非web环境Velocity tool的使用

功能：使用Velocity的tool功能，去格式化日期字段，

条件限制：非web环境，velocity1.4.jar + velocity-tool-view-1.1.jar

思路：模拟web环境下的ChainedContext，来定制一个context即可

public class VelocityUtil
{
    public static final String ENCODING = "UTF-8";
    
    public static final String TOOLBOX_PATH = "velocity/template/toolbox.xml";
    
    private VelocityUtil(){};

    private static VelocityContext getContext(Map<String, Object> params) throws Exception
    {
        ToolboxContext toolboxContext = new ToolboxContext(params);
        XMLToolboxManager xmlManager = new XMLToolboxManager();
        String toolboxFile = VelocityUtil.class.getClassLoader().getResource(TOOLBOX_PATH).getPath();
        xmlManager.load(new FileInputStream(new File(toolboxFile)));
        ChainedContext context = new ChainedContext(toolboxContext);
        context.setToolbox(xmlManager.getToolboxContext(context));
        return context;
    }
    
    private static VelocityEngine init(String templatePath) throws Exception
    {
        VelocityEngine ve = new VelocityEngine();
        Properties prop = new Properties();
        prop.setProperty("file.resource.loader.path", VelocityUtil.class.getClassLoader().getResource(templatePath).getPath());
        prop.setProperty("input.encoding", ENCODING);
        prop.setProperty("output.encoding", ENCODING);
        ve.init(prop);
        return ve;
    }
    /**
     * generate string from template
     * @param templatePath    : template files' directionary, example as : velocity/template/hp/execforum
     * @param fileName        : template file's name, suce as : 
     * @param params
     * @return
     * @throws Exception
     */
    public static String generate(String templatePath, String fileName, Map<String, Object> params) throws Exception
    {
        VelocityEngine ve = init(templatePath);
        Template template = ve.getTemplate(fileName, ENCODING);
        VelocityContext context = getContext(params);
        StringWriter writer = new StringWriter();
        template.merge(context, writer);
        //System.out.println("----------\n" + writer.toString());
        return writer.toString();
    }
    
    private static class ChainedContext extends VelocityContext
    {
        private static final long serialVersionUID = 5729583723890287479L;
        private ToolboxContext toolboxContext = null;

        public ChainedContext(Context ctx)
        {
            super(null, ctx );
        }
        public void setToolbox(ToolboxContext box)
        {
            toolboxContext = box;
        }
        public Object internalGet( String key )
        {
            Object o = null;
            if (toolboxContext != null)
            {
                o = toolboxContext.get(key);
                if (o != null)
                {
                    return o;
                }
            }
            o = super.internalGet(key);
            return o;
        }
    }
}

 

然后在.vm模板中，使用下面的方式来格式化日期，

 

$date.format('h:mm a', $item.startDatetime)

输出：10:10 下午

 

如果要指定日期的locale，可以继承DateTool，override父类的getLocale方法（例如返回：Locale.US），最后将该类注册到 toolbox.xml即可

输出：10:10 PM