MSCF/CMU 1

More on Web Services

Maintaining State

Legacy Code

Asynchronous Calls

MSCF/CMU 2

State Management

• Web Service objects are single call objects

• The object is created and destroyed on each visit

• Client Activated objects hold state associated with each client

• How can we do the same with Web Services?

• Use an Http Session object

MSCF/CMU 3

State Management Example

• Suppose we need a web service object to store a person’s name.

• The name is to be available over many visits from the same client.

• More than one client can use the service at the same time.

MSCF/CMU 4

Step by step

1. Write the remote object that uses a session object

2. Compile to a .dll and store in a directory named bin

3. Write a .asmx file and store it in the directory immediately above bin

4. Build a virtual directory named PersonName and point it at the directory immediately above bin

MSCF/CMU 5

Step by step

5. Visit http://localhost/PersonName

6. Click the .asmx file

7. Experiment with the service

8. Download the WSDL document

9. Run wsdl and generate a C# proxy

10. Compile the proxy to a .dll

11. Write a client with cookies enabled

12. Compile with csc –r:theProxy.dll MyClient.cs

MSCF/CMU 6

The Web Serviceusing System;using System.Runtime.Remoting.Lifetime;using System.Web.Services;

namespace SessionDemo{

public class PersonName : System.Web.Services.WebService {

[WebMethod(EnableSession=true)] public void setName(String n) {

// write the name to the Session object

Session["PersonName"] = n; }

MSCF/CMU 7

[WebMethod(EnableSession=true)] public String getName()

{ // read from the session object String n = (String)Session["PersonName"]; return n; }

}}

MSCF/CMU 8

PersonName.asmx

<%@ WebService Language="c#"

Class="SessionDemo.PersonName"

CodeBehind="PersonName.cs" %>

The pointer to the .cs file is misleading. This is used by Visual Studio to switch between views. We are not using Visual Studio here.

MSCF/CMU 9

The Clientusing System;

public class PersonNameClient {

static void Main(string[] args){

Console.WriteLine("Visit http://localhost/PersonName");

PersonName p = new PersonName(); p.CookieContainer = new System.Net.CookieContainer();

MSCF/CMU 10

// make 2000 visits

for(int k = 0; k < 2000; k++) { p.setName(""+k); String s = p.getName(); Console.WriteLine("Visit #" + k + " " + s); } }}

Test by running the client twice, at the sametime and from two different DOS screens.

MSCF/CMU 11

Web Services & Legacy Code

• Many web services will be developed from scratch.

• Many web services will want to make use of existing code.

• Existing code is typically “unmanaged”.

• In this demonstration we will use Visual Studio .NET to create a web service from managed legacy code.

• The example will use the genetic algorithm project from the previous course.

MSCF/CMU 12

C++ As A Web Service

• Run Visual Studio .NET

• Select New Project

• New Project Type = Visual C++

• Template = Managed C++ web service

• Enter a file and directory name

• Look over the Readme.txt file and the directory structure

MSCF/CMU 13

Files Created (From Readme.txt)

ACPlusPlusExample.vcproj

-- main project file for VC++ projects

-- holds information about the platforms,

configurations,

and project features selected with the

Application Wizard.

MSCF/CMU 14

ACPlusPlusExample.cpp

This is the main web source file. The

default is a “hello world” application.

In this demo, we’ll write some C++

code to this file.

MSCF/CMU 15

ACPlusPlusExample.h -- This header file contains the declarations of the Web Service. The default file contains a function prototype for the hello world web service. -- We’ll add new prototypes (method signatures) to this file.

AssemblyInfo.cpp

-- Contains custom attributes for modifying assembly metadata.

MSCF/CMU 16

ACPlusPlusExample.vsdisco -- discovery file for your web service. -- through the discovery process Web Service clients learn that a Web Service exists, what its capabilities are, and how to properly interact with it. -- an XML document that contains links to other resources that describe the Web Service.

MSCF/CMU 17

Web.Config

-- This file allows you to override the default configuration settings for your service.

An .asmx file

-- created as a pointer to this web application.

MSCF/CMU 18

Edit the C++ code

• Select build

• Select Run icon

• View the service in a browser

• On the client side Run wsdl.exe to create a proxy

wsdl -o:Proxy.cs http://localhost/ACPlusPlusExample/ACPlusPlusExample.asmx?

WSDL

• Write a client that uses the proxy

MSCF/CMU 19

A Client of the Genetic Algorithm

using System;public class CallGeneticWebService { public static void Main(string[] args) { double[] values = { 6.5, 1.0, 0.0, 2.0, 7.3, 1.1, 0.0, 2.0, 8.5, 1.15, 1.0, 2.0, 8.7, 1.4, 0.0, 3.0, 9.8, 1.7, 1.0, 3.0, 10.5, 1.8, 1.0, 4.0, 9.5, 1.9, 0.0, 3.0, 12.5, 1.9, 1.0, 4.0, 12.5, 2.1, 2.0, 4.0, 13.7, 2.1, 2.0, 4.0, 15.0, 2.3, 2.0, 4.0 };

MSCF/CMU 20

Class1 p = new Class1();

string result = p.GeneticAlgorithm(11,3,values);

Console.WriteLine(result);

}}

This will not work without a proxy class generated from the webservice WSDL document.

MSCF/CMU 21

MyClientOur data set is

6.5 1 0 27.3 1.1 0 28.5 1.15 1 28.7 1.4 0 39.8 1.7 1 310.5 1.8 1 49.5 1.9 0 312.5 1.9 1 412.5 2.1 2 413.7 2.1 2 415 2.3 2 4

MSCF/CMU 22

Our function is

0.1777 = ((0.907132 + ((0.727165 + x1) + (x2 + ((0.727165 + (((x0 + x2) - (0.172155 * ((0.907132 + (((((x0 + x0) - x1) / x2) + x1) + x2)) + ((((0.727165 + x1) + (x0 + ((0.727165 +0.727165) + x0))) + x0) – (0.172155 * x0))))) / x2)) + x0)))) + x0)

MSCF/CMU 23

Web Service

BrowserBrowserTest and Learn

WSDL = Web Services Description Language

WSDL.EXE Proxy code to handlecommunications and marshalling Of parameters

MSCF/CMU 24

Genetic Client

Proxy

C++ Web Service

SOAP

MSCF/CMU 25

Asynchronous Web Service

• The generated proxy contains code for asynchronous calls.

• We make a call to the service and then continue executing

• We have two ways to get the result:

(1) Provide a callback method

(2) Call a specific method to get the result

MSCF/CMU 26

A Second Client// AsyncGeneticlient/MyClient.cs// Each method in the proxy has a BeginXXX and EndXXX // where XXX is the name of the web service method.

using System;using System.Threading;

public class CallGeneticWebServiceAsync {

class MyStateObject { public AutoResetEvent Event = new AutoResetEvent(false); public Class1 calc = new Class1(); }

MSCF/CMU 27

public static void MyFinishProc(IAsyncResult iar) {

MyStateObject o = (MyStateObject) iar.AsyncState;

string result = o.calc.EndGeneticAlgorithm(iar);

Console.WriteLine(result);

o.Event.Set(); // tell the main thread }

MSCF/CMU 28

public static void Main(string[] args) {

double[] values = { 6.5, 1.0, 0.0, 2.0, 7.3, 1.1, 0.0, 2.0, 8.5, 1.15, 1.0, 2.0, 8.7, 1.4, 0.0, 3.0, 9.8, 1.7, 1.0, 3.0, 10.5, 1.8, 1.0, 4.0, 9.5, 1.9, 0.0, 3.0, 12.5, 1.9, 1.0, 4.0, 12.5, 2.1, 2.0, 4.0, 13.7, 2.1, 2.0, 4.0, 15.0, 2.3, 2.0, 4.0 };

MSCF/CMU 29

MyStateObject stateObject = new MyStateObject();

IAsyncResult iar =

stateObject.calc.BeginGeneticAlgorithm(11, 3, values, new AsyncCallback(MyFinishProc), stateObject);

Console.WriteLine("Waiting for call back to complete");

stateObject.Event.WaitOne(); }}

MSCF/CMU 30

AsyncGeneticClient>MyClientWaiting for call back to completeOur data set is

6.5 1 0 27.3 1.1 0 28.5 1.15 1 28.7 1.4 0 39.8 1.7 1 310.5 1.8 1 49.5 1.9 0 312.5 1.9 1 412.5 2.1 2 413.7 2.1 2 415 2.3 2 4Our function is

0.213383 = ((((x0 + x0) + x0) + (x1 + (0.569536 * (((((((((x0 + 0.303568) + x0)+ x1) / (x0 + x0)) + x0) + 0.303568) + x0) + (x1 + (0.569536 * ((((((x0 + 0.303568) + x2) + (x1 + (0.569536 * (((x0 + 0.64922) + x1) / (x0 + x0))))) + 0.64922)+ ((x0 + 0.303568) + x0)) / (x0 + x0))))) / (x0 + x0))))) + x2)