResult.addErrorMessage(I18N_RESOLVER.getMessage("user.wrongpassword"));            return executeResult;        }        executeResult.setResult(userInfo);        return executeResult;    }