Class Descriptors (3.19.4)

Contains a collection of classes which describe protocol message types.

Every message type has a Descriptor , which lists all its fields and other information about a type. You can get a message type's descriptor by calling MessageType.getDescriptor() , or (given a message object of the type) message.getDescriptorForType() . Furthermore, each message is associated with a FileDescriptor for a relevant .proto file. You can obtain it by calling Descriptor.getFile() . A FileDescriptor contains descriptors for all the messages defined in that file, and file descriptors for all the imported .proto files.

Descriptors are built from DescriptorProtos, as defined in google/protobuf/descriptor.proto .