Understanding the Autogenerated Code
Learn about the classes generated by the protoc compiler, which will be used to create gRPC client and server.
In gRPC, the .proto file serves as the contract defining the service methods and message types exchanged between the server and client. However, this file alone isn’t sufficient for communication. It needs to be compiled into programming language-specific classes. In gRPC, compiled Protobuf code is the backbone of communication. The compiled auto-generated classes serve as the building blocks for the gRPC server and client implementations. These classes are automatically generated by the Protocol Buffers compiler (protoc) from the .proto files. In this lesson, we’ll explore the significance of auto-generated classes in the gRPC server and client implementation and how they facilitate gRPC communication. Auto-generated classes for service methods and message types simplify development by providing a structured and type-safe way to interact with gRPC services.
Generating Java code from .proto file
The ftp_service.proto file contains the service, messages, and other definitions specific to our FTP service. To generate Java classes from this file, we need to run the protocol buffer compiler (protoc). The POM file lists the protoc compiler for Java, which will be used to build the project using the mvn install command.
If you are following along on your local machine along as we advance towards other lessons, compile the updated module subsequently by executing the mvn install command to make sure there are no errors.
When the code is compiled, a target directory is created. We can see the protoc-3.19.2... executable in the protoc-plugins folder. Maven downloads this executable and uses it to read the ftp_service.proto file to create Java classes. These auto-generated classes can be found in the generated-sources folder. Since we have used the java_package option, the code will be placed io.datajek.ftpservice.autogenerated package inside the generated_sources directory. The protocol buffer compiler will automatically create the io/datajek/ftpservice/autogenerated directory structure.
Classes: The java_multiple_files option means that the compiler will create a separate .java files for each of the top-level message, enumeration, and service declared in the .proto file. The classes directory contains files named AddFileRequest.java, FileChunk.java, ...