Web Services
Dr. Herbert Praehofer
Institute for System Software
Johannes Kepler University Linz
Dr. Dietrich Birngruber
Software Architect
TechTalk
www.techtalk.at
© University of Linz, Institute for System Software, 2004
published under the Microsoft Curriculum License
Web Services
Introduction
Web Services in .NET
SOAP
SOAP and .NET
Service Description with WSDL
Discovery of Web Services: UDDI and DISCO
Preview of Web Services .NET 2.0
Summary
Motivation
• Integration of heterogonous, distributed systems
– globally distributed
– different programming languages
– different APIs
• B2C and B2B applications
• Usage of globally distributed services
Example: Travel Agent Service
taken from:
Web Services Architecture Usage Scenarios,
W3C Working Group Note, 11 February 2004,
http://www.w3.org/TR/2004/NOTE-ws-arch-scenarios-20040211/
3
What are Web Services?
• Middleware for distributed applications
• For remote procedure calls und data exchange
• Open standard based on XML
• For loosely coupled software services
• Independent of programming languages and operating
systems
• Utilizing existing Internet protocols and server architectures
4
Definition Web Service (by W3C)
• Software application identified by URI
• interface description in XML
• with interaction on the basis of XML encoded messages
• and message exchange on the basis of Internet protocols
5
Independence and Integration through ...
• SOAP
– XML standard for message encoding
– independent of transport protocol
– independent of client and server implementations: Java, .NET, Python, …
• Web Services Description Language - WSDL (1.1)
– Interface description in XML
• communication on the basis of existing protocols and server
architectures
– HTTP and Web server
– SMTP and mail server
– FTP and FTP server
• Standardisation (W3C)
– SOAP 1.2, WSDL 1.1 (1.2 und 2.0)
– additional protocols based on SOAP and WSDL
– protocol bindings (HTTP)
6
Web Services Scenario
Web
Service A
script client
SOAP
HTTP
Java client
SOAP
HTTP
.NET client
SOAP
HTTP
WebService C
... client
SOAP
protocol X
web server + Java
web service
container
Web
Service B
SOAP
HTTP
IIS (.NET web service container)
SOAP
SMTP
Web
Service
D
SOAP
SMTP
e-mail server +
SOAP processor
SOAP
protocol
remote
procedure call
7
Web Services in Comparison
Java RMI
.NET Remoting
CORBA
Web services
Programming
language
Java
.NET languages
(C#, VB.NET, ..)
independent
independent
Interface
definition
Java Interfaces
C# Interfaces
CORBA IDL
WSDL (XMLbased)
Data structures
Java objects
.NET objects
IDL-specified
objects
XML data
Transport
protocol
RMI-IIOP
binary or OAP
GIOP/IIOP
HTTP, HTTPS,
SMTP, FTP
Packaging
Java object
serialisation
.NET object
serialisation
ORB/CDR
SOAP
Infrastructure
Java RMI
infrastructure
.NET remoting
infrastructure
ORBs
Web, Mail, FTP
server
8
Pros and Cons
• Pros
– independent of programming language, run time environment and
operating system
– Built on existing Internet infrastructure
– standardized
– promoted from important players (Microsoft, IBM, SAP, Sun)
• Cons
– performance (XML)
9
Web Service Infrastructure
Discover Services
What services do exist?
Where are they? (URL)
E.g.: UDDI,
DISCO
client(s)
Servide Description (in WSDL)
What message does the service
know and how are those called?
Service Calls
Using services via
SOAP, HTTP, XML-RPC, ...
Web Service
+ container
10
Web Service Architecture
Discovery service
WSD1
URL1
WSD2
URL2
...
...
sh
se
a
bli
rc
h
pu
Web service
container
Client
inquiry
call
Web
Service
11
Web Service Architecture (2)
Discovery service
WSD1
URI1
WSD2
URI2
...
...
sh
se
a
bli
rc
h
pu
service inquiry (URI)
service description (WSD)
Client
service call (SOAP)
result: SOAP
service inquiry
Web service
container
service description (WSD)
Web
service
service call
result
12
Web Services
Introduction
Web Services in .NET
SOAP
SOAP and .NET
Service Description with WSDL
Discovery of Web Services: UDDI and DISCO
Preview of Web Services .NET 2.0
Summary
Web Services in .NET
• IIS and ASP.NET infrastructure support web services
• .NET Framework provides several
– base classes
– attributes
– protocols
for the realization of web services
• Visual Studio.NET provides powerful tools for developing
web services
–
–
–
–
implementation
testing
administration of IIS
generation of proxy code (wsdl.exe)
14
.NET Namespaces
• System.Web.Services
– for developing web services (e.g.: WebService, WebMethod)
• System.Web.Services.Configuration
– for extending SOAP
• System.Web.Services.Description
– for creating and manipulating WSDL descriptions
• System.Web.Services.Discovery
– for using DISCO
• System.Web.Services.Protocols
– for implementation of communication protocols (e.g. SOAPHTTP)
• System.Xml.Serialization
– for XML serialization
15
Implementation of Web Services
• in asmx-file with @WebService directive
<%@ WebService Language="C#" Class="MyWebService" %>
• deriving from base class System.Web.Services.WebService
public class MyWebService : WebService {
• Identification and settings by .NET attributes
–
–
–
–
identification of web service methods
definition of format and encoding
XML namespaces and element names to use
etc.
[WebMethod(Description= “comment ")]
[…]
public Returntype MyWebMethod( …) {
…
16
Example: TimeService
TimeService.asmx
<%@ WebService Language="C#" Class="TimeService" %>
WebService directive
using System;
using System.Web.Services;
public class TimeService : WebService {
[WebMethod(Description="Returns the current time")]
public string GetTime(bool shortForm) {
if (shortform) return DateTime.Now.ToShortTimeString();
else return DateTime.Now.ToLongTimeString();
}
deriving from WebService
Attribute [WebMethod]
identifies web service
method
}
17
Example: Simple .NET Client
• wsdl.exe generated proxy for client (TimeClient.TimeService)
> wsdl.exe /namespace:TimeClient /out:TimeServiceProxy.cs
http://localhost/netsem-ws/MyFirstService.asmx
• Client program creates TimeService object and calls GetTime
using System;
using TimeClient; //Namespace des erzeugten Proxies
public class NetClient {
public static void Main(string[] args) {
TimeService service = new TimeService();
Console.WriteLine("Die Zeit am Server ist: ");
string time = service.GetTime(true);
Console.WriteLine(time);
}
}
18
Example: Simple Java Client
• Using GLUE tool + Java libraries:
– wsdl2Java create Java interface (ITimeServiceSoap) and proxy
(TimeServiceHelper)
import Kapitel7.GLUEProxy.*; // import generated GLUE proxy classes
/** Simple XML web service client in Java using GLUE */
public class JavaClientGLUE {
public static void main(String[] args) {
try {
// Calling service using class and interface generated by wsdl2java
ITimeServiceSoap service = TimeServiceHelper.bind();
String time = service.GetTime(true);
System.out.println(“The time on the server is: \n" + time);
} catch (Exception ex) { ex.printStackTrace(); }
}
}
19
Web Services
Introduction
Web Services in .NET
SOAP
SOAP and .NET
Service Description with WSDL
Discovery of Web Services: UDDI and DISCO
Preview of Web Services .NET 2.0
Summary
SOAP
• Simple message protocol in XML
– for packaging arbitrary application data
– single messages only („one-way“)
– asynchronous
• Independent of transport protocol
• SOAP does not define:
–
–
–
–
distributed object model
communication protocol
distributed garbage collection
distributed events (distributed callbacks)
21
Application of SOAP
• SOAP is extendable
–
–
–
–
method call protocol (RPC)
security
authentication
etc.
• Protocol realisation by combination of messages (message exchange
patterns)
– one-way, request-response, multicast, …
e.g.: request-response for RPC by 2 messages
Client
1: GetTime_Request
2: GetTime_Response
Server
22
SOAP Messages
SOAP messages comparable to letters with
<Envelope>
<Header>
Message Header
Message Header
<Body>
• envelope (<Envelope>) as container
• letter head (<Header>)
with meta information
(Message Headers)
• letter (<Body>)
Data
• with arbitrary XML data
<Fault>
Fault Descriptions
• fault descriptions
23
XML Structure (simplified, SOAP 1.2)
<?xml version="1.0" ?>
<soap:Envelope xmlns:soap="...">
<soap:Header> <!-- (optional and extendable) -->
<m:my xmlns:m="anURI" soap:mustUnderstand=“true" soap:role=“uri2" />
...
</soap:Header>
<soap:Body>
data (depends on encoding and format)
<soap:Fault>
<soap:Code>...who is responsible?... </Code>
<soap:Reason>...textual description...</soap:Reason>
<soap:Detail>...more error details...</soap:Detail>
</soap:Fault>
</soap:Body>
</soap:Envelope>
24
Data in <Body> Part
• Message format:
– document
structure defined by XML schema
– rpc
structure defined by SOAP for RPC
• Data encoding:
– literal
encoding defined by XML schema
– encoded
encoding defined by SOAP encoding rules
• Usual combinations:
– document/literal
standard in .NET
– rpc/encoded
often used by Java servers
25
HTTP Binding
• HTTP-GET, HTTP-POST
– call encoded in HTTP (URL encoded)
– response encoded in XML
Restricted to simple calls (no headers, no structured data)
• SOAP over HTTP-POST
– data part of POST request contains SOAP encoded call
– response SOAP encoded
 No restrictions
26
Example: HTTP-POST
Call of GetTime(bool shortForm) of web service
http://localhost/time/TimeService.asmx
• Call :
http://localhost/time/TimeService.asmx/GetTime?shortForm=true
• HTTP response:
HTTP/1.1 200 OK Content-Type: text/xml; charset=utf-8 Content-Length: length
<?xml version="1.0" encoding="utf-8"?>
<string xmlns="http://tempuri.org/">string</string>
27
Example: SOAP over HTTP (1)
• SOAP over HTTP-POST:
POST /time/TimeService.asmx HTTP/1.1
Content-type: text/xml; charset=utf-8
SOAPAction: http://dotnet.jku.at/GetTime
Content-length: 198
User-Agent: Java1.4.0
Host: localhost
Accept: text/html, image/gif, image/jpeg, *; q=.2, */*; q=.2
Connection: keep-alive
HTTP-header SOAPAction
identifies SOAP-request
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<GetTime xmlns="http://tempuri.org/"
<shortForm>
true
</shortForm>
< /GetTime>
</soap:Body>
</soap:Envelope>
Web method
Parameter
28
Example: SOAP over HTTP (2)
• SOAP encoded response:
HTTP/1.1 200 OK Content-Type: text/xml; charset=utf-8 Content-Length: length
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap=http://schemas.xmlsoap.org/soap/envelope/
xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance
xmlns:xsd="http://www.w3.org/2001/XMLSchema">
Return
<soap:Body>
<GetTimeResponse xmlns="http://tempuri.org/">
value
<GetTimeResult>string</GetTimeResult>
</GetTimeResponse>
</soap:Body>
</soap:Envelope>
29
Web Services
Introduction
Web Services in .NET
SOAP
SOAP and .NET
Service Description with WSDL
Discovery of Web Services: UDDI and DISCO
Preview of Web Services .NET 2.0
Summary
SOAP and .NET
.NET provides support for
– defining message format and encoding
– encoding of .NET data types
– development of message headers
– life cycle management
31
Message Format and Encoding (1)
[SoapRpcMethod(Use=SoapBindingUse.Encoded
Action="http://dotnet.jku.at/Sample/AddAddressRpc“,
// SOAP action
RequestNamespace="http://dotnet.jku.at/Sample/Request",
RequestElementName="AddAddressRpcRequest",
// SOAP element name
ResponseNamespace="http://dotnet.jku.at/Sample/Response",
ResponseElementName="AddAddressRpcResponse")]
// SOAP element name
[WebMethod(Description="Adds an address DataSet for the specified user")]
public void AddAddressRpc(long userID, Address address) { ... }
• Attributes SoapRpcService and SoapRpcMethod for rpc format
• with parameters
-
Use: encoding (SoapBindingUse.Literal or SoapBindingUse.Encoded)
Action: URI for SOAPAction-HTTP header
RequestNamespace and RequestElementName:
namespace and name of SOAP element for request
ResponseNamespace and ResponseElementName:
namespace and name of SOAP element for response
32
Message Format and Encoding (2)
[SoapDocumentMethod(Use=SoapBindingUse.Literal,
Action="http://dotnet.jku.at/Sample/AddAddressDocLit",
// SOAPAction
RequestNamespace="http://dotnet.jku.at/Sample/Request",
RequestElementName="AddAddressDocLitRequest",
// SOAP element name
ResponseNamespace="http://dotnet.jku.at/Sample/Response",
ResponseElementName="AddAddressDocLitResponse")]
// SOAP element name
[WebMethod(Description="Adds an address DataSet for the specified user")]
public void AddAddressDocLit(long userID, Address address) { ... }
[SoapDocumentService(Use=SoapBindingUse.Encoded)]
public class TimeService : WebService { ... }
• Attributes SoapDocumentService and SoapDocumentMethod for
document format
33
SOAP Encoding of .NET Data Types
• Serializing of .NET data types
– on the basis of SOAP encoding rules
http://schemas.xmlsoap.org/soap/encoding
– adjusted by attributes (namespace System.Web.Serialization)
SoapAttributeAttribute
Serializing field as XML attribute
SoapElementAttribute
Serializing field as XML element
SoapIgnoreAttribute
No serialization of field
SoapIncludeAttribute
Including a type
SoapEnumAttribute
Adapting name of enumeration
34
Example: Encoding of a Type (1)
•
Web method GetTimeDesc uses type TimeDesc for return value
[WebMethod(Description="Returns the time description of the server")]
public TimeDesc GetTimeDesc() {
TimeDesc td = new TimeDesc();
// ...
return td;
}
•
Encoding of TimeDesc adjusted by attribute [SoapAttribute]
 fields encoded as XML attributes
public struct TimeDesc {
[SoapAttribute] public string TimeLong;
[SoapAttribute] public string TimeShort;
[SoapAttribute (AttributeName = "ZoneID")] public int TimeZone;
}
35
Example: Encoding of a Type (2)
•
SOAP encoded response
...
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" ...
<soap:Body soap:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<types:GetTimeDescResponse>
<GetTimeDescResult href="#id1" />
</types:GetTimeDescResponse>
<types:TimeDesc id="id1" xsi:type="types:TimeDesc"
types:TimeLong="10:00:25" types:TimeShort="10:00" types:ZoneID="1" />
</soap:Body>
</soap:Envelope>
36
Including Types
• SoapIncludeAttribute allows inclusion of types
 important for specializations
Example: PersonService
Web method with return value of type
Person[]
Person has 2 specializations
Customer and Employee
public class PersonService : WebService {
Person
[WebMethod]…
public Person[ ] GetAll() {…}
}
Customer
Employee
 Customer and Employee have to be included
explicitly into web service description!
37
Example: PersonService (1)
• Classes Person, Customer and Employee
public abstract class Person { …}
public class Customer : Person { …}
public class Employee : Person {…}
• PersonService defines web method GetAll with return type Person[]
• SoapInclude attribute includes Customer and Employee types
<%@ WebService Language="C#" Class="PersonService" %>
using System; … using System.Xml.Serialization;
public class PersonService : WebService {
[WebMethod] [SoapRpcMethod]
[SoapInclude(typeof(Customer)), SoapInclude(typeof(Employee))]
public Person[] GetAll() {
Person[] data = new Person[2];
data[0] = new Customer("1“, "Max Customer", "EMP-33");
data[1] = new Employee("EMP-33", "Tom Employee");
return data;
}
}
38
Example: PersonService (2)
• SOAP encoded response
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" ... >
<soap:Body soap:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
<tns:GetAllResponse>
<GetAllResult href="#id1" />
</tns:GetAllResponse>
<soapenc:Array id="id1" soapenc:arrayType="types:Person[2]">
<Item href="#id2" />
<Item href="#id3" />
</soapenc:Array>
<types:Customer id="id2" xsi:type="types:Customer">
<SSN xsi:type="xsd:string">1</SSN>
<Name xsi:type="xsd:string">Max Customer</Name>
<EmpSSN xsi:type="xsd:string">EMP-33</EmpSSN>
</types:Customer>
<types:Employee id="id3" xsi:type="types:Employee">
<SSN xsi:type="xsd:string">EMP-33</SSN>
<Name xsi:type="xsd:string">Tom Employee</Name>
</types:Employee>
</soap:Body>
</soap:Envelope>
39
SOAP Header Entries
• SOAP header entries are used for metainfos in messages
• Arbitrary header entries are possible
• All header entries have attributes
– recipient of entry (Actor)
– if it must be handled by recipient (mustUnderstand)
• .NET supports header entries by:
– Class SoapHeader: development of header entry classes
– Attribute SoapHeaderAttribute: Defining header entries for web methods
40
Classes SoapHeader
and SoapHeaderAttribute
SoapHeader
//----- properties
public string Actor { get; set; }
public bool MustUnderstand { get; set; }
public bool DidUnderstand { get; set; }
...
• Recipient
public string Actor {get; set;}
• Header must be handled
public bool MustUnderstand {get; set;}
• Header handled successfully
SoapHeaderAttribute
//----- properties
public SoapHeaderDirection Direction {get; set;}
public string MemberName {get; set;}
...
• In-, Out-, InOut direction of headers
public SoapHeaderDirection Direction
{get; set;}
• Name of field of web service class for
header entry
public string MemberName {get; set;}
public bool DidUnderstand {get; set;}
41
Example: AuthHeader (1)
User indentification in TimeService
– Login returns identification code (cookie)
– GetTime sends back identification code in header entry
•
Header class AuthHeader defines public field cookie
public class AuthHeader : SoapHeader { public string cookie; }
•
Web service class defines field curUser to store AuthHeader object
[WebService(Namespace="http://dotnet.jku.at/time/")]
public class HeaderTimeService : WebService {
public AuthHeader curUser;
•
Login with user and password returns identification string
[WebMethod (Description="Authenticates the user")]
public string Login(string user, string pwd) { ... create cookie ... }
bool ValidateCookie(string cookie) { ... validate cookie ... }
42
Example: AuthHeader (2)
•
•
GetTime requires header entry of type AuthHeader
which will be stored in field curUser
Validates user based on login data
[WebMethod(Description="Returns the current time")]
[SoapHeader("curUser")]
public string GetTime() {
if (curUser != null && ValidateCookie(curUser.cookie))
return System.DateTime.Now.ToLongTimeString();
else throw new SoapHeaderException("Access denied!",
SoapException.ClientFaultCode);
}
43
Example: AuthHeader (3)
•
Client
– creates service proxy and AutHeader object
HeaderTimeService proxy = new HeaderTimeService();
AuthHeader entry = new AuthHeader();
– receives cookie from call to Login
entry.cookie = proxy.Login(user, pwd);
– sets the AuthorHeader in proxy
– calls GetTime with AuthHeader header entry
entry.cookie = proxy.Login(user, pwd);
proxy.AuthHeaderValue = entry;
Console.WriteLine(proxy.GetTime());
<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://..." ... >
<soap:Header>
<AuthHeader xmlns="http://dotnet.jku.at/time/">
<cookie>aewt12348cvNNgrt55</cookie>
</AuthHeader>
</soap:Header>
<soap:Body>
<GetTime xmlns="http://dotnet.jku.at/time/" />
</soap:Body>
</soap:Envelope>
44
Life Cycle
• Web service objects are stateless
• Are created for each call
• Data can be stored in properties of
– Application state object or
public HttpApplicationState Application {get;}
– Sesssion state object
public HttpApplicationState Session {get;}
public sealed class HttpSessionState : ICollection, IEnumerable {
public object this[ string name ] {get; set;}
public object this[ int index ] {get; set;}
…
}
45
Example: StateDemo (1)
Web service StateDemo demonstrates storage of data
<%@ WebService Language="C#" Class="StateDemo" %>
using System.Web.Services;
[WebService(Namespace="http://dotnet.jku.at/StateDemo/")]
public class StateDemo : WebService {
• IncApplication increases property "Hit" of Application state object
[WebMethod()]
public int IncApplication() {
int hit = (Application["Hit"] == null) ? 0 : (int) Application["Hit"];
hit++;
Application["Hit"] = hit;
return hit;
}
46
Example: StateDemo (2)
• Parameter EnableSession enables usage of Session object
• IncSeesion increases property "Hit" of Session state object
[WebMethod(EnableSession=true)]
public int IncSession() {
int hit = (Session["Hit"] == null) ? 0 : (int) Session["Hit"];
hit++;
Session["Hit"] = hit;
return hit;
}
}
47
Web Services
Introduction
Web Services in .NET
SOAP
SOAP and .NET
Service Description with WSDL
Discovery of Web Services: UDDI and DISCO
Preview of Web Services .NET 2.0
Summary
Web Service Description Language (WSDL)
•
•
WSDL is an XML based IDL for web services
a WSD describes:
–
–
–
–
–
used data types
structure of messages
operations (methods)
protocols to call operations
addresses of web service
current version in .NET: WSDL 1.1 (http://schemas.xmlsoap.org/wsdl/)
Working Draft: WSDL 2.0 (10/4/2004)
49
Structure of WSDL 1.1
<definitions>
<types>
</types>
<message>
<part>
</part>
</message>
<portType>
<operation>
<input>
<output>
</operation>
</portType>
<binding>
<operation>
</binding>
<service>
<port>
</service>
</definitions>
WSDL description of a web services
types defined in <xsd:schema>
simple messages
parts of messages
interface specification
operations of an interface
input message
output message
abstract
part
binding of interface to protocols and encoding
description of the binding for each operation
service description
URI and binding to port
concrete
part
50
Example: WSDL for TimeService (1)
• WSDL description created by web container (IIS)
http://localhost/WebProject1/TimeService.asmx?WSDL
<?xml version="1.0" encoding="utf-8"?>
<definitions xmlns:soap=http://schemas.xmlsoap.org/wsdl/soap/
xmlns:tns="http://dotnet.jku.at/time/"
xmlns:s="http://www.w3.org/2001/XMLSchema“
xmlns:http="http://schemas.xmlsoap.org/wsdl/http/“
xmlns:mime="http://schemas.xmlsoap.org/wsdl/mime/“
xmlns:soapenc="http://schemas.xmlsoap.org/soap/encoding/“
targetNamespace="http://dotnet.jku.at/time/"
xmlns="http://schemas.xmlsoap.org/wsdl/">
<types />
<message name="GetTimeSoapIn" />
<message name="GetTimeSoapOut">
<part name="GetTimeResult" type="s:string" />
</message>
<portType name="TimeServiceSoap">
<operation name="GetTime">
<input message="tns:GetTimeSoapIn" />
<output message="tns:GetTimeSoapOut" />
</operation>
</portType>
…
abstract
part
51
Example: WSDL for TimeService (2)
…
<binding name="TimeServiceSoap" type="tns:TimeServiceSoap">
<soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="rpc" />
<operation name="GetTime">
<soap:operation soapAction="http://dotnet.jku.at/time/GetTime" style="rpc" />
<input>
<soap:body use="encoded" namespace="http://dotnet.jku.at/time/“
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
</input>
<output>
<soap:body use="encoded" namespace="http://dotnet.jku.at/time/“
concrete
encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" />
part
</output>
</operation>
</binding>
<service name="TimeService">
<documentation>Simple web service for querying the time</documentation>
<port name="TimeServiceSoap" binding="tns:TimeServiceSoap">
<soap:address location="http://localhost/time/TimeService.asmx" />
</port>
</service>
</definitions>
52
Web Services
Introduction
Web Services in .NET
SOAP
SOAP and .NET
Service Description with WSDL
Discovery of Web Services: UDDI and DISCO
Preview of Web Services .NET 2.0
Summary
Universal, Description, Discovery and
Integration (UDDI)
http://www.uddi.org
• Standardized protocol for searching for and using web services
• Provides web services interface
2.) search
1.) register
Directory
(UDDI)
Client
3.) connect
4.) call
Web
Service A
Web
Service B
54
DISCO
• Microsoft’s technique for dynamic usage of web services
• DISCO file
– contains XML document with URIs pointing to web services
– can be the result to a UDDI inquiry
• .NET support in namespace
System.Web.Services.Discovery
55
DISCO Descriptions
• Creation of DISCO descriptions:
– by command tool disco.exe
> disco.exe /out:WebProject1 WebProject1/TimeService.asmx
– by IIS
http://localhost/WebProject1/TimeService.asmx?DISCO
<?xml version="1.0" encoding="utf-8" ?>
<discovery xmlns:xsd="http://www.w3.org/2001/XMLSchema„
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance„
xmlns="http://schemas.xmlsoap.org/disco/">
<contractRef ref="http://localhost/WebProject1/TimeService.asmx?wsdl„
docRef="http://localhost/WebProject1/TimeService.asmx„
xmlns="http://schemas.xmlsoap.org/disco/scl/" />
<soap address="http://localhost/WebProject1/TimeService.asmx„
xmlns:q1="http://tempuri.org/" binding="q1:TimeServiceSoap„
xmlns="http://schemas.xmlsoap.org/disco/soap/" />
</discovery>
56
Example: TimeService Discovery (1)
• 2 variants of TimeService
– TimeService1
<%@ WebService Language="C#" Class="TimeService1" %>
using System.Web.Services;
[WebService(Namespace="http://dotnet.jku.at/time/", Name="TimeService")]
public class TimeService1 : WebService {
[WebMethod(Description="Returns the current server time")]
public string GetTime() { return System.DateTime.Now.ToLongTimeString(); }
}
– TimeService2
<%@ WebService Language="C#" Class="TimeService2" %>
using System.Web.Services;
[WebService(Namespace="http://dotnet.jku.at/time/", Name="TimeService")]
public class TimeService2 : WebService {
[WebMethod]
public string GetTime() { return "I don’t know the time!"; }
}
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Example: TimeService Discovery (2)
• Disco client with discovery of DISCO file
using System; using System.Web.Services.Discovery; using System.Collections;
public class DiscoSample {
public static void Main(string[] args) {
– loading the DISCO files
DiscoveryClientProtocol discoClient = new DiscoveryClientProtocol();
foreach (string uri in args) {
discoClient.Discover(uri);
}
– iterating over all DISCO descriptions
discoClient.ResolveAll();
TimeService proxy = new TimeService();
foreach (object obj in discoClient.Documents.Values) {
DiscoveryDocument dDoc = obj as DiscoveryDocument;
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Example: TimeService Discovery (3)
– iterating over all <contactRef>-elements and retrieve URLs
ContractReference contr = null;
IEnumerator it = dDoc.References.GetEnumerator();
while (contr == null && it.MoveNext())
contr = it.Current as ContractReference;
– given URL connect to web service and call web method
if (contr != null) {
proxy.Url = contr.DocRef;
Print("Connecting proxy to " + proxy.Url);
proxy.Discover();
Print("Result of GetTime: " + proxy.GetTime());
}
}
}
}
static void Print(string msg) { System.Console.WriteLine(msg); }
}
59
Web Services
Introduction
Web Services in .NET
SOAP
SOAP and .NET
Service Description with WSDL
Discovery of Web Services: UDDI and DISCO
Preview of Web Services .NET 2.0
Summary
Indigo
• Web services in .NET 2.0 are integrated in Indigo
• Indigo unites
– .NET remoting
– Web services
– .NET Enterprise Services
in one uniform programming model
• Indigo provides
–
–
–
–
–
–
transactions
reliable communication
secure communication and authentication
independence of transport protocols
host independence
message-based server activation
61
Indigo Architecture
service
message flow
typed channel
untyped channel
port
formatter
transport
to destination
62
Indigo Web Service Example (1)
• Implementation of web service TimeService
using System; using System.MessageBus.Services;
[DatagramPortType(Name="TimeService", Namespace="http://dotnet.jku.at/WS")]
public class TimeService {
[ServiceMethod]
public DateTime GetTime() {
DateTime now = DateTime.Now;
Console.WriteLine ("Time request at {0}", now); // output to monitor server
return now;
}
}
• Compiling and creation of assembly
csc /target:library /reference:System.MessageBus.dll TimeService.cs
• Creating the WSDL description
wsdlgen TimeService.dll
63
Indigo Web Service Example (2)
• Implementation of the server application
using System; using System.MessageBus.Services; using System; using System.MessageBus;
class Server {
static void Main () {
ServiceEnvironment se = null;
try {
se = ServiceEnvironment.Load();
se.Open();
Console.WriteLine("Press enter to stop the service ...");
Console.ReadLine();
} finally { if (se != null) se.Close(); }
}
}
64
Indigo Web Service Example (3)
• Configuration of the server in file Server.exe.config
<configuration>
<system.messagebus>
<serviceEnvironments>
<serviceEnvironment name="main">
<port>
<identityRole>
soap.tcp://localhost:12345/TimeService/
</identityRole>
</port>
<remove name="securityManager"/> <!-- Security disabled!!! -->
<policyManager>
<areUntrustedPolicyAttachmentsAccepted> true
</areUntrustedPolicyAttachmentsAccepted>
<isPolicyReturned> true </isPolicyReturned>
</policyManager>
<serviceManager>
<activatableServices>
<add type="TimeService, TimeService" />
</activatableServices>
</serviceManager>
</serviceEnvironment>
</serviceEnvironments>
</system.messagebus>
</configuration>
65
Indigo Web Service Example (4)
• Compilation of the server application
csc /reference:System.MessageBus.dll Server.cs
• Creation of the proxy for the client
wsdlgen dotnet_jku_at.WS.wsdl dotnet_jku_at.WS.xsd
• Compilation of the proxy code
csc /target:library /reference:System.MessageBus.dll dotnet_jku_at.WS.cs
66
Indigo Web Service Example (5)
• Implementation of the client application
using System; using System.MessageBus.Services;
public class Client {
public static void Main () {
ServiceEnvironment se = null;
try {
se = ServiceEnvironment.Load();
ServiceManager sm = se[typeof(ServiceManager)] as ServiceManager;
if (sm == null) throw new Exception("ServiceManager is not available.");
se.Open();
Uri uri = new Uri("soap.tcp://localhost:12345/TimeService/");
// get a channel to the web service from the default service manager
ITimeServiceChannel channel = (ITimeServiceChannel)
sm.CreateChannel(typeof(ITimeServiceChannel), uri);
Console.WriteLine(channel.GetTime());// invoke web service method
} catch (Exception e) { Console.WriteLine(e);
} finally { if (se != null) se.Close(); }
}
}
• Configuration of the client (analogous to the server) and compilation
csc /reference:System.MessageBus.dll,dotnet_jku_at.WS.dll Client.cs
67
Indigo Web Service Example (6)
• Starting the server and the client
//----- Server
> Host.exe
Press enter to stop the service ...
Time request at 1/29/2004 3:35:51 PM
>
//----- Client
> Client.exe
Time request at 1/29/2004 3:35:51 PM
>
68
Web Services
Introduction
Web Services in .NET
SOAP
SOAP and .NET
Service Description with WSDL
Discovery of Web Services: UDDI and DISCO
Preview of Web Services .NET 2.0
Summary
Summary
•
•
•
•
Web services are a middleware technology
on the basis of XM and Internet protocols
independent of programming language and run time system
for the integration of heterogeneous, distributed systems
• .NET supports web services
– development of web services
– development of web service clients
– discovery and dynamic connection to web services
• In .NET 2.0 Indigo unites the different remoting technologies
70
Resources (apart from dotnet.jku.at)
• UDDI & Co
www.uddi.org: Homepage of UDDI initiative
www-3.ibm.com/services/uddi: Discovery service from IBM
uddi.microsoft.com: Discovery service from Microsoft
www.xmethods.com: Catalogue with UDDI- und DISCO entries
• For developers
www.w3.org: Specifications
www.webservices.org: Articles and tutorials about web services
www.gotdotnet.com: Site for .NET technology, including web services
groups.yahoo.com/group/soapbuilders: Discussion group for SOAP
• Java implementations
xml.apache.org/axis/: Web service server in Java based on Apache
www.themindelectric.com: GLUE: web service server in Java
71