keep using log4j-over-slf4j
<groupId>edu.uci.ics</groupId>
<artifactId>crawler4j</artifactId>
<version>3.5</version>
+ <exclusions>
+ <exclusion>
+ <groupId>log4j</groupId>
+ <artifactId>log4j</artifactId>
+ </exclusion>
+ </exclusions>
</dependency>
<dependency>
<groupId>com.google.gwt</groupId>
