Distributed Internet Applications - DIA. Web Services XML-RPC and SOAP

Transcription

1 Distributed Internet Applications - DIA Web Services XML-RPC and SOAP

2 Introduction A few years ago, most application were: non-distributed, running in an almost homogeneous environment developed with a stable set of requirements, using a limited set of external interfaces, using proprietary technology. This approach does not work anymore.

3 Introduction In the new age most applications are: distributed, running in an increasingly heterogeneous environment, developed with an instable set of requirements, interoperating with many different external interfaces, using standard technologies. This approach works but has some drawbacks.

4 Introduction WEB services: Network services available over the Internet using a standardized XML messaging system It is promoted as a new way to build network applications from distributed components that are language- and platform-independent XML XML Computer A Language: Ruby Operating System: Unix Computer B Language: Java Operating System: Windows XP

5 Introduction It is promoted as a new way to build network applications from distributed components that are language- and platform-independent. web service Client The Web web service web service

6 Definition of a Web service It is available over the Internet or private networks Uses a standardized XML messaging system Is not tied to any one operating system or programming language Is self-describing via a common XML grammar Is discoverable via a simple find mechanism

7 Integration Network services can be integrated dynamically. Network services are registered with a service registry; a service consumer looks up the registry to fulfill its needs. The binding of a consumer to the service can occur at runtime.

8 Architecture Web service roles Web service protocol stack

9 Web service roles Service provider Service Service requestor 1 Discover service registry Service registry Service requestor Invoke service 2 Service provider

10 Web service protocol stack Service transport responsible for transporting messages between applications XML messaging responsible for encoding messages in a common XML format Service description responsible for describing the public interface to a specific web service Service discovery responsible for centralizing services into a common registry providing publish/find functionality

11 Web service protocol stack Discovery Description XML messaging Transport UDDI WSDL XML-RPC,SOAP,XML HTTP,SMTP,FTP,BEEP UDDI - Universal Description, Discovery Protocol WSDL - Web Service Description Language XML-RPC - XML Remote Procedure Call SOAP - Simple Object Access Protocol HTTP - HyperText Transfer Protocol SMTP - Simple Mail Transfer Protocol FTP - File Transfer Protocol BEEP - Blocks Extensible Exchange Protocol

12 XML messaging There are several XML-RPC alternatives for XML messaging. SOAP HTTP POST/GET XML document

13 XML-RPC XML-RPC consists of three small parts: XML-RPC data model: A set of types for use in passing parameters, return values, and faults XML-RPC request structures: An HTTP POST request containing method and parameter information XML-RPC response structures: An HTTP response that contains return values or fault information

14 XML-RPC Data Model - Basic Types Six basic data types int or i4 (32-bit integers): double (64-bit float): <int>27</int> or <i4>27</i4> <double> </double> boolean (true(1) or false(0)): <boolean>1</boolean> string (ASCII text, Unicode): <string>hello World!</string> datetime.iso8601 (yyyymmddthh:mm:ss): <datetime> t10:25:00</datetime> base64 (binary info encoded as base 64): <base64>sgvsbg8sifdvcmxkiq==</base64>

15 XML-RPC Data Model - Compound Types Two compounds data types: array struct

16 Array An array that contains two strings: Array are indicated by the array element <value> <array> <data> <value><string>this is line 1 </string></value> <value><string>this is line 2.</string></value> </data> </array> </value>

17 Struct Structs contain unordered content, identified by name. <value> <struct> <member> <name>givenname</name> <value><string>morteza</string></value> </member> <member> <name>familyname</name> <value><string>nahrwar</string></value> </member> <member> <name>age</name> <value><int>60</int></value> </member> </struct> </value>

18 XML-RPC Request Structure XML-RPC requests are a combination of XML content and HTTP headers. Each request contains a single XML document, whose root element is a methodcall element. Each methodcall element contains a methodname element and a params element. Each params element contains a list of param elements. Each param element contains value elements.

19 XML-RPC Request: Example <?xml version="1.0"?> <methodcall> <methodname>circlearea</methodname> <params> <param> <value><double>2.41</double></value> </param> </params> </methodcall>

20 XML-RPC Request: Example <?xml version="1.0"?> <methodclall> <methodname>sortarray</methosname> <params> <param> <value> <array> <data> <value><int>10</int></value> <value><int>30</int></value> <value><int>20</int></value> </data> </array> </value> </param> <param> <value> <array> <data> <value><string>a</string></value> <value><string>c</string></value> <value><string>b</string></value> </data> </array> </value> </param> </params> </methodcall>

21 Ruby and XML-RPC require 'webrick' require 'xmlrpc/server' xml_servlet = XMLRPC::WEBrickServlet.new xml_servlet.add_handler("circle_area") do r (r**2)*3.14 end xml_servlet.add_multicall server = WEBrick::HTTPServer.new(:Port => 2000) server.mount("/rpc2", xml_servlet) trap("int"){server.shutdown} server.start

22 Ruby and XML-RPC require 'xmlrpc/client' server = XMLRPC::Client.new("localhost", "/RPC2",2000) puts server.call("circle_area",0) puts server.call("circle_area",20) puts server.multicall(['circle_area', 10], ['circle_area',20]) Output:

23 SOAP SOAP is a protocol which applies XML for message exchange in support of remote method calls over the Internet. SOAP is a Remote Procedure Calling protocol that works over HTTP. The body of the request is in XML. A procedure executes on the server, and the value it returns is also formatted in XML. Procedure parameters and returned values can be scalars, numbers, strings, dates, complex record and list structures

24 SOAP SOAP is web-based and is not subject to firewall restrictions. SOAP is language-independent. SOAP can provide justin-time service integration.

25 RPC using HTTP method name, parameter list service Web Web object server return value client HTTP request HTTP response

26 SOAP messages Every envelope element must contain exactly one Body element. If an envelope contains a SOAP envelope SOAP header Header block Header block SOAP body Header element, it must contain no more than one. Message body

27 An XML-encoded SOAP RPC <soap:envelope xmlns:soap=" <soap:header> <-- Headers go here --> </soap:header> <soap:body> <-- Request goes here --> </soap:body> </soap:envelope>

28 A sample SOAP message <soap:envelope xmlns :soap=' <soap:header> <h:log xmlns :h=' example.org /cvs/logging'> <trace>4</trace> </h:log> <h: PServer xmlns :h=' example.org /cvs/pserver' soap: mustunderstand ='true' > < username </username > <password> anoncvs</password> </h: PServer> </soap:header> <soap:body> <m:checkout xmlns :m=' /cvs'> <source>/ xml/soap/webservices /cvs</source> <revision>1.1</revision> <destination>/etc/ usr/marting/source/ xml</destination> </ m:checkout> </soap:body> </soap:envelope> source:

29 A sample SOAP request <?xml version='1.0' encoding='utf-8'?> <SOAP-ENV:Envelope xmlns:soap_env=" xmlns:xsi=" xmlns:xsd=" <SOAP-ENV:Body> <ns1:getweather xmlns:ns1="urn:examples:weatherservice" SOAP-ENV:encodingStyle=" <zipcode xsi:type="xsd:string">6414em</zipcode> </ns1:getweather> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

30 A sample SOAP response <?xml version='1.0' encoding='utf-8'?> <SOAP-ENV:Envelope xmlns:soap_env=" xmlns:xsi=" xmlns:xsd=" <SOAP-ENV:Body> <ns1:getweatherresponse xmlns:ns1="urn:examples:weatherservice" SOAP-ENV:encodingStyle=" <return xsi:type="xsd:int">4</return> </ns1:getweatherresponse> </SOAP-ENV:Body> </SOAP-ENV:Envelope>

31 A sample SOAP error response <?xml version="1.0"?> <SOAP-ENV:Envelope SOAP-ENV:encodingStyle=" xmlns:soap-env=" xmlns:xsd=" xmlns:xsi=" <SOAP-ENV:Body> <SOAP-ENV:Fault> <faultcode>soap-env:client</faultcode> <faultstring> Can't call getstatename because there are too many parameters. </faultstring> </SOAP-ENV:Fault> </SOAP-ENV:Body> </SOAP-ENV:Envelope>