REST in Peace with Web services

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REST in Peace with Web services

• Eran Chinthaka (chinthaka_at_apache.org)
• Samisa Abeysinghe (samisa_at_apache.org)
• WSO2 Inc.

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Who We Are

• Eran Chinthaka
• Member Apache Software Foundation
• Lead Developer Apache Axiom, Axis2, Synapse,
  Tungsten
• W3C WS-Addressing working group member
• Senior Software Engineer- WSO2 Inc.
• Samisa Abeysinghe
• Member Apache Software Foundation
• Lead Developer Apache Axis2/C and Axis C
• Software Architect WSO2 Inc.

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Agenda

• What is REST and Web services?
• SOAP vs. REST
• How WSDL 2.0 enables REST?
• How can it be implemented? Axis2 Architecture
• Getting your feet wet with 'code'

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What is REST ...?

• REpresentational State Transfer
• Representational State Transfer is intended to
  evoke an image of how a well-designed Web
  application behaves a network of web pages (a
  virtual state-machine), where the user progresses
  through an application by selecting links (state
  transitions), resulting in the next page
  (representing the next state of the application)
  being transferred to the user and rendered for
  their use. - Roy T. Fielding
• Architectural Style of network systems

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Why is it called REST ?

• Web comprised of resources
• Accessing http//www.wso2.net/products/tungsten
• Representation of the resource is accessed
• Places client application in a state
• Client application changes (transfers)

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REST, a standard?

• An architectural style
• Not a standard
• But uses standards
• http
• url
• xml/html/gif/jpeg, etc media types
• text/xml, text/html, etc MIME types

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SOAP

• SOAP is a messaging protocol
• has three parts
• ltenvelopegt
• ltHeader/gt
• ltBody/gt
• lt/envelopegt
• Body is for payload
• Header is for QoS
• Addressing, Security, RM

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REST vs. SOAP

• REST
• Fixed interface
• URI for GET case
• XML for POST case
• Mostly HTTP Transport
• Lighter bandwidth
• QoS support based on transport
• Suited for lightweight scenarios

• SOAP
• Flexible interface
• POST with SOAP envelope
• Transport agnostic
• Comparatively higher bandwidth
• Wide array of message level QoS options WS-
• Suited for heavyweight scenarios

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REST?

• Our objectives
• Support plain old XML interaction with services
  over POST
• Support HTTP GET bindings for services
• Non-objectives
• Support all of REST

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How WSDL 2.0 Enabled the REST WS Marriage

• WSDL 2.0 HTTP binding enables services to be used
  with GET and POST
• Specify how to take (certain styles of) an XML
  Schema and formulate a GET/POST request out of it

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WSDL 2.0 Rules for HTTP Binding

• binding type should be
  http//www.w3.org/2006/01/wsdl/htt
  p
• Formulating a HTTP message, contents of payload
  defined in MessageReference or InterfaceFault
• Schema should adhere to IRI style

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IRI Style

• An element style defined on the schema of the
  payload
• Rules
• The content model of this element is defined
  using a complex type that contains a sequence
  from XML Schema.
• The sequence MUST only contain elements. It MUST
  NOT contain other structures such as xschoice.
• The sequence MUST contain only local element
  children. These child elements MAY contain the
  nillable attribute.
• The localPart of the element's QName MUST be the
  same as the Interface Operation component's
  name.

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IRI Style

• Rules
• The complex type that defines the body of the
  element or its children elements MUST NOT contain
  any attributes.
• If the children elements of the sequence are
  defined using an XML Schema type, they MUST
  derive from xssimpleType, and MUST NOT be of the
  type or derive from xsQName, xsNOTATION,
  xshexBinary or xsbase64Binary.

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Input and Output Serialization Formats

• Default

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Input and Output Serialization Formats
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Input and Output Serialization Formats

• Allowed Formats

source
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Operation Styles Required
source
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Implementing in Apache Axis2

• Apache Axis2/Java
• Apache Axis2/C
• Understand REST implementation --gt Understand
  Axis2 Architecture ....

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Axis2 Messaging Engine

• Piped view

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Axis2 - Dispatching

• Finding the correct service and operation a
  message is destined to.
• Dispatchers
• RequestURIBasedDispatcher
• AddressingBasedDispatcher
• SOAPActionBasedDispatcher
• SOAPMessageBodyBasedDispatcher

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Axis2 Content Type Handling

• Builders for different content types
• StAXOMBuilder
• StAXSOAPModelBuilder
• MTOMSOAPBuilder

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Marrying REST with Axis2 Receiving REST Requests

• Axis2 engine needs SOAPEnvelope to process a
  message.
• On receiving the message --gt dispatch
• Get schema and check the message, construct
  SOAPBody in accordance with the schema
• Create SOAPEnvelope and pass it to the engine

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Marrying REST with Axis2 Receiving REST Requests

• Engine doesn't know about REST, except a flag
• Works with GET and POST with any content type

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Marrying REST with Axis2 Sending REST Requests

• Client API is the same for SOAP and REST
  requests, except
• a flag to notify its REST
• HTTP method (optional)
• content type (optional)
• TransportSender serializes the proper way

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Getting Your Feet Wet ...

• Sending a SOAP Request ...
• Sending REST Request (minimal config)

Options options new Options() options.setTo(new
EndpointReference(toEpr))
ServiceClient sender new ServiceClient() send
er.setOptions(options) OMElement result
sender.sendReceive(getPayload())
Options options new Options() options.setTo(new
EndpointReference(toEpr)) options.setProperty(C
onstants.Configuration.ENABLE_REST
, Constants.VALUE_TRUE)
ServiceClient sender new ServiceClient() sende
r.setOptions(options) OMElement result
sender.sendReceive(getPayload())
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More Control

• Sending REST Request (optional configuration)
• Setting content type
• Available content types
• MEDIA_TYPE_X_WWW_FORM - application/x-www-form-ur
  lencoded
• MEDIA_TYPE_TEXT_XML - text/xml
• MEDIA_TYPE_MULTIPART_RELATED - multipart/related
• MEDIA_TYPE_APPLICATION_XML - application/xml

options.setProperty(Constants.Configuratio
n.CONTENT_TYPE,
contentType)
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More Control ....

• Sending REST Request (optional configuration)
• Setting HTTP Method
• Available Web Methods
• HTTP_METHOD_GET
• HTTP_METHOD_POST (Default)

options.setProperty(Constants.Configuratio
n.HTTP_METHOD,
webMethod)
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REST Configuration in Axis2 Server Side

• Any service that abides with WSDL 2.0 HTTP
  Binding is REST enabled.

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• I'm a C fan, Can I also REST ?

YES !!!
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Getting Your Feet Wet (again) with C

• Sending a SOAP Request ...

endpoint_ref axis2_endpoint_ref_create(env,
address) options axis2_options_create(env)
AXIS2_OPTIONS_SET_TO(options, env,
endpoint_ref) svc_client axis2_svc_client_creat
e(env, client_home) AXIS2_SVC_CLIENT_SET_OPTI
ONS(svc_client, env, options) ret_node
AXIS2_SVC_CLIENT_SEND_RECEIVE(svc_client, env,
get_payload(env))
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Getting Your Feet Wet (again) with C ...

• Enabling REST at the client side
• AXIS2_OPTIONS_SET_PROPERTY(options, env,
  AXIS2_ENABLE_REST,
  AXIS2_VALUE_TRUE)

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Getting Your Feet Wet ...

• Sending REST Request ...

endpoint_ref axis2_endpoint_ref_create(env,
address) options axis2_options_create(env)
AXIS2_OPTIONS_SET_TO(options, env,
endpoint_ref) AXIS2_OPTIONS_SET_PROPERTY(options,
env, AXIS2_ENABLE_REST, AXIS2_VALUE_TRUE) svc_cl
ient axis2_svc_client_create(env,
client_home) AXIS2_SVC_CLIENT_SET_OPTIONS(svc
_client, env, options) ret_node
AXIS2_SVC_CLIENT_SEND_RECEIVE(svc_client, env,
get_payload(env))
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More Control
AXIS2_OPTIONS_SET_PROPERTY(options, env,
AXIS2_CONTENT_TYPE, content_type) AXIS2_OPTIONS_
SET_PROPERTY(options, env, AXIS2_HTTP_METHOD,
web_method)
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Summary

• What is REST and Web services ?
• SOAP vs. REST
• How WSDL 2.0 enables REST
• How can it be implemented Axis2 Architecture
• Getting your feet wet with code

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Questions ... ?
Download presentation from http//people.apache.
org/chinthaka/presentations/ApacheConEU2006/RES
TInPeaceWithWS.ppt
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Thank You .