alias: '/errorServlet' is already in use in this or another context when register more than one errorPage servlet

[Nhut Thai Le]

Hello,

I have a few error page servlets to handle 403, 404 and 500 errors. They are annotated according to osgi cmpn R6  as  follow:

@Component(

service = Servlet.class,

enabled=true,

property = {

"osgi.http.whiteboard.servlet.errorPage=403",

"osgi.http.whiteboard.context.select=(osgi.http.whiteboard.context.name=WebviewerServletContextHelper)"

},

scope = ServiceScope.PROTOTYPE

)

public final class Error403Servlet extends HttpServlet {...}

@Component(

service = Servlet.class,

enabled=true,

property = {

"osgi.http.whiteboard.servlet.errorPage=404",

"osgi.http.whiteboard.context.select=(osgi.http.whiteboard.context.name=WebviewerServletContextHelper)"

},

scope = ServiceScope.PROTOTYPE

)

public final class Error404Servlet extends HttpServlet {..}

@Component(

service = Servlet.class,

enabled=true,

property = {

"osgi.http.whiteboard.servlet.errorPage=500",

"osgi.http.whiteboard.context.select=(osgi.http.whiteboard.context.name=WebviewerServletContextHelper)"

},

scope = ServiceScope.PROTOTYPE

)

public final class Error500Servlet extends HttpServlet {..}

When i start the server, i got this error:

13:13:53.716 [paxweb-config-1-thread-1] ERROR o.o.p.w.e.w.i.WebApplication - Registration skipped for [ServletWebElement{mapping=DefaultServletMapping{httpContextId=WebviewerServletContextHelper,urlPatterns=null,initParams={},servlet=com.castortech.iris.ba.webviewer.internal.Error500Servlet@1399c32a, alias=/errorServlet, servletNameError500Servlet}}] due to error during registration

org.osgi.service.http.NamespaceException: alias: '/errorServlet' is already in use in this or another context

at org.ops4j.pax.web.service.spi.model.ServerModel.addServletModel(ServerModel.java:124)

at org.ops4j.pax.web.service.internal.HttpServiceStarted.registerServlet(HttpServiceStarted.java:243)

at org.ops4j.pax.web.service.internal.HttpServiceStarted.registerServlet(HttpServiceStarted.java:223)

at org.ops4j.pax.web.service.internal.HttpServiceStarted.registerServlet(HttpServiceStarted.java:207)

at org.ops4j.pax.web.service.internal.HttpServiceProxy.registerServlet(HttpServiceProxy.java:69)

at org.ops4j.pax.web.extender.whiteboard.internal.element.ServletWebElement.register(ServletWebElement.java:88)

Tracing the code to the ServletWebElement.register(), i see that all my error page servlets above have the same alias (/errorServlet) which cause pax.web to throw exception and skip registration when it encounter the 2nd error page servlet. Is this a known bug and how do I get around this?

I am using pax-web-extender-whiteboard 7.2.4

Thai Le

[Grzegorz Grzybek]

Hello

The error is correct - you didn't specify the patterns for error servlets, thus "/errorServlet" was assumed.

You have two options:

1. add @javax.servlet.annotation.WebServlet annotation and use "value" or "urlPatterns" params of this annotation - these will be used instead of "/errorServlet"

2. use "alias" or "urlPatterns" service properties on @Component annotation

I hope this helps.

regards

Grzegorz Grzybek

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[Nhut Thai Le]

Thank you Grzegorz,

I did what you said and the error does go away but from time to time i got this:

java.lang.IllegalArgumentException: Error page for [403] already registered.
	at org.ops4j.pax.web.service.spi.model.ServiceModel.addErrorPageModel(ServiceModel.java:315)
	at org.ops4j.pax.web.service.internal.HttpServiceStarted.registerErrorPage(HttpServiceStarted.java:961)
	at org.ops4j.pax.web.service.internal.HttpServiceProxy.registerErrorPage(HttpServiceProxy.java:343)
	at org.ops4j.pax.web.extender.whiteboard.internal.element.ServletWebElement.register(ServletWebElement.java:107)
	at org.ops4j.pax.web.extender.whiteboard.internal.WebApplication.registerWebElement(WebApplication.java:392)

Is it possible that this is due to race condition in scr?

Thai

[Grzegorz Grzybek]

Hello

So back to the case you've described in your email "error page servlet register twice" ;)

Is there a chance to get some logs?

regards

Grzegorz Grzybek

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[Nhut Thai Le]

Yes, I'll update the other question with logs

Thai

On Tuesday, August 6, 2019 at 1:28:13 PM UTC-4, Nhut Thai Le wrote: