How to mantain the state between 2 call of the same WebService?

  • Thread starter Alessandro Benedetti
  • Start date
A

Alessandro Benedetti

Hi. I'm calling two methods of a .NET Webservice (A) from another Webservice
(B).

The A Webservice is made like this:

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{
private int X = 0;

[WebMethod(EnableSession=true)]
public void WM1()
{
X = 1;
}

[WebMethod(EnableSession=true)]
public string WM2()
{
return(X);
}
}

In B WebService I make only one instantion of the A Webservice's proxy class
and then call first method (WM1) and then the second one (WM2) but WM2 always
return 0.
So, I've used Session to save my variable, but I would like to know if there
is another way that doesn't use session that I don't like.

Thank you.
Alessandr
 
B

Brock Allen

WebServices don't inherently support tracking the correlation of discrete
calls, as it's intended to be a disconnected messaging mechanism. So, if
you want this, you need to build in the correlation yourself. Here's an example:

// My Order Service
[WebMethod] string PlaceOrder( ... ) { ... return OrderID; }
[WebMethod] string GetOrderStatusOrder( string OrderID ) { ... }
[WebMethod] bool CancelOrder( string OrderID ) { ... }

Anyway, simple idea, but notice how the WebMethods track the user? The first
call returns an OrderID. This is now the token that identifies the user and
for all the other operations the user needs to present this information so
the web service knows who it's talking to.

The idea is the same with HTML applications. When you go to amazon.com you
need to pass some info in to "remind" the web server who you were so it can
continue whatever conversation it was having with you...
 
K

Kevin Spencer

is another way that doesn't use session that I don't like.

You have the same intrinsic objec ts available from the HttpContext that you
have with an ASP.Net app, which includes Application, Sessin, Server, etc.
Take your pick.

I'm a bit curious, however, as to why you "don't like" Session. Kind of an
odd statment coming from a programmer. Reminds me of a carpenter saying "I'd
like to cut this plywood, but I don't like table saws, so I'll use a
circular saw instead." Table saws and Session have their place.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
What You Seek Is What You Get.
 
A

Alessandro Benedetti

Hello Brock, thank you or your answer. Your solution is correct if I have
to work only with primitive type. The problem is that I have to work with
a custom class like this example:

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{

CL1 test;

public WSA()
{
this.test=new CL1;
}

[WebMethod(EnableSession=true)]
public void WM1() { test.SomeMethod(); }

[WebMethod(EnableSession=true)]
public string WM2() { return(test.SomeValue); }

}

public class CL1
{
....
}
WebServices don't inherently support tracking the correlation of
discrete calls, as it's intended to be a disconnected messaging
mechanism. So, if you want this, you need to build in the correlation
yourself. Here's an example:

// My Order Service
[WebMethod] string PlaceOrder( ... ) { ... return OrderID; }
[WebMethod] string GetOrderStatusOrder( string OrderID ) { ... }
[WebMethod] bool CancelOrder( string OrderID ) { ... }
Anyway, simple idea, but notice how the WebMethods track the user? The
first call returns an OrderID. This is now the token that identifies
the user and for all the other operations the user needs to present
this information so the web service knows who it's talking to.

The idea is the same with HTML applications. When you go to amazon.com
you need to pass some info in to "remind" the web server who you were
so it can continue whatever conversation it was having with you...

Hi. I'm calling two methods of a .NET Webservice (A) from another
Webservice (B).

The A Webservice is made like this:

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{
private int X = 0;
[WebMethod(EnableSession=true)]
public void WM1()
{
X = 1;
}
[WebMethod(EnableSession=true)]
public string WM2()
{
return(X);
}
}
In B WebService I make only one instantion of the A Webservice's
proxy
class
and then call first method (WM1) and then the second one (WM2) but
WM2
always
return 0.
So, I've used Session to save my variable, but I would like to know
if
there
is another way that doesn't use session that I don't like.
Thank you.
Alessandro
 
A

Alessandro Benedetti

Hello Kevin,
You have the same intrinsic objec ts available from the HttpContext
that you have with an ASP.Net app, which includes Application, Sessin,
Server, etc. Take your pick.

I'm a bit curious, however, as to why you "don't like" Session. Kind
of an odd statment coming from a programmer. Reminds me of a carpenter
saying "I'd like to cut this plywood, but I don't like table saws, so
I'll use a circular saw instead." Table saws and Session have their
place.

Well, session variables are perfect for many application but they use a lot
of memory and have a session timeout. The webservice that I've to consume
have to do long operation (a lot of minutes). Since I don't know how much
time the webservice work I can't use session variables because I can't set
the correct timeout. Moreover to use sessions I have to implement System.Net.CookieContainer,
but if I want to call the Webservice from another language like Java or ASP
or PHP I don't know to do it.
So I think that I can use Table saws and I have to find my circular saw ;-)

Thank you.

Alessandro

PS: Sorry for my bad english, I'm from Italy.
Kevin Spencer
Microsoft MVP
.Net Developer
What You Seek Is What You Get.
Hi. I'm calling two methods of a .NET Webservice (A) from another
Webservice (B).

The A Webservice is made like this:

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{
private int X = 0;
[WebMethod(EnableSession=true)]
public void WM1()
{ X = 1;
}
[WebMethod(EnableSession=true)]
public string WM2()
{ return(X);
}
}
In B WebService I make only one instantion of the A Webservice's
proxy
class and then call first method (WM1) and then the second one (WM2)
but
WM2 always return 0.
So, I've used Session to save my variable, but I would like to know
if
there is another way that doesn't use session that I don't like.
Thank you.
Alessandro
 
K

Kevin Spencer

Hi Alessandro,

Let me tell you about a Web Service client app that we are building that use
a SWF for the front end, and a Web Service for the back end. It keeps track
of who is logged on using Session. Now, I don't know where you got the idea
that "they use a lot of memory" but that is not true. Does a variable use a
lot of memory? The answer is, it uses as much memory as you store in it.
Same thing goes for Session. Now, our app uses Session, but it doesn't store
a whole lot there. To handle the Timeout issue, we created a WebMethod
called "Ping" which simply passes the user id to the server, and keeps their
Session alive. The beauty part is, if they close their browser or navigate
away, the Session cleans everything up automaticallly when it ends. And it
ends 20 minutes after the last Request.

--
HTH,

Kevin Spencer
Microsoft MVP
..Net Developer
What You Seek Is What You Get.

Alessandro Benedetti said:
Hello Kevin,
You have the same intrinsic objec ts available from the HttpContext
that you have with an ASP.Net app, which includes Application, Sessin,
Server, etc. Take your pick.

I'm a bit curious, however, as to why you "don't like" Session. Kind
of an odd statment coming from a programmer. Reminds me of a carpenter
saying "I'd like to cut this plywood, but I don't like table saws, so
I'll use a circular saw instead." Table saws and Session have their
place.

Well, session variables are perfect for many application but they use a
lot of memory and have a session timeout. The webservice that I've to
consume have to do long operation (a lot of minutes). Since I don't know
how much time the webservice work I can't use session variables because I
can't set the correct timeout. Moreover to use sessions I have to
implement System.Net.CookieContainer, but if I want to call the Webservice
from another language like Java or ASP or PHP I don't know to do it.
So I think that I can use Table saws and I have to find my circular saw
;-)

Thank you.

Alessandro

PS: Sorry for my bad english, I'm from Italy.
Kevin Spencer
Microsoft MVP
.Net Developer
What You Seek Is What You Get.
Hi. I'm calling two methods of a .NET Webservice (A) from another
Webservice (B).

The A Webservice is made like this:

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{
private int X = 0;
[WebMethod(EnableSession=true)]
public void WM1()
{ X = 1;
}
[WebMethod(EnableSession=true)]
public string WM2()
{ return(X);
}
}
In B WebService I make only one instantion of the A Webservice's
proxy
class and then call first method (WM1) and then the second one (WM2)
but
WM2 always return 0.
So, I've used Session to save my variable, but I would like to know
if
there is another way that doesn't use session that I don't like.
Thank you.
Alessandro
 
B

Brock Allen

The problem is that I have to
work with a custom class like this example:

So that's fine. I don't see what the problem is then? Every request in creates
a new instance of the WSA class. This protocol is not stateful. That's why
you're going to have to build in your own correlation mechanism as I mentioned
before. This stuff isn't easy -- don't let the VS.NET wizards fool you.

Also, I'd beware of using things like Session, as that relies upon an out
of band contract of using cookies from the client. The web service specs
don't incorporate these like browsers do. If you do use Sessions/cookies,
then what's a java client going to do? What about a perl script client? Where
in the WSDL does it to say use cookies? If you have to explain to them outside
of your WSDL file that cookies are required on their end, then you're no
longer really doing web services... at least in the spirt of the web service
specs. You've just built your own XML protocol that sorta looks like SOAP....
 
A

Alessandro Benedetti

Hello Kevin, as Brock Allen replied me, Session variable is not the correct
way. I paste his comment:

" Also, I'd beware of using things like Session, as that relies upon an out
of band contract of using cookies from the client. The web service specs
don't incorporate these like browsers do. If you do use Sessions/cookies,
then what's a java client going to do? What about a perl script client? Where
in the WSDL does it to say use cookies? If you have to explain to them outside
of your WSDL file that cookies are required on their end, then you're no
longer really doing web services... at least in the spirt of the web service
specs. You've just built your own XML protocol that sorta looks like SOAP....
"

.... moreover I have to add that Session protocol relies on text files (cookies)
and I think (but it is only my opinion) that session variables occupies more
memory because the data have to be transformed in text data (like base64
I think). Not only, as Brock wrote, if you use Session variables you have
the data in server memory and in client too (in cookie file). At least if
client doesn't accept cookies (don't ask me why some people are scared by
cookies ;-) ), he can't use the webservice.

Your solution is perfect for your example, but I have to do with a lot of
webservice request (like thousand per hour) and every request can take from
a few seconds to more than 3 hours, so I have to generate too many traffic
using a ping solution.

Thanks.
Alessandro Benedetti
Hi Alessandro,

Let me tell you about a Web Service client app that we are building
that use a SWF for the front end, and a Web Service for the back end.
It keeps track of who is logged on using Session. Now, I don't know
where you got the idea that "they use a lot of memory" but that is not
true. Does a variable use a lot of memory? The answer is, it uses as
much memory as you store in it. Same thing goes for Session. Now, our
app uses Session, but it doesn't store a whole lot there. To handle
the Timeout issue, we created a WebMethod called "Ping" which simply
passes the user id to the server, and keeps their Session alive. The
beauty part is, if they close their browser or navigate away, the
Session cleans everything up automaticallly when it ends. And it ends
20 minutes after the last Request.

Kevin Spencer
Microsoft MVP
.Net Developer
What You Seek Is What You Get.
Hello Kevin,
is another way that doesn't use session that I don't like.

You have the same intrinsic objec ts available from the HttpContext
that you have with an ASP.Net app, which includes Application,
Sessin, Server, etc. Take your pick.

I'm a bit curious, however, as to why you "don't like" Session. Kind
of an odd statment coming from a programmer. Reminds me of a
carpenter saying "I'd like to cut this plywood, but I don't like
table saws, so I'll use a circular saw instead." Table saws and
Session have their place.
Well, session variables are perfect for many application but they use
a
lot of memory and have a session timeout. The webservice that I've to
consume have to do long operation (a lot of minutes). Since I don't
know
how much time the webservice work I can't use session variables
because I
can't set the correct timeout. Moreover to use sessions I have to
implement System.Net.CookieContainer, but if I want to call the
Webservice
from another language like Java or ASP or PHP I don't know to do it.
So I think that I can use Table saws and I have to find my circular
saw
;-)
Thank you.

Alessandro

PS: Sorry for my bad english, I'm from Italy.
Kevin Spencer
Microsoft MVP
.Net Developer
What You Seek Is What You Get.
Hi. I'm calling two methods of a .NET Webservice (A) from another
Webservice (B).

The A Webservice is made like this:

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{
private int X = 0;
[WebMethod(EnableSession=true)]
public void WM1()
{ X = 1;
}
[WebMethod(EnableSession=true)]
public string WM2()
{ return(X);
}
}
In B WebService I make only one instantion of the A Webservice's
proxy
class and then call first method (WM1) and then the second one
(WM2)
but
WM2 always return 0.
So, I've used Session to save my variable, but I would like to know
if
there is another way that doesn't use session that I don't like.
Thank you.
Alessandro
 
A

Alessandro Benedetti

Hello Brock, I don't know if I've understanding correctly your answer. You
are telling me that I can return any object from a WebService?

So in my example I can do this?

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{

[WebMethod(EnableSession=true)]
public CL1 WM1()
{
CL1 test;
test.SomeMethod();
}

[WebMethod(EnableSession=true)]
public string WM2(CL1 LocalTest)
{
return(LocalTest.SomeValue);
}

}

public class CL1
{
....
}


And if I can, how tha caller that doesn't know the object CL1 can send this
parameter?

Thank you.
Alessandro Benedetti
 
M

Manohar Kamath

Allesandro,

Why not simply do a:

[WebMethod(EnableSession=true)]
public MyClass WM1()
{
//Assuming X is an object of type MyClass
return X;
}


The MyClass object will be serialized and sent across.
 
B

Brock Allen

No, WebServices are not about objects. This is the point I'm trying to make.
The Wizards and VS.NET are trying to hide the details form you (which is
good in some scenarios), but you still must understand at least the concepts
and limitations of the underlying technology. Web Services are about passing
XML messages. The fact that in your C# code the XML message is presented
as an object is simply an artifact of the tool/framework you're using.

So... in a sense, yes you can send back objects, but realize those objects
are just being mapped onto XML. And then the XML is sent back to the client.
The XML is all they end up with (and it might get mapped into some programming
language specific construct on their side, but that's their business). So,
objects in WebServices in .NET are just there to map the state of the object
onto XML and the XML onto the state of an object. There are many things you
can build with objects that don't map correctly onto XML as used by Web Services.

So, yes, your toolkit (VS.NET) allows you to hand around object, but I'd
suggest making simple objects to hold this data and be aware that that's
the only purpose of the object. Here's a short sample (I hope the formatting
isn't messed up... sorry if it is):

public class Stock
{
public int Shares;
public string Ticker;
}

public class Portfolio
{
public double TotalValue;
public Stock[] Stocks;
}

public class StockQuote : System.Web.Services.WebService
{
[WebMethod]
public Portfolio GetPortfolio(string cutomer)
{
Portfolio p = new Portfolio();
p.TotalValue = 3456;
p.Stocks = new Stock[1];
p.Stocks[0] = new Stock();
p.Stocks[0].Shares = 400;
p.Stocks[0].Ticker = "WCOM";
return p;
}

[ WebMethod ]
public double GetQuote(string ticker)
{
switch (ticker)
{
case "MSFT": return 67.89;
case "IBM": return 43.12;
case "DELL": return 12.34;
case "WCOM": return 0.000000645;
default: return 0;
}
}
}

So this example uses objects, but their purpose in life (as parameters and
return values to/from the web service) is just to model the underlying XML.
Like I said, this stuff isn't easy but once you understand where the framework
relates to the real underlying technology then it becomes easier... HTH




Hello Brock, I don't know if I've understanding correctly your answer.
You are telling me that I can return any object from a WebService?

So in my example I can do this?

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{
[WebMethod(EnableSession=true)]
public CL1 WM1()
{
CL1 test;
test.SomeMethod();
}
[WebMethod(EnableSession=true)]
public string WM2(CL1 LocalTest)
{
return(LocalTest.SomeValue);
}
}

public class CL1
{
...
}
And if I can, how tha caller that doesn't know the object CL1 can send
this parameter?

Thank you.
Alessandro Benedetti
So that's fine. I don't see what the problem is then? Every request
in creates a new instance of the WSA class. This protocol is not
stateful. That's why you're going to have to build in your own
correlation mechanism as I mentioned before. This stuff isn't easy --
don't let the VS.NET wizards fool you.

Also, I'd beware of using things like Session, as that relies upon an
out of band contract of using cookies from the client. The web
service specs don't incorporate these like browsers do. If you do use
Sessions/cookies, then what's a java client going to do? What about a
perl script client? Where in the WSDL does it to say use cookies? If
you have to explain to them outside of your WSDL file that cookies
are required on their end, then you're no longer really doing web
services... at least in the spirt of the web service specs. You've
just built your own XML protocol that sorta looks like SOAP....
 
A

Alessandro Benedetti

Hello Manohar, yours is the same solution as Brock Allen i think. I didn't
know that it is possibile to do that with any type of object. I will try
(and I'll read documentation about serialization because I don't know nothing
about it).
My question is, if the client is a Java application for example, the app
have to save the result in a generic object?

Thank you
Alessandro Benedetti
Allesandro,

Why not simply do a:

[WebMethod(EnableSession=true)]
public MyClass WM1()
{
//Assuming X is an object of type MyClass
return X;
}
The MyClass object will be serialized and sent across.

Hi. I'm calling two methods of a .NET Webservice (A) from another
Webservice

(B).

The A Webservice is made like this:

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{
private int X = 0;
[WebMethod(EnableSession=true)]
public void WM1()
{
X = 1;
}
[WebMethod(EnableSession=true)]
public string WM2()
{
return(X);
}
}
In B WebService I make only one instantion of the A Webservice's
proxy
class

and then call first method (WM1) and then the second one (WM2) but
WM2
always

return 0.
So, I've used Session to save my variable, but I would like to know
if there

is another way that doesn't use session that I don't like.

Thank you.
Alessandro
 
M

Manohar Kamath

As long as these custom classes have fundamental types, you should be able
to build a proxy in Java, and talk to a .NET web service. Although I haven't
worked on such architectures, I am guessing types like DataSet probably
won't be as easy.

--
Manohar Kamath
Editor, .netWire
www.dotnetwire.com


Alessandro Benedetti said:
Hello Manohar, yours is the same solution as Brock Allen i think. I didn't
know that it is possibile to do that with any type of object. I will try
(and I'll read documentation about serialization because I don't know nothing
about it).
My question is, if the client is a Java application for example, the app
have to save the result in a generic object?

Thank you
Alessandro Benedetti
Allesandro,

Why not simply do a:

[WebMethod(EnableSession=true)]
public MyClass WM1()
{
//Assuming X is an object of type MyClass
return X;
}
The MyClass object will be serialized and sent across.

Hi. I'm calling two methods of a .NET Webservice (A) from another
Webservice

(B).

The A Webservice is made like this:

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{
private int X = 0;
[WebMethod(EnableSession=true)]
public void WM1()
{
X = 1;
}
[WebMethod(EnableSession=true)]
public string WM2()
{
return(X);
}
}
In B WebService I make only one instantion of the A Webservice's
proxy
class

and then call first method (WM1) and then the second one (WM2) but
WM2
always

return 0.
So, I've used Session to save my variable, but I would like to know
if there

is another way that doesn't use session that I don't like.

Thank you.
Alessandro
 
B

Brock Allen

Correct Alessandro. A DataSet (by default) serializes as a <xs:any> to XML
schema, which makes it essentially useless to a client programming against
the WSDL (which is the contract of the XML data passed back and forth). A
strongly typed dataset works better though... Personally, I stay away from
those and build my own classes (as in my previous post) specifically for
the web service.




As long as these custom classes have fundamental types, you should be
able to build a proxy in Java, and talk to a .NET web service.
Although I haven't worked on such architectures, I am guessing types
like DataSet probably won't be as easy.

Hello Manohar, yours is the same solution as Brock Allen i think. I
didn't know that it is possibile to do that with any type of object.
I will try (and I'll read documentation about serialization because I
don't know
nothing

about it).
My question is, if the client is a Java application for example, the
app
have to save the result in a generic object?
Thank you
Alessandro Benedetti
Allesandro,

Why not simply do a:

[WebMethod(EnableSession=true)]
public MyClass WM1()
{
//Assuming X is an object of type MyClass
return X;
}
The MyClass object will be serialized and sent across.

Hi. I'm calling two methods of a .NET Webservice (A) from another

Webservice

(B).

The A Webservice is made like this:

[WebService(Namespace="WebServiceA")]
public class WSA: System.Web.Services.WebService
{
private int X = 0;
[WebMethod(EnableSession=true)]
public void WM1()
{
X = 1;
}
[WebMethod(EnableSession=true)]
public string WM2()
{
return(X);
}
}
In B WebService I make only one instantion of the A Webservice's
proxy
class

and then call first method (WM1) and then the second one (WM2) but
WM2

always

return 0.
So, I've used Session to save my variable, but I would like to know
if
there

is another way that doesn't use session that I don't like.

Thank you.
Alessandro
 

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