5.2. 使用 ProtoStream 的 Marshalling User Types

流程

1. 将 protostream-processor 依赖项添加到 pom.xml 中。

   <dependencyManagement>
     <dependencies>
       <dependency>
         <groupId>org.infinispan</groupId>
         <artifactId>infinispan-bom</artifactId>
         <version>${version.infinispan}</version>
         <type>pom</type>
       </dependency>
     </dependencies>
   </dependencyManagement>
   
   <dependencies>
     <dependency>
       <groupId>org.infinispan.protostream</groupId>
       <artifactId>protostream-processor</artifactId>
       <!--
         This dependency should be declared in the "provided" scope or made "optional"
         because it is a compile-only dependency and is not required at runtime.
         Transitive propagation of this dependency should be also be avoided.
       -->
       <scope>provided</scope>
     </dependency>
   </dependencies>

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2. 使用 @ProtoField 和 @ProtoFactory 注解您要 marshall 的 Java 对象。

   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
   }

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   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
   }

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3. 定义扩展 SerializationContextInitializer 的接口，并使用 @AutoProtoSchemaBuilder 标注。

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

   1

   
         schemaFilePath = "proto/", 

   2

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

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   1

   将生成的 .proto 模式文件命名为 .proto。

   2

   在生成 schema 文件的 target/classes 下设置路径。

流程

1. 创建一个 Protobuf 模式 .proto 文件，为 marshall 提供 Java 对象的结构化表示。

   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;
   }

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   前面的 .library.proto 文件定义了名为 Book 的实体(Protobuf 消息类型)，该实体包含在 book_sample 软件包中。本书 声明了原语类型的多个字段以及名为 author 的数组(Protobuf 可重复字段)，即 Author 消息类型。

   • 您可以嵌套消息，但生成的结构严格是一个树，而不是图形。
   • 类型继承是不可能的。
   • 不支持集合，但您可以使用重复字段模拟数组。

2. 使用 org.infinispan.protostream.MessageMarshaller 接口为您的类实施 marshallers。

   注意

   MessageMarshaller 接口现已弃用。

   下一个版本的 Data Grid 提供了一种替代的实现，可让您创建一个 adaptor 类，该类将 @ProtoAdaptor 注释用于任何外部的第三方 Java 对象类。

   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);
      }
   }

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   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);
      }
   }

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3. 创建一个 SerializationContextInitializer 实现，它使用 SerializationContext 注册 .proto 模式和 ProtoStream marshaller 实现。

   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());
      }
   }

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