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From James Brady <james.colin.br...@gmail.com>
Subject Re: ClassCastException from custom request handler
Date Tue, 04 Aug 2009 15:45:40 GMT
Hi Chantal!
I've included a stack trace below.

I've attached a debugger to the server starting up, and it is finding my
class file as expected... I agree it looks like something wrong with how
I've deployed the compiled code, but perhaps different Solr versions at
compile time and run time? However, I've checked and rechecked that and
can't see a problem!

The actually ClassCastException is being thrown in a anonymous
AbstractPluginLoader instance's create method:
http://svn.apache.org/viewvc/lucene/solr/tags/release-1.3.0/src/java/org/apache/solr/util/plugin/AbstractPluginLoader.java?revision=695557

It's the cast to SolrRequestHandler which fails.

Aug 4, 2009 4:24:25 PM org.apache.solr.util.plugin.AbstractPluginLoader load
INFO: created /update/csv:
org.apache.solr.core.RequestHandlers$LazyRequestHandlerWrapper
Aug 4, 2009 4:24:25 PM org.apache.solr.util.plugin.AbstractPluginLoader load
INFO: created /admin/: org.apache.solr.handler.admin.AdminHandlers
Aug 4, 2009 4:24:25 PM org.apache.solr.common.SolrException log
SEVERE: java.lang.ClassCastException: com.jmsbrdy.LiveCoresHandler
    at
org.apache.solr.core.RequestHandlers$1.create(RequestHandlers.java:152)
    at
org.apache.solr.core.RequestHandlers$1.create(RequestHandlers.java:161)
    at
org.apache.solr.util.plugin.AbstractPluginLoader.load(AbstractPluginLoader.java:140)
    at
org.apache.solr.core.RequestHandlers.initHandlersFromConfig(RequestHandlers.java:169)
    at org.apache.solr.core.SolrCore.<init>(SolrCore.java:444)
    at org.apache.solr.core.CoreContainer.create(CoreContainer.java:323)
    at org.apache.solr.core.CoreContainer.load(CoreContainer.java:216)
    at
org.apache.solr.core.CoreContainer$Initializer.initialize(CoreContainer.java:104)
    at
org.apache.solr.servlet.SolrDispatchFilter.init(SolrDispatchFilter.java:69)
    at org.mortbay.jetty.servlet.FilterHolder.doStart(FilterHolder.java:99)

At the moment, my "deployment" is:

   1. compile my single Java file from an Ant script (pointing at the Solr
   JARs from an exploded solr.war)
   2. copy that class file's directory tree
   (com/jmsbrdy/LiveCoresHandler.class) to a "lib" in the root of my jetty
   install
   3. add "lib" to Jetty's class path
   4. add the Solr JARs from the exploded war to Jetty's class path
   5. start the server

Can you see any problems there?

2009/8/4 Chantal Ackermann <chantal.ackermann@btelligent.de>

> Hi James!
>
> James Brady schrieb:
>
>> There is *something* strange going on with classloaders; when I put my
>> .class files in the right place in WEB-INF/lib in a repackaged solr.war
>> file, it's not found by the plugin loader ("Error loading class").
>>
>> So the plugin classloader isn't seeing stuff inside WEB-INF/lib.
>>
>> That explains why the plugin loader sees my class files when I point
>> jetty.class.path at the right directory, but in that situation I also need
>> to point jetty.class.path at the Solr JARs explicitly.
>>
>
> you cannot be sure that it sees *your* files. It only sees a class that
> qualifies with the name that is requested in your code. It's obviously not
> the class the code expects, though - as it results in a ClassCastException
> at some point. It might help to have a look at where and why that casting
> went wrong.
>
> I wrote a custom EntityProcessor and deployed it first under
> WEB-INF/classes, and now in the plugin directory, and that worked without a
> problem. My first guess is that something with your packaging is wrong -
> what do you mean by "default" package? What is the full name of your class
> and how does its path in the file system look like?
>
> Can you paste the stack trace of the exception?
>
> Chantal
>
>
>
>> Still, how would ClassCastExceptions be caused by class loader paths not
>> being set correctly? I don't follow you... To get a ClassCastException,
>> the
>> class to cast to must have been found. The cast-to class must not be in
>> the
>> object's inheritance hierarchy, or be built against a different version,
>> no?
>>
>> 2009/8/4 Noble Paul നോബിള്‍ नोब्ळ् <noble.paul@corp.aol.com>
>>
>>  I guess this is a classloader issue. it is worth trying to put it in
>>> the WEB-INF/lib of the solr.war
>>>
>>>
>>> On Tue, Aug 4, 2009 at 5:35 PM, James Brady<james.colin.brady@gmail.com>
>>> wrote:
>>>
>>>> Hi, the LiveCoresHandler is in the default package - the behaviour's the
>>>> same if I have it in a properly namespaced package too...
>>>>
>>>> The requestHandler name can start either be a path (starting with '/')
>>>> or
>>>>
>>> a
>>>
>>>> qt name:
>>>> http://wiki.apache.org/solr/SolrRequestHandler
>>>>
>>> starting w/ '/' helps in accessing it directly
>>>
>>>> 2009/8/4 Noble Paul നോബിള്‍ नोब्ळ् <noble.paul@corp.aol.com>
>>>>
>>>>> what is the package of LiveCoresHandler ?
>>>>> I guess the requestHandler name should be name="/livecores"
>>>>>
>>>>> On Tue, Aug 4, 2009 at 5:04 PM, James Brady<
>>>>> james.colin.brady@gmail.com
>>>>> wrote:
>>>>>
>>>>>> Solr version: 1.3.0 694707
>>>>>>
>>>>>> solrconfig.xml:
>>>>>>   <requestHandler name="livecores" class="LiveCoresHandler" />
>>>>>>
>>>>>> public class LiveCoresHandler extends RequestHandlerBase {
>>>>>>   public void init(NamedList args) { }
>>>>>>   public String getDescription() { return ""; }
>>>>>>   public String getSource() { return ""; }
>>>>>>   public String getSourceId() { return ""; }
>>>>>>   public NamedList getStatistics() { return new NamedList(); }
>>>>>>   public String getVersion() { return ""; }
>>>>>>
>>>>>>   public void handleRequestBody(SolrQueryRequest req,
>>>>>>
>>>>> SolrQueryResponse
>>>
>>>>  rsp) {
>>>>>>       Collection<String> names =
>>>>>> req.getCore().getCoreDescriptor().getCoreContainer().getCoreNames();
>>>>>>       rsp.add("cores", names);
>>>>>>       // if the cores are dynamic, you prob don't want to cache
>>>>>>       rsp.setHttpCaching(false);
>>>>>>   }
>>>>>> }
>>>>>>
>>>>>> 2009/8/4 Avlesh Singh <avlesh@gmail.com>
>>>>>>
>>>>>>  I'm sure I have the class name right - changing it to something
>>>>>>>> patently
>>>>>>>> incorrect results in the expected
>>>>>>>> "org.apache.solr.common.SolrException:
>>>>>>>> Error loading class ...", rather thanthe ClassCastException.
>>>>>>>>
>>>>>>>>  You are right about that, James.
>>>>>>>
>>>>>>> Which Solr version are you using?
>>>>>>> Can you please paste the relevant pieces in your solrconfig.xml
and
>>>>>>>
>>>>>> the
>>>
>>>>  request handler class you have created?
>>>>>>>
>>>>>>> Cheers
>>>>>>> Avlesh
>>>>>>>
>>>>>>> On Mon, Aug 3, 2009 at 10:51 PM, James Brady
>>>>>>> <james.colin.brady@gmail.com
>>>>>>>
>>>>>>>> wrote:
>>>>>>>> Hi,
>>>>>>>> Thanks for your suggestions!
>>>>>>>>
>>>>>>>> I'm sure I have the class name right - changing it to something
>>>>>>>> patently
>>>>>>>> incorrect results in the expected
>>>>>>>> "org.apache.solr.common.SolrException: Error loading class
...",
>>>>>>>> rather
>>>>>>>> than
>>>>>>>> the ClassCastException.
>>>>>>>>
>>>>>>>> I did have some problems getting my class on the app server's
>>>>>>>> classpath.
>>>>>>>> I'm
>>>>>>>> running with solr.home set to "multicore", but creating a
>>>>>>>> multicore/lib
>>>>>>>> directory and putting my request handler class in there resulted
in
>>>>>>>>
>>>>>>> "Error
>>>>>>>
>>>>>>>> loading class" errors.
>>>>>>>>
>>>>>>>> I found that setting jetty.class.path to include multicore/lib
(and
>>>>>>>> also
>>>>>>>> explicitly point at Solr's core and common JARs) fixed the
"Error
>>>>>>>> loading
>>>>>>>> class" errors, leaving these ClassCastExceptions...
>>>>>>>>
>>>>>>>> 2009/8/3 Avlesh Singh <avlesh@gmail.com>
>>>>>>>>
>>>>>>>>  Can you cross check the class attribute for your handler
in
>>>>>>>>>
>>>>>>>> solrconfig.xml?
>>>>>>>>
>>>>>>>>> My guess is that it is specified as "solr.LiveCoresHandler".
It
>>>>>>>>> should
>>>>>>>>>
>>>>>>>> be
>>>>>>>
>>>>>>>> fully qualified class name - com.foo.path.to.LiveCoresHandler
>>>>>>>>> instead.
>>>>>>>>>
>>>>>>>>> Moreover, I am damn sure that you did not forget to drop
your jar
>>>>>>>>> into
>>>>>>>>> solr.home/lib. Checking once again might not be a bad
idea :)
>>>>>>>>>
>>>>>>>>> Cheers
>>>>>>>>> Avlesh
>>>>>>>>>
>>>>>>>>> On Mon, Aug 3, 2009 at 9:11 PM, James Brady <
>>>>>>>>>
>>>>>>>> james.colin.brady@gmail.com
>>>>>>>
>>>>>>>>  wrote:
>>>>>>>>>> Hi,
>>>>>>>>>> I'm creating a custom request handler to return a
list of live
>>>>>>>>>> cores
>>>>>>>>>>
>>>>>>>>> in
>>>>>>>
>>>>>>>>  Solr.
>>>>>>>>>>
>>>>>>>>>> On startup, I get this exception for each core:
>>>>>>>>>>
>>>>>>>>>> Jul 31, 2009 5:20:39 PM org.apache.solr.common. SolrException
>>>>>>>>>>
>>>>>>>>> log
>>>
>>>>   SEVERE: java.lang.ClassCastException: LiveCoresHandler
>>>>>>>>>>       at
>>>>>>>>>>
>>>>>>>>>> org.apache.solr.core.RequestHandlers$1.create(RequestHandlers.java:152)
>>>
>>>>         at
>>>>>>>>>>
>>>>>>>>>> org.apache.solr.core.RequestHandlers$1.create(RequestHandlers.java:161)
>>>
>>>>         at
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>> org.apache.solr.util.plugin.AbstractPluginLoader.load(AbstractPluginLoader.java:140)
>>>
>>>>         at
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>> org.apache.solr.core.RequestHandlers.initHandlersFromConfig(RequestHandlers.java:169)
>>>
>>>>         at
>>>>>>>>>>
>>>>>>>>> org.apache.solr.core.SolrCore.<init>(SolrCore.java:444)
>>>
>>>>   I've tried a few variations on the class definition, including
>>>>>>>>>>
>>>>>>>>> extending
>>>>>>>>
>>>>>>>>> RequestHandlerBase (as suggested here:
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>
>>> http://wiki.apache.org/solr/SolrRequestHandler#head-1de7365d7ecf2eac079c5f8b92ee9af712ed75c2
>>>
>>>>   )
>>>>>>>>>> and implementing SolrRequestHandler directly.
>>>>>>>>>>
>>>>>>>>>> I'm sure that the Solr libraries I built against
and those I'm
>>>>>>>>>>
>>>>>>>>> running
>>>>>>>
>>>>>>>> on
>>>>>>>>
>>>>>>>>> are the same version too, as I unzipped the Solr war
file and
>>>>>>>>>> copies
>>>>>>>>>>
>>>>>>>>> the
>>>>>>>>
>>>>>>>>> relevant jars out of there to build against.
>>>>>>>>>>
>>>>>>>>>> Any ideas on what could be causing the ClassCastException?
I've
>>>>>>>>>>
>>>>>>>>> attached
>>>>>>>>
>>>>>>>>> a
>>>>>>>>>
>>>>>>>>>> debugger to the running Solr process but it didn't
shed any
>>>>>>>>>>
>>>>>>>>> light
>>>
>>>>   on
>>>>>>>>>>
>>>>>>>>> the
>>>>>>>>
>>>>>>>>> issue...
>>>>>>>>>>
>>>>>>>>>> Thanks!
>>>>>>>>>> James
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>> http://twitter.com/goodgravy
>>>>>>>> 512 300 4210
>>>>>>>> http://webmynd.com/
>>>>>>>> Sent from Bury, United Kingdom
>>>>>>>>
>>>>>>>>
>>>>>>
>>>>>> --
>>>>>> http://twitter.com/goodgravy
>>>>>> 512 300 4210
>>>>>> http://webmynd.com/
>>>>>> Sent from Bury, United Kingdom
>>>>>>
>>>>>>
>>>>>
>>>>> --
>>>>> -----------------------------------------------------
>>>>> Noble Paul | Principal Engineer| AOL | http://aol.com
>>>>>
>>>>
>>>>
>>>> --
>>>> http://twitter.com/goodgravy
>>>> 512 300 4210
>>>> http://webmynd.com/
>>>> Sent from Bury, United Kingdom
>>>>
>>>
>>>
>>> --
>>> -----------------------------------------------------
>>> Noble Paul | Principal Engineer| AOL | http://aol.com
>>>
>>>
>>
>>
>> --
>> http://twitter.com/goodgravy
>> 512 300 4210
>> http://webmynd.com/
>> Sent from Bury, United Kingdom
>>
>
> --
> Chantal Ackermann
> Consultant
>
> mobil    +49 (176) 10 00 09 45
> email    chantal.ackermann@btelligent.de
>
>
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-- 
http://twitter.com/goodgravy
512 300 4210
http://webmynd.com/
Sent from Bury, United Kingdom

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