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

View Code 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