Search code examples
javaprotocol-buffersprotocolsprotoc

Java : Proto parser library

I want to parse a proto file. Wanted to check is there any java library available which can parse proto files. Based on my requirement I cannot use descriptor parseFrom method or protoc command. Please suggest thanks in advance.

$ protoc --include_imports --descriptor_set_out temp *.proto // I don't want to do this manual step 
or 
DescriptorProtos.FileDescriptorProto descriptorProto = DescriptorProtos.FileDescriptorProto.parseFrom(proto.getBytes());

Appreciate suggestion thanks

Solution

  • Possible solution: io.protostuff:protostuff-parser library

    Let's consider the 3.1.38 version of the io.protostuff:protostuff-parser library as the current version.

    Example program

    Please, consider the below example program as a draft to get started with the library.

    Input file

    Let's assume the /some/directory/data/test.proto file exist with the following content:

    message SearchRequest {
  string query = 1;
  int32 page_number = 2;
  int32 result_per_page = 3;
  enum ContentType {
    WEB = 1;
    IMAGES = 2;
    VIDEO = 3;
  }
  ContentType content_type = 4;
}

    pom.xml: Dependencies

    <project>
    <dependencies>
        <dependency>
            <groupId>io.protostuff</groupId>
            <artifactId>protostuff-parser</artifactId>
            <version>3.1.38</version>
        </dependency>
        <dependency>
            <groupId>com.google.inject</groupId>
            <artifactId>guice</artifactId>
            <version>5.1.0</version>
        </dependency>
    </dependencies>
</project>

    Program

    import com.google.inject.Guice;
import com.google.inject.Injector;
import io.protostuff.compiler.ParserModule;
import io.protostuff.compiler.model.Message;
import io.protostuff.compiler.model.Proto;
import io.protostuff.compiler.parser.Importer;
import io.protostuff.compiler.parser.LocalFileReader;
import io.protostuff.compiler.parser.ProtoContext;
import java.nio.file.Path;
import java.util.List;

public final class Program {
    public static void main(final String[] args) {
        final Injector injector = Guice.createInjector(new ParserModule());
        final Importer importer = injector.getInstance(Importer.class);
        final ProtoContext protoContext = importer.importFile(
            new LocalFileReader(Path.of("/some/directory/data")),
            "test.proto"
        );

        final Proto proto = protoContext.getProto();

        final List<Message> messages = proto.getMessages();
        System.out.println(String.format("Messages: %s", messages));

        final Message searchRequestMessage = proto.getMessage("SearchRequest");
        System.out.println(String.format("SearchRequest message: %s", searchRequestMessage));

        final List<Enum> searchRequestMessageEnums = searchRequestMessage.getEnums();
        System.out.println(String.format("SearchRequest message enums: %s", searchRequestMessageEnums));
    }
}

    The program output:

    Messages: [Message{name=SearchRequest, fullyQualifiedName=..SearchRequest, fields=[Field{name=query, typeName=string, tag=1, options=DynamicMessage{fields={}}}, Field{name=page_number, typeName=int32, tag=2, options=DynamicMessage{fields={}}}, Field{name=result_per_page, typeName=int32, tag=3, options=DynamicMessage{fields={}}}, Field{name=content_type, typeName=ContentType, tag=4, options=DynamicMessage{fields={}}}], enums=[Enum{name=ContentType, fullyQualifiedName=..SearchRequest.ContentType, constants=[EnumConstant{name=WEB, value=1, options=DynamicMessage{fields={}}}, EnumConstant{name=IMAGES, value=2, options=DynamicMessage{fields={}}}, EnumConstant{name=VIDEO, value=3, options=DynamicMessage{fields={}}}], options=DynamicMessage{fields={}}}], options=DynamicMessage{fields={}}}]
SearchRequest message: Message{name=SearchRequest, fullyQualifiedName=..SearchRequest, fields=[Field{name=query, typeName=string, tag=1, options=DynamicMessage{fields={}}}, Field{name=page_number, typeName=int32, tag=2, options=DynamicMessage{fields={}}}, Field{name=result_per_page, typeName=int32, tag=3, options=DynamicMessage{fields={}}}, Field{name=content_type, typeName=ContentType, tag=4, options=DynamicMessage{fields={}}}], enums=[Enum{name=ContentType, fullyQualifiedName=..SearchRequest.ContentType, constants=[EnumConstant{name=WEB, value=1, options=DynamicMessage{fields={}}}, EnumConstant{name=IMAGES, value=2, options=DynamicMessage{fields={}}}, EnumConstant{name=VIDEO, value=3, options=DynamicMessage{fields={}}}], options=DynamicMessage{fields={}}}], options=DynamicMessage{fields={}}}
SearchRequest message enums: [Enum{name=ContentType, fullyQualifiedName=..SearchRequest.ContentType, constants=[EnumConstant{name=WEB, value=1, options=DynamicMessage{fields={}}}, EnumConstant{name=IMAGES, value=2, options=DynamicMessage{fields={}}}, EnumConstant{name=VIDEO, value=3, options=DynamicMessage{fields={}}}], options=DynamicMessage{fields={}}}]