XML Web service – Simple SOAP client

Here you'll have complete example on how to invoke a web-service, in a simple Java client, using SOAP as a messaging protocol over HTTP, given the webservice WSDL file of the previous post. That may help you better understand webservice / client communication in distributed systems.
Client will read SOAP request from a local xml file, then make HTTP connection to webservice url and send SOAP message over the given connection.


First, lets design the xml SOAP request, to invoke sayHi method of the previous webservice:

- Envelope element: root element of SOAP request, contains namespace declaration of soap; xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
- Body: contains elements of actual request message (with fully qualified name), i.e: the method to be invoked and input parameters if any,
<sayHi xmlns="http://test">
<name>clientName</name>
</sayHi>

Notes:
* namespace uri is the same one used to define target namespace in wsdl
* child element of method is the input parameter of sayHi; which is called "name" of type string. (see previous post)

SOAP request looks like this:

<?xml version="1.0" ?>
<soapenv:Envelope
xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<sayHi xmlns="http://test">
<name>clientName</name>
</sayHi>
</soapenv:Body>
</soapenv:Envelope>


lets save soap request in xml file, say at C:/soapclient.xml

To complete SOAP request, we will add the following to http header (using POST method):
* Content-Length : -length of request data-
* Content-Type: text/xml; charset=utf-8
* SOAPAction: "" (as mentioned in wsdl, inside soap:binding of 'sayHi' operation)


Client code will open fileInput stream to read C:/soapclient.xml, and send the content to webservice URL: http://localhost:8080/service/services/MainService
(as mentioned in wsdl under <wsdlsoap:address>)


public class MainClient {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

String urlStr=
"http://localhost:8080/service/services/MainService";
try {
URL url=new URL(urlStr);
HttpURLConnection conn=(HttpURLConnection)url.openConnection();
FileInputStream fin = new FileInputStream("C:/soapclient.xml");

ByteArrayOutputStream bout = new ByteArrayOutputStream();

// Copy the SOAP file to the open connection.
copy(fin,bout);
fin.close();

byte[] b = bout.toByteArray();

// Set the appropriate HTTP parameters.
conn.setRequestProperty( "Content-Length",
String.valueOf( b.length ) );
conn.setRequestProperty("Content-Type",
"text/xml; charset=utf-8");
conn.setRequestProperty("SOAPAction","");
conn.setRequestMethod( "POST" );
conn.setDoOutput(true);
conn.setDoInput(true);

// Everything's set up; send the XML that was read in to b.
OutputStream out = conn.getOutputStream();
out.write( b );
out.close();

// Read the response and write it to standard out.

InputStreamReader isr =
new InputStreamReader(conn.getInputStream());
BufferedReader in = new BufferedReader(isr);

String inputLine;

while ((inputLine = in.readLine()) != null)
System.out.println(inputLine);

in.close();
}
catch (Exception e) {
e.printStackTrace();
}
}

// copy method from From E.R. Harold's book "Java I/O"
public static void copy(InputStream in, OutputStream out)
throws IOException {

// do not allow other threads to read from the
// input or write to the output while copying is
// taking place

synchronized (in) {
synchronized (out) {

byte[] buffer = new byte[256];
while (true) {
int bytesRead = in.read(buffer);
if (bytesRead == -1) break;
out.write(buffer, 0, bytesRead);
}
}
}
}
}

Output of client will show SOAP response in console screen:

<?xml version="1.0" encoding="utf-8"?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<sayHiResponse xmlns="http://test">
<sayHiReturn>hi clientName</sayHiReturn>
</sayHiResponse>
</soapenv:Body>
</soapenv:Envelope>

Resources:
http://www.ibm.com/developerworks/xml/library/x-soapcl/
http://www.ibm.com/developerworks/xml/library/x-soapcl/listing1.html
http://www.ibm.com/developerworks/webservices/library/ws-intwsdl2/

Next, I'm going to show how to generate and invoke client using Axis2 apis.