Multi Client Development with Spring

Multi Client Development with Spring MVC
@ Java2Days
Josh Long
Spring Developer Advocate
SpringSource, a Division of VMware
http://www.joshlong.com || @starbuxman || josh.long@springsource.com

© 2009 VMware Inc. All rights reserved

About Josh Long

twitter: @starbuxman
josh.long@springsource.com

2

About Josh Long

twitter: @starbuxman
josh.long@springsource.com

Contributor To:

•Spring Integration
•Spring Batch
•Spring Hadoop
•Activiti Workflow Engine
•Akka Actor engine

3

Why Are We Here?

“ Software entities (classes,
modules, functions, etc.) should
be open for extension, but closed
for modification.
”
-Bob Martin

4

Why Are We Here?

do NOT reinvent
the Wheel!

5

Spring’s aim:
bring simplicity to java development
data
web tier
batch integration & access
& service tier mobile
processing messaging / NoSQL /
RIA
Big Data

The Spring framework
the cloud: lightweight traditional
CloudFoundry WebSphere
tc Server
Google App Engine JBoss AS
Tomcat
Amazon BeanStalk WebLogic
Jetty
Others (on legacy versions, too!)

6

Not All Sides Are Equal

7

Spring Web Support

8

New in 3.1: XML-free web applications

 In a servlet 3 container, you can also use Java configuration,
negating the need for web.xml:

public class SampleWebApplicationInitializer implements WebApplicationInitializer {

public void onStartup(ServletContext sc) throws ServletException {

AnnotationConﬁgWebApplicationContext ac =
new AnnotationConﬁgWebApplicationContext();
ac.setServletContext(sc);
ac.scan( “a.package.full.of.services”, “a.package.full.of.controllers” );

sc.addServlet("spring", new DispatcherServlet(webContext));

}
}

9

Thin, Thick, Web, Mobile and Rich Clients: Web Core

 Spring Dispatcher Servlet
• Objects don’t have to be web-specific.
• Spring web supports lower-level web machinery: ‘
• HttpRequestHandler (supports remoting: Caucho, Resin, JAX RPC)
• DelegatingFilterProxy.
• HandlerInterceptor wraps requests to HttpRequestHandlers
• ServletWrappingController lets you force requests to a servlet through the Spring Handler chain
• OncePerRequestFilter ensures that an action only occurs once, no matter how many filters are
applied. Provides a nice way to avoid duplicate filters
• Spring provides access to the Spring application context using
WebApplicationContextUtils, which has a static method to look up the context, even in
environments where Spring isn’t managing the web components

Thin, Thick, Web, Mobile and Rich Clients: Web Core

 Spring provides the easiest way to integrate with your web
framework of choice
• Spring Faces for JSF 1 and 2
• Struts support for Struts 1
• Tapestry, Struts 2, Stripes, Wicket, Vaadin, Play framework, etc.
• GWT, Flex

Thin, Thick, Web, Mobile and Rich Clients: Spring MVC

12

The Anatomy of a Spring MVC @Controller
Spring MVC configuration - config

@Controller
public class CustomerController {

}

13


@Controller

@RequestMapping(value=”/url/of/my/resource”)
public String processTheRequest() {
// ...
return “home”;
}

}

GET http://127.0.0.1:8080/url/of/my/resource

14


@Controller

@RequestMapping(value=”/url/of/my/resource”,
method = RequestMethod.GET)
public String processTheRequest() {
// ...
return “home”;
}

}


15


@Controller

public String processTheRequest( HttpServletRequest request) {
String contextPath = request.getContextPath();
// ...
return “home”;
}

}


16


@Controller

public String processTheRequest( @RequestParam(“search”) String searchQuery ) {
// ...
return “home”;
}

}

GET http://127.0.0.1:8080/url/of/my/resource?search=Spring

17


@Controller

@RequestMapping(value=”/url/of/my/{id}”,
public String processTheRequest( @PathVariable(“id”) Long id) {
// ...
return “home”;
}

}

GET http://127.0.0.1:8080/url/of/my/2322

18


@Controller

@RequestMapping(value=”/url/of/my/{id}” )
public String processTheRequest( @PathVariable(“id”) Long customerId,
Model model ) {
model.addAttribute(“customer”, service.getCustomerById( customerId ) );
return “home”;
}

@Autowired CustomerService service;

}

GET http://127.0.0.1:8080/url/of/my/232

19


@Controller

public String processTheRequest( HttpServletRequest request, Model model) {
return “home”;
}

}

20


@Controller

public View processTheRequest( HttpServletRequest request, Model model) {
return new XsltView(...);
}

}

21


@Controller

public InputStream processTheRequest( HttpServletRequest request, Model model) {
return new FileInputStream( ...) ;
}

}

22

DEMO
 Demos
• Simple Spring MVC based Application

Not confidential. Tell everyone.

the new hotness...

24

dumb terminals ruled the earth....

25

then something magical happened: the web

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but the web didn’t know how to do UI state... so we hacked...

27

....then the web stopped sucking

28

How Powerful is JavaScript? ...It Boots Linux!!

29

Thin, Thick, Web, Mobile and Rich Clients: REST

 Origin
• The term Representational State Transfer was introduced and defined in 2000 by Roy
Fielding in his doctoral dissertation.
 His paper suggests these four design principles:
• Use HTTP methods explicitly.
• POST, GET, PUT, DELETE
• CRUD operations can be mapped to these existing methods
• Be stateless.
• State dependencies limit or restrict scalability
• Expose directory structure-like URIs.
• URI’s should be easily understood
• Transfer XML, JavaScript Object Notation (JSON), or both.
• Use XML or JSON to represent data objects or attributes

CONFIDENTIAL
31

REST on the Server

 Spring MVC is basis for REST support
• Spring’s server side REST support is based on the standard controller model
 JavaScript and HTML5 can consume JSON-data payloads

REST on the Client

 RestTemplate
• provides dead simple, idiomatic RESTful services consumption
• can use Spring OXM, too.
• Spring Integration and Spring Social both build on the RestTemplate where possible.
 Spring supports numerous converters out of the box
• JAXB
• JSON (Jackson)

Building clients for your RESTful services: RestTemplate

 Google search example
RestTemplate restTemplate = new RestTemplate();
String url = "https://ajax.googleapis.com/ajax/services/search/web?v=1.0&q={query}";
String result = restTemplate.getForObject(url, String.class, "SpringSource");

 Multiple parameters
RestTemplate restTemplate = new RestTemplate();
String url = "http://example.com/hotels/{hotel}/bookings/{booking}";
String result = restTemplate.getForObject(url, String.class, "42", “21”);

CONFIDENTIAL
34

Thin, Thick, Web, Mobile and Rich Clients: RestTemplate

 RestTemplate class is the heart the client-side story
• Entry points for the six main HTTP methods
• DELETE - delete(...)
• GET - getForObject(...)
• HEAD - headForHeaders(...)
• OPTIONS - optionsForAllow(...)
• POST - postForLocation(...)
• PUT - put(...)
• any HTTP operation - exchange(...) and execute(...)

CONFIDENTIAL
35


@Controller

public @ResponseBody Customer processTheRequest( ... ) {
Customer c = service.getCustomerById( id) ;
return c;
}

@Autowired CustomerService service;

}

36


@Controller

@RequestMapping(value=”/url/of/my/someurl”,
method = RequestMethod.POST)
public String processTheRequest( @RequestBody Customer postedCustomerObject) {
// ...
return “home”;
}

}

POST http://127.0.0.1:8080/url/of/my/someurl

37


@Controller

@RequestMapping(value=”/url/of/my/{id}”,
method = RequestMethod.POST)
public String processTheRequest( @PathVariable(“id”) Long customerId,
@RequestBody Customer postedCustomerObject) {
// ...
return “home”;
}

}

POST http://127.0.0.1:8080/url/of/my/someurl

38

What About the Browsers, Man?

• Problem: modern browsers only speak GET and POST
• Solution: use Spring’s HiddenHttpMethodFilter only then send _method request
parameter in the request

<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>

DEMO
 Demos:
• Spring REST service
• Spring REST client


Thin, Thick, Web, Mobile and Rich Clients: Mobile

 Best strategy? Develop Native
• Fallback to client-optimized web applications
 Spring MVC 3.1 mobile client-specific content negotiation and
rendering
• for other devices
• (there are other devices besides Android??)

42

DEMO
 Demos:
• Mobile clients using client specific rendering



 Spring REST is ideal for mobile devices
 Spring MVC 3.1 mobile client-specific content
negotiation and rendering
• for other devices
 Spring Android
• RestTemplate

45


CustomerServiceClient - client

! private <T> T extractResponse( ResponseEntity<T> response) {
! ! if (response != null && response().value() == 200) {
! ! ! return response.getBody();
! ! }
! ! throw new RuntimeException("couldn't extract response.");
! }

! @Override
! public Customer updateCustomer(long id, String fn, String ln) {
! ! String urlForPath = urlForPath("customer/{customerId}");!!
! ! return extractResponse(this.restTemplate.postForEntity(
urlForPath, new Customer(id, fn, ln), Customer.class, id));
! }

47


 Demos:
• consuming the Spring REST service from Android

And The REST of it

• Spring Data REST - exposes (JPA, MongoDB, GemFire, Neo4J, Redis) repositories built
on Spring Data repositories (See my friend Sergi’s talk!)
• Spring HATEOAS - take your REST-fu to the next level with support for HTTP as the
engine of application state
• Spring Security OAuth - secure RESTful web services using OAuth, the same security
technology that Twitter, Facebook, etc.
• Spring Social - RestTemplate is powerful, but some APIs are overwhelming, and OAuth
client communication can be daunting. Spring Social makes it easier.

@starbuxman | josh.long@springsource.com
http://slideshare.net/joshlong

Questions?

Multi Client Development with Spring

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