[Bug] Protoc plugin issue when generating java class files.

[chickenlj]

Pre-check

• I am sure that all the content I provide is in English.

Search before asking

• I had searched in the issues and found no similar issues.

Apache Dubbo Component

Java SDK (apache/dubbo)

Dubbo Version

3.3.0-beta

Steps to reproduce this issue

1. plugin does not support generating all source codes into one single file. Currently must set option java_multiple_files = true;
2. OuterClass is not generated by default but Service class relies on OuterClass, Currently must set option java_outer_classname = "MDSSyncServiceOuterClass";
3. java_package does not work, classes still created in package not in java_package

What you expected to happen

1. support single file mode by default or plugin can automatically use multiple files mode by force.
2. Generate OuterClass by default or does not rely on OuterClass by default.
3. java_package takes precedence of package if set.

Anything else

No response

Are you willing to submit a pull request to fix on your own?

• Yes I am willing to submit a pull request on my own!

Code of Conduct

• I agree to follow this project's Code of Conduct