自定义Tag 中调用其他模板出现 NPE

[liufuxi]

自定义 tag 实现如下：

@JetAnnotations.Tags
public class MyTags {
    private static final TimedSizeCache cache = new TimedSizeCache(128);

    public static void cache(JetTagContext ctx, String name, int timeout) throws IOException {

        Map<String, Object> context = new HashMap<String, Object>();
        context.put("userlist", DaoUtils.getUserList());
        String templateName = "/users.jetx";
        JetTemplate template = ctx.getEngine().getTemplate(templateName);
        OutputStream out = new java.io.ByteArrayOutputStream();

        template.render(context, out);
        String value = out.toString();
        System.out.println(value+"\n");

        ctx.getWriter().print(value);
        out.close();
    }
}

报以下错误：

jetbrick.template.runtime.InterpretException: tag invoke error: demo.MyTags#cache()
template: index.jetx: 527,5
-------------------------------------------------------------------------------
 525: <div>
 526: 
 527: #tag cache("CACHE-ME-30-MIN", 30*60)
           ^ -- here
 528:     今天天气: 
 529: #end
-------------------------------------------------------------------------------
] with root cause
java.lang.NullPointerException
    at jetbrick.template.runtime.JetTagContext.getWriter(JetTagContext.java:75)
    at jetbrick.demo.MyTags.cache(MyTags.java:31)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at jetbrick.bean.MethodInfo.invoke(MethodInfo.java:192)
    at jetbrick.template.resolver.tag.TagInvoker.invoke(TagInvoker.java:41)
    at jetbrick.template.parser.ast.AstDirectiveTag.doInvoke(AstDirectiveTag.java:70)
    at jetbrick.template.parser.ast.AstDirectiveTag.execute(AstDirectiveTag.java:51)
    at jetbrick.template.parser.ast.AstStatementList.execute(AstStatementList.java:202)
    at jetbrick.template.parser.ast.AstTemplate.execute(AstTemplate.java:37)
    at jetbrick.template.JetTemplateImpl.doInterpret(JetTemplateImpl.java:156)
    at jetbrick.template.JetTemplateImpl.render(JetTemplateImpl.java:147)
    at jetbrick.template.web.springmvc.JetTemplateView.renderMergedTemplateModel(JetTemplateView.java:37)
    at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:167)
    at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:303)
    at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1228)
    at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1011)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:955)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:877)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:966)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:857)