J2EE 1.4 APIs For Web Services

1
J2EE 1.4 APIs For Web Services

• Michael D. Thomas
• mdthomas_at_ibiblio.org

2
Agenda

• Quick Tour Of J2EE APIs
• Service Oriented Architecture
• SOAP WSDL The 10 minute guide
• JAX-RPC
• SAAJ
• JAXP
• JAXR

3
A Simple Example

• Company has web app that looks up invoices
• The customers like it
• Customer wants to pass the data automatically to
  another application
• Typical situation for a web service
• Will do it with
• Straight XML (JAXP)
• SAAJ Wrapper around SOAP and HTTP
• JAX-RPC Uses SOAP and WSDL, but you never have
  to see it

4
Invoice Screen
5
Invoice App Structure
6
Invoice JSP

• lthtmlgt
• ltheadgt
• lttitlegtInvoicelt/titlegt
• lt/headgt
• ltbody bgcolor"white"gt
• lt_at_ page language"java"
• import"org.ibiblio.mdthomas.ws.autopart
  ssupplier." gt
• ltjspuseBean id"invoiceHelper"
• scope"request"
• class"org.ibiblio.mdthomas.ws.autopartssuppli
  er.InvoiceHelper"/gt
• ltjspsetProperty nameinvoiceHelper
• property/gt
• lt
• InvoiceBean invoice invoiceHelper.getInvoiceByI
  d()
• CustomerBean customer invoice.getCustomer()
• InvoiceItemBean items invoice.getInvoiceItems
  ()
• gt
• Continued . . . .

7
Invoice JSP

• lt for (int i0 iltitems.lengthi) gt
• lttrgt
• lttdgtlt itemsi.getName() gtlt/tdgt
• lttdgtlt itemsi.getProductId() gtlt/tdgt
• lttdgtlt itemsi.getQuantity() gtlt/tdgt
• lttd align"right"gt
• lt itemsi.getPerItemPrice() gt
• lt/tdgt
• lttd align"right"gt
• lt itemsi.getTotalLineItemPrice() gt
• lt/tdgt
• lt/trgt
• lt gt
• Continued . . . .

8
Invoice Helper

• package org.ibiblio.mdthomas.ws.autopartssupplier
  
• import java.rmi.Remote
• import java.rmi.RemoteException
• public class InvoiceHelper
• long id
• InvoiceBusinessDelegate invoiceBusinessDelegate
  
• public InvoiceHelper ()
• invoiceBusinessDelegate
• BusinessDelegateFactory.getInvoiceBusinessDele
  gate()
• public void setInvoiceId (long id)
• this.id id
• public long getInvoiceId()
• return id
• public InvoiceBean getInvoiceById()
• return invoiceBusinessDelegate.getInvoiceById(
  this.id)

9
InvoiceBean (incomplete)

• package org.ibiblio.mdthomas.ws.autopartssupplier
  
• public class InvoiceBean implements Serializable
  
• private CustomerBean customer
• private InvoiceItemBean invoiceItems
• private long invoiceId
• private float total
• private float shippingCharge
• private float subTotal
• public InvoiceBean()
• public float getTotal()
• return total
• public void setTotal(float total)
• this.total total
• public void setCustomer(CustomerBean customer)
  
• this.customer customer
• public CustomerBean getCustomer()
  
• return customer
  

10
New XML Architecture
11
XML Invoice
12
XML Invoice JSP

• lt?xml version"1.0"?gt
• ltorderinginvoice xmlnsordering"http//www.tinas
  autoparts.com/xmlns/orders"gt
• lt_at_ page language"java" import"org.ibiblio.mdtho
  mas.ws.autopartssupplier." gt
• ltjspuseBean id"invoiceHelper"
• scope"request"
• class"org.ibiblio.mdthomas.ws.autopartssuppl
  ier.InvoiceHelper" /gt
• ltjspsetProperty name"invoiceHelper"
  property""/gt
• lt
• InvoiceBean invoice invoiceHelper.getInvoice
  ById()
• CustomerBean customer invoice.getCustomer()
  
• InvoiceItemBean items invoice.getInvoiceIt
  ems()
• gt
• ltorderinginvoiceIdgt
• lt invoice.getInvoiceId() gt
• lt/orderinginvoiceIdgt
• Continued . . .

13
Web Services Requestor

• public static void main(String args) throws
  Exception
• long invoiceId 0
• if (args.lengthgt0)
• invoiceId Long.parseLong(args0)
• // Create the URL and encode the invoiceId
  param
• String base
• "http//localhost8080/jsp-examples/ch03/in
  voiceAsXml.jsp?"
• String invoiceParam "invoiceId"invoiceId""
  
• URL invoiceURL new URL(baseinvoiceParam)
• // Connect to the URL
• URLConnection conn invoiceURL.openConnection()
  
• conn.connect()
• // Get the result and create the XML
• InputStream invoiceStream conn.getInputStream(
  )
• DocumentBuilderFactory dbf
• DocumentBuilderFactory.newInstance()

14
Web Services Requestor

• private static void handleXML(Document doc)
• float invoiceTotal 0f
• int totalQuantities 0
• float shippingCharge 0f
• Element docRoot doc.getDocumentElement()
  
• NodeList children docRoot.getChildNodes()
• for (int i0iltchildren.getLength()i)
• Node node children.item(i)
• System.out.println("node name
  "node.getNodeName())
• short nodeType node.getNodeType()
• if (node.getNodeName().equals("orderingcustome
  r"))
• Element customerElement (Element)node
• NodeList nodeList
• customerElement.getElementsByTagName("or
  deringcustomerName")
• Element customerNameElem (Element)nodeList.it
  em(0)
• Node customerNameText customerNameElem.getFir
  stChild()
• String customerName customerNameText.ge
  tNodeValue()

15
Basic XML Web Services Issues

• Satisfies the business requirement
• Not standards based doesnt use SOAP or WSDL
• Had to handle HTTP directly

16
SAAJ SOAP Approach

• Uses SOAP standard
• Similar to previous example, but requestor
  handles SOAP details
• SOAP data (Body) and meta-data (Header)
• Contained in a SOAP envelope
• Can attach data outside of the SOAP envelope
• SAAJ handles HTTP requests, wraps JAXP in SOAP
  specific nature (like JDOM)

17
SOAP Request

• POST /invoice-jaxrpc/invoice HTTP/1.1
• Content-Type text/xml charset"utf-8"
• Content-Length 246
• SOAPAction ""
• Cache-Control no-cache
• Pragma no-cache
• User-Agent Java/1.4.2
• Host localhost9090
• Accept text/html, text/xml, image/gif,
  image/jpeg, q.2, / q.2
• Connection keep-alive
• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap/en
  velope/"gt
• ltSOAP-ENVBodygt
• ltgetInvoiceById
• xmlns"http//www.ibiblio.org/mdthomas/invoice/
  types"gt
• ltlong_1 xmlns""gt9845lt/long_1gt
• lt/getInvoiceByIdgt
• lt/SOAP-ENVBodygt

18
SOAP Request

• POST /invoice-jaxrpc/invoice HTTP/1.1
• Content-Type text/xml charset"utf-8"
• Content-Length 246
• SOAPAction ""
• Cache-Control no-cache
• Pragma no-cache
• User-Agent Java/1.4.2
• Host localhost9090
• Accept text/html, text/xml, image/gif,
  image/jpeg, q.2, / q.2
• Connection keep-alive
• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap/en
  velope/"gt
• ltSOAP-ENVBodygt
• ltgetInvoiceById
• xmlns"http//www.ibiblio.org/mdthomas/invoice/
  types"gt
• ltlong_1 xmlns""gt9845lt/long_1gt
• lt/getInvoiceByIdgt
• lt/SOAP-ENVBodygt

19
SOAP Request

• POST /invoice-jaxrpc/invoice HTTP/1.1
• Content-Type text/xml charset"utf-8"
• Content-Length 246
• SOAPAction ""
• Cache-Control no-cache
• Pragma no-cache
• User-Agent Java/1.4.2
• Host localhost9090
• Accept text/html, text/xml, image/gif,
  image/jpeg, q.2, / q.2
• Connection keep-alive
• ltSOAP-ENVEnvelope
• xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap/en
  velope/"gt
• ltSOAP-ENVBodygt
• ltgetInvoiceById
• xmlns"http//www.ibiblio.org/mdthomas/invoice/
  types"gt
• ltlong_1 xmlns""gt9845lt/long_1gt
• lt/getInvoiceByIdgt
• lt/SOAP-ENVBodygt

20
SOAP Response (incomplete)

• HTTP/1.1 200 OK
• X-Powered-By Servlet/2.4
• SOAPAction ""
• Content-Type text/xml charset"utf-8"
• Transfer-Encoding chunked
• Date Sun, 23 Nov 2003 160017 GMT
• Server Sun-Java-System/JWSDP-1.3
• lt?xml version"1.0" encoding"UTF-8"?gt
• ltenvEnvelope xmlnsenv"http//schemas.xmlsoap.or
  g/soap/envelope/" xmlnsxsd"http//www.w3.org/200
  1/XMLSchema" xmlnsxsi"http//www.w3.org/2001/XML
  Schema-instance" xmlnsenc"http//schemas.xmlsoap
  .org/soap/encoding/" xmlnsns0"http//www.ibiblio
  .org/mdthomas/invoice/types"gt
• ltenvBodygt
• ltns0getInvoiceByIdResponsegt
• ltresultgt
• ltcustomergt
• data
• lt/customergt
• ltinvoiceIdgt9845lt/invoiceIdgt
• ltinvoiceItemgt
• data

21
SAAJ Provider

• public class InvoiceSAAJProvider extends
  HttpServlet
• MessageFactory messageFactory
• public void doPost (HttpServletRequest
  request,
• HttpServletResponse
  response)
• throws ServletException,
  IOException
• response.setContentType("text/xml")
• response.setBufferSize(8192)
• OutputStream out response.getOutputStream(
  )
• try
• // initialize the messageFactory
• messageFactory MessageFactory.newInstance()
• // Get the requested invoice
• long invoiceId getInvoiceId(request)
• InvoiceHelper invoiceHelper new
  InvoiceHelper()
• InvoiceBean invoice invoiceHelper.getInvoiceB
  yId(invoiceId)
• // Create the SOAP output message
• SOAPMessage outputMessage createOutputSOAPMes
  sage(invoice)
• // Write the output SOAP message to the
  response output stream

22
SAAJ Provider

• private long getInvoiceId(HttpServletRequest
  request) throws
• SOAPException, IOException
• // create the input SOAP message from the
  request's inputStream
• MimeHeaders mimeHeaders getMimeHeaders(request
  )
• InputStream inputStream request.getInputStream
  ()
• SOAPMessage inputMessage
• messageFactory.createMessage(mimeHeaders,inp
  utStream)
• // get the SOAP body
• SOAPPart inputPart inputMessage.getSOAPPart()
  
• SOAPEnvelope inputEnvelope inputPart.getEnvelo
  pe()
• SOAPBody inputBody inputMessage.getSOAPBody()
  
• // get the invoice id as a String
• Name getInvName inputEnvelope.createName("getI
  nvoiceById",
• null,
• "http//www.ibiblio.org/mdt
  homas/invoice/types")
• Iterator it inputBody.getChildElements(getInvN
  ame)
• SOAPElement getInvoiceElem (SOAPElement)it.nex
  t()
• Name idName inputEnvelope.createName("long_1")
  )

23
Creating output

• private SOAPMessage createOutputSOAPMessage(Invoic
  eBean invoice)
• throws SOAPException
• // Create a message
• SOAPMessage outputMessage messageFactory.creat
  eMessage()
• SOAPPart outputSoapPart outputMessage.getSOAPP
  art()
• SOAPEnvelope outputEnvelope
  outputSoapPart.getEnvelope()
• outputEnvelope.addNamespaceDeclaration("ns0",
• "http//www.ibiblio.org/mdthomas/invoice/
  types")
• // Get the SOAP header from the message and
  remove it
• SOAPHeader header outputMessage.getSOAPHeader(
  )
• header.detachNode()
• // Get the SOAP body from the message
• SOAPBody body outputMessage.getSOAPBody()
• // Add the top level elements
• Name responseName outputEnvelope.createName(
• "getInvoiceByIdRespon
  se",
• "ns0",

// add customer CustomerBean customer
invoice.getCustomer() SOAPElement
customerElem resultElem.addChildElement("custome
r") SOAPElement customerNameElem
customerElem.addChildElement("name")
24
Creating output (incomplete)

• //add invoice items
  
• InvoiceItemBean items invoice.getInvoiceItem
  s()
• for (int i0iltitems.lengthi)
  
• SOAPElement invoiceItemElem
• resultElem.addChildElement("invoiceItems
  ")
• SOAPElement nameElem invoiceItemElem.addChil
  dElement("name")
• String name itemsi.getName()
• nameElem.addTextNode(name)
• SOAPElement perItemPriceElem
• invoiceItemElem.addChildElement("perItemP
  rice")
• float perItemPrice itemsi.getPerItemPrice(
  )
• perItemPriceElem.addTextNode(String.valueOf(pe
  rItemPrice))
• SOAPElement totalLineItemPriceElem
• invoiceItemElem.addChildElement(
  "totalLineItemPrice")
• float totalLineItemPrice itemsi.getTotalLi
  neItemPrice()
• totalLineItemPriceElem.addTextNode(
• String.valueOf(totalLineItemPrice))
  
• SOAPElement quantityElem

25
Creating output (incomplete)

• // save and return
• outputMessage.saveChanges()
  
• return outputMessage

26
SAAJ Requestor

• public static SOAPMessage createSOAPRequest(long
  invoiceId)
• throws SOAPException
• // Create message factory
• MessageFactory messageFactory
  MessageFactory.newInstance()
• // Create a message
• SOAPMessage message messageFactory.createMessa
  ge()
• SOAPPart soapPart message.getSOAPPart()
• SOAPEnvelope envelope soapPart.getEnvelope()

27
SAAJ Requestor

• // Get the SOAP header from the message and
  remove it
• SOAPHeader header message.getSOAPHeader()
• header.detachNode()
• // Get the SOAP body from the message
• SOAPBody soapBody message.getSOAPBody()
• // create the outer invoice element
• Name getInvoiceName
• envelope.createName("getInvoiceById",
• null,
• "http//ibiblio.org/invoice/types")
• SOAPBodyElement getInvoiceElem
• soapBody.addBodyElement(getInvoiceName)
  

28
SAAJ Requestor

• // create the invoice parameter
• Name invoiceIdName envelope.createName("long_
  1",null,"")
• SOAPElement invoiceIdElem
• getInvoiceElem.addChildElement(invoiceIdNam
  e)
• invoiceIdElem.addNamespaceDeclaration("","")
• invoiceIdElem.addTextNode(String.valueOf(invoice
  Id))
• message.saveChanges()
• return message

29
SAAJ Code Problems

• Compliant with SOAP
• Still havent done anything with WSDL
• Lots and lots of XML creation and parsing
• Absolutely no error checking not even simple
  type checking
• Have to handle all interoperability problems

30
JAX-RPC
31
JAX-RPC Service Endpoint Interface

• package org.ibiblio.mdthomas.ws.autopartssupplier
  
• import java.rmi.Remote
• import java.rmi.RemoteException
• public interface InvoiceWebService extends Remote
  
• public InvoiceBean getInvoiceById(long id)
• throws RemoteException

32
JAX-RPC Servant

• public class InvoiceHelper implements
  InvoiceWebService
• // existing code

33
Run the tools

• SEI-to-WSDL tool and WSDL-to-SEI tool are
  required by JAX-RPC specification
• Wscompile and wsdeploy with the Java Web Services
  Development Pack from Sun
• Java2WSDL with Apache Axis

34
Web Service home page
35
Web Service WSDL
36
JAX-RPC Requestor

• public static void main(String args)
• try
• // Get the web service port
• InvoiceWebService_Service wsDef
• new InvoiceWebService_Service_Impl()
  
• InvoiceWebService_PortType stub
• wsDef.getInvoiceWebServicePort()
• // Create the input parameter
• GetInvoiceById idWrapper new
  GetInvoiceById(1000)
• // Make the remote call to the web service
• GetInvoiceByIdResponse invoiceWrapper
  
• stub.getInvoiceById(idWrapper)
• // Unwrap the result
• InvoiceBean invoice invoiceWrapper.getResult()
  
• // Print some data
• CustomerBean customer invoice.getCustomer()
  
• System.out.println("Customer
  "customer.getName())

37
JAX-RPC Requestor

• public static void main(String args)
• try
• // Get the web service port
• InvoiceWebService_Service wsDef
• new InvoiceWebService_Service_Impl()
  
• InvoiceWebService_PortType stub
• wsDef.getInvoiceWebServicePort()
• // Create the input parameter
• GetInvoiceById idWrapper new
  GetInvoiceById(1000)
• // Make the remote call to the web service
• GetInvoiceByIdResponse invoiceWrapper
  
• stub.getInvoiceById(idWrapper)
• // Unwrap the result
• InvoiceBean invoice invoiceWrapper.getResult()
  
• // Print some data
• CustomerBean customer invoice.getCustomer()
  
• System.out.println("Customer
  "customer.getName())

38
.NET C Requestor

• Generate C requestor based on WSDL
• gtwsdl.exe /languageCS /protocolSOAP \
• http//localhost8080/invoice/jaxrpc/invoice?WSDL
• Entry point
• public getInvoiceByIdResponse getInvoiceById(
• System.Xml.Serialization.XmlElementAttribute
  ("getInvoiceById",
• Namespace"http//www.ibiblio.org/mdthomas/in
  voice/types")
• getInvoiceById getInvoiceById1)
• object results this.Invoke("getInvoice
  ById",
• new object getInvoiceById1)
• return ((getInvoiceByIdResponse)(results0
  ))

39
.NET C Requestor

• class JAXClient
• STAThread
• static void Main(string args)
• // Create the stub
• InvoiceWebService service new
  InvoiceWebService()
• // Set the endpoint
• if (args.Length 1)
• service.Url args0
• else
• service.Url "http//localhost8080/invoice-
  jaxrpc/invoice"
• // create and send the request
• getInvoiceById idWrapper new
  getInvoiceById()
• idWrapper.long_1 1000
• getInvoiceByIdResponse responseWrapper
  service.getInvoiceById(idWrapper)
• // Receive and process the result

40
Web Services Architecture

• Web Services as a presentation layer technology
• Service Oriented Architecture (SOA) Web
  Services
• Message Exchange Patterns (MEPs)
• RPC centric vs. Document centric approaches
• Relevant SOAP WSDL details

41
Web Services And Presentation Layer
42
Web Services And Presentation Layer
43
Fallacies Of Distributed Computing (Peter Deutch)

• The network is reliable
• Latency is zero
• Bandwidth is infinite
• The network is secure
• Topology doesnt change
• There is one administrator
• Transport cost is zero
• The network is homogeneous

44
Waldo On Distributed Computing

• work in distributed object-oriented systems
  that is based on a model that ignores or denies
  the differences between local and remote
  objects is doomed to failure, and could easily
  lead to an industry-wide rejection of the notion
  of distributed object-based systems."
• -- Jim Waldo et al, A Note on Distributed
  Computing, 1994

45
Local objects are different than remote objects

• Local objects are different than remote objects
  because
• Different address spaces (by reference vs. by
  copy)
• Latency
• Partial failure
• Concurrency

46
Service Oriented Architecture (SOA)

• Services have network interfaces
• Service providers and consumers are loosely
  coupled
• Interfaces are coarse grained
• Location is transparent
• Services can be looked up in a registry
• Consumer can bind to a provider at runtime

47
SOA applied to EJBs

• EJBs do distributed computing
• J2EE patterns that promote SOA tenets
• Session Façade pattern with Value Objects for
  bind and execute
• Service Locator pattern for find

48
SOA Applied to EJBs
49
SOA Applied To Web Services
50
Message Exchange Patterns

• Message Exchange Patterns (MEPs) how messages
  are exchanged
• There are really two
• Request-response
• One way
• WSDL defines two others, notification and solicit
  response, which arent supported by J2EE and
  arent widely used
• Code to MEPs, not to the underlying protocol

51
Request-response over HTTP
52
One way MEP over HTTP
53
Request-response MEP over SMTP
54
RPC Centric vs. Document Centric

• RPC Centric Web services transmit objects as XML
• Document Centric Web services transmit XML
  documents. Applications on either end create and
  parse XML documents
• RPC is more closely associated with the
  request-response MEP
• Document centric is more closely associated with
  the one way MEP

55
Document Centric Approach
56
RPC Centric Approach
57
RPC vs. Doc and J2EE

• JAX-RPC is an RPC centric approach
• JAXM is document centric
• SAAJ is low-level document centric by default
• Document centric is best when you are really
  dealing with documents newsfeeds for example
• Doesnt make sense to change XML to objects back
  to XML again
• Usually, you want to deal with objects, not XML
• However
• Business tends to think in documents (P.O.,
  Invoice)
• Documents are more naturally coarse grained

58
WSDL SOAP

• SOAP wire-line protocol
• SOAP envelope, body and headers
• Body Just transporting the data
• Header Meta-data. Higher standards use headers
• Envelope just a container
• WSDL describes the web service
• Similar to Java method signatures
• WSDL is very interesting
• Helps to understand WSDL to do JAX-RPC
• Can go a long way with JAX-RPC without knowing
  anything about SOAP

59
WSDL compared to Java
60
WSDL
61
Interoperability Challenges

• Interoperability is the chief challenge of web
  services
• Tools generating SOAP, WSDL, UDDI, etc. need to
  be interoperable
• A more complex variation of the Browser Wars of
  the 1990s
• Web Services Interoperability (WS-I) dedicated to
  Interoperability
• WS-I Basic Profile 1.0 declares an interoperable
  web services platform

62
WS-I Basic Profile

• WS-I Basic Profile 1.0
• SOAP 1.1
• WSDL 1.1
• Must use HTTP binding, should use HTTP 1.1
• XML Schema Part 1, Part 2
• May use HTTPS
• SOAP messages should use document/literal
• Similar to the J2EE certification program

63
JAX-RPC

• Big selling point Never have to program against
  SOAP
• Big value add Generated code (not the APIs)
• Addresses interoperability problems because the
  code generators can adhere to WS-I Basic Profile
  1.0
• Uses Façade and Value Object patterns
• RPC-centric, though you can start with defined
  WSDL and XSD
• Tends to use request-response MEP, but can work
  with one-way MEP

64
JAX-RPC
65
JAX-RPC Interoperability
66
JAX-RPC SEI-first Provider Development

• Service Endpoint Interface first web services
  enabling existing Java code
• Define a Service Endpoint Interface
• Implement the Servant ties to business logic
• Generate WSDL with JAX-RPC
• Create WAR
• Deploy to servlet container

67
JAX-RPC SEI-first Provider Development

• lt?xml version"1.0" encoding"UTF-8"?gt
• ltconfiguration
• xmlns"http//java.sun.com/xml/ns/jax-rpc/ri/con
  fig"gt
• ltservice name"InvoiceWebService"
• targetNamespace"http//www.ibiblio.org/mdthoma
  s/invoice"
• typeNamespace"http//www.ibiblio.org/mdthomas/
  invoice/types"
• packageName"org.ibiblio.mdthomas.ws.autopartss
  upplier"gt
• ltinterface name"org.ibiblio.mdthomas.ws.autopar
  tssupplier.InvoiceWebService"/gt
• lt/servicegt
• lt/configurationgt

68
JAX-RPC Requestor Development

• Point at the WSDL file
• Generate stubs
• Code against the stubs
• Stubs mirror the WSDL entities
• The SEI is generated for the requestor side
• Value objects are generated
• SEI and value objects are usually in a different
  package
• Can generate a JAX-RPC Requestor against non
  JAX-RPC generated WSDL documents

69
JAX-RPC Requestor Development

• lt?xml version"1.0" encoding"UTF-8"?gt
• ltconfiguration
• xmlns"http//java.sun.com/xml/ns/jax-rpc/ri/conf
  ig"gt
• ltwsdl location"InvoiceWebService.wsdl"
• packageName"invoicestub"/gt
• lt/configurationgt

70
JAX-RPC WSDL-first Development

• Point to the WSDL
• Generate SEI, value objects
• Code Servant
• Generate Ties
• Create WAR
• Deploy to servlet container

71
WSDL generated Java

• WSDL supersets Java in several areas
• Can define multiple OUT and IN/OUT parameters
• JAX-RPC uses holder objects for these
• Can define one-way operations
• WSDL can do stronger typing than Java (e.g.,
  regular expression facets)
• Headers can be mapped as explicit context to an
  SEI call a header will be passed to the SEI
  method as a parameter

72
Service Endpoint Interfaces (SEIs)

• Must extend java.rmi.Remote
• Every method must throw RemoteException
• No constant declarations
• Parameters and return types must be valid JAX-RPC
  types
• 4 is the big one

73
JAX-RPC Types

• XML (and thus web services) is data-centric not
  object-centric
• Valid JAX-RPC types are what could be considered
  value types
• Java primitives and primitive wrappers (int,
  Integer, long, Long, etc.)
• Some standard Java classes (e.g., String, Date)
• Java value types (method-less Java classes or,
  roughly, JavaBeans)
• Arrays

74
JAX-RPC Standard Types

• java.lang.String
• java.math.BigInteger
• java.math.BigDecimal
• java.util.Calendar
• java.util.Date
• java.xml.namespace.QName
• java.net.URI

75
Value Object Types

• Default no object constructor
• Must not implement Remote
• Methods are not mapped to the transmitted XML
• Java Bean properties and public, non-final,
  non-static fields are mapped
• Fields/properties can be any valid JAX-RPC type

76
Value Object

• public class PersonValueType
• public String name
• public Date birthDate
• public boolean smoker
• public String sex
• public int cholestrolLevel
• public URI webSite
• public PersonValueType mom
• public PersonValueType dad
• public PersonValueType children

77
Exceptions SOAP Faults

• Can declare exceptions in an SEI
• Will declare an equivalent fault in the WSDL file
• Exception will be thrown on the requestor when a
  fault is received
• Exceptions in the SEI must not extend
  RuntimeException

78
JAX-RPC Polymorphism

• Subtypes of a declared return type can be
  returned
• Must tell the code generation tool about the
  sub-types if they dont appear elsewhere in the
  SEI
• WSDL supports extensible types
• Can downcast in the JAX-RPC requestor code

79
Handlers

• JAX-RPC message handlers give you a way to access
  a SOAP message before or after its ultimate
  processing
• Handler interface has three methods
• handleRequest
• handleResponse
• handleFault

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JAX-RPC Handlers
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ServletEndpointInterface

• ServletEndpointInterface provides access to the
  underlying servlet context
• Can use it inside a JAX-RPC servant to
• Get/set values to an HTTPSession
• Interface with HTTP authentication
• Get resources
• Be careful
• SOAP is designed to be transport (i.e., HTTP)
  independent (but WS-I says its okay to use HTTP
  cookies)
• The requestor must support cookies and behave
  correctly! (Not the same as assuming a web
  browser will behave correctly)

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ServletEndpointContext

• public class HttpAccessServant implements
  HttpAccess, ServiceLifecycle
• ServletEndpointContext context
• public void init(Object o)
• context (ServletEndpointContext)o
• public void destroy()
• public void setHttpSessionAttribute(String key,
  String val)
• throws RemoteException
• HttpSession session context.getHttpSession(
  )
• session.setAttribute(key,val)

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2.1 Stateless Session Beans and Web Services

• EJB 2.1 specifies that Stateless Session Beans
  may declare a SEI
• Similar to a remote component interface
• EJB container is a JAX-RPC runtime manages
  requests to the SEI
• One step simpler than a servlet based SEI that
  accesses the Stateless Session Bean through a
  Session Façade pattern

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Differences Between Servlet JAX-RPC EJB
Container JAX-RPC

• Different network architecture May not want
  outside HTTP connections to the EJB Container
• Differences in transport implementation
• EJB 2.1 does not require that the EJB container
  support HTTP sessions

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Static vs. Dynamic Requestors

• Static proxy Use stubs generated by WSDL-to-Java
  tool at compile time
• Dynamic proxy Use proxy created at runtime,
  though SEI is generated at compile time
• Dynamic Invocation Interface (DII) Completely
  dynamic. Signature of web service and WSDL
  doesnt need to be known until runtime
• Requestors and providers are usually somewhat
  coupled at compile time, even if you use DII

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Apache Axis

• Axis is a web services engine
• Implements JAX-RPC 1.1, SAAJ 1.2 specification
• Axis details beyond J2EE standards
• JWS deployment similar to JSP
• WSDD for deploying web services
• Currently, some weaknesses in supporting WS-I
  Basic Profile (e.g., document/literal)
• Should be addressed soon

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SAAJ

• SAAJ is a wrapper for XML parsing and can handle
  HTTP calls
• SAAJ provides convenience methods for accessing
  the SOAP envelope, headers and body
• Similar to JDOM
• Can bridge to W3C DOM APIs

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JAXM Messaging

• JAXM is an asynchronous, queue-based messaging
  API
• Not part of J2EE 1.4
• Uses queues on either side
• Doesnt provide WSDL facilities
• Can be used in conjunction with JAXB to convert
  to objects

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JAXR

• JAXR API for XML registries
• Generic Can be used with any XML registry
• Support for UDDI and ebXML
• Has support for querying and for publishing
• Publishing requires authentication
• Can set up your own private UDDI registries
  that act as a naming service

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Conclusions

• JAX-RPC quickest solution for synchronous, RPC
  style web services and for service-enabling
  existing code
• RPC model isnt always best if its too fine
  grained it violates SOA
• SOA coarse grained, loosely coupled interfaces
• JAXP Avoid if possible. Use JAXB/Castor to
  translate into an object model
• JAXM Good for message style services
• SOAP WSDL WSDL is more interesting
• JAXR Used for access to XML Registries (i.e.,
  UDDI)