Hello,
You have two options:
1) Using VizJs
This is a port to Javascript of GraphViz.
Explanation here http://plantuml.com/vizjs
In that case, you have to install some other jar.
This solution gives the best result
2) Using Smetana
This is a port to Java of GraphViz
Explanation here http://plantuml.com/smetana02
Running this is simplier, you just have to add "!pragma graphviz_dot jdot" to your diagram.
@startuml
!pragma graphviz_dot jdot
class Foo1
Foo1 --> Foo2
Foo1 --> Foo3
Foo1 ---> Foo4 : test 4
Foo1 ----> Foo5 : test 5
@enduml
Unfortunatly, this is still alpha: the port is not completed yet.
Tell us if this helps you.