使用XFire調用WebService接口的步驟如下：

1. 添加XFire的依賴

<dependency>
    <groupId>org.codehaus.xfire</groupId>
    <artifactId>xfire-core</artifactId>
    <version>1.2.6</version>
</dependency>

2. 創建一個XFire的Service對象

import org.codehaus.xfire.XFireFactory;
import org.codehaus.xfire.service.Service;
import org.codehaus.xfire.client.Client;
import org.codehaus.xfire.transport.http.CommonsHttpMessageSender;

Service serviceModel = new ObjectServiceFactory().create(serviceClass, serviceName, namespace, endpoint);
XFire xfire = XFireFactory.newInstance().getXFire();
serviceModel.setProperty(CommonsHttpMessageSender.HTTP_CLIENT, new HttpClient());
Client client = new Client(serviceModel, xfire.getTransportManager(), xfire.getBindingProvider());

3. 設置WebService的地址

client.setUrl("http://localhost:8080/mywebservice");

4. 調用WebService的方法

Object[] result = client.invoke(operationName, params);

完整的示例代碼如下：

import org.codehaus.xfire.XFireFactory;
import org.codehaus.xfire.service.Service;
import org.codehaus.xfire.client.Client;
import org.codehaus.xfire.transport.http.CommonsHttpMessageSender;
import org.apache.commons.httpclient.HttpClient;

public class XFireWebServiceClient {
    public static void main(String[] args) throws Exception {
        // 創建WebService的Service對象
        Service service = new ObjectServiceFactory().create(ServiceInterface.class, "service", "http://localhost:8080/Service", null);
        
        // 創建XFire對象
        XFire xfire = XFireFactory.newInstance().getXFire();
        
        // 創建WebService的Client對象
        Client client = new Client(service, xfire.getTransportManager(), xfire.getBindingProvider());
        
        // 設置WebService的地址
        client.setUrl("http://localhost:8080/mywebservice");
        
        // 調用WebService的方法
        Object[] result = client.invoke("operationName", new Object[]{"param1", "param2"});
    }
}

注意：在調用WebService接口之前，需要確保WebService的地址、命名空間、接口名和方法名等參數正確。