Wanting to write a SOAP server.

Question

I'm a Java programmer of 8 years experience, worked in J2EE, good knowledge of the usual XML APIs, the HTTP protocol etc, just so we know where we're starting...
I'd like to write a SOAP server to expose certain routines to a Java client. Obviously I'd be writing the client side which would be in a web app.
Now, the server side must be in this 3GL, non-OO proprietary language which my employer is wedded to (Synergy DBL). All the data are in that proprietary language's ISAM files. This is a requirement.
That language has an XML parser, and an HTTP API, so I can read, parse, generate and send XML documents.
Am I right in thinking that I don't need to write a WSDL description of the web service? That is generally used to generate Java sketeon/stub routines is it not?
There exists a proprietary form of exposing certain DBL methods, and the interface is described by an XML document, for example as a proof of concept, I am exposing this method:
<?xml version='1.0'?>
<component name="fclasp" repository="/usr2/fclenv/51A/DATA/SYS/FCLmain.ism" smc="/usr2/fclenv/51A/DATA/SYS/" >
  <structure name="Asp_wt_filters" size="126" >
    <field name="Buyer_name" type="alpha" size="35" />
    <field name="Buyer_ref" type="alpha" size="15" />
    <field name="Supplier_name" type="alpha" size="35" />
    <field name="Supplier_ref" type="alpha" size="15" />
    <field name="Country_code_1" type="alpha" size="2" />
    <field name="Country_code_2" type="alpha" size="2" />
    <field name="Country_code_3" type="alpha" size="2" />
    <field name="Country_code_4" type="alpha" size="2" />
    <field name="Start_status" type="decimal" size="1" />
    <field name="End_status" type="decimal" size="1" />
    <field name="Start_date" type="user" size="8" />
    <field name="End_date" type="user" size="8" />
  </structure>
  <interface name="asp">
    <method name="asp_wt_list" id="asp_wt_list" elb="ELB:ASPLIB" >
      <methodresult type="integer" size="4" />
      <param name="p_request_mode" type="integer" size="4" />
      <param name="asp_wt_filters" type="structure" structureName="Asp_wt_filters" />
      <param name="p_output_format" type="integer" size="4" />
      <param name="r_tracking_ref" type="alpha" size="7" dir="out" />
      <param name="r_desc_buffer" type="alpha" size="660" dir="out" />
      <param name="r_data_buffer" type="alpha" size="660" dir="out" />
      <param name="r_break_flag" type="integer" size="4" dir="out" />
      <param name="r_break_reason" type="alpha" size="100" dir="out" />
      <param name="r_no_fields" type="integer" size="4" required="no" dir="out" />
      <param name="r_field_positions" type="integer" size="4" dim="1" required="no" dir="out" />
      <param name="r_field_lengths" type="integer" size="4" dim="1" required="no" dir="out" />
    </method>
  </interface>
</component>You can see it is a very primitive WSDL descriptor - it describes compound data types, and the methods in an interface.
Could I use the SAAJ API to call that routine from the Java/web tier? The SAAJ API just looks like a simplified XML API, not much to do with SOAP, and SOAP looks like it just sends arbitrary XML documents inside the soap Body.
How, in SAAJ, do I create a standard SOAP message to represent an invocation of that method?
I plan to generate a Java proxy to implement the interface, but I need to know how to work SOAP with SAAJ, so then I can examine the generated XML, and parse it appropriately in a generated Synergy DBL skeleton at the server end.
Another consideration, is that in the current "RPC", a sessoni is established between client and server, and state is preserved between calls. The above method returns data from a query line by line in subsequent calls. Obviously this needs some kind of routing servlet to handle ths incoming SOAP packet and maintain correlation between client, and a specific instance of a DBL Synergy SOAP server to which it redirects requests..
If anyone can help with suggestions, tips, links, whatever I'd be very grateful. I'm finding this a bit of a steep learning curve - none of the online resources go into SOAP ni any meaningful way, it's all just a skim saying how it's a simple form of RPC. But I need to know how to drive it!

Answer 1

Would it help if you are shown how a SAAJ client can contact a WSDL Webservice.
>
How, in SAAJ, do I create a standard SOAP
message to represent an invocation of that method?Would it help if you are shown how a SAAJ client can contact a WSDL Webservice. You will have to download JWSDP 1.4 for that. And then i can provide more info on how to write the SAAJ client. Also look at JWSDP 1.4 Tutorial, it will give you a lot of useful information.
Another consideration, is that in the current "RPC", a
sessoni is established between client and server, and
state is preserved between calls. The above method
returns data from a query line by line in subsequent
calls. Obviously this needs some kind of routing
servlet to handle ths incoming SOAP packet and
maintain correlation between client, and a specific
instance of a DBL Synergy SOAP server to which it
redirects requests..Have you read the SOAP version 1.2 Part 0: Primer document. It gives useful insights into how to do such things.
http://www.w3.org/TR/soap12-part0/
>
If anyone can help with suggestions, tips, links,
whatever I'd be very grateful. I'm finding this a bit
of a steep learning curve - none of the online
resources go into SOAP ni any meaningful way, it's all
just a skim saying how it's a simple form of RPC. But
I need to know how to drive it!The SOAP 1.2 primer also explains how SOAP is a simple form of RPC (very nicely).