I think that you have an older version of Netty 4 on your classpath (maybe you accidentally included 4.0.11.Final or you have another dependency that depends on an older version of 4.0.x.Final of Netty? I say this because that method (io.netty.buffer.CompositeByteBuf io.netty.buffer.CompositeByteBuf#addComponents(boolean, java.lang.Iterable)) has existed through the life of the 4.1.x.Final series of Netty but not always in 4.0.x.Final. If you have an older 4.0.x.Final on the classpath then you can see exactly this error. Double check your dependencies and ensure that you have the right version and not a second version (explicitly or transitively).