Dickson K.W. Chiu

1
CSIT600c Web Services Programming Java Web
Services Programming

• Dickson K.W. Chiu
• PhD, SMIEEE
• Deitel et al., Java Web Services for Experienced
  Programmers

2
Java Web Services DevelopmentPack (JWSDP)

• Now integrated into J2EE 1.4
• Provides a convenient all-in-one package
• Geared for developers
• Contains
• JAXP (Java API for XML Processing)
• JAX-RPC (Java API for XML-based RPC)
• SAAJ (SOAP with Attachments API for Java)
• JAXR (Java API for XML Registries)
• JAXM (Java API for XML Messaging)
• See http//java.sun.com/webservices/

3
JAX-RPC and JAXM

• Both based on SOAP with Attachments
• For web service programming
• Sun recommends JAX-RPC easier to program
• SAAJ / JAXM
• Interoperability (e.g. calling other clients)
• Non-blocking option

4
JAX-RPC

• Java API for XML-based RPC
• RPC requests and responses represented using SOAP
  
• Both Web service endpoints and clients use
  JAX-RPC
• Services are described using WSDL
• Key technology for Web Services in the upcoming
  J2EE 1.4 platform

5
Remote Procedure Call (RPC)

• RPC, COM, CORBA, RMI
• Synchronous communication - calling process
  blocks until there is a response
• Tightly coupled - client must find recipients and
  know method arguments
• Non persistent

6
JAX-RPC Design Goal

• Easy to use programming model
• Defining a service
• Using a service
• Hides all the plumbing complexity of SOAP
  messaging
• SOAP and WSDL-based interoperability
• Interoperate with any SOAP compliant peers
• Extensibility and Modularity
• Support future versions of XML specification,
  i.e., XMLP (SOAP 1.2 and beyond)
• Message handler architecture

7
JAX-RPC Architecture Diagram
8
What happen during an RPC?

• To call a remote procedure, the HelloClient
  program invokes a method on a stub, a local
  object that represents the remote service.
• The stub invokes routines in the JAX-RPC runtime
  system.
• The runtime system converts the remote method
  call into a SOAP message and then transmits the
  message as an HTTP request.
• When the server receives the HTTP request, the
  JAX-RPC runtime system extracts the SOAP message
  from the request and translates it into a method
  call.
• The JAX-RPC runtime system invokes the method on
  the tie object.
• The tie object invokes the method on the
  implementation of the HelloWorld service.
• The runtime system on the server converts the
  method's response into a SOAP message and then
  transmits the message back to the client as an
  HTTP response.
• On the client, the JAX-RPC runtime system
  extracts the SOAP message from the HTTP response
  and then translates it into a method response for
  the HelloClient program.

9
What happen during an RPC?
10
Service Description and WSDL
JAX-RPC describes a Web Service as a
collection of remote interfaces and methods
Tools are used to convert between WSDL documents
and sets of Java remote interfaces
WSDL describes a Web Service as a collection of
ports and operations

• JAX-RPC service endpoint mapped to WSDL service
  description
• WSDL enables export of a JAX-RPC service endpoint
  across heterogeneous environments
• JAX-RPC specifies the standard WSDLlt-gt Java
  mapping
• Mapping between service endpoint interface and
  WSDL definitions
• Binding to specific protocol and transport
• XML lt-gt Java data types

11
WSDL Mapping

• wsdlportType mapped into a Java Interface
  (Service Definition Interface) that extends
  java.rmi.Remote
• wsdloperation mapped into a method of the
  Service definition interface
• wsdlmessage's are mapped into parameters of the
  method
• wsdltype's of wsdlmessage's are mapped into the
  types of the parameters

12
WSDL Mapping Example

• lt!------------------- WSDL Document
  -------------------------------------gt
• ltmessage nameGetLastTradePriceInputgt
• ltpart nametickerSymbol typexsdstring/gt
• lt/messagegt
• ltmessage nameGetLastTradePriceOutput?
• ltpart nameresult typexsdfloat/gt
• lt/messagegt
• ltportType nameStockQuoteProvidergt
• ltoperation nameGetLastTradePrice
  parameterOrdertickerSymbolgt
• ltinput messagetnsGetLastTradePriceInput/gt
• ltoutput messagetnsGetLastTradePriceOutput/gt
• lt/operationgt
• lt/portTypegt
• public interface StockQuoteProvider extends
  java.rmi.Remote
• float getLastTradePrice(String tickerSymbol)
• throws java.rmi.RemoteException

13
Supported Java Type

• See J2EE tutorial
• Note all objects are passed by copy
• Java primitive types
• String, Date, Calendar, BigInteger, BigDecimal
• Multi-dimensional Java arrays
• JAX-RPC value type classes youve written for
  your applications, based on the above
• JavaBean Components also based on the above

14
Developing a JAX-RPC Web Service

1. Define service endpoint
2. Implement Service endpoint
3. Compile code and generate WSDL
4. Packaging WAR and deploy

15
0. Setting the Port

• If you do not use the default port 8080, edit
• ltINSTALLgt/j2eetutorial14/examples/common/build.pro
  perties
• ltINSTALLgt/j2eetutorial14/examples/jaxrpc/staticstu
  b/config-wsdl.xml
• ltINSTALLgt/j2eetutorial14/examples/jaxrpc/dynamicp
  roxy/config-wsdl.xml
• ltINSTALLgt/j2eetutorial14/examples/jaxrpc/appclient
  /config-wsdl.xml
• ltINSTALLgt/j2eetutorial14/examples/jaxrpc/webclient
  /config-wsdl.xml
• ltINSTALLgt/j2eetutorial14/examples/jaxrpc/webclien
  t/web/response.jsp
• ltINSTALLgt/j2eetutorial14/examples/security/basica
  uthclient/SecureHello.wsdl
• ltINSTALLgt/j2eetutorial14/examples/security/mutual
  authclient/SecureHello.wsdl

16
1. Service Endpoint Definition

• Specified in Service Definition Interface
• Could be generated from WSDL document using a
  tool or
• Could be written in Java programming language
  directly
• No assumption about type of client that would use
  this service definition interface
• package hello
• import java.rmi.Remote
• import java.rmi.RemoteException
• public interface HelloIF extends Remote
• public String sayHello(String s) throws
  RemoteException

17
2. Service Implementation

• Service implementation class is an ordinary Java
  class
• Invocation done inside the servlet container
• JAX-RPC defines Servlet-based Endpoint model
• Other endpoint models (e.g., stateless session
  beans) will be defined in J2EE 1.4 / EJB 2.1
• Optional ServiceLifecycle interface for
  initialization and destruction callbacks
• package hello
• public class HelloImpl implements HelloIF
• public String message new String("Hello ")
• public String sayHello(String s)
• return new String(message s)

package hello import java.rmi.Remote import
java.rmi.RemoteException public interface
HelloIF extends Remote public String
sayHello(String s) throws RemoteException
18
3. Compiling / WSDL generation

• Use the ant tool simplifies the job
• Compile HelloIF.java and HelloImpl.java, go to
  the ltINSTALLgt/j2eetutorial14/examples/jaxrpc/hello
  service/ directory and type the following ant
  build
• compile-service compiles HelloIF.java and
  HelloImpl.java, writing the class files to the
  build subdirectory
• generate-wsdl runs wscompile, creating
  MyHelloService.wsdl and mapping.xml
• Customize wsdl generation with config-interface.xm
  l
• lt?xml version"1.0" encoding"UTF-8"?gt
• ltconfiguration xmlns"http//java.sun.com/xml/ns/j
  ax-rpc/ri/config"gt
• ltservice name"MyHelloService"
  targetNamespace"urnFoo"
• typeNamespace"urnFoo" packageName"hellose
  rvice"gt
• ltinterface name"helloservice.HelloIF"/gt
• lt/servicegt
• lt/configurationgt

19
4. Packaging the WAR file (i)

• Use Deploytool to create a standalone WAR module

20
4. Packaging the WAR file (ii)

• Use Deploytool to create a standalone WAR module

21
4. Packaging the WAR file (iii)

• Enter context root
• Add alias hello
• Update the endpoint address to hello (see
  previous slide)
• Save and Deploy

22
4. Another way to deploy the WAR file

• To create the WAR file that contains the service
  code
• asant create-war
• Set your admin port, username, and password in
  ltINSTALLgt/j2eetutorial14/examples/common/build.pro
  perties.
• To deploy the WAR file
• asant deploy-war
• Note this may create different
• naming

23
JAX-RPC Clients

• Independent of how an XML based RPC service
  (service endpoint) is implemented on the server
  side
• Generates a Java based client side representation
  for a service from WSDL document
• Not tied to a specific XML based protocol,
  transport or any JAX-RPC implementation specific
  mechanism
• Can use either J2SE or J2EE
• 3 programming modes
• Static stub-based least dynamic, easiest to
  program - you know everything about the services
  and pre-generate the stub
• Dynamic proxy - call location dynamic
  (URL/service/name), information about the service
  by looking up WSDL document at run time (but
  signature of method fixed)
• Dynamic invocation interface (DII) everything
  dynamic, but more tedious and more time to set up
  a call

24
WSDL Generated

• lt?xml version"1.0" encoding"UTF-8"?gt
• ltdefinitions name"MyHelloService"
  targetNamespace"urnFoo" xmlnstns"urnFoo"
  xmlns"http//schemas.xmlsoap.org/wsdl/"
  xmlnsxsd"http//www.w3.org/2001/XMLSchema"
  xmlnssoap"http//schemas.xmlsoap.org/wsdl/soap/"
  gt
• lttypes/gt
• ltmessage name"HelloIF_sayHello"gt
• ltpart name"String_1" type"xsdstring"/gtlt/mes
  sagegt
• ltmessage name"HelloIF_sayHelloResponse"gt
• ltpart name"result" type"xsdstring"/gtlt/messa
  gegt
• ltportType name"HelloIF"gt
• ltoperation name"sayHello" parameterOrder"Str
  ing_1"gt
• ltinput message"tnsHelloIF_sayHello"/gt
• ltoutput message"tnsHelloIF_sayHelloRespons
  e"/gtlt/operationgtlt/portTypegt
• ltbinding name"HelloIFBinding"
  type"tnsHelloIF"gt
• ltsoapbinding transport"http//schemas.xmlsoa
  p.org/soap/http" style"rpc"/gt
• ltoperation name"sayHello"gt
• ltsoapoperation soapAction""/gt
• ltinputgt
• ltsoapbody encodingStyle"http//schemas.x
  mlsoap.org/soap/encoding/" use"encoded"
  namespace"urnFoo"/gtlt/inputgt
• ltoutputgt
• ltsoapbody encodingStyle"http//schemas.x
  mlsoap.org/soap/encoding/" use"encoded"
  namespace"urnFoo"/gtlt/outputgtlt/operationgtlt/bindin
  ggt

25
WSDL Mapping - binding, port, service

• wsdlservice is mapped into an implementation of
  javax.xml.rpc.Service interface
• JAX-RPC runtime provides the implementation
• A javax.xml.rpc.Service class acts as a factory
  of either
• Instance of a generated stub class
• Dynamic proxy for a service port
• Instance of the object javax.xml.rpc.Call for the
  dynamic invocation of a remote operation on a
  service port

26
Static Stub - Client Code

• package staticstub
• import javax.xml.rpc.Stub
• public class HelloClient
• private String endpointAddress
• public static void main(String args)
• System.out.println("Endpoint address "
  args0)
• try
• Stub stub (Stub) (new
  MyHelloService_Impl().getHelloIFPort())
• stub._setProperty(javax.xml.rpc.Stub.E
  NDPOINT_ADDRESS_PROPERTY, args0)
• HelloIF hello (HelloIF) stub
• System.out.println(hello.sayHello("Duk
  e!"))
• catch (Exception ex)
• ex.printStackTrace()
• // output Hello Duke!

Generated by wscompile before writing this
program (i.e., static and implementation-specific)
27
Static Stub build and run

• To automate the rest of the steps, go to the
  ltINSTALLgt/j2eetutorial14/examples/jaxrpc/staticstu
  b/ directory and type the following asant build
• generate-stubs wscompile -genclient -d build
  -classpath build config-wsdl.xml
• ltconfiguration xmlns"http//java.sun.com/xml/ns/
  jax-rpc/ri/config"gt   
• ltwsdl location"http//localhost8080/hello-ja
  xrpc/hello?WSDL
• packageName"staticstub"/gt
• lt/configurationgt
• compile-client compiles src/HelloClient.java and
  writes the class file to the build subdirectory.
• package-client packages the files created by the
  generate-stubs and compile-client tasks into the
  dist/client.jar file.
• Run the client - asant run

28
Dynamic Proxy-based Client

• Client calls a remote procedure through a dynamic
  proxy
• Client gets information about the service by
  looking up its WSDL document at runtime - call
  location (URL/service/name)
• But the signature (parameters and their types) of
  the method is fixed
• The Service class that is created during runtime
• Similar usage of asant
• However, only the service endpoint interface
  class of the sample target is used but not the
  generated stub

29
Example Dynamic Proxy-based Client

• package dynamicproxy
• import java.net.URL
• import javax.xml.rpc.Service
• import javax.xml.rpc.JAXRPCException
• import javax.xml.namespace.QName
• import javax.xml.rpc.ServiceFactory
• import dynamicproxy.HelloIF
• public class HelloClient
• public static void main(String args)
• try
• String UrlString args0 "?WSDL"
• String nameSpaceUri "urnFoo"
• String serviceName
  "MyHelloService"
• String portName "HelloIFPort"
• System.out.println("UrlString "
  UrlString)

• ServiceFactory serviceFactory
  ServiceFactory.newInstance()
• Service helloService
• serviceFactory.createService(hello
  WsdlUrl,
• new QName(nameSpaceUri,
  serviceName))
• dynamicproxy.HelloIF myProxy
• (dynamicproxy.HelloIF)
  helloService.getPort
• (new QName(nameSpaceUri,portName),
• dynamicproxy.HelloIF.class)
• System.out.println(myProxy.sayHello(B
  uzz))
• catch (Exception ex)
• ex.printStackTrace()

30
Dynamic Invocation Interface (DII) Client

• Dynamic invocation of an operation on the target
  service endpoint
• Enables broker model
• Client finds (through search criteria) from a
  UDDI directory and invokes a service during
  runtime through a broker
• Note the code in the following example does not
  show the lookup and simply hardcode the services
  in strings
• Used when service definition interface is not
  known until runtime
• Set all operation and parameters during runtime
• From the Service object create Call object first
• Similar usage of asant

31
DII Client Example

• package dii
• import javax.xml.rpc.Call
• import javax.xml.rpc.Service
• import javax.xml.rpc.JAXRPCException
• import javax.xml.namespace.QName
• import javax.xml.rpc.ServiceFactory
• import javax.xml.rpc.ParameterMode
• public class HelloClient
• private static String qnameService
  "MyHelloService"
• private static String qnamePort "HelloIF"
• private static String BODY_NAMESPACE_VALUE
  "urnFoo"
• private static String ENCODING_STYLE_PROPERTY
  
• "javax.xml.rpc.encodingstyle.namespace.uri
  "
• private static String NS_XSD
  "http//www.w3.org/2001/XMLSchema"
• private static String URI_ENCODING
• "http//schemas.xmlsoap.org/soap/encoding/
  "
• public static void main(String args)

• ServiceFactory factory
  ServiceFactory.newInstance()
• Service service factory.createServic
  e(new QName(qnameService))
• QName port new QName(qnamePort)
• Call call service.createCall(port)
• call.setTargetEndpointAddress(args0)
  
• call.setProperty(Call.SOAPACTION_USE_P
  ROPERTY, new Boolean(true))
• call.setProperty(Call.SOAPACTION_URI_P
  ROPERTY, "")
• call.setProperty(ENCODING_STYLE_PROPER
  TY, URI_ENCODING)
• QName QNAME_TYPE_STRING new
  QName(NS_XSD, "string")
• call.setReturnType(QNAME_TYPE_STRING)
  
• call.setOperationName(new
  QName(BODY_NAMESPACE_VALUE, "sayHello"))
• call.addParameter(String_1,
  QNAME_TYPE_STRING,
• ParameterMode.IN)
• String params "Murph!"
• String result (String)
  call.invoke(params)
• System.out.println(result)
• catch (Exception ex)
• ex.printStackTrace()

32
JAXM

• Java API for XML Messaging
• Java support for sending and receiving SOAP XML
  document oriented messages
• Two JAXM API Programming Models
• Point-to-point model simpler
• JAXM Provider-based" (like a "messaging server")
  model - supports Asynchronous messaging
• Design Goals
• Build on SOAP with Attachments
• Add support to plug higher-level messaging
  protocols (e.g., ebXML)
• Design for easy porting of applications from one
  container to another specifically from web
  containers to that of J2EE
• Dont attempt to build a full-fledged messaging
  API (e.g., JMS)

33
JAXM Point-to-Point Model

• Synchronous Request-response interaction
• Calling process blocks until there is a response
• Connection established directly to the ultimate
  recipient
• No persistence
• can be difficult to scale

34
JAXM Provider Model

• Asynchronous (or Synchronous you choose)
• Sender is not blocked, Receiver does not have to
  be available
• Reliable - Message can be stored and forwarded
  (routed) until it can be delivered
• JAXM Provider works behind the scene

35
JAXM Provider

• Offers message routing and reliable messaging as
  all messages go through it
• Assign message identifiers and keeping track of
  messages
• JAXM client makes JAXM method calls, and the
  provider (working with container) makes
  everything happen
• JAXM providers are responsible for producing an
  error message and sending it to the offending
  JAXM client when receiving a malformed message
• Responsibility of JAXM application to consume
  error messages and take corrective actions

36
JAXM client

• Not using JAXM provider
• Just a standalone J2SE application
• Point to point operation
• Establishes a connection directly with the
  service (using a URL)
• Synchronous only
• Request/response interaction

• Using JAXM provider
• Maintains a connection with JAXM provider, and
  all messages go through the provider
• JAXM client deployed in a web or EJB container
• MessageDrivenBean
• JAXMServlet
• Send and receive messages synchronously or
  asynchronously

37
JAXM vs. JMS

• Similarities
• Both supports Messaging Provider model
• Reliable, secure message delivery
• Routing
• Both supports asynchronous message delivery

• Differences
• JAXM provider could be lightweight while JMS
  provider is usually heavyweight
• JAXM supports standalone mode while JMS does not
• JAXM client is interoperable over any SOAP
  compatible client while JMS client is
  interoperable only with other JMS client over the
  same messaging system
• Delivery endpoint model is different

38
Using SAAJ API to call a Web Service

• Steps
• Create SOAP message
• Populate SOAP message
• Add attachments (optional)
• Initialize SOAP connection
• Send SOAP message
• Analyze response message
• Code based on J2EE tutorial p.398 request.java
• Library files required
• H/Sun/Appserver/lib/j2ee.jarH/Sun/Appserver/li
  b/saaj-impl.jarH\Sun\AppServer\lib\endorsed\xerc
  esImpl.jarH\Sun\AppServer\lib\endorsed\dom.jar.
  
• Example based on URL
• http//www.mindreef.net/tide/scopeit/start.do?refe
  rerxmethodsurlhttp//services.xmethods.net/soap
  /urnxmethods-delayed-quotes.wsdl

39
SAAJ Example Code

• import javax.xml.soap.
• import java.util.
• import java.net.URL
• public class Request
• public static void main(String args)
• try
• SOAPConnectionFactory soapConnectionFactory
  SOAPConnectionFactory.newInstance()
• SOAPConnection connection
  soapConnectionFactory.createConnection()
• SOAPFactory soapFactory
  SOAPFactory.newInstance()
• MessageFactory factory
  MessageFactory.newInstance()
• SOAPMessage message factory.createMessage(
  )
• SOAPHeader header message.getSOAPHeader()
  
• SOAPBody body message.getSOAPBody()
• header.detachNode()

40
SAAJ Example Code (2)

• Name bodyName soapFactory.createName(
  "getQuote", "m",
• "urnxmethods-delayed-quotes")
• SOAPBodyElement bodyElement
  body.addBodyElement(bodyName)
• Name name soapFactory.createName("symbol")
  
• SOAPElement symbol bodyElement.addChildEle
  ment(name)
• symbol.addTextNode(args0)
• URL endpoint new URL("http//64.124.140.30
  9090/soap")
• SOAPMessage response connection.call(messa
  ge, endpoint)
• connection.close()
• response.writeTo(System.out)
• catch (Exception ex)
• ex.printStackTrace()

• ltSOAP-ENVEnvelope xmlnsSOAP-ENV
• "http//schemas.xmlsoap.org/soap/envelope/"gt
• ltSOAP-ENVBodygt
• ltmgetQuote xmlnsm" urnxmethods-delayed-quotes
  "gt
• ltsymbolgtXXXXlt/symbolgt
• lt/mgetQuotegt
• lt/SOAP-ENVBodygt
• lt/SOAP-ENVEnvelopegt

41
SAAJ Result Message

• ltsoapEnvelope
• soapencodingStyle"http//schemas.xmlsoap.org/so
  ap/encoding/"
• xmlnssoap"http//schemas.xmlsoap.org/soap/envel
  ope/" xmlnsxsi"http//www.w3.org/2001/XMLSchema-
  instance" xmlnsxsd"http//www.w3.org/2001/XMLSch
  ema" xmlnssoapenc"http//schemas.xmlsoap.org/soa
  p/encoding/"gt
• ltsoapBodygt
• ltngetQuoteResponse xmlnsn"urnxmethods-dela
  yed-quotes"gt
• ltResult xsitype"xsdfloat"gt4.15lt/Resultgt
• lt/ngetQuoteResponsegt
• lt/soapBodygt
• lt/soapEnvelopegt

42
Adding Attachment with SAAJ

• // We're using a HTTP image repository here
• // to get the data for an image
• URL url new URL ("http//images.wombats.com/w.jp
  g")
• // Create a JAF DataHandler with this URL
• DataHandler dh new DataHandler(url)
• // Create and Add an AttachmentPart
• message.addAttachmentPart(
• message.createAttachmentPart(dh))

43
Summary Calling Web Services in Java

• Use JAX-RPC
• Static Stub you know everything about the
  services and pre-generate the stub
• Dynamic Proxy call location dynamic
  (URL/service/name), information about the service
  by looking up WSDL document at run time (but
  signature of method fixed)
• DII everything lookup at run time, i.e., call
  and parameters prepared at runtime
• Send SOAP messages with SAAJ
• for most flexibility
• target is not RPC