camel-velocity can't find resource - apache-camel

Question

I'm learning how to use Apache Velocity with Apache Camel (in Karaf) to host dynamic webpages, but when I try to include a velocity file inside another one, I get a resource error even though they are in the same directory.
If I remove the line #parse("${page}.vm") from the first file, everything works as expected.
Here is my entire setup. Aside from installing camel-velocity and jetty-9, everything not listed here is the default ServiceMix 7.0.0 setup.
Camel Route
<route id="web_route">
<from uri="jetty:http://localhost:8080/test?sessionSupport=true&matchOnUriPrefix=true"/>
<to uri="velocity:file:web/vm/webpage.vm?contentCache=false"/>
</route>
/web/vm/webpage.vm contents
Hello sir $!{headers.name}! Welcome to the VM World!
#set($page="$headers.CamelHttpUrl")
#set($page="$page.substring($page.lastIndexOf('/')).substring(1)")
#parse("${page}.vm")
/web/vm/hello.vm contents
Hello World!
localhost:8080/test/hello
org.apache.velocity.exception.ResourceNotFoundException: Unable to find resource 'hello.vm'
at org.apache.velocity.runtime.resource.ResourceManagerImpl.loadResource(ResourceManagerImpl.java:474)
at org.apache.velocity.runtime.resource.ResourceManagerImpl.getResource(ResourceManagerImpl.java:352)
at org.apache.velocity.runtime.RuntimeInstance.getTemplate(RuntimeInstance.java:1533)
at org.apache.velocity.runtime.directive.Parse.render(Parse.java:197)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342)
at org.apache.velocity.runtime.RuntimeInstance.render(RuntimeInstance.java:1378)
at org.apache.velocity.runtime.RuntimeInstance.evaluate(RuntimeInstance.java:1314)
at org.apache.velocity.app.VelocityEngine.evaluate(VelocityEngine.java:272)
at org.apache.camel.component.velocity.VelocityEndpoint.onExchange(VelocityEndpoint.java:212)
at org.apache.camel.impl.ProcessorEndpoint$1.process(ProcessorEndpoint.java:71)
at org.apache.camel.util.AsyncProcessorConverterHelper$ProcessorToAsyncProcessorBridge.process(AsyncProcessorConverterHelper.java:61)
at org.apache.camel.processor.SendProcessor.process(SendProcessor.java:145)
at org.apache.camel.management.InstrumentationProcessor.process(InstrumentationProcessor.java:77)
at org.apache.camel.processor.RedeliveryErrorHandler.process(RedeliveryErrorHandler.java:460)
at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:196)
at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:196)
at org.apache.camel.component.jetty.CamelContinuationServlet.service(CamelContinuationServlet.java:191)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:812)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1669)
at org.eclipse.jetty.servlets.MultiPartFilter.doFilter(MultiPartFilter.java:146)
at org.apache.camel.component.jetty.CamelFilterWrapper.doFilter(CamelFilterWrapper.java:43)
at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1652)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:585)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:221)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1127)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:515)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:185)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1061)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:97)
at org.eclipse.jetty.server.Server.handle(Server.java:499)
at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:311)
at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:257)
at org.eclipse.jetty.io.AbstractConnection$2.run(AbstractConnection.java:544)
at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:635)
at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:555)
at java.lang.Thread.run(Thread.java:745)
So why can't it import hello.vm?

Answer 1

You need to specify the file location where you refer to the home directory of Karaf.
You should use
<to uri="velocity:file:${karaf.home}/web/vm/webpage.vm?contentCache=false"/>
See more details at: http://camel.apache.org/using-propertyplaceholder.html

Answer 2

I found out that #parse() and #include() reference files relative to %karaf_home%, not the current directory. So if you want to include a resource at %karaf_home%/web/vm/hello.vm, you have to use #include("/web/vm/hello.vm").

Answer 3

Despite to an accepted answer I think it would be useful for others to leave here a way how one can use #include or #parse in his templates if he isn't lucky enough to use Apache Camel in the Karaf
The main idea is to specify velocity's TEMPLATE_ROOT and if your route is in XML the only way I know about is to use propertiesFile option
<to uri="velocity:file:/home/webpage.vm?propertiesFile=conf/velocity.properties"/>
with the file velocity.properties
resource.loader = file
file.resource.loader.path = /opt/templates
Note that this path have to be absolute. Since it is not so convenient to have it there as a string literal you may use the property with even an empty value
resource.loader = file
file.resource.loader.path =
and pass the actual template path (relative to that value or absolute if empty) via say an exchange property or a header, e.g.
#parse(${exchange.properties.templatePath})
In this you are allowed to use say property placeholder, so the path doesn't have to be hardcoded