WebMagic
A scalable web crawler framework for Java
... include the fact that it is multi-thread and has distribution support. WebMagic is very easy to integrate. Add dependencies to your pom.xml. WebMagic use slf4j with slf4j-log4j12 implementation. If you customized your slf4j implementation, please exclude slf4j-log4j12. You can write a class implementation of PageProcessor.