Architecting Web Services

1. Architecting Web Services Lorna Mitchell, Ibuildings

2. About Me <ul><li>PHP Developer/Consultant/Trainer with Ibuildings

3. PHP community evangelist

4. Blog at http://lornajane.net </li></ul>

5. Web Services <ul><li>Provide information in machine-readable format

6. For local or remote consumption

7. For consumption by discrete/modular systems </li></ul>

8. Why Web Services

9. Why Web Services

10. Why Web Services

11. Why Web Services

12. Service Types <ul><li>RPC (Remote Procedure Call)

13. SOAP

14. REST (REpresentational State Transfer) </li></ul>

15. RPC <ul><li>All URLs point to a single endpoint

16. Parameters give method names

17. Request body can take a variety of formats </li></ul>

18. RPC Advantages <ul><li>RPC is a great format for wrapping existing functionality

19. Can abstract between existing systems

20. Familiar functional paradigm </li></ul>

21. RPC Example Flickr's XML-RPC Request <methodCall> <methodName> flickr.test.echo </methodName> <params> <param><value><struct> <member> <name> name </name> <value><string> value </string></value> </member> <member> <name> name2 </name> <value><string> value2 </string></value> </member> </struct></value></param> </params> </methodCall>

22. RPC Example Flickr's XML-RPC Response <?xml version="1.0" encoding="utf-8" ?> <methodResponse> <params> <param> <value> <string> [escaped-xml-payload] </string> </value> </param> </params> </methodResponse>

23. Delivering RPC <ul><li>Consumers will need </li></ul><ul><ul><li>Service URL

24. Docs of functions and arguments

25. If this was an existing system, existing docs may suffice </li></ul></ul>

26. SOAP <ul><li>Special case of RPC using XML

27. Has given formats for messages and errors

28. Libraries exist for creating server and client in most languages </li></ul>

29. PHP SOAP Server Example require_once('lib/myClass.php'); ini_set("soap.wsdl_cache_enabled", "0"); $server = new SoapServer("service.wsdl"); $server->setClass("MyClass"); $server->handle();

30. PHP SOAP Client Example ini_set('soap.wsdl_cache_enabled','0'); require_once('lib/Snapshot.php'); $wsdl = "Service.wsdl"; $client = new SoapClient($wsdl, $params); $output = $client->requestShot( 'http://www.php.net','', 300, 400);

31. WSDL <ul><li>Web Service Description Language

32. Widely used with SOAP

33. Describes the methods, arguments and data types available

34. IDEs can read this and hint

35. Validity of requests is checked before they are sent </li></ul>

36. WSDL <?xml version ='1.0' encoding ='UTF-8' ?> <definitions name='MyClass' targetNamespace='urn:MyClassInventory' xmlns:tns='urn:MyClassInventory' xmlns:soap=' http://schemas.xmlsoap.org/wsdl/soap/ ' xmlns:xsd=' http://www.w3.org/2001/XMLSchema ' xmlns:soapenc=' http://schemas.xmlsoap.org/soap/encoding/ ' xmlns:wsdl=' http://schemas.xmlsoap.org/wsdl/ ' xmlns='http://schemas.xmlsoap.org/wsdl/'> <message name='getAccountStatusRequest'> <part name='accountID' type='xsd:string'/> </message> <message name='getAccountStatusResponse'> <part name='accountID' type='xsd:string'/> <part name='counter' type='xsd:float' /> </message> <portType name='MyClassPortType'> <operation name='getAccountStatus'> <input message='tns:getAccountStatusRequest'/> <output message='tns:getAccountStatusResponse'/> </operation> </portType> <binding name='MyClassBinding' type='tns:MyClassPortType'> <soap:binding style='rpc' transport='http://schemas.xmlsoap.org/soap/http'/> <operation name='getAccountStatus'> <soap:operation soapAction='urn:xmethods-delayed-quotes#getAccountStatus'/> <input> <soap:body use='encoded' namespace='urn:xmethods-delayed-quotes' encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'/> </input> <output> <soap:body use='encoded' namespace='urn:xmethods-delayed-quotes' encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'/> </output> </operation> </binding> <service name='MyClassService'> <port name='MyClassPort' binding='tns:MyClassBinding'> <soap:address location='http://rivendell.local:10002/MyClassServiceServer.php'/> </port> </service> </definitions>

37. Delivering SOAP <ul><li>In WSDL mode, only the WSDL needs to be supplied

38. Otherwise method names, arguments and types will be needed </li></ul>

39. REST <ul><li>A series of concepts

40. Generally uses HTTP (HyperText Transfer Protocol)

41. URLs are resource locations

42. Verbs tell the service what to do

43. Status codes indicate what the outcome was </li></ul>

44. Implementing REST <ul><li>Standard application architecture

45. Routing to map requests to internal functionality

46. Output not always HTML </li></ul>

47. REST Examples <ul><li>GET http://example.com/users/lorna

48. POST http://example.com/users

49. PUT http://example.com/users/lorna

50. GET http://example.com/users </li></ul>

51. Delivering REST <ul><li>Full documentation including URL formats, data types, and response formats

52. Must include information about error handling </li></ul>

53. REST as an inspiration <ul><li>RESTful is a strict definition

54. REST is full of great ideas

55. REST is great for clean, simple, robust services

56. Cherry-pick the bits that work </li><ul><li>Just don't call it "RESTful" :) </li></ul></ul>

57. General Architecture Considerations

58. Machine-Readable Formats 1111011110101000001101011011110001001101011111011000101010001011010100001110110111101001111110011100110010100110011000111100011000000111100000011001001101000001011100101101011011100010010111000001111010000100100010010101010101110110000000100101101110100000111001000010100010011111111010001010110000010100000101011000001000000100110000100100110010101001110101100001010110001111000101110111011110010011110101101100110111100111101000001010100100110111001111111010000000000111000000011101000000010011001101100110000101011111010100111011100100000000111010010110100011110110111000011100000010111010010011111011001001010110111011111101110000011111100010010000011010100010010011100000111111101100111111000001000100101011011100001101111011100010101010011000000100011011010000111010000000001100010011011011010010000101110111110110111101110111000111010100001001101011010101110101010100111000010110001110001111001011100011110100000110100110000000100011101011010010011100111011001111111011111000011101000111100110

59. Machine-Readable Formats <ul><li>XML (eXtensible Markup Language)

60. JSON (JavaScript Object Notation)

61. Key/value pairs

62. Form variables </li></ul>

63. Background: XML <menu id="file" value="File"> <popup> <menuitem value="New" onclick="CreateNewDoc()" /> <menuitem value="Open" onclick="OpenDoc()" /> <menuitem value="Close" onclick="CloseDoc()" /> </popup> </menu>

64. Background: JSON {"menu": { "id": "file", "value": "File", "popup": { "menuitem": [ {"value": "New", "onclick": "CreateNewDoc()"}, {"value": "Open", "onclick": "OpenDoc()"}, {"value": "Close", "onclick": "CloseDoc()"} ] } }}

65. Choosing Formats <ul><li>XML needed for SOAP, widely supported in most languages

66. JSON easier for JavaScript, use with AJAX-esque requests

67. Or make both available

68. Use built-in libraries for your platform </li></ul>

69. Error Handling <ul><li>Will you ignore extra fields? Error?

70. How about incorrect data types? Cast or reject?

71. Make error messages meaningful and unique </li></ul>

72. Asynchronous Handling <ul><li>Consider swift response and offline processing

73. Manage job queues and retries

74. Will users poll for a change?

75. Could implement callbacks </li></ul>

76. Versions and Formats <ul><li>Include as parameters to your service: </li></ul><ul><ul><li>The service version (allows for future upgrades)

77. The preferred response format </li></ul></ul>

78. Building Blocks <ul><li>Some frameworks have functionality built-in for services

79. Can be convenient

80. Consider performance </li></ul>

81. Resources <ul><li>RESTful Web Services – Leonard Richardson and Sam Ruby

82. http://uk.php.net/sca

83. http://benramsey.com

84. http://lornajane.net </li></ul>

87. WSDL: Service <service name='MyClassService'> <port name='MyClassPort' binding='tns:MyClassBinding'> <soap:address location='http://rivendell.local:10002/MyClassServiceServer.php'/> </port> </service>

89. WSDL: Binding <binding name='MyClassBinding' type='tns:MyClassPortType'> <soap:binding style='rpc' transport='http://schemas.xmlsoap.org/soap/http'/> <operation name='getAccountStatus'> <soap:operation soapAction='urn:xmethods-delayed-quotes#getAccountStatus'/> <input> <soap:body use='encoded' namespace='urn:xmethods-delayed-quotes' encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'/> </input> <output> <soap:body use='encoded' namespace='urn:xmethods-delayed-quotes' encodingStyle='http://schemas.xmlsoap.org/soap/encoding/'/> </output> </operation> </binding>

91. WSDL: Port Type <portType name='MyClassPortType'> <operation name='getAccountStatus'> <input message='tns:getAccountStatusRequest'/> <output message='tns:getAccountStatusResponse'/> </operation> </portType>

93. WSDL: Message <message name='getAccountStatusRequest'> <part name='accountID' type='xsd:string'/> </message> <message name='getAccountStatusResponse'> <part name='accountID' type='xsd:string'/> <part name='counter' type='xsd:float' /> </message>

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