Assuming jetty uses child-first a.k.a. local-first class loading order, I would recommend to bundle slf4j and logback jar in your war file. Jetty used to have the opposite class loading order, i.e. parent-first, but I am under the impression that it changed to local-first class loading in recent versions. BTW, Tomcat uses local-first class loading by default. HTH, On 04/02/2010 9:28 AM, Aleksey Didik wrote:
Hello Ceki, Thanks for explanation. It's clear now. I'll try to make something with this situation.
Aleksey.
03.02.2010 21:46, Ceki Gulcu пишет:
Hello Aleksey,
I am not totally surprised by what you describe. According to the java laguage specification (JLS) two classes loaded by distinct class loaders are deemed incompatible even if the classes are bitwise identical.
When the jetty class loader loads ch.qos.classic.Logger it also needs to load org.slf4j.Logger which it can, and does. When the ch.qos.classic.Logger is returned to your web-application as a org.slf4j.Logger as requested by your web-application, the returned Logger is not compatible with the expected Logger, even if they are both of type org.slf4j.Logger. Your web-application expects it to be loaded by the web-app's class loader but the returned instance is loaded by the jetty class loader, hence the error you observe.
HTH,
On 03.02.2010 18:36, Aleksey Didik wrote:
Hello, I have caught a problem of using embedded Jetty and slf4j, may be you can help me.
Jetty tell me this one:
java.lang.LinkageError: loader constraint violation: when resolving method "org.slf4j.impl.StaticLoggerBinder.getLoggerFactory()Lorg/slf4j/ILoggerFactory;"
the class loader (instance of org/eclipse/jetty/webapp/WebAppClassLoader) of the current class, org/slf4j/LoggerFactory, and the class loader (instance of sun/misc /Launcher$AppClassLoader) for resolved class, org/slf4j/impl/StaticLoggerBinder, have different Class objects for the type org/slf4j/ILoggerFactory used in the signature [main o.e.j.u.l.Slf4jLog.warn:111]
I have next jars:
Embedded Jetty classpath: slf4j-api-1.5.10.jar logback-classic-0.9.18.jar
War libs: slf4j-api-1.5.10.jar
But I add slf4j-api-1.5.10.jar logback-classic-0.9.18.jar to WAR libs and delete logback-classic-0.9.18.jar from jetty classpath, all work fine.
Best regards, Aleksey Didik
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