Can i use Axis2 to write a client for SalesForce API?

Yes. Just run WSDL2Java with the following Options (with the forthcoming Axis2 1.3 Final):

wsdl2java -Eofv -g -uw -u -uri enterprise.wsdl

Notes:

• -Eofv : tells wsdl2java to be a little lax with the schema validation
• -g : tells wsdl2java generate all the classes specified in the schema, since usually WSDL2Java with ADB databinding generates only those complextypes / elements that are actually used in the wsdl
• -uw : Unwrap the parameters, makes it a little bit easier to write code
• -u : Unpacks the databinding classes, since by default when generating clients WSDL2Java generates all data types in the same Stub class
• -uri : location of the wsdl

Here's some sample code:

import com.sforce.soap.enterprise.LoginResult;
import com.sforce.soap.enterprise.QueryResult;
import com.sforce.soap.enterprise.SessionHeader;
import com.sforce.soap.enterprise.SforceServiceStub;
import com.sforce.soap.enterprise.sobject.Account;
import com.sforce.soap.enterprise.sobject.SObject;

import org.apache.axis2.client.Options;
import org.apache.axis2.transport.http.HTTPConstants;


public class Main {
    public static void main(String[] args) throws Exception {
        SforceServiceStub stub = new SforceServiceStub();
        Options options = stub._getServiceClient().getOptions();
        options.setProperty(HTTPConstants.MC_ACCEPT_GZIP, Boolean.TRUE);
        options.setProperty(HTTPConstants.MC_GZIP_REQUEST, Boolean.TRUE);

        LoginResult lr = stub.login("my@gmail.com", "abcdef", null);

        SessionHeader sh = new SessionHeader();
        sh.setSessionId(lr.getSessionId());

        stub = new SforceServiceStub(lr.getServerUrl());
        options = stub._getServiceClient().getOptions();
        options.setProperty(HTTPConstants.MC_ACCEPT_GZIP, Boolean.TRUE);
        options.setProperty(HTTPConstants.MC_GZIP_REQUEST, Boolean.TRUE);

        QueryResult qr = stub.query("select Name, numberOfEmployees, Id, Industry from Account",
                sh, null, null);

        System.out.println("Query has " + qr.getSize() + " records total");

        SObject[] sObjects = qr.getRecords();

        for (int i = 0; i < sObjects.length; i++) {
            Account sObject = (Account) sObjects[i];
            System.out.println(i + "\t: [" + sObject.getId() + "][" +
                sObject.getName() + "]");
        }
    }
}

Here's the sample output:

C:\axis2-1.3\sforce\client>java Main
Query has 13 records total
0       : [0017000000Kn04OAAR][GenePoint]
1       : [0017000000Kn04PAAR][United Oil & Gas, UK]
2       : [0017000000Kn06qAAB][United Oil & Gas, Singapore]
3       : [0017000000Kn06rAAB][Edge Communications]
4       : [0017000000Kn06sAAB][Burlington Textiles Corp of America]
5       : [0017000000Kn06tAAB][Pyramid Construction Inc.]
6       : [0017000000Kn06uAAB][Dickenson plc]
7       : [0017000000Kn06vAAB][Grand Hotels & Resorts Ltd]
8       : [0017000000Kn06wAAB][Express Logistics and Transport]
9       : [0017000000Kn06xAAB][University of Arizona]
10      : [0017000000Kn06yAAB][United Oil & Gas Corp.]
11      : [0017000000Kn06zAAB][sForce]
12      : [0017000000KmzIhAAJ][ABCED]