Currently some public API methods are defined in GenreatedMessage.java
and they have a generric return type:
class GeneratedMessage {
class Builder<BuilderType extends Builder<BuilderType>> {
public BuilderType setField(...);
public BuilderType setExtension(...);
}
}
With these definitions, the compiled byte code of a callsite will have
a direct reference to GeneratedMessage. For example:
fooBuilder.setField(...);
becomes:
##: invokevirtual // Method Builder.setField:(...)LGeneratedMessage.Builder
##: checkcast // class Builder
This will prevent us from updating generated classes to subclass a
different versioned GeneratedMessageV3 class in the future (we can't do
it in a binary compatible way).
This change addresses the problem by overriding these methods directly
in the generated class:
class Foo {
class Builder extends GeneratedMessage.Builder<Builder> {
public Builder setField(...) {
return super.setField(...);
}
}
}
After this, fooBuilder.setField(...) will be compiled to:
##: invokevirtual // Method Builder.setField:(...)LFoo.Builder
The callsites will no longer reference GeneratedMessage directly and we
can change Foo to subclass GeneratedMessageV3 without breaking binary
compatiblity.
The downside of this change is:
1. It increases generated code size (though it saves some instructions
on the callsites).
2. We can never stop generating these overrides because doing that
will break binary compatibility.
Change-Id: I879afbbc1325a66324a51565e017143489b06e97
Moving the files to their original location, so that opensource changes
can be picked during the internal merge. Those files will be moved into
the correct location after merging with internal code.
Note: do NOT merge this into master without the other internal
down-integration commit.
protobuf/java will become a parent pom that will contain two modules:
core - contains all of the code for the protobuf-java artifact
util - contains all of the code for the protobuf-java-util artifact
Also cleaned up various Maven warnings.
