REST and JAX-RS

JAX-RS
… and the REST will follow

Guy Nir

Agenda

» REST – What ? Who ? Why ?
» JAX-RS (JSR-311) - Digg’n in
» Security
» Application-Level Protocol
» Summary

2

What ? Who ? Why ?
… and how

What ? Who ? Why ?

Architectural overview

GET http://weather.yahoo.com/israel/tel-aviv/ramat-gan-1967869/

HTTP request
Yahoo’s weather
HTTP client web-server
HTTP response

RESPONSE CODE: 200 (OK) + BODY

4

What ? Who ? Why ?

Architectural overview


Read, The weather in Israel at Tel-Aviv area
(Ramat Gan).

5

What ? Who ? Why ?

HTTP request overview
GET /israel/tel-aviv/ramat-gan-1967869/ HTTP/1.1
Host: weather.yahoo.com
Accept: image/gif, application/xaml+xml, */*
Accept-Language: en-us
User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; ... )
Accept-Encoding: gzip, deflate
Connection: Keep-Alive
Cookie: BA=ba=2139&ip=82.80.99.106&t=1258874241;


HTTP request Yahoo’s weather

6

What ? Who ? Why ?

Cookie: BA=ba=2139&ip=82.80.99.106&t=1258874241;



7

What ? Who ? Why ?

Accept: image/gif, text/plain, application/xml, */*
Cookie: BA=ba=2139&ip=82.80.99.106&t=1258874241;



8

What ? Who ? Why ?

Cookie: BA=2139&ip=82.80.99.106&t=1258874241;



9

What ? Who ? Why ?




HTTP/1.1 200 OK
Connection: close
Content-Type: text/html;charset=utf-8
Cache-Control: private
Content-Length: 69947
Date: Sun, 22 Nov 2009 07:59:11 GMT
Set-Cooie: t=164531234;

10

What ? Who ? Why ?




HTTP/1.1 200 OK
Connection: close
Date: Sun, 22 Nov 2009 07:59:11 GMT
Set-Cooie: t=164531234;

11

What ? Who ? Why ?




HTTP/1.1 200 OK
Connection: close
Date: Sun, 22 Nov 2009 07:59:11 GMT
Set-Cooie: t=164531234;

12

What ? Who ? Why ?




HTTP/1.1 200 OK
Connection: close
Date: Sun, 22 Nov 2009 07:59:11 GMT
Set-Cooie: t=164531234;

13

What ? Who ? Why ?

Everything is a resource …
» A resource is …
 A network-accessible data
object or service identified by
[1]
an URI (IRI ):
• Images,
• Documents (HTML, PDF, …),
• Geo-location,
• Weather
[1] Section 3, Atom Publishing Protocol

14

What ? Who ? Why ?

Resources:
» Collections
 http://portal/bicycles/

» Members/Items:
 http://portal/documents/mydog.doc

[1] Section 3, Atom Publishing Protocol

15

What ? Who ? Why ?

HTTP defines more than just ‘GET’ and ‘POST’:
Method REST Operation Description
POST CREATE (INSERT) Create or update
GET READ (QUERY) Query about the resource
PUT UPDATE (CHANGE) Update
DELETE DELETE (DELETE) I want to delete what-ever-it-is ….
HEAD I’m something like ‘GET’ [1]
OPTIONS JAX-RS mumbles something about me.
TRACE
CONNECT

[1] Unique extension of JAX-RS.

16

What ? Who ? Why ?

Roy Fielding defines REST as:
» Free of any platform or language,
» Free of any schema or protocol (beyond that of HTTP),
» No ALP (Application- or Presentation- layer Protocol)
coercion

[1]
» Only a set of recommendations !

[1] Principled Design of the Modern Web Architecture - Roy T. Fielding, Richard N. Taylor - section 4.

17

What ? Who ? Why ?

Some important points …
» REST recommends using URIs instead of query-based
URLs:
 Don’t use:
http://host.com/service?type=weather&when=today
 Use:
http://host.com/service/weather/today
» Atom Publishing Protocol (APP).
 RFC-5023 (text-only)

18

What ? Who ? Why ?

REST is …
» Architectural style, not technology !
 Client/server + Request/response approach.
» Everything is a RESOURCE.
» CRUD (Create / Read / Update / Delete) … [1]

» Stateless by nature (excellent for distributed systems),
» Cacheable (naturally supported !)
» A great way to web-service !

[1] Reference to other acronyms at Wikipedia

19

JAX-RS (JSR-311)

JAX-RS goals[1]:
» POJO-based,
» HTTP-centric,
» Format independent,
» Container independent,
» Availability as standalone and enterprise platforms.

[1] JSR-311, section 1.2 - Goals

21

JAX-RS (JSR-311)

HTTP JAX-RS

22

JAX-RS (JSR-311)

This page is intentionally left blank

Gesture for times when we used to read books ….

23

JAX-RS (JSR-311)

http://www.disney.com/muppets/...

24

JAX-RS (JSR-311)

POJO + Annotation = JAX-RS resource
/**
* http://www.disney.com/muppets/catalog Relative context
*/
@Path("/catalog")
public class MuppetCatalogController {

}

25

JAX-RS (JSR-311)

Reading the catalog
GET …/catalog
CLIENT SERVER
List all items available for sale.

/**
* http://www.disney.com/muppets/catalog
*/
@Path("/catalog")
public class MuppetCatalogController {

@GET
public String findAllCatalogItems() {
String list = ... // Compile a list of all items.
return list;
}
}

26

JAX-RS (JSR-311)

Reading the catalog
GET …/catalog?muppetId=650
CLIENT SERVER
Properties of Kermit
public void doGet(HttpServletRequest req,
HttpServletResponse resp) throws ... {
int muppetId;
String stringId = req.getParameter("muppetId");
if (stringId != null) {
// Hoping for no exception to occur!
muppetId = Integer.parseInt(stringId);
} else {
muppetId = ... // Use some default value …
}
Muppet muppet = findMuppet(muppetId);
generateTextualOutput(muppet, resp.getWriter());
}
27

JAX-RS (JSR-311)

URI template
CLIENT SERVER
@GET
@Path(“/catalog/{muppetId}”)
public String findItem(@QueryParam(“muppetId”)int muppedId) {
return ...
}

28

JAX-RS (JSR-311)

URI template
CLIENT SERVER
@GET
public String findItem(@DefaultValue(“0”)
@QueryParam(“muppetId”)int muppedId) {
return ...
}

29

JAX-RS (JSR-311)

URI template
GET …/catalog/650
CLIENT SERVER
@GET
public String findItem(@PathParam(“muppetId”)int muppedId) {
// ... Do something
}

30

JAX-RS (JSR-311)

URI template
GET …/catalog/650
CLIENT SERVER
@GET Regular expression
@Path(“/catalog/{muppetId:[0-9]+}”)
// ... Do something
}

31

JAX-RS (JSR-311)

URI template
GET …/catalog/650
CLIENT SERVER
@GET
@Path(“/catalog/{muppetId:[0-9]+}”)
// ... Do something
}

// ACCEPT: http://.../catalog/-477
@GET
@Path(“/catalog/{muppetId:-[0-9]+}”)
public String findItem2(@PathParam(“muppetId”)int muppedId) {
// ... Do something
}

32

JAX-RS (JSR-311)

Cookies, headers and friends …
Internet

http://www.disney.com

Public
SERVER
client

Intranet
GET /muppet/catalog HTTP/1.1
host: crm.intranet http://crm.intranet
accept: text/plain
User-Agent: Mozilla/4.0 (...) Internal
CRM
Cookie: user-type=ADMIN client

Cookie

33

JAX-RS (JSR-311)

Cookies, headers and friends …
@PUT
@Path("/catalog/{muppetId}/{propertyName}")
public void updateItem(
@HeaderParam("host") String hostname,
@CookieParam("user-type") UserType type, ...) {

if (!hostname.equals("crm.intranet")) { throw ... }

if (!UserType.CUSTOMER_CARE.equals(type)) { throw ... }

// ... handle the request.
}

enum UserType { ADMIN, CUSTOMER_CARE, TECHNICAL; }

34

JAX-RS (JSR-311)

@Context
» UriInfo
» Request
» HttpHeaders
» SecurityContext

public void handleRequest(
@Context UriInfo uri,
@Context SecurityContext security,
@QueryParam ("username") String username) { ... }

35

JAX-RS (JSR-311)

Content negotiation (or: cache is always money!)

36

JAX-RS (JSR-311)

CLIENT SERVER

GET http://..../muppets/muppetOfTheMonth/image
+
Content negotiation precondition

RESPONSE:
• 200 (OK) + body
• 304 (Not Modified)

37

JAX-RS (JSR-311)

Content negotiation
@GET
@Path("/muppetOfTheMonth/image")
public Response findMuppetOfTheMonth(
@Context UriInfo uri, @Context Request request) {

File file = locateFile(uri.getRequestUri());
EntityTag tag = calculateTag(file);
Date modified = new Date(file.lastModified());

ResponseBuilder r = request.evaluatePreconditions(modified,
tag);

// ...
}

38

JAX-RS (JSR-311)

The @HEAD method
HEAD …/catalog/650/image
CLIENT SERVER
HTTP/1.1 200 OK
Content-type: text/plain
Content-length: 1024256

39

JAX-RS (JSR-311)

The @HEAD method
@GET
@Path("/catalog/{muppetId}/image")
public Response fetchThumbnailHeadAndBody() {
return ...;
}

@HEAD
@Path("/catalog/{muppetId}/image")
public Response fetchThumbnailHeadOnly(...) {
int size = getThumbnailSize(muppetId);
ResponseBuilder builder = Response.noContent();
builder.header("Content-length", size);
builder.header(“Is-ReadOnly", true);

return builder.build();
{

40

JAX-RS (JSR-311)

Bridging between the two worlds ….

HTTP Java

MessageBodyReader

MessageBodyWriter
The Millau Viaduct bridge, part E11 highway - connecting Paris and Barcelona. The highest bridge ever
constructed.

41

JAX-RS (JSR-311)

Providers:
» Provides adaptation between the “HTTP world” and
our own application domain:
 MessageBodyReader,
 MessageBodyWriter
Java object
HTTP Request
MessageBodyReader
Resource class
MessageBodyWriter
HTTP Response

42

JAX-RS (JSR-311)

@Path("users/{id}/properties")
public class UserPropertiesResource {

@GET
@Produces(“application/json")
public User findUser(@PathParam("id") int userId) {
return userDao.getUser(userId);
{

@GET
@Produces(“application/atom+xml")
public User findUser(@PathParam("id") int userId) { ... }

@POST
public void findUser(User user) {
userDao.persist(user);
}
{

43

JAX-RS (JSR-311)

@Provider
@Path("users/{id}/properties")
@Produces("application/json")
public classclass UserPropertiesResource {
public JSONWriter implements MessageBodyWriter<User> {

@Override@GET
@Produces(“application/json")
public long getSize(User user, ...) {
public User findUser(@PathParam("id") int userId) {
return JSON.toString(user).length();
{ // ...
{
@Override
@POST
public boolean isWriteable(java.lang.Class<?> type, ...) {
return User.class.equals(type);user) {
public void findUser(User
{ // ...
}
{
@Override
public void writeTo(User user, ... OutputStream out) {
JSON.write(user, out);
{

44

JAX-RS (JSR-311)

Leading JAX-RS implementations
» Glassfish Jersey project (Sun Microsystems),
 https://jersey.dev.java.net/
» RESTEasy (JBoss),
 http://www.jboss.org/resteasy/
» Apache CXF (Apache Software Foundation),
 http://cxf.apache.org/
» Wink (ASF incubation project),
 http://incubator.apache.org/wink/
» Restlet (Noelios Technologies).
 http://www.restlet.org/

46

Security

Security
» Authentication
 Who’s calling ?
» Authorization
 What am I allowed to do ?
» Content delivery:
 Integrity,
 Confidentiality,
 Authentication.

48

Security

Security
» Authentication
» Authorization
 Integrity,
 Authentication.

49

Security

Security
» Authentication
» Authorization
 Integrity,
 Authentication.

50

Application-Level Protocols
Marshalling REST data

Content deliver

Suggestions:
» Proprietary (custom made) solution,
» Hessian binary web-service protocol (Caucho),
» Burlap XML-based web-service protocol (Caucho),
» Avro / Buffers protocol,
» JSON (JavaScript Object Notion),
» Protocol Buffers (by Google) ,
» Kyro (only for hard-core programmers)

52

Content deliver

Proprietary (custom made) solution
» When we have a really simple format:
 Short-message strings,
 Single result objects
» Specific binary format,
 Multimedia (Images, Movies, etc…),
 Proprietary protocol.
» Bound to certain technology:
 JAXB, DOM-based (JAXP),
 Java native (binary) serialization.

53

Content deliver

Hessian binary web-service protocol
» Binary, compact format.
» Very lightweight,
 Extremely suitable to mobile or other limited devices.
 Provide J2ME libraries.
» No external IDL or schema,
» Language independent,
» Support for compression, encryption, signatures (with
partial external support).

54

Content deliver

Burlap XML-based web-service protocol
» Minimal XML-based format,
» Very lightweight (considering XML format),
 Provide J2ME libraries.
» No external IDL or schema,
» Language independent (as XML is !),
» Suffice to operate EJB –
 Cell phone -> Burlap -> RESTEasy -> EJB !

55

Content deliver

Avro serialization stack
» Part of Hadoop stack,
» Lightweight, but not as the other protocols.
» Requires schema:
 Pluggable architecture to support multiple formats (JSON,
XML, etc …)
» Dynamic typing (very reach with its support),
» Untagged data.

56

Summary

» REST is a simple WS.
» JAX-RS is a reflection of the HTTP world.
 Using Java-5 annotations only.
» Lack of concrete security model.

57

REST and JAX-RS

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