Chapter 8. Marshalling Custom Java Objects with ProtoStream

Procedure

1. Add the protostream-processor dependency to your pom.xml.

   <dependencyManagement>
     <dependencies>
       <dependency>
         <groupId>org.infinispan</groupId>
         <artifactId>infinispan-bom</artifactId>
         <version>${version.infinispan}</version>
         <type>pom</type>
       </dependency>
       <dependency>
         <groupId>org.infinispan.protostream</groupId>
         <artifactId>protostream-processor</artifactId>
         <scope>provided</scope>
       </dependency>
     </dependencies>
   </dependencyManagement>

2. Annotate the Java objects that you want to marshall with @ProtoField and @ProtoFactory.

   Book.java

   import org.infinispan.protostream.annotations.ProtoFactory;
   import org.infinispan.protostream.annotations.ProtoField;
   ...
   
   public class Book {
      @ProtoField(number = 1)
      final String title;
   
      @ProtoField(number = 2)
      final String description;
   
      @ProtoField(number = 3, defaultValue = "0")
      final int publicationYear;
   
      @ProtoField(number = 4, collectionImplementation = ArrayList.class)
      final List<Author> authors;
   
      @ProtoFactory
      Book(String title, String description, int publicationYear, List<Author> authors) {
         this.title = title;
         this.description = description;
         this.publicationYear = publicationYear;
         this.authors = authors;
      }
      // public Getter methods omitted for brevity
   }

   Author.java

   import org.infinispan.protostream.annotations.ProtoFactory;
   import org.infinispan.protostream.annotations.ProtoField;
   
   public class Author {
      @ProtoField(number = 1)
      final String name;
   
      @ProtoField(number = 2)
      final String surname;
   
      @ProtoFactory
      Author(String name, String surname) {
         this.name = name;
         this.surname = surname;
      }
      // public Getter methods omitted for brevity
   }

3. Define an interface that extends SerializationContextInitializer and is annotated with @AutoProtoSchemaBuilder.

   @AutoProtoSchemaBuilder(
         includeClasses = {
               Book.class,
               Author.class,
         },
         schemaFileName = "library.proto", 

   1

   
         schemaFilePath = "proto/", 

   2

   
         schemaPackageName = "book_sample")
   interface LibraryInitializer extends SerializationContextInitializer {
   }

   1

   names the generated .proto schema file.

   2

   sets the path under target/classes where the schema file is generated.

Procedure

1. Create a .proto schema with Protobuf messages.

   package book_sample;
   
   message Book {
       optional string title = 1;
       optional string description = 2;
       optional int32 publicationYear = 3; // no native Date type available in Protobuf
   
       repeated Author authors = 4;
   }
   
   message Author {
       optional string name = 1;
       optional string surname = 2;
   }

2. Use the org.infinispan.protostream.MessageMarshaller interface to implement marshallers for your classes.

   BookMarshaller.java

   import org.infinispan.protostream.MessageMarshaller;
   
   public class BookMarshaller implements MessageMarshaller<Book> {
   
      @Override
      public String getTypeName() {
         return "book_sample.Book";
      }
   
      @Override
      public Class<? extends Book> getJavaClass() {
         return Book.class;
      }
   
      @Override
      public void writeTo(MessageMarshaller.ProtoStreamWriter writer, Book book) throws IOException {
         writer.writeString("title", book.getTitle());
         writer.writeString("description", book.getDescription());
         writer.writeInt("publicationYear", book.getPublicationYear());
         writer.writeCollection("authors", book.getAuthors(), Author.class);
      }
   
      @Override
      public Book readFrom(MessageMarshaller.ProtoStreamReader reader) throws IOException {
         String title = reader.readString("title");
         String description = reader.readString("description");
         int publicationYear = reader.readInt("publicationYear");
         List<Author> authors = reader.readCollection("authors", new ArrayList<>(), Author.class);
         return new Book(title, description, publicationYear, authors);
      }
   }

   AuthorMarshaller.java

   import org.infinispan.protostream.MessageMarshaller;
   
   public class AuthorMarshaller implements MessageMarshaller<Author> {
   
      @Override
      public String getTypeName() {
         return "book_sample.Author";
      }
   
      @Override
      public Class<? extends Author> getJavaClass() {
         return Author.class;
      }
   
      @Override
      public void writeTo(MessageMarshaller.ProtoStreamWriter writer, Author author) throws IOException {
         writer.writeString("name", author.getName());
         writer.writeString("surname", author.getSurname());
      }
   
      @Override
      public Author readFrom(MessageMarshaller.ProtoStreamReader reader) throws IOException {
         String name = reader.readString("name");
         String surname = reader.readString("surname");
         return new Author(name, surname);
      }
   }

3. Create a SerializationContextInitializer implementation that registers the .proto schema and the ProtoStream marshaller implementations with a SerializationContext.

   ManualSerializationContextInitializer.java

   import org.infinispan.protostream.FileDescriptorSource;
   import org.infinispan.protostream.SerializationContext;
   import org.infinispan.protostream.SerializationContextInitializer;
   ...
   
   public class ManualSerializationContextInitializer implements SerializationContextInitializer {
      @Override
      public String getProtoFileName() {
         return "library.proto";
      }
   
      @Override
      public String getProtoFile() throws UncheckedIOException {
         // Assumes that the file is located in a Jar's resources, we must provide the path to the library.proto file
         return FileDescriptorSource.getResourceAsString(getClass(), "/" + getProtoFileName());
      }
   
      @Override
      public void registerSchema(SerializationContext serCtx) {
         serCtx.registerProtoFiles(FileDescriptorSource.fromString(getProtoFileName(), getProtoFile()));
      }
   
      @Override
      public void registerMarshallers(SerializationContext serCtx) {
         serCtx.registerMarshaller(new AuthorMarshaller());
         serCtx.registerMarshaller(new BookMarshaller());
      }
   }