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Web Services Broker (OMWSB) |
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WSB provides a set of functions that enable you to create a server application that acts as a host and broker for web service requests sent from client applications and processed by service applications. Note the distinction between the roles of the client application, the server application and the service application:
Note: The WSB library will not run with OmniMark Single Processing Engine or with the OmniMark Fast VM under OmniMark Studio for Eclipse (the "Execute Project" option).
The WSB library provides functions that can be used by the server application to host services, route requests, and process requests for which no service exists. It also provides functions that can be used by service applications to implement a service and to receive and interpret a request. The WSB library does not provide functions for use in web service clients. However, the functions required by clients to communicate with servers and to interpret responses are provided by OmniMark's TCP/IP library and by OmniMark's built in XML processing capability.
The WSB library runs service applications in threads, allowing the WSB server to handle multiple simultaneous requests.
Web services may use a variety of communication protocols (SOAP, XML-RPC, etc) and a variety of transport mechanisms (HTTP, Mail, etc.). The current version of the Web Services Broker library supports SOAP 1.1, XML-RPC, and user-defined protocols over HTTP.
Here is an example of a WSB application using the SOAP protocol. It consists of four programs, the server, the service, a client, and a "die" client, designed to shut down the server remotely. The example implements a time service.
This example, as well as examples using XML-RPC and a user-defined protocol, are included with your OMWSB installation. Please note that these samples are designed to illustrate the operation of the Web Service Broker and should not be taken as complete or robust implementation of the SOAP or XML-RPC protocols.
This is the code for the server.
import 'omwsb.xmd' prefixed by wsb.
process
local wsb.server server
; set up the server
set server to wsb.create-server on 3556 of-type wsb.soap-service
; build the service map
wsb.add-service to server named "http://omnimark.com/TIME"
handled-by "times.xvc"
; start the server
wsb.start-servicing-requests on server
put #error "OMWSB Server started on port 3556%n"
repeat
local wsb.request request
; Wait for requests. Requests not in map handled here.
set request to wsb.wait-for-request on server
do when (wsb.request-name of request) = "http://omnimark.com/DIE"
local stream responder
open responder as wsb.writer of request
put responder "HTTP/1.0 200 OK%13#%10#"
|| "Content-Type: text/xml; charset=%"utf-8%"%13#%10#"
|| "Content-Length: 0"
|| "%13#%10#%13#%10#"
close responder
log-message "DIE action received. Shutting down.%n"
exit
else
;else report bad request
log-message "Unknown request received."
log-message "Header: " || wsb.request-header of request
log-message "Body: " || wsb.reader of request
done
catch #external-exception
identity catch-id
message catch-msg
location catch-loc
log-message '%g(catch-id) : %g(catch-msg)%n%g(catch-loc)'
; exit if server has fatal error
rethrow when catch-id = "OMWSB000"
again
Here is an example of a WSB service application. It implements a time service. The server program above is designed to act as host and broker for this service. Note that this program must be compiled to create "times.xvc" and that the "times.xvc" file must be in the current working directory of the server program.
; times.xom
; a time service
import 'omwsb.xmd' prefixed by wsb.
include 'omdate.xin'
global stream the-time
declare catch parse-error
reason value string message
process
repeat
local wsb.request request
local stream responder
local stream response
; Parse the request
set request to wsb.wait-for-request
using group process-soap
do xml-parse scan wsb.reader of request
suppress
catch parse-error reason message
open responder as wsb.writer of request
put responder "HTTP/1.1 404 Invalid request%13#%10#%13#%10#"
put responder "XML error in request:%n" || message || "%n"
close responder
exit
done
; Build the response
set response
to "<SOAP-ENV:Envelope%13#%10#"
|| " xmlns:SOAP-ENV=%"http://schemas.xmlsoap.org/soap/envelope/%"%13#%10#"
|| " SOAP-ENV:encodingStyle=%"http://schemas.xmlsoap.org/soap/encoding/%"%13#%10#"
|| " xmlns:time=%"http://schemas.omnimark.com/time%">%13#%10#"
|| " <SOAP-ENV:Body>%13#%10#"
|| " <time:current-time>%13#%10#"
|| the-time
|| " </time:current-time>%13#%10#"
|| " </SOAP-ENV:Body>%13#%10#"
|| "</SOAP-ENV:Envelope>%13#%10#"
open responder as wsb.writer of request
put responder "HTTP/1.0 200 OK%13#%10#"
|| "Content-Type: text/xml; charset=%"utf-8%"%13#%10#"
|| "Content-Length: "
|| "d" % length of response
|| "%13#%10#%13#%10#"
|| response
close responder
catch #external-exception identity catch-id
rethrow when catch-id = "OMWSB000"
again
;ensure a clean exit
catch #program-error
code error-code
message error-message
location error-location
log-message ('An error occurred in the TIME service:%n'
|| '%d(error-code): %g(error-message)%n%g(error-location)%n')
;rules for processing the SOAP packet
group process-soap
element #base "Envelope"
suppress
element #base "Body"
suppress
element #base "request"
suppress
element #base "zone"
local stream zone initial {"%c"}
set the-time
to ymdhms-to-arpadate ymdhms-adjust-time-zone
now-as-ymdhms to-be zone
markup-error
throw parse-error
reason (#message || " At line %d(#line-number)")
group #implied
Here is a client that uses the time service.
import 'omtcp.xmd' prefixed by tcp.
include "omdate.xin"
global integer port initial {3556}
global stream hostname initial {"localhost"}
define string source function my-time-zone as output now-as-ymdhms drop any{14}
;default to local time zone
global stream zone initial {my-time-zone};{now-as-ymdhms drop any{14}}
define string source function generate-soap-request
action value string soap-action
as
local stream contents
set contents
to "<SOAP-ENV:Envelope%13#%10#"
|| " xmlns:SOAP-ENV=%"http://schemas.xmlsoap.org/soap/envelope/%"%13#%10#"
|| " SOAP-ENV:encodingStyle=%"http://schemas.xmlsoap.org/soap/encoding/%"%13#%10#"
|| " xmlns:time=%"http://schemas.omnimark.com/time%">%13#%10#"
|| " <SOAP-ENV:Body>%13#%10#"
|| " <time:request>%13#%10#"
|| " <time:zone>" || zone || "</time:zone>%13#%10#"
|| " </time:request>%13#%10#"
|| " </SOAP-ENV:Body>%13#%10#"
|| "</SOAP-ENV:Envelope>%13#%10#"
output "POST /SOAPServer HTTP/1.0%13#%10#"
|| "Host: www.soapserver.com%13#%10#"
|| "Content-Type: text/xml; charset=%"utf-8%"%13#%10#"
|| "SOAPAction: " || soap-action || "%13#%10#"
|| "Content-Length: "
|| "d" % length of contents
|| "%13#%10#%13#%10#"
|| contents
process
local tcp.connection conn
;check for valid time zone format
do unless zone matches (["+-"] digit{4})
log-message ('Incorrect time zone format "' || #args[1] || '"%n'
|| "Use '-'/'+' hhmm format. E.g. +0200")
halt with 1
done
set conn to tcp.connect to hostname on port
tcp.put-string to conn from
(generate-soap-request action "http://omnimark.com/TIME")
; receive response
do scan tcp.reader of conn
; See if valid response. If so, decode data. Otherwise, report error
match (any** "HTTP/" digit+ "." digit+ blank+ digit{3} => response-code)
(any** "Content-Type:" blank+ [\ " ;"]+ => content-type)?
(any** 'charset="' any++ => charset '"')?
(any** "Content-Length:" blank* digit+ => content-length)?
(any** "%13#%10#%13#%10#")?
do when response-code = "200"
do xml-parse scan #current-input
suppress
done
else
log-message ("HTTP error. Code=" || response-code)
done
match lookahead any
log-message ("Invalid response received:%n" || #current-input)
halt with 1
done
;-------------------------------------------------------
; SOAP Processing rules
;
element #base "Envelope"
suppress
element #base "Body"
suppress
element #base "current-time"
log-message "%nThe time is: " || "%sc" drop white-space* || "%n"
It is important that you shut down a WSB server by sending it a message telling it to shut down. If you shut it down by killing the server process, (for example by typing Ctrl-C on the command line) the service programs hosted by the server will not have an opportunity to clean up any resources they are using. Here is a client that will send a shutdown command to the server application shown above.
import 'omtcp.xmd' prefixed by tcp.
global integer port initial {3556}
global stream hostname initial {"localhost"}
define string source function generate-soap-request
action value string soap-action
as
output "POST /SOAPServer HTTP/1.0%13#%10#"
|| "Host: www.soapserver.com%13#%10#"
|| "Content-Type: text/xml; charset=%"utf-8%"%13#%10#"
|| "SOAPAction: " || soap-action || "%13#%10#"
|| "Content-Length: 0"
|| "%13#%10#%13#%10#"
process
local tcp.connection conn
set conn to tcp.connect to hostname on port
tcp.put-string to conn from
(generate-soap-request action "http://omnimark.com/DIE")
Copyright © Stilo International plc, 1988-2010.
