For some weeks I had read about the steps to run an errai application and finally I found the article posted at: http://community.jboss.org/wiki/WorkingwithGWTCDIandErrai, after I read all that quickly I do everything recommended but at the end I always get the same error: SLF4J: Class path contains multiple SLF4J bindings. SLF4J: Found binding in [jar:file:/home/sandy/.m2/repository/org/slf4j/slf4j-log4j12/1.5.10/slf4j-log4j12-1.5.10.jar!/org/slf4j/impl/StaticLoggerBinder.class] SLF4J: Found binding in [jar:file:/home/sandy/.m2/repository/org/jboss/weld/servlet/weld-servlet/1.1.0.Beta2/weld-servlet-1.1.0.Beta2.jar!/org/slf4j/impl/StaticLoggerBinder.class] SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation. log4j:WARN No appenders could be found for logger (org.jboss.weld.Version). log4j:WARN Please initialize the log4j system properly. in some sites like http://slf4j.42922.n3.nabble.com/Bug-138-New-Class-path-contains-multiple... recommend to solve the problem: In org.slf4j.LoggerFactory.singleImplementationSanityCheck() method in line 192 getResources somehow returns 2 exactly the same bindings: Enumeration paths = LoggerFactory.class.getClassLoader().getResources( STATIC_LOGGER_BINDER_PATH); So using Set implementationSet = new HashList(); in line 194 instead of List implementationList = new ArrayList(); will solve such irrelevant warning. but I really don't know if it's true or if the solution is other, anyway I don't know how to do that because org.slf4j.LoggerFactory is a binary file (.class) and how could I modify it ??? Finally I couldn't run my first Errai application generated from Maven. If somebody can help me, I'll be grateful. thanks to all...