How can I extend Java code generated by JAXB, CXF or Hibernate tools?

With generated Java source code, like

• code generated with Hibernate tools
• code generated with JAXB schema binding (xjc)
• code generated with WDSL2Java (cxf)

all generated classes are "value object" types, without business logic. And if I add methods to the generated source code, I will loose these methods if I repeat the source code generation.

Do these Java code generation tools offer ways to "extend" the generated code?

For example,

• to override the ToString method (for logging)
• to implement the visitor pattern (for data analysis / validation)