使用Velocity/FreeMarker模板进行国际化电子邮件

Question

如何使用Velocity或FreeMarker等模板引擎来构建邮件正文？

通常人们倾向于创建以下模板:

<h3>${message.hi} ${user.userName}, ${message.welcome}</h3>
<div>
   ${message.link}<a href="mailto:${user.emailAddress}">${user.emailAddress}</a>.
</div>

并使用以下属性创建资源包:

message.hi=Hi
message.welcome=Welcome to Spring!
message.link=Click here to send email.

这就产生了一个基本问题:如果我的.vm文件变得很大,文本行很多,那么在单独的资源包(.properties)文件中翻译和管理它们就变得很繁琐.

我要做的是,.vm为每种语言创建一个单独的文件,类似于mytemplate_en_gb.vm, mytemplate_fr_fr.vm, mytemplate_de_de.vm然后以某种方式告诉Velocity/Spring根据输入Locale选择正确的文件.

这在春天有可能吗？或者我应该考虑更简单明了的替代方法？

注意:我已经看过如何使用模板引擎创建电子邮件主体的Spring教程.但它似乎没有回答我关于i18n的问题.

Answer 1

事实证明,使用一个模板和多个language.properties文件胜过多个模板.

这会产生一个基本问题:如果我的.vm文件变得很大,文本行很多,那么在单独的资源包(.properties)文件中翻译和管理它们就变得很繁琐.

如果您的电子邮件结构在多个.vm文件上重复,则更难维护.此外,人们将不得不重新发明资源包的回退机制.资源包尝试在给定区域设置的情况下找到最接近的匹配.例如,如果语言环境是en_GB,它会尝试按顺序查找下面的文件,如果它们都不可用,则回退到最后一个文件.

• language_en_GB.properties
• language_en.properties
• language.properties

我将发布(详细)我必须做什么来简化在Velocity模板中阅读资源包.

访问Velocity模板中的Resource Bundle

弹簧配置

<bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
    <property name="basename" value="content/language" />
</bean>

<bean id="velocityEngine" class="org.springframework.ui.velocity.VelocityEngineFactoryBean">    
    <property name="resourceLoaderPath" value="/WEB-INF/template/" />
    <property name="velocityProperties">
        <map>
            <entry key="velocimacro.library" value="/path/to/macro.vm" />
        </map>
    </property>
</bean>

<bean id="templateHelper" class="com.foo.template.TemplateHelper">
    <property name="velocityEngine" ref="velocityEngine" />
    <property name="messageSource" ref="messageSource" />
</bean>

TemplateHelper类

public class TemplateHelper {
    private static final XLogger logger = XLoggerFactory.getXLogger(TemplateHelper.class);
    private MessageSource messageSource;
    private VelocityEngine velocityEngine;

    public String merge(String templateLocation, Map<String, Object> data, Locale locale) {
        logger.entry(templateLocation, data, locale);

        if (data == null) {
            data = new HashMap<String, Object>();
        }

        if (!data.containsKey("messages")) {
            data.put("messages", this.messageSource);
        }

        if (!data.containsKey("locale")) {
            data.put("locale", locale);
        }

        String text =
            VelocityEngineUtils.mergeTemplateIntoString(this.velocityEngine,
                templateLocation, data);

        logger.exit(text);

        return text;
    }
}

速度模板

#parse("init.vm")
#msg("email.hello") ${user} / $user,
#msgArgs("email.message", [${emailId}]).
<h1>#msg("email.heading")</h1>

我必须创建一个简写宏,msg以便从消息包中读取.它看起来像这样:

#**
 * msg
 *
 * Shorthand macro to retrieve locale sensitive message from language.properties
 *#
#macro(msg $key)
$messages.getMessage($key,null,$locale)
#end

#macro(msgArgs $key, $args)
$messages.getMessage($key,$args.toArray(),$locale)
#end

资源包

email.hello=Hello
email.heading=This is a localised message
email.message=your email id : {0} got updated in our system.

用法

Map<String, Object> data = new HashMap<String, Object>();
data.put("user", "Adarsh");
data.put("emailId", "adarsh@email.com");

String body = templateHelper.merge("send-email.vm", data, locale);

Answer 2

这是Freemarker的解决方案(一个模板,几个资源文件).

主程序

// defined in the Spring configuration file
MessageSource messageSource;

Configuration config = new Configuration();
// ... additional config settings

// get the template (notice that there is no Locale involved here)
Template template = config.getTemplate(templateName);

Map<String, Object> model = new HashMap<String, Object>();
// the method called "msg" will be available inside the Freemarker template
// this is where the locale comes into play 
model.put("msg", new MessageResolverMethod(messageSource, locale));

MessageResolverMethod类

private class MessageResolverMethod implements TemplateMethodModel {

  private MessageSource messageSource;
  private Locale locale;

  public MessageResolverMethod(MessageSource messageSource, Locale locale) {
    this.messageSource = messageSource;
    this.locale = locale;
  }

  @Override
  public Object exec(List arguments) throws TemplateModelException {
    if (arguments.size() != 1) {
      throw new TemplateModelException("Wrong number of arguments");
    }
    String code = (String) arguments.get(0);
    if (code == null || code.isEmpty()) {
      throw new TemplateModelException("Invalid code value '" + code + "'");
    }
    return messageSource.getMessage(code, null, locale);
  }

}

Freemarker模板

${msg("subject.title")}