Protobuf Lesson 1: compile

The first lesson I learned in protobuf compiling is:
the --java_out must be accurate.

example: project structure is maven style, the protobuf message's java-package value is "com.xxx.common.vo",

then your --java_out value should be
$project-home$\src\main\java

otherwise, the generated message bean would have compilation error (name space related, nested class cannot be resolved to a type) and you are not recommended to edit the generated java file.