Re: Inconsistent and strange NPE when initializing Velocity

So is the default behavior that once a macro is loaded it can't be
overloaded by in another template? (basically, it's just defined once for
the lifetime of the VelocityEngine)

On Wed, Jun 27, 2012 at 4:41 PM, Nathan Bubna <[email protected]> wrote:

> A VelocityEngine allows for global macros and template caching, both
> configurable, of course.  Context data is never cached or shared by
> the engine, though you can yourself reuse a context across multiple
> merges.
>
> On Wed, Jun 27, 2012 at 1:03 PM, Bradley Wagner
> <[email protected]> wrote:
> > Thanks, Nathan, I'll give that a shot.
> >
> > Offhand, is there anything else I need to be aware of that could be
> > persisting across template renders (like velocimacros) since I'm now
> using
> > a single instance of engine?
> >
> > On Wed, Jun 27, 2012 at 3:51 PM, Nathan Bubna <[email protected]> wrote:
> >
> >> On Wed, Jun 27, 2012 at 11:04 AM, Bradley Wagner
> >> <[email protected]> wrote:
> >> > None explicitly specified.
> >> >
> >> > I looked at a default velocity properties that's in our project but
> that
> >> > we're not using:
> >> >
> >> > velocimacro.library = VM_global_library.vm
> >> > velocimacro.permissions.allow.inline = true
> >> > velocimacro.permissions.allow.inline.to.replace.global = false
> >> > velocimacro.permissions.allow.inline.local.scope = false
> >> > velocimacro.context.localscope = false
> >> >
> >> > I'm guessing this has something to do with these things being scoped
> >> > globally by default or something?
> >>
> >> yeah, you should set
> >>
> >> velocimacro.permissions.allow.inline.local.scope = true
> >>
> >> > On Wed, Jun 27, 2012 at 12:39 PM, Nathan Bubna <[email protected]>
> wrote:
> >> >
> >> >> What are the macro settings in your velocity.properties?
> >> >>
> >> >> On Mon, Jun 25, 2012 at 7:40 PM, Bradley Wagner
> >> >> <[email protected]> wrote:
> >> >> > We're noticing something now that may or may not be related to our
> >> change
> >> >> > to only use a single instance of the Velocity Engine.
> >> >> >
> >> >> > Macros that we define in one template seem to be sticking around
> and
> >> >> being
> >> >> > used when we go to merge or evaluate a different template.
> >> >> >
> >> >> > Is this possible related and to be expected when using a single
> >> instance
> >> >> of
> >> >> > the VelocityEngine?
> >> >> >
> >> >> > On Thu, Jun 7, 2012 at 5:28 PM, Bradley Wagner <
> >> >> > [email protected]> wrote:
> >> >> >
> >> >> >> Thanks Will. We'll make sure to just initialize it once.
> >> >> >>
> >> >> >>
> >> >> >> On Thu, Jun 7, 2012 at 3:36 PM, Will Glass-Husain <
> >> >> [email protected]>wrote:
> >> >> >>
> >> >> >>> Hi,
> >> >> >>>
> >> >> >>> You should use either the Velocity static calls or the
> >> VelocityEngine
> >> >> but
> >> >> >>> not both-- it's confusing.  They don't technically interfere with
> >> each
> >> >> >>> other, but it'll be simpler and less error prone not to mix.
> >> >> >>>
> >> >> >>> It's also a performance hit to continually reinitialize Velocity.
> >> >>  There's
> >> >> >>> no need to do this every time you process a page.  Besides the
> cost
> >> of
> >> >> >>> initialization, it also prevents you from doing any caching.
> >> >> >>>
> >> >> >>> Here's the general pattern
> >> >> >>> * On app start up, initialize a VelocityEngine.  Store it
> somewhere.
> >> >> >>> * Every time you need to process a template
> >> >> >>>     --> get the template
> >> >> >>>     --> create and populate a context
> >> >> >>>     --> using the velocity engine, merge the template (with the
> >> >> context)
> >> >> >>>
> >> >> >>> WILL
> >> >> >>>
> >> >> >>>
> >> >> >>> On Thu, Jun 7, 2012 at 8:26 AM, Bradley Wagner <
> >> >> >>> [email protected]> wrote:
> >> >> >>>
> >> >> >>> > Thanks Will.
> >> >> >>> >
> >> >> >>> > So looking over the developer documentation about
> initialization
> >> and
> >> >> our
> >> >> >>> > code, it looks like we're using a mix of the Singleton Velocity
> >> >> Engine
> >> >> >>> and
> >> >> >>> > Separate Instances in certain cases. However, in all these
> cases,
> >> >> we're
> >> >> >>> > using the same set of properties. The documentation suggests
> that
> >> the
> >> >> >>> > Separate Instance method is the newer way to do it, but you're
> >> saying
> >> >> >>> that
> >> >> >>> > if we can get away with initializing Velocity one using
> >> >> Velocity.init()
> >> >> >>> we
> >> >> >>> > should do that for better performance, yes? Are both mechanisms
> >> for
> >> >> >>> > evaluating templates thread-safe?
> >> >> >>> >
> >> >> >>> > In one place we're doing:
> >> >> >>> >
> >> >> >>> > VelocityContext context = new VelocityContext(contextMap)
> >> >> >>> > Properties props = VelocityProperties.getProperties();
> >> >> >>> > Velocity.init(props);
> >> >> >>> > String templatePath =
> >> >> VelocityTemplates.getTemplatePath(templateName);
> >> >> >>> > Template template = Velocity.getTemplate(templatePath);
> >> >> >>> > StringWriter writer = new StringWriter();
> >> >> >>> > template.merge(context, writer);
> >> >> >>> > return writer.toString();
> >> >> >>> >
> >> >> >>> > and in another we're doing:
> >> >> >>> >
> >> >> >>> > VelocityEngine engine = new VelocityEngine();
> >> >> >>> > Properties velocityProps = VelocityProperties.getProperties();
> >> >> >>> > engine.init(velocityProps);
> >> >> >>> >
> >> >> >>> > // Get a template as stream.
> >> >> >>> > StringWriter writer = new StringWriter();
> >> >> >>> > StringReader reader = new StringReader(template);
> >> >> >>> > // create a temporary template name
> >> >> >>> > String tempTemplateName = "velocityTransform-" +
> >> >> >>> > System.currentTimeMillis();
> >> >> >>> >
> >> >> >>> > // ask Velocity to evaluate it.
> >> >> >>> > boolean result = engine.evaluate(context, writer,
> >> tempTemplateName,
> >> >> >>> > reader);
> >> >> >>> >
> >> >> >>> > String strResult = null;
> >> >> >>> > if (result)
> >> >> >>> > {
> >> >> >>> >    strResult = writer.getBuffer().toString();
> >> >> >>> > }
> >> >> >>> > return strResult;
> >> >> >>> >
> >> >> >>> > Thanks a bunch for your help!
> >> >> >>> >
> >> >> >>> > On Wed, Jun 6, 2012 at 6:34 PM, Will Glass-Husain <
> >> >> >>> [email protected]>
> >> >> >>> > wrote:
> >> >> >>> > >
> >> >> >>> > > You only need to initialize Velocity once.  Performance is
> much
> >> >> better
> >> >> >>> > that
> >> >> >>> > > way.
> >> >> >>> > >
> >> >> >>> > > WILL
> >> >> >>> > >
> >> >> >>> > > On Wed, Jun 6, 2012 at 2:37 PM, Bradley Wagner <
> >> >> >>> > > [email protected]> wrote:
> >> >> >>> > >
> >> >> >>> > > > The odd part about that is that while I could see this
> being a
> >> >> race
> >> >> >>> > > > condition... once Velocity gets into this state it doesn't
> >> matter
> >> >> >>> how
> >> >> >>> > many
> >> >> >>> > > > times we call Velocity.init, it returns the NPE every
> time. I
> >> >> guess
> >> >> >>> I
> >> >> >>> > > > should have mentioned that in the original post. Basically
> >> once
> >> >> it
> >> >> >>> > starts
> >> >> >>> > > > returning NPE our only recourse is to restart Tomcat, which
> >> fixes
> >> >> >>> the
> >> >> >>> > > > problem, until  it pops up again.
> >> >> >>> > > >
> >> >> >>> > > > On Wed, Jun 6, 2012 at 5:35 PM, Bradley Wagner <
> >> >> >>> > > > [email protected]> wrote:
> >> >> >>> > > >
> >> >> >>> > > > > Ha, that's a good question. Yes, we're initializing
> Velocity
> >> >> LOTS
> >> >> >>> of
> >> >> >>> > > > > times. Basically every time we use it to create these
> >> messages
> >> >> in
> >> >> >>> our
> >> >> >>> > > > > message util. I'm guessing that's not recommended?
> >> >> >>> > > > >
> >> >> >>> > > > >
> >> >> >>> > > > > On Wed, Jun 6, 2012 at 1:53 PM, Will Glass-Husain <
> >> >> >>> > > > [email protected]>wrote:
> >> >> >>> > > > >
> >> >> >>> > > > >> Hi Bradley,
> >> >> >>> > > > >>
> >> >> >>> > > > >> Are you initializing Velocity multiple times?
> >> >> >>> > > > >>
> >> >> >>> > > > >> Though I haven't heard of this issue before, it sounds
> >> like a
> >> >> >>> race
> >> >> >>> > > > >> condition, perhaps if the initialization is called
> twice at
> >> >> the
> >> >> >>> same
> >> >> >>> > > > time.
> >> >> >>> > > > >>
> >> >> >>> > > > >> WILL
> >> >> >>> > > > >>
> >> >> >>> > > > >> On Wed, Jun 6, 2012 at 8:37 AM, Bradley Wagner <
> >> >> >>> > > > >> [email protected]> wrote:
> >> >> >>> > > > >>
> >> >> >>> > > > >> > Hi,
> >> >> >>> > > > >> >
> >> >> >>> > > > >> > I sent this message before I had subscribed to the
> list
> >> so I
> >> >> >>> > wasn't
> >> >> >>> > > > >> sure if
> >> >> >>> > > > >> > the original made it. My apologies if this is a
> >> duplicate.
> >> >> >>> > > > >> >
> >> >> >>> > > > >> > One of our clients running our software is
> *occasionally*
> >> >> >>> running
> >> >> >>> > into
> >> >> >>> > > > >> the
> >> >> >>> > > > >> > stack trace at the bottom when Velocity is
> initialized. A
> >> >> >>> restart
> >> >> >>> > > > tends
> >> >> >>> > > > >> to
> >> >> >>> > > > >> > fix this problem. But it pops back up after running
> the
> >> >> system
> >> >> >>> for
> >> >> >>> > a
> >> >> >>> > > > >> while.
> >> >> >>> > > > >> >
> >> >> >>> > > > >> > They're running:
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >   - Velocity 1.7
> >> >> >>> > > > >> >   - Tomcat 6.0.35
> >> >> >>> > > > >> >   - Using the 3.2 of the Apache Commons Collections
> >> library
> >> >> >>> > > > >> >   - Running Java 1.6.0_31 in Mac OS X 10.6.8
> >> >> >>> > > > >> >
> >> >> >>> > > > >> > Unfortunately we don't have the ability to debug this
> >> >> problem
> >> >> >>> > > > remotely,
> >> >> >>> > > > >> so
> >> >> >>> > > > >> > we can't see exactly what's going on, but having
> looked a
> >> >> bit
> >> >> >>> at
> >> >> >>> > the
> >> >> >>> > > > >> > Extended Properties class, it doesn't seem like it
> >> should be
> >> >> >>> > possible
> >> >> >>> > > > to
> >> >> >>> > > > >> > get an NPE at that line, because of the containsKey()
> >> check
> >> >> a
> >> >> >>> few
> >> >> >>> > > > lines
> >> >> >>> > > > >> > before.
> >> >> >>> > > > >> >
> >> >> >>> > > > >> > java.lang.NullPointerException
> >> >> >>> > > > >> > at
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> org.apache.commons.collections.ExtendedProperties.clearProperty(ExtendedProperties.java:797)
> >> >> >>> > > > >> > at
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> org.apache.commons.collections.ExtendedProperties.setProperty(ExtendedProperties.java:722)
> >> >> >>> > > > >> > at
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> org.apache.commons.collections.ExtendedProperties.combine(ExtendedProperties.java:783)
> >> >> >>> > > > >> > at
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> org.apache.velocity.runtime.RuntimeInstance.setProperties(RuntimeInstance.java:657)
> >> >> >>> > > > >> > at
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> org.apache.velocity.runtime.RuntimeInstance.init(RuntimeInstance.java:645)
> >> >> >>> > > > >> > at
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> org.apache.velocity.runtime.RuntimeSingleton.init(RuntimeSingleton.java:226)
> >> >> >>> > > > >> > at
> >> org.apache.velocity.app.Velocity.init(Velocity.java:97)
> >> >> >>> > > > >> > at
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> com.hannonhill.cascade.velocity.VelocityEngineUtil.generateMessage(VelocityEngineUtil.java:66)
> >> >> >>> > > > >> >
> >> >> >>> > > > >> > Also, here's the code that's calling the
> Velocity.init:
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >        Properties velocityProps =
> >> >> >>> > VelocityProperties.getProperties();
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >        Velocity.init(velocityProps);
> >> >> >>> > > > >> >
> >> >> >>> > > > >> > Velocity Properties are just loading the following
> file
> >> >> >>> contents
> >> >> >>> > into
> >> >> >>> > > > a
> >> >> >>> > > > >> > properties object:
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> > # This controls if Runtime.error(), info() and warn()
> >> >> messages
> >> >> >>> > include
> >> >> >>> > > > >> the
> >> >> >>> > > > >> > # whole stack trace. The last property controls
> whether
> >> >> invalid
> >> >> >>> > > > >> references
> >> >> >>> > > > >> > # are logged.
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> > runtime.log.error.stacktrace = false
> >> >> >>> > > > >> > runtime.log.warn.stacktrace = false
> >> >> >>> > > > >> > runtime.log.info.stacktrace = false
> >> >> >>> > > > >> > runtime.log.invalid.reference = true
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> > # Configuration for the Log4JLogSystem.
> >> >> >>> > > > >> > # You must define the runtime.log.logsystem.class
> >> property
> >> >> to
> >> >> >>> be:
> >> >> >>> > > > >> > #   org.apache.velocity.runtime.log.Log4JLogSystem
> >> >> >>> > > > >> > #
> >> >> >>> > > > >> > # You must also include Log4J's .jar files into your
> >> >> classpath.
> >> >> >>> > They
> >> >> >>> > > > are
> >> >> >>> > > > >> > # included with the Velocity distribution in the
> >> build/lib
> >> >> >>> > directory.
> >> >> >>> > > > >> > #
> >> >> >>> > > > >> > # There are several different options that you can
> >> >> configure.
> >> >> >>> > > > >> > # Uncomment the ones that you want and also define
> their
> >> >> >>> settings.
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> > # T E M P L A T E  E N C O D I N G
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> > input.encoding=UTF-8
> >> >> >>> > > > >> > output.encoding=UTF-8
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> > # F O R E A C H  P R O P E R T I E S
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> > # These properties control how the counter is
> accessed in
> >> >> the
> >> >> >>> > #foreach
> >> >> >>> > > > >> > # directive. By default the reference $velocityCount
> >> will be
> >> >> >>> > available
> >> >> >>> > > > >> > # in the body of the #foreach directive. The default
> >> >> starting
> >> >> >>> > value
> >> >> >>> > > > >> > # for this reference is 1.
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> > directive.foreach.counter.name = velocityCount
> >> >> >>> > > > >> > directive.foreach.counter.initial.value = 1
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> > # T E M P L A T E  L O A D E R S
> >> >> >>> > > > >> >
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>> >
> >> >> >>>
> >> >>
> >>
> #----------------------------------------------------------------------------
> >> >> >>> > > > >> > resource.loader = class
> >> >> >>> > > > >> > class.resource.loader.description = Velocity Classpath
> >> >> Resource
> >> >> >>> > Loader
> >> >> >>> > > > >> > class.resource.loader.class =
> >> >> >>> > > > >> >
> >> >> >>> >
> >> org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader
> >> >> >>> > > > >> >
> >> >> >>> > > > >>
> >> >> >>> > > > >
> >> >> >>> > > > >
> >> >> >>> > > >
> >> >> >>> >
> >> >> >>>
> >> >> >>
> >> >> >>
> >> >>
> >> >> ---------------------------------------------------------------------
> >> >> To unsubscribe, e-mail: [email protected]
> >> >> For additional commands, e-mail: [email protected]
> >> >>
> >> >>
> >>
> >> ---------------------------------------------------------------------
> >> To unsubscribe, e-mail: [email protected]
> >> For additional commands, e-mail: [email protected]
> >>
> >>
>
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