Java Saturday, Ciklum Odessa, Oct 29-2011

1. Yaroslav Pogrebnyak Software Developer, Ciklum [email_address] www.pogrebnyak.info Rapid Java Backend & API Development for Mobile Devices

2. Devices & Apps Hell How to interact? A lot of work for backend developers ]:->

3. Device ↔ Server interaction

4. How to define API? HTTP + MediaType + ... = REST? It Depends! - URI - Media-Type: xml, json, etc - Operations: create, update, delete, … - Custom conventions GET http://example.com/users/ POST http://example.com/users/ DELETE http://example.com/users/42

5. Data Interchange Protocols PlainText, XML, JSON, ProtocolBuffers , BERT, BSON, Thrift, MessagePack, Custom Protocol... 1. Size 2. Performance 3. Usability 4. Platforms

6. 68 bytes: { &quot;status&quot; : &quot;OK&quot; , &quot;response&quot; : { &quot;id&quot; : 42 } } 5 bytes (hex dump): 0801 102a 0a JSON vs XML vs Protocol Buffers 119 bytes: <? xml version=&quot;1.0&quot;?> < message > < status >OK</ status > < response > < id >42</ id > </ response > </ message >

7. HTTP POST /api/register/ Content-Type: application/x-protobuf Accept: application/x-protobuf serialize deserialize HTTP 200 OK Content-Type: application/x-protobuf Content-Length: 5 serialize deserialize Protocol Buffers scenario

8. Implementation

9. API requires strength , Java-world's advantage: Static Typing

10. Java + Maven + Spring + Jersey + Protocol Buffers

11. Create project Jersey Simple Webapp $ mvn archetype:generate -DarchetypeCatalog= http://download.java.net/maven/2 Spring + Jersey $ mvn archetype:generate -DarchetypeCatalog= http://seratch.github.com/mvn-repo/releases DIY $ cd project $ vim pom.xml :) Minimalistic Secret Template :) http://pogrebnyak.info/ciklum/spring_jersey_gpb.zip

12. Protocol Buffers Schema package myapi ; // POST /api/register message RegisterRequest { required string login = 1; optional string email = 2; } // Response message RegisterResponse { enum Status { SUCCESS = 0; ALREADY_EXISTS = 1; } required Status status = 1; required string id = 2; }

13. Conventions /some/endpoint Request: message Name Request { … } Response: message Name Response { enum Status { … } required Status status = 1; ... }

14. Configuration Implement Protocol Buffers Serializer/Deserializer for Jersey @Provider @Component @Consumes ( “application/x-protobuf” ) public class ProtobufMessageReader implements MessageBodyReader<Message> { // ... @Provider @Component @Produces ( “application/x-protobuf” ) public class ProtobufMessageWriter implements MessageBodyWriter<Message> { // ...

15. applicationContext.xml DataSource & transaction management web.xml Jersey Spring Servlet & Spring context listeners Protofile & package for generated files Controller classes Services & dao Other Stuff Protobuf serializers pom.xml project configuration

16. Jersey Сontroller Example @Component @Transactional @Path ( &quot;/api&quot; ) public class ApiController { @Autowired private ClientUserService userService; @POST @Path ( &quot;/register&quot; ) public RegisterResponse register( RegisterRequest r) { User user = new User(r.getLogin()); userService.createUser(user); return RegisterResponse . newBuilder () .setStatus(Status.Success) .setId(user.getId()) .build(); } }

18. Thank you! Yaroslav Pogrebnyak [email_address] www.pogrebnyak.info Presentation: http://pogrebnyak.info/ciklum/spring_jersey_gpb.ppt Sample project: http://pogrebnyak.info/ciklum/spring_jersey_gpb.zip