[vjoer]

Hello

I need to send a HTTP request (GET) to a URL and get the response (JSON). I havent found such example in the forum.
Could you give such example?

Thank you
Regards

[Thomas Linder Puls]

This is done in the Vip8 Commercial Edition examples in <examples>\vewService\jsonRpcClient.

See also Web_Services#Visual_Prolog_Client.

[vjoer]

Hello Thomas

I am using 7.3. Can I use the example in 7.3?

Thank you

[Thomas Linder Puls]

Some of it is most likely usefull in Vip7.3, but other things you will have to do yourself.

The essential part of the example is here:

Code: Select all

predicates
    httpPOST : (string Method, jsonObject Params).
clauses
    httpPOST(Method, Params) :-
        RequestObject = jsonRpcRequest::newNextId(),
        RequestObject:method := Method,
        RequestObject:params := some(json::o(Params)),
        BaseURL = serverUrl_ctl:getText(),
        textStatusCell:text := string::format("% ...", BaseUrl),
        URL = string::format("%/jsonRpc", BaseUrl),
        RequestString = RequestObject:asString(),
        stdio::writef("POST %\n", RequestString),
        % delayCall to empty the message queue, so the message control receives a WM_PAINT event
        delayCall(1, {  :- httpPOST2(Url, RequestString) }).
 
predicates
    httpPOST2 : (string Url, string RequestString).
clauses
    httpPOST2(URL, RequestString) :-
        try
            XmlHttp = xmlhttp60::new(),
            XmlHttp:open_predicate("POST", URL, comDomains::boolean(false), comDomains::null, comDomains::null),
            XmlHttp:setRequestHeader("Content-Type", "application/json-rpc; charset=UTF-8"),
            XmlHttp:send(comDomains::string(RequestString)),
            handleResponse(XmlHttp)
        catch TraceId do
            if ComException = exception::tryGetDescriptor(TraceId, exceptionHandling_exception::genericComException) and
                unsigned(0x800C0005) = exception::tryGetExtraInfo(ComException, exceptionHandling_exception::hResult_parameter)
            then
                stdio::writef("Cannot connect to %\n", Url)
            else
                ExtraInfo = [namedValue("request", string(RequestString)), namedValue("url", string(Url))],
                exception::continueDetailed(TraceId, exception::unknown, ExtraInfo)
            end if
        finally
            textStatusCell:text := "",
            setAllEnabled(true)
        end try.
 
class predicates
    handleResponse : (xmlhttp60 XmlHttp).
clauses
    handleResponse(XmlHttp) :-
        Hdrs = XmlHttp:getAllResponseHeaders(),
        Resp = XmlHttp:responseText,
        JsonResp = jsonObject::fromString(Resp),
        stdio::writef("HEADERS:\n%\n", Hdrs),
        if Error = JsonResp:tryGet_object("error") then
            if Code = Error:tryGet_integer("code") then
                stdio::writef("Code: %\n", Code)
            end if,
            if Msg = Error:tryGet_string("message") then
                stdio::writef("Message: %\n", Msg)
            end if,
            if Data = Error:tryGet_string("data") then
                stdio::writef("Data: %\n", Data)
            else
                stdio::writef("Error: %\n", Error:asString())
            end if
        elseif Result = JsonResp:tryGet_object("result") then
            stdio::writef("Result: %\n", Result:asString())
        else
            stdio::writef("Unexpected response: %\n", Resp)
        end if.

[Tonton Luc]

Hi,

Here is a VP 7.3 code sample :

Code: Select all

    serveur = "your_server.com",
    Req = format("GET http://%/your_folder/your_php_file.php?x=%\n\n",serveur,Action),
    trap(SOCKET = msgSocketBlocking::msglay_Connect(serveur, 80, []),_,(stdio::write("msglay_Connect : not ok\n"),fail())),
    msglay_WriteStr(SOCKET,Req),
    stdio::write(""),
    msgSocketBlocking::msglay_read(SOCKET,100,Event_ReadBin),
    Event_ReadBin = e_ReadBin(ReponseBin),
    SL = binary::binary8ToStringList(ReponseBin),
    SL = [Reponse|_],
    stdio::write("Respons = ",Reponse),stdio::nl,
    msglayer::msglay_Close(SOCKET),
    clear_msgl_socket_eventqueue_db(SOCKET),
    msgSocketBlocking::msglay_CloseSession(),

[Thomas Linder Puls]

Thanks for sharing.

May I suggest that you use try-catch try instead of the trap/3 predicate:

Code: Select all

        serveur = "your_server.com",
        Req = format("GET http://%/your_folder/your_php_file.php?x=%\n\n", serveur, Action),
        try
            SOCKET = msgSocketBlocking::msglay_Connect(serveur, 80, [])
        catch _ do
            stdio::write("msglay_Connect : not ok\n"),
            fail()
        end try,
        msglay_WriteStr(SOCKET, Req),
        ...

This is of course example code, but for "production" code I will recommend that you don't throw away the exception trace; sometimes you actually get good error messages from Windows. (See exception handling).

You should notice that this code will not work for secure connections (i.e. https).

[Tonton Luc]

Hi,

Is it possible to use msglay_Connect with HTTPS or not ?

[Thomas Linder Puls]

Not.