Protobuf converter

protobuf-converter is library for transforming your Domain Model Objects into Google Protobuf Messages and vice versa.

Maven/Gradle

You can add this library as a dependency to your Maven or Gradle project through JitPack.

How to use it ?

Domain model classes that have to be transformed into protobuf messages must satisfy conditions:

• Class has to be marked by @ProtoClass annotaion that contains reference on related protobuf message class.
• Class fields has to be marked by @ProtoField annotaion. These fields must have getters and setters.

E.g.:

@ProtoClass(ProtobufUser.class)
public class User {

	@ProtoField
	private String name;
	@ProtoField
	private String password;

	// getters and setters for 'name' and 'password' fields
	...
}

Code for conversion User instance into related protobuf message:

User userDomain = new User();
...
ProtobufUser userProto = Converter.create().toProtobuf(ProtobufUser.class, userDomain);

Code for backward conversion:

User userDomain = Converter.create().toDomain(User.class, userProto);

Conversion of lists of objects is similar to single object conversion.

@ProtoClass

Annotation attibutes:

• value - required. Contains reference to protobuf message class.
• mapper - optional. Contains reference to class that performs field value mapping between domain and protobuf objects during conversion. Default value - DefaultMapperImpl.class

mapper attribute is useful when domain model class and protobuf message class has different structure. In such case you have to create own Mapper implementation and specify it as value of mapper attribute.

If type of domain class field is complex (marked by @ProtoClass) protobuf-converter will convert this field value to related protobuf message (DefaultMapperImpl.class has to be specified as mapper attribute value)

@ProtoField

Annotation attibutes:

1. name - optional. Related protobuf field name.
2. converter - optional. Contains reference to class that performs field value transformation. Default value - DefaultConverterImpl.class
3. nullValue - optional. Contains reference to class that test protobuf object field for nullability . Default value - DefaultNullValueInspectorImpl.class
4. defaultValue - optional. Contains reference to class that initialize domain object field if related protobuf field is not initialized. Default value - SimpleDefaultValueImpl.class

Use name attribute when domain class field name is different from name specified in the *.proto file.

converter attribute is useful when domain class field type is different from protobuf message field type. E.g.: date value in the domain class is stored into java.util.Date and protobuf message uses int64(java.lang.Long). For field data tarnsformation you must specify DateLongConverterImpl.class as value of converter attribute. You can create own field type converter if you implement TypeConverter interface.

Fields Ignore

In case when you need to prevent transforming some domain fields values into protobuf message field values use FieldsIgnore.class.

E.g.: field password of User.class has not be tansformed into ProtobufUser.class field when server generates response on user info request sent by client application. You need to add field password into ignored list:

User userDomain = new User();
...
FieldsIgnore ignoredFiedls = new FieldsIgnore().add(User.class, "password");
Configuration configuration = Configuration.builder().addIgnoredFields(ignoredFiedls).build();
ProtobufUser userProto = Converter.create(configuration).toProtobuf(ProtobufUser.class, userDomain);

Also FieldsIgnore.class allows to ignore single field as well as field data types. E.g.: it is possible to ignore all fields with type java.lang.String:

User userDomain = new User();
...
FieldsIgnore ignoredFiedls = new FieldsIgnore().add(String.class);
Configuration configuration = Configuration.builder().addIgnoredFields(ignoredFiedls).build();
ProtobufUser userProto = Converter.create(configuration).toProtobuf(ProtobufUser.class, userDomain);

Obfuscation

Main Proguard options:

-keep interface net.badata.protobuf.converter.** { *; }

-keep public class * implements net.badata.protobuf.converter.mapping.Mapper {
     public <init>();
}

-keep public class * implements net.badata.protobuf.converter.type.TypeConverter {
     public <init>();
}

-keep public class * implements net.badata.protobuf.converter.inspection.DefaultValue {
     public <init>();
}

-keep public class * implements net.badata.protobuf.converter.inspection.NullValueInspector {
     public <init>();
}

Keep your domain objects (replace your.package.name with name of package where domain objects stored):

-keepclassmembers @net.badata.protobuf.converter.annotation.ProtoClass public class your.package.name.** {
     @net.badata.protobuf.converter.annotation.ProtoField <fields>;
     public <init>();
     public void set*(***);
     public boolean is*();
     public  *** get*();
}

Example

protobuf-converter capabilities is demonstrated by project located in the example folder.

Assemble example project:

gradle assemble

Start server:

java -jar example.jar "server"

Start client:

java -jar example.jar

License

MIT License