Java EE developers are increasingly required to embrace thin-server-architecture client application development while leveraging their existing components. On the surface, this appears to simply mean using JAX-RS to expose RESTful services. But the real challenges are often misunderstood and underestimated. EclipseLink has solved a large part of this problem through its new JPA-RS feature which integrates JAX-RS, JAXB and JPA to allow developers to expose their persistent entities over REST with support for all lifecycle operations and query execution. In building JPA-RS, EclipseLink faced and overcame many of the challenges developers face when realizing a REST resource model, addressing HATEOS, and the infrastructure for JSON and XML binding.

1. Practical RESTful Persistence
with EclipseLink JPA-RS
Shaun Smith
Oracle
#DV13 #JPARS
@shaunMsmith

2. •
•
•
•
JPA 2.0 (EE 6) and 2.1 (EE 7) reference implementation
JPA provider in GlassFish and Oracle WebLogic
Project founded on mature Oracle TopLink codebase
EPL and EDL licensed open source JPA and JAXB
implementation
#DV13 #JPARS
@shaunMsmith

3. Browser
Database
#DV13 #JPARS
@shaunMsmith

4. Browser
Java
Database
#DV13 #JPARS
@shaunMsmith

5. Browser
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

6. Browser
JAX-RS
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

7. Browser
JAX-RS
EclipseLink JAXB / JSON Binding
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

8. Browser
JAX-RS
EclipseLink MOXy
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

9. Browser
JAX-RS
EclipseLink MOXy
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

10. Browser
Browser
HTML5
JAX-RS
EclipseLink MOXy
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

11. Browser
JAX-RS
EclipseLink MOXy
{
id: 5,
…
}
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

12. Browser
{
id: 5,
…
}
JAX-RS
EclipseLink MOXy
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

13. Browser
JAX-RS
EclipseLink MOXy
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

14. Browser
JAX-RS
EclipseLink MOXy
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

15. Browser
JAX-RS
Binding Persistence
EclipseLink MOXy
XML / JSON
Java
Java Persistence
EclipseLink JPA
Relational / NoSQL
Database
#DV13 #JPARS
@shaunMsmith

16. Browser
JAX-RS
Binding Persistence
EclipseLink MOXy
XML / JSON
Java
Java Persistence
EclipseLink JPA
Relational / NoSQL
Database
#DV13 #JPARS
@shaunMsmith

17. EclipseLink MOXy
•
•
•
JAXB for Java/XML binding—covert Java to/from XML
Java/JSON binding—convert Java to/from JSON
Currently no Java/JSON binding standard
• Java API for JSON Processing (JSR 535) is parsing, not binding
• EclipseLink interprets JAXB XML bindings for JSON
• Content-type selectable by setting property on
Marshaller/Unmarshaller
#DV13 #JPARS
@shaunMsmith

18. XML and JSON from JAXB Mappings
{
"phone-numbers" : [ {
"id" : 2,
"num" : "512-555-9999",
"type" : "mobile"
} ],
"address" : {
"city" : "New York",
"id" : 1,
"street" : "Central Park East"
},
"firstName" : "Woody",
"id" : 1,
"lastName" : “Allen"
<?xml version="1.0" encoding="UTF-8"?>
<customer>
<phone-numbers>
<phone-number>
<id>2</id>
<num>512-555-1234</num>
<type>home</type>
</phone-number>
</phone-numbers>
<address>
<city>New York</city>
<id>1</id>
<street>Central Park East</street>
</address>
<firstName>Bill</firstName>
<id>1</id>
<lastName>Allen</lastName>
</customer>
}
#DV13 #JPARS
@shaunMsmith

19. Challenges – Binding JPA Entities to
XML/JSON
<customer>
<phone-numbers>
<phone-number>
<id>1</id>
...
<type>mobile</type>
</phone-number>
</phone-numbers>
</customer>
•
•
•
JAXB
Composite Keys/Embedded Key Classes
Byte Code Weaving
Bidirectional/Cyclical Relationships
#DV13 #JPARS
JPA
@shaunMsmith

20. Bidirectional Relationship
@Entity
public class Customer{
...
@OneToMany(mappedBy="owner")
private List<Phone> phones;
}
@Entity
public class Phone{
...
@ManyToOne
private Customer owner;
}
#DV13 #JPARS
@shaunMsmith

21. What about @XmlTransient?
@Entity
public class Customer{
...
@OneToMany(mappedBy=“owner")
private List<Phone> phones;
}
@Entity
public class Phone{
...
@ManyToOne
@XmlTransient
private Customer owner;
}
#DV13 #JPARS
@shaunMsmith

22. With @XmlTransient
Loses the relationship!
owner
Customer
phones
#DV13 #JPARS
Phone
<customer>
<phone-numbers>
<phone-number>
<id>1</id>
...
<type>mobile</type>
</phone-number>
</phone-numbers>
</customer>
Marshall
Marshall
X
Customer
Unmarshall
Unmarshall
Phone
phones
@shaunMsmith

23. EclipseLink XmlInverseReference
@Entity
public class Customer{
...
@OneToMany(mappedBy=“owner")
private List<Phone> phones;
}
@Entity
public class Phone{
...
@ManyToOne
@XmlInverseReference(mappedBy=“phones")
private Customer owner;
}
#DV13 #JPARS
@shaunMsmith

24. With @XmlInverseReference
EclipseLink restores relationships on unmarshall!
owner
Customer
phones
#DV13 #JPARS
Phone
<customer>
<phone-numbers>
<phone-number>
<id>1</id>
...
<type>mobile</type>
</phone-number>
</phone-numbers>
</customer>
Marshall
Marshall
owner
Customer
Unmarshall
Unmarshall
Phone
phones
@shaunMsmith

25. Demo
#DV13 #JPARS
@shaunMsmith

26. Browser
JAX-RS
JAX-RS
Binding Persistence
EclipseLink MOXy
XML / JSON
Java
Java Persistence
EclipseLink JPA
Relational / NoSQL
Database
#DV13 #JPARS
@shaunMsmith

27. JAX-RS with JPA Example
public class InvoiceService {...
public Invoice read(int id) {
return null;
}
...
#DV13 #JPARS
@shaunMsmith

28. JAX-RS with JPA Example
@Stateless
public class InvoiceService {...
public Invoice read(int id) {
return entityManager.find(Invoice.class, id);
}
...
#DV13 #JPARS
@shaunMsmith

29. JAX-RS with JPA Example
@Path("/invoice")
@Stateless
public class InvoiceService {...
public Invoice read(int id) {
return entityManager.find(Invoice.class, id);
}
...
#DV13 #JPARS
http://[machine]:[port]/[web-context]/invoice
http://[machine]:[port]/[web-context]/invoice
@shaunMsmith

30. JAX-RS with JPA Example
@Path("/invoice")
@Stateless
public class InvoiceService {...
@Path("{id}”)
public Invoice read(@PathParam("id") int id) {
return entityManager.find(Invoice.class, id);
}
...
#DV13 #JPARS
http://[machine]:[port]/[web-context]/invoice/4
http://[machine]:[port]/[web-context]/invoice/4
@shaunMsmith

31. JAX-RS with JPA Example
@Path("/invoice")
@Stateless
public class InvoiceService {...
@GET
@Path("{id}”)
public Invoice read(int id) {
return entityManager.find(Invoice.class, id);
}
...
#DV13 #JPARS
GET http://[machine]:[port]/[web-context]/invoice/4
GET http://[machine]:[port]/[web-context]/invoice/4
@shaunMsmith

32. JAX-RS with JPA Example
@Path("/invoice")
@Stateless
public class InvoiceService {...
@Produces({"application/xml"})
@GET
@Path("{id}")
public Invoice read(@PathParam("id") int id) {
return entityManager.find(Invoice.class, id);
}
...
#DV13 #JPARS
GET http://[machine]:[port]/[web-context]/invoice/4
GET http://[machine]:[port]/[web-context]/invoice/4
@shaunMsmith

33. JAX-RS with JPA
GET http://.../invoice/4
GET http://.../invoice/4
http://.../invoice/4 mapped to
http://.../invoice/4 mapped to
JAX-RS
JAX-RS
beanGET http://.../invoice/4 mapped to method
beanGET http://.../invoice/4 mapped to method
Invoice Bean
GET
GET
GET
GET
GET
GET
GET
GET
Bean uses JPA
Bean uses JPA
Contract Bean
GET
GET
GET
GET
GET
GET
Payment Bean
GET
GET
GET
GET
GET
GET
...
Accounting PU
JPA
#DV13 #JPARS
@shaunMsmith

34. Browser
JAX-RS
JAX-RS
EclipseLink MOXy
EclipseLink MOXy
Java
Java
EclipseLink JPA
EclipseLink JPA
JPA-RS
JPA-RS
Database
#DV13 #JPARS
@shaunMsmith

35. EclipseLink JPA-RS
•
Automatically provides REST operations for entities in
persistence unit (GET, PUT, POST, DELETE)
•
Automatic generation of XML and JSON bindings
• Leverages EclipseLink’s JAXB/JPA fidelity features to avoid lossy
transformations
•
Automatic publication of REST API metadata
#DV13 #JPARS
@shaunMsmith

36. EclipseLink JPA-RS
•
Supports invocation of named queries via HTTP
•
Server side caching—EclipseLink clustered cache
•
Automatic injection of links for entity relationships
• Default Resource Model generation
#DV13 #JPARS
@shaunMsmith

37. {
"id": 2,
"city": ”Toronto",
…
}
...
Browser
"id": 1,
"lastName": "Smith",
…
"address": {
"_link": {
"href": "http:/…/Address/2",
"method": "GET",
"rel": "self"
}
}
{
1
1
2
2
...
Java
Database
#DV13 #JPARS
@shaunMsmith

38. Configuring JPA-RS
•
Add JPA-RS web fragment jar to WEB-INF/lib!
#DV13 #JPARS
@shaunMsmith

39. JPA-RS
GET http://.../persistence/Accounting/Invoice/4
GET http://.../persistence/Accounting/Invoice/4
JAX-RS http://.../persistence/Accounting/Invoice/4
JAX-RS http://.../persistence/Accounting/Invoice/4
JAX-RS
JAX-RS
mapped to JPA-RS service
mapped to JPA-RS service
Accounting
JPA-RS
JPA-RS maps URI
JPA-RS maps URI
http://.../persistence/Accounting/Invoice/4 to
http://.../persistence/Accounting/Invoice/4 to
Human Resources
Accounting PU and Invoice entity
Accounting PU and Invoice Benefits
entity
...
JPA
#DV13 #JPARS
@shaunMsmith

40. Demo
#DV13 #JPARS
@shaunMsmith

41. Demo Model
#DV13 #JPARS
@shaunMsmith

42. EclipseLink JPA-RS Roadmap
•
Resource Model
• Scope of resource
• Entity format
• partial entities/projections
• Configuration
• URL mapping/customization
• Manage Entity exposure
• Meta-data
• JSON Schema? Swagger? ...
#DV13 #JPARS
@shaunMsmith

43. Browser
JAX-RS
EclipseLink MOXy
Java
EclipseLink JPA
Database
#DV13 #JPARS
@shaunMsmith

44. Summary
•
•
•
Java EE stack has (most of) what you need to build Thin Server
Architecture applications
You have to be aware of various impedance mismatches
EclipseLink JPA-RS
• Integrates JAX-RS / JAXB / JPA
• Eliminates JAX-RS boilerplate for data access
• Simplifies Java EE Thin Server Architecture applications
☛ www.eclipse.org/eclipselink
#DV13 #JPARS
@shaunMsmith

45. The preceding is intended to outline our general product
direction. It is intended for information purposes only, and may
not be incorporated into any contract. It is not a commitment to
deliver any material, code, or functionality, and should not be
relied upon in making purchasing decisions. The development,
release, and timing of any features or functionality described for
Oracle’s products remains at the sole discretion of Oracle.
#DV13 #JPARS
@shaunMsmith