code: public static void merge(Template template, VelocityContext context, Writer writer) {
  		if (template == null) {
  			throw new UtilException("Template is null");
  		}
  		if (context == null) {
  			context = new VelocityContext(globalContext);
  		} else {
  			// 加入全局上下文
  			for (Entry<String, Object> entry : globalContext.entrySet()) {
  				context.put(entry.getKey(), entry.getValue());
  			}
  		}
  
  		template.merge(context, writer);
  	}
docs: 融合模板和内容并写入到Writer
  
  @param template 模板
  @param context 内容
  @param writer Writer