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How to consume an ASP.NET webservice from Java via SOAP

, 15 Jan 2004
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Demonstrates how to call ASP.NET webservices from the client within other languages and platforms.

Sample Image - WSfromJava.jpg

Introduction

This article will be useful if you need to consume ASP.NET webservices from languages or platforms without .NET support. In this example, I am consuming a webservice from a Java applet, but it would take very little work to adapt my code to run as a Java application. Although I have only tested this on Windows XP, the code should run on other platforms, providing cross-platform client-side consumption of ASP.NET webservices.

I developed this solution because I needed to add complex client-side processing to my ASP.NET application. I did not want to have to cope with all of the slightly different JavaScript implementations used by the main browsers, and this led me to consider a Java applet.

This article shows you how to use a Java applet in your webpage and get it to communicate back to ASP.NET by consuming an XML webservice on the client.

Background

There are, no doubt, many reasons why somebody might want cross-platform consumption of ASP.NET webservices, but this is my story:

I have an ASP.NET application where I needed to add client side image manipulation facilities. I looked into writing the client-side code in JavaScript which seemed like the obvious choice, but was frustrated by different implementations in the browsers, especially when trying to use image manipulation features. For example, if you want to alpha blend your image, you would have to use img.style.MozOpacity in Netscape, img.filters.alpha.opacity in Internet Explorer and there is no way to do this at all in Opera. I really didn't want to have to write special code for each browser or downgrade the functionality to the lowest common denominator.

Therefore, I decided to try writing my client-side code in Java 1.1. Note that I'm using the Java 1.1 SDK, as Internet Explorer currently does not support code developed with Java SDKs after 1.1.4 (although it seems to me that Java SDK 1.1.7 code seems to work OK in IE). A Java applet can do all of the image manipulation I needed and is supported by many browsers. Finally, I don't have to write separate code for each browser.

The next problem was, how do I get the result of the data processing done in the Java applet back into my ASP.NET application? The answer that I came up with was to create an ASP.NET webservice and consume it in the Java applet.

A Simple Example

Take a look at the following very basic webservice:

    [WebMethod]
    public string ConcatWithSpace(string one, string two)
    {
        return one+" "+two;
    }

It could be consumed very simply by making the Java applet perform a request to: webservice.asmx/ConcatWithSpace?one=FirstValue&two=SecondValue... But what if we wanted to send larger amounts of data to the webservice? How would we go about implementing a SOAP request and response in a Java applet...? There are probably many options if you are using a more recent Java SDK, but because I want to support many browsers including Internet Explorer, I'm stuck with the Java 1.1 SDK. However, this gives us a better opportunity to understand how to talk to ASP.NET web services on other languages and platforms. Therefore, I have written my own SoapRequestBuilder class in Java that makes it quite easy to consume a service and return a single string response. Take a look at this example, which consumes the webservice above:

    SoapRequestBuilder s = new SoapRequestBuilder();
    s.Server = "127.0.0.1"; // server ip address or name
    s.MethodName = "ConcatWithSpace";
    s.XmlNamespace = "http://tempuri.org/";
    s.WebServicePath = "/SimpleService/Service1.asmx";
    s.SoapAction = s.XmlNamespace+s.MethodName;
    s.AddParameter("one", "David");
    s.AddParameter("two", "Hobbs");
    String response = s.sendRequest();

In this example, the response string is filled with the result from the webservice after we sent it two parameters. The full source code of the SoapRequestBuilder class is included in the source files.

That's it! It's only a very simple example and at the moment, I'm only interested in returning a single value back from the webservice, but I have used something similar with a webservice that talks to my back-end database and this allows my Java applet to store data which can then be accessed by the ASP.NET pages.

To run the example code, set up the webservice first, then copy the Java applet files to any folder on the same machine and double-click the HTML file. All of the parameters are configured inside the HTML file, so you can change the values passed to the webservice by editing the HTML; you should not have to re-compile the Java source. I have tested the example in IE 6.0, Netscape 7.1 and Opera 7.23 on Windows XP.

Notes

Some Java Virtual Machines (like the Microsoft one) only allow you to make a socket connection to the same machine that hosts the Java class files. Therefore, if you're using an applet like me, you will need to host the Java class files on the same machine where the webservice resides.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

David S Hobbs
Web Developer
United Kingdom United Kingdom
I have been developing software on various platforms for over 14 years. For my sins I recently spent two years managing a development team at some large Redmond-based software company....
 
I'm now enjoying working as a freelance software developer from home, although I seem to be working harder than ever. My main area of work is ASP.Net development with C#.
 
I like to take as many holidays as possible, but always end up taking a book on software development with me. I'm not happy unless I'm learning something new.

Comments and Discussions

 
QuestionGetting Error PinmemberM.T. Sheikh30-May-13 1:05 
QuestionThanks for the code PinmemberArelowo Alao16-Jun-12 7:29 
QuestionHow to modify program not to use APPLET Pinmembersaimay1-Mar-12 4:35 
QuestionThanks Pinmembersanya.fesak21-Sep-11 19:06 
Where to get Java?
GeneralMy vote of 3 Pinmemberflzgkc7-Oct-10 21:02 
Generalgetting access denied: java.net.socketexception error PinmemberMember 116639322-Jul-10 5:42 
QuestionHow do I pass a parameter to a .NET Web Service from a Java client PinmemberMember 39953809-Mar-10 20:13 
AnswerRe: How do I pass a parameter to a .NET Web Service from a Java client Pinmemberabhi_here30-Mar-10 4:32 
GeneralPlz help !!!! PinmemberManjesh Yadav9-Aug-09 21:52 
GeneralHELP Pinmemberitcraps30-May-09 21:27 
QuestionCan return DAO/DTO? PinmemberAlessio84134-Apr-09 5:10 
GeneralConnect Applet ant .net Services using SSL Pinmembertropocolo16-Feb-09 3:44 
Generalcontent length Pinmembergaryemiller23-Jan-09 8:28 
GeneralException unhandled by usercode PinmemberTsubash5-Dec-08 0:22 
GeneralRe: Exception unhandled by usercode Pinmembercircle-driver5-Dec-08 8:46 
GeneralSolution for many problems Pinmembercircle-driver22-Nov-08 3:48 
GeneralRe: Solution for many problems PinmemberFerry Sumendap26-Nov-08 18:19 
GeneralRe: Solution for many problems Pinmembercircle-driver27-Nov-08 2:23 
Questionhow to call .net web sevice in java client using apache axis as iam new in web services Pinmembervymokesha16-Oct-08 6:12 
AnswerRe: how to call .net web sevice in java client using apache axis as iam new in web services Pinmembervymokesha7-Nov-08 9:01 
Generalmy asp.ner web service in unavailable for other program Pinmemberazijoon1-Aug-08 6:24 
GeneralRe: my asp.ner web service in unavailable for other program Pinmembercircle-driver22-Nov-08 3:53 
QuestionMethod with no parameter or x parameter other then 2 does not work? PinmemberEinstein's pal16-Jul-08 3:30 
GeneralRe: Method with no parameter or x parameter other then 2 does not work? PinmemberDecusterra24-Feb-09 5:19 
AnswerRe: Method with no parameter or x parameter other then 2 does not work? PinmemberTopzung213-Oct-11 1:43 

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