Multi Client Development with Spring for SpringOne 2GX 2013 with Roy Clarkson

© 2013 SpringOne 2GX. All rights reserved. Do not distribute without permission.
Building Smart Clients with Spring
by Josh Long and Roy Clarkson

WHAT IS REST?
REST is an architectural constraint based on HTTP 1.1,
and created as part of Roy Fielding’s doctoral
dissertation in 2000.
It embraces HTTP.
It’s a style, not a standard
http://en.wikipedia.org/wiki/Representational_state_transfer

WHAT IS REST?
REST has no hard and fast rules.
REST is an architectural style, not a standard.
REST uses Headers to describe requests & responses
REST embraces HTTP verbs

HTTP VERBS
GET /users/21
GET requests retrieve information.
GET can have side-effects (but it’s unexpected)
GET can be conditional, or partial:
If-Modiﬁed-Since, Range

HTTP VERBS
DELETE requests that a resource be removed, though
the deletion doesn’t have to be immediate.
DELETE /users/21

HTTP VERBS
POST requests that the resource do something with the
enclosed entity
POST can be used to create or update.
POST /users
{ “ﬁrstName”: “Juergen” }

HTTP VERBS
PUT requests that the entity be stored at a URI
PUT can be used to create or update.
PUT /users/21
{ “ﬁrstName”: “Juergen” }

THE MATURITY MODEL
The Richardson Maturity Model is a way to grade your
API according to the REST constraints with 4 levels of
increasing compliance
http://martinfowler.com/articles/richardsonMaturityModel.html

THE MATURITY MODEL
The Richardson Maturity Model
Level 0: swamp of POX
Uses HTTP mainly as a tunnel through one URI
e.g., SOAP, XML-RPC
Usually features on HTTP verb (POST)

THE MATURITY MODEL
Level 1: resources
Multiple URIs to distinguish related nouns
e.g., /articles/1, /articles/2, vs. just /articles

THE MATURITY MODEL
Level 2: HTTP verbs
leverage transport-native properties to enhance service
e.g., HTTP GET and PUT and DELETE and POST
Uses idiomatic HTTP controls like status codes, headers

HTTP VERBS
GET /users/21
DELETE /users/21
POST /users
PUT /users/21
retrieves a resource from a URI
removes the resource
creates a new record; returns a Location
updates a resource
<filter>
<filter-name>hiddenHttpMethodFilter</filter-name>
<filter-class>org.springframework.web.filter.HiddenHttpMethodFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>hiddenHttpMethodFilter</filter-name>
<url-pattern>/</url-pattern>
<servlet-name>appServlet</servlet-name>
</filter-mapping>

STATUS CODES
status codes convey the result of the server’s attempt to
satisfy the request.
Categories:
1xx: informational
2xx: success
3xx: redirection
4xx: client error
5xx: server error

REST 101
200 OK - Everything worked
201 Created - Returns a Location header for new resource
202 Accepted - server has accepted the request, but it is not yet
complete. Status URI optionally conveyed in Location header

REST DESIGN WITH SPRINGREST 101
ACCEPTABLE
406:
NOT

REST 101
400 Bad Request - Malformed Syntax. Retry with change.
401 Unauthorized - authentication is required
403 Forbidden - server has understood, but refuses request
404 Not Found - server can’t find a resource for URI
406 Not Found - incompatible Accept headers specified
409 Conﬂict - resource conflicts with client request

REST 101
Clients and services must agree on a representation media type
through content negotiation.
Client specifies what it wants through Accept header
Server specifies what it produces through Content-Type header

REST 101
Spring MVC supports multiple types of content negotiation through its
ContentNegotiationStrategy:
e.g., Accept header, URL extension, request parameters, or a fixed type

Demonstration
Basic RESTful service, REST shells

HATEOAS
Level 3: Hypermedia Controls (aka, HATEOAS)
No a priori knowledge of service required
Navigation options are provided by service and hypermedia controls
Promotes longevity through a uniform interface

HATEOAS
Links provide possible navigations from a given resource
Links are dynamic, based on resource state.
<link href=“http://...:8080/users/232/customers”
rel= “customers”/>

Demonstration
Spring HATEOAS, Rest Shell

SPRING DATA REST
Spring Data REST simplifies the
generic data-centric @Controllers
Builds on top of Spring Data Repository support:
@RestResource (path = "users", rel = "users")
public interface UserRepository extends PagingAndSortingRepository<User, Long> {
User ﬁndByUsername(@Param ("username") String username);

SPRING DATA REST
User ﬁndByUsername(@Param ("username") String username);

select u from User where u.username = ?

SPRING DATA REST

List<User> findUsersByFirstNameOrLastNameOrUsername(
@Param ("firstName") String firstName,
@Param ("lastName") String lastName,
@Param ("username") String username);
}

SPRING DATA REST

List<User> findUsersByFirstNameOrLastNameOrUsername(
@Param ("firstName") String firstName,
@Param ("lastName") String lastName,
@Param ("username") String username);
}
select u from User u
where u.username = ?
or u.firstName = ?
or u.lastName = ?

Demonstration
Spring Data, Spring Data REST

SECURITY
Security can be as simple, or complex, as you want...
If you can trust the client to keep a secret like a password:
...HTTP Basic if you have TLS
... HTTP Digest if you want extra security

OAUTH
Security can be as simple, or complex, as you want...
Can’t trust the client to keep a secret? (HTML page?)
Application has a user context and you don’t want clients to have a
user’s password?
...use OAuth

Demonstration
Spring Security OAuth

SPRING SOCIAL
Spring Social provides an authentication and
authorization client for OAuth (1.0, 1.0a, 2.0)
Provides type-safe API bindings for various services

SPRING ANDROID
Spring Social provides an authentication and
authorization client for OAuth (1.0, 1.0a, 2.0)
Provides type-safe API bindings for various services

SPRING ANDROID
Spring Android brings Spring core’s RestTemplate.
Spring Social and Spring HATEOAS work as well.

SPRING ANDROID
More than
500,000
activations
every day
More than
500,000
activations
every day

Demonstration
Spring Android-powered UI client

REST DESIGN WITH SPRING
iOS provides an HTTP client (NSURLConnection),
a JSON processor (NSJSONSerialization), and
a rich set of data structures (NSData, NSDictionary, and NSArray)

BASIC HTTP REQUEST
NSURL *url = [NSURL URLWithString:@"http://localhost"];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];
NSData *data = [NSURLConnection sendSynchronousRequest:request
returningResponse:nil
error:nil];

BASIC HTTP REQUEST... IMPROVED
NSURLResponse *response;
NSError *error;
returningResponse:&response
error:&error];
NSInteger status = [(NSHTTPURLResponse *)response statusCode];
if (status == 200 && data.length > 0 && error == nil)
{
// do something with data
}

ASYNCHRONOUS HTTP REQUESTS
[NSURLConnection
sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response,
NSData *data, NSError *error)
{
{
}
}

HTTP HEADERS
NSMutableURLRequest *request =
[[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:@"PUT"];
[request setValue:@"application/json"
forHTTPHeaderField:@"Accept"];
forHTTPHeaderField:@"Content-Type"];
[request setValue:contentLength
forHTTPHeaderField:@"Content-Length"];
[request setHTTPBody:postData];

JSON SERIALIZATION
// deserialize JSON data
NSError *error;
NSDictionary *d = [NSJSONSerialization JSONObjectWithData:data
options:0
error:&error];
// serialize JSON data
NSError *error;
NSData *data = [NSJSONSerialization dataWithJSONObject:dictionary
options:0
error:&error];

• HTTP Client
– NSURLConnection
• JSON Processor (iOS 5)
– NSJSONSerialization
• Data
– NSData
– NSDictionary
– NSArray
49

• Loading Data Synchronously
+ sendSynchronousRequest:returningResponse:error:
• Loading Data Asynchronously
+ sendAsynchronousRequest:queue:completionHandler:
50

51
returningResponse:nil
error:nil];

52
NSURLResponse *response;
NSError *error;
returningResponse:&response
error:&error];
{
}

53
[NSURLConnection
sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response,
NSData *data, NSError *error)
{
{
}
}

54
NSMutableURLRequest *request =
[[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:@"PUT"];
forHTTPHeaderField:@"Accept"];
forHTTPHeaderField:@"Content-Type"];
[request setValue:contentLength
forHTTPHeaderField:@"Content-Length"];
[request setHTTPBody:postData];

55
// deserialize JSON data
NSError *error;
NSDictionary *d = [NSJSONSerialization JSONObjectWithData:data
options:0
error:&error];
// serialize JSON data
NSError *error;
NSData *data = [NSJSONSerialization dataWithJSONObject:dictionary
options:0
error:&error];

• Spring MVC Reference
http://static.springsource.org/spring-framework/docs/current/spring-framework-
reference/html/mvc.html
• URL Loading System Programming Guide
http://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/
URLLoadingSystem/URLLoadingSystem.html
• Ben Hale’s presentation at SpringOne 2GX
http://www.youtube.com/watch?v=wylViAqNiRA
58

• Spring Roo Beginning Guide
http://static.springsource.org/spring-roo/reference/html/
beginning.html#beginning-step-1
59

GREAT RESOURCES
Roy Fielding’s Dissertation introduces REST
http://www.ics.uci.edu/~fielding/pubs/dissertation/evaluation.htm#sec_6_1%7C
The Spring REST Shell
http://github.com/jbrisbin/rest-shell
Spring Security, Security OAuth, Spring Data REST, HATEOAS, Social
http://github.com/SpringSource
Spring MVC Test Framework
http://static.springsource.org/spring-framework/docs/current/spring-framework-reference/
html/testing.html#spring-mvc-test-framework

GREAT RESOURCES
Oliver Gierke’s talk on Hypermedia from Øredev
@ http://vimeo.com/53214577
Lez Hazelwood’s talk on designing a beautiful JSON+REST API
Ben Hale’s talk on REST API design with Spring from SpringOne2GX 2012
@ http://www.youtube.com/watch?v=wylViAqNiRA
My links:
github.com/joshlong/the-spring-rest-stack
slideshare.net/joshlong/rest-apis-with-spring
@starbuxman

REST DESIGN WITH SPRING
Any
Questions?
@starbuxman | jlong@gopivotal.com | http://slideshare.net/joshlong
@royclarkson | rclarkson@gopivotal.com |http://www.slideshare.net/royclarkson
github.com/joshlong/the-spring-rest-stack

Multi Client Development with Spring for SpringOne 2GX 2013 with Roy Clarkson

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Multi Client Development with Spring for SpringOne 2GX 2013 with Roy Clarkson