使用Axis2的底层API开发Web Service

    本文是在理解官方指南的基础上，用实例实现Axis2提供的4种调用机制，并给出测试结果。
Blog: http://zhangjunhd.blog.51cto.com/

1．使用Axis2的底层API开发Web Service Server端
1.1创建一个WebService(取名为MyService)
    在MyService中有两个operations,如下所示。
public void ping(OMElement element){}//IN-ONLY模式。仅仅接收OMElement，并对其处理。
public OMElement echo(OMElement element){}//IN_OUT模式。接收OMElemen，并返回OMElement。

1.2如何写Web Service
1）创建实现服务的类。
2）创建services.xml来解析这个Web Service。
3）将其打包成一个*.aar文档（Axis Archive）。
4）部署Web Service。

1.2.1 创建实现服务的类
    此类中提供的方法必须与Web Service（在services.xml中声明）中的operations对应。除非你提供了数据绑定，否则所有的方法只能接收一个参数，其类型为OMElement。
public class MyService{
  public void ping(OMElement element){...}
  public OMElement echo(OMElement element){...}
}
MyService.java
package userguide.example1;
import org.apache.axiom.om.OMElement;
import org.apache.axis2.AxisFault;
import javax.xml.stream.XMLStreamException;
public class MyService {
    public OMElement echo(OMElement element) throws XMLStreamException {
        //Praparing the OMElement so that it can be attached to another OM Tree.
        //First the OMElement should be completely build in case it is not fully built and still
        //some of the xml is in the stream.
        element.build();
        //Secondly the OMElement should be detached from the current OMTree so that it can
        // be attached some other OM Tree. Once detached the OmTree will remove its
       // connections to this OMElement.
        element.detach();
        return element;
    }
    public void ping(OMElement element) throws XMLStreamException {
        //Do some processing
    }
    public void pingF(OMElement element) throws AxisFault{
        throw new AxisFault("Fault being thrown");
    }
}

1.2.2 创建services.xml
    Axis2使用services.xml来充当一个Web Servicea的配置文件。每一个使用Axis2部署的Web Service都必须拥有一个services.xml。
<services>
  <description>
    This is a sample Web Service with two operations,echo and ping.
  </description>
  <parameter name=”ServiceClass” locked=”false”>
  userguide.example1.MyService
  </parameter>
  <operation name=”echo”>
    <messageReceiver class=”org.apache.axis2.receivers.RawXMLINOutMessageReceiver”/>
    <actionMapping>urn:echo</actionMapping>
  </operation>
  <operation name=”ping”>
    <messageReceiver class=”org.apache.receivers.RawXMLINOnlyMessageReceiver”/>
    <actionMapping>urn:ping</actionMapping>
  </operation>
</service>
注：The actionMapping is required only if you want to enable WS-Addressing.
    可以创建一个services.xml，其中包含一组服务。这样在运行期，你可以在这些服务间共享信息。
<serviceGroup>
  <service name=”Service1”>
    <!--details for Services1-->
  </service>
<service name=”Service2”>
    <!--details for Services2-->
  </service>
  <module ref=”ModuleName”/>
  <parameter name=”serviceGroupParam1” locked=”false”>value1</parameter>
</serviceGroup>
注：name of the service is a compulsory attribute.

1.2.3打包与部署
    这里不再详述，参见《基于Tomcat5.0和Axis2开发Web Service应用实例 》。

2．使用Axis2底层APIs实现Web Service客户端
2.1ClientUtil
    创建一个客户端通用的SOAP包装Util文件。封装"getEchoOMElement"和"getPingOMElement"分别对应"echo"和"ping"这两个operation。
ClientUtil.java
package userguide.clients;
import org.apache.axiom.om.OMAbstractFactory;
import org.apache.axiom.om.OMElement;
import org.apache.axiom.om.OMFactory;
import org.apache.axiom.om.OMNamespace;
public class ClientUtil {
    public static OMElement getEchoOMElement() {
        OMFactory fac = OMAbstractFactory.getOMFactory();
        OMNamespace omNs = fac.createOMNamespace(
                "http://example1.org/example1", "example1");
        OMElement method = fac.createOMElement("echo", omNs);
        OMElement value = fac.createOMElement("Text", omNs);
        value.addChild(fac.createOMText(value, "Axis2 Echo String "));
        method.addChild(value);
        return method;
    }
    public static OMElement getPingOMElement() {
        OMFactory fac = OMAbstractFactory.getOMFactory();
        OMNamespace omNs = fac.createOMNamespace(
                "http://example1.org/example1", "example1");
        OMElement method = fac.createOMElement("ping", omNs);
        OMElement value = fac.createOMElement("Text", omNs);
        value.addChild(fac.createOMText(value, "Axis2 Ping String "));
        method.addChild(value);
        return method;
    }
}

2.2EchoBlockingClient
    Axis2向用户提供了从blocking single channel调用到non-blocking dual channel调用的多种调用Web Service的模式。下面用最简单的blocking调用机制来实现”MyService”中的"echo" operation。
EchoBlockingClient.java
package userguide.clients;
import org.apache.axiom.om.OMElement;
import org.apache.axis2.AxisFault;
import org.apache.axis2.addressing.EndpointReference;
import org.apache.axis2.client.Options;
import org.apache.axis2.client.ServiceClient;
/**
* Sample for synchronous single channel blocking service invocation.
* Message Exchage Pattern IN-OUT
*/
public class EchoBlockingClient {
private static EndpointReference targetEPR =
new EndpointReference("http://localhost:8080/axis2/services/MyService");
    public static void main(String[] args) {
try {
            OMElement payload = ClientUtil.getEchoOMElement();
            Options options = new Options();
            options.setTo(targetEPR); // this sets the location of MyService service
            ServiceClient serviceClient = new ServiceClient();
            serviceClient.setOptions(options);
            OMElement result = sender.sendReceive(payload);
            System.out.println(result);
} catch (AxisFault axisFault) {
         axisFault.printStackTrace();
}
}
    绿色部分显示了为了调用一个Web Service而需要对operation作的设置。剩下的部分是用来创建OMElement，用来发送和显示相应的OMElement。

结果：
<example1:echo xmlns:example1="http://example1.org/example1"
xmlns:tns="http://ws.apache.org/axis2">
<example1:Text>
Axis2 Echo String
</example1:Text>
</example1:echo>

2.3 PingClient
    在”MyService”中，我们有一种IN-ONLY模式的名为"ping"的operation。应用它的客户端代码如下：
PingClient.java
package userguide.clients;
import org.apache.axiom.om.OMElement;
import org.apache.axis2.AxisFault;
import org.apache.axis2.addressing.EndpointReference;
import org.apache.axis2.client.Options;
import org.apache.axis2.client.ServiceClient;
/**
* Sample for fire-and-forget service invocation
* Message Exchage Pattern IN-Only
*/
public class PingClient {
private static EndpointReference targetEPR =
new EndpointReference("http://localhost:8080/axis2/services/MyService");
    public static void main(String[] args) {
try {
       OMElement payload = ClientUtil.getPingOMElement();
       Options options = new Options();
       options.setTo(targetEPR);
       ServiceClient serviceClient = new ServiceClient();
       serviceClient.setOptions(options);
       serviceClient.fireAndForget(payload);
        /**
         * We have to block this thread untill we send the request , the problem
         * is if we go out of the main thread , then request wont send ,so
         * you have to wait some time
         */
       Thread.sleep(500);
     }
catch (AxisFault axisFault) {
            axisFault.printStackTrace();
     }
}
    由于我们在访问一个IN-ONLY模式的operation，所以我们可以直接使用ServiceClient中的"fireAndForget()"方法来调用这个operation。而且那样做的话，不会阻塞发起端，因此，它会立刻将控制权返回给客户端。

2.4 EchoNonBlockingClient
    在客户端EchoBlockingClient，一旦调用"serviceClient.sendReceive(payload);"，客户端将会被阻塞直到operation完成。这种方式在有很多Web Service需要在一个单一的客户端应用程序中启动时很不可取。一种解决方法是使用Non-Blocking API来调用这些Web Services。Axis2提供给用户一种基于回叫机制的non-blocking API。
EchoNonBlockingClient.java
package userguide.clients;
import org.apache.axiom.om.OMElement;
import org.apache.axis2.AxisFault;
import org.apache.axis2.addressing.EndpointReference;
import org.apache.axis2.client.Options;
import org.apache.axis2.client.ServiceClient;
import org.apache.axis2.client.async.AsyncResult;
import org.apache.axis2.client.async.Callback;
/**
* Sample for asynchronous single channel non-blocking service invocation.
* Message Exchage Pattern IN-OUT
*/
public class EchoNonBlockingClient {
private static EndpointReference targetEPR =
new EndpointReference("http://127.0.0.1:8080/axis2/services/MyService");
    public static void main(String[] args) {
        ServiceClient sender = null;
        try {
            OMElement payload = ClientUtil.getEchoOMElement();
            Options options = new Options();
            options.setTo(targetEPR);
            //Callback to handle the response
            Callback callback = new Callback() {
                public void onComplete(AsyncResult result) {
                    System.out.println(result.getResponseEnvelope());
                }
                public void onError(Exception e) {
                    e.printStackTrace();
                }
            };
            //Non-Blocking Invocation
            sender = new ServiceClient();
            sender.setOptions(options);
            sender.sendReceiveNonBlocking(payload, callback);
            //Wait till the callback receives the response.
            while (!callback.isComplete()) {
                Thread.sleep(1000);
            }
        } catch (AxisFault axisFault) {
            axisFault.printStackTrace();
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            try {
                sender.finalizeInvoke();
            } catch (AxisFault axisFault) { }
        }
    }
}

结果：
<?xml version='1.0' encoding='utf-8'?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
<soapenv:Header />
<soapenv:Body>
<example1:echo xmlns:example1="http://example1.org/example1"
xmlns:tns="http://ws.apache.org/axis2">
<example1:Text>
Axis2 Echo String
</example1:Text>
</example1:echo>
</soapenv:Body>
</soapenv:Envelope>
    sender.sendReceiveNonBlocking(payload, callback);这个调用接受一个callback对象作为参数。Axis2客户端API提供了一个抽象类CallBack，其中提供了方法：
public abstract void onComplete(AsyncResult result);
public abstract void onError(Exception e);
public boolean isComplete() {}
    用户需要重写"onComplete " 和 "onError "方法。一旦客户端收到Web Service的response，onComplete方法将会被调用，这样将中止阻塞状态。

2.5EchoNonBlockingDualClient
    当调用的Web Service需要很长一段时间来完成时，这种由Non-Blocking API提供的解决方式将有一定的局限性。这种局限性是由使用单一的传输连接来调用Web Service并接收response造成的。换句话说，客户端提供一种没有阻塞的调用机制，但request和response的传输使用单一的传输（双工方式）连接（如HTTP）。长时间运行的Web Service调用或Web Service调用使用单工传输方式（如SMTP）不能简单地利用一个没有阻塞的调用。
    一种尝试地解决方法是request和response各自使用单独的传输连接（单工或双工均可）。这种方式产生的问题是如何解决相关性（关联request和response）。WS-Addressing提供了一种很好的解决方法，在头中使用<wsa:MessageID> 和 <wsa:RelatesTo> 标签。Axis2对这种基于关联机制的寻址方式提供了支持。
    用户可以选择Blocking 或Non-Blocking APIs的Web Service，并使用两个传输连接。通过使用一个布尔标记，同一个API可以调用多个在两个传输连接上的Web Services(IN-OUT operations)。下例使用Non-Blocking API 以及两个传输连接来实现上文中提到的"echo" operation。
EchoNonBlockingDualClient.java
package userguide.clients;
import org.apache.axiom.om.OMElement;
import org.apache.axis2.AxisFault;
import org.apache.axis2.Constants;
import org.apache.axis2.addressing.EndpointReference;
import org.apache.axis2.client.Options;
import org.apache.axis2.client.ServiceClient;
import org.apache.axis2.client.async.AsyncResult;
import org.apache.axis2.client.async.Callback;
import javax.xml.namespace.QName;
/**
* Sample for asynchronous dual channel non-blocking service invocation.
* Message Exchage Pattern IN-OUT
* Ulitmate asynchronous service invocation sample.
*/
public class EchoNonBlockingDualClient {
private static EndpointReference targetEPR =
new EndpointReference("http://127.0.0.1:8080/axis2/services/MyService");
    public static void main(String[] args) {
        ServiceClient sender = null;
        try {
            OMElement payload = ClientUtil.getEchoOMElement();
            Options options = new Options();
            options.setTo(targetEPR);
            options.setTransportInProtocol(Constants.TRANSPORT_HTTP);
            options.setUseSeparateListener(true);
            options.setAction("urn:echo");  // this is the action mapping we put within the service.xml
            //Callback to handle the response
            Callback callback = new Callback() {
                public void onComplete(AsyncResult result) {
                    System.out.println(result.getResponseEnvelope());
                }
                public void onError(Exception e) {
                    e.printStackTrace();
                }
            };
            //Non-Blocking Invocation
           ConfigurationContext sysContext = ConfigurationContextFactory
            .createConfigurationContextFromFileSystem(
             "D:\\Dvp\\Axis2\\axis2\\WEB-INF", null);//见注解①
            sender = new ServiceClient(sysContext, null);
            sender.engageModule(new QName(Constants.MODULE_ADDRESSING));
            sender.setOptions(options);
            sender.sendReceiveNonBlocking(payload, callback);
            //Wait till the callback receives the response.
            while (!callback.isComplete()) {
                Thread.sleep(1000);
            }
            //Need to close the Client Side Listener.
        } catch (AxisFault axisFault) {
            axisFault.printStackTrace();
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            try {
                sender.finalizeInvoke();
            } catch (AxisFault axisFault) {
                //have to ignore this
            }
        }
    }
}
注解①
RE: [Axis2] 0.95 WS-Addressing web SERVICE-SIDE: module not found
    I now have managed to get EchoNonBlockingDualClient working. I still can't get the original code to work, where ever I put addressing-0.95.mar, but the ConfigurationContext works.
    The code I ended up with was:
ConfigurationContext sysContext = ConfigurationContextFactory
           .createConfigurationContextFromFileSystem(
            "C:\\axis2", null);
  sender = new ServiceClient(sysContext, null);
    with no need, obviously, for the .engageModule method.
    I did discover though that the directory which the ConfigurationContext points to has to have two directories within it: "conf", which must contain the axis.xml configuration file, and the "modules" directory which contains addressing-0.95.mar.
    在方法"options.setUseSeparateListener(...)"中的布尔标记通知通知Axis2引擎使用两个不同的传输连接来分别处理request和response。Finally中的 "serviceClient.finalizeInvoke()"方法通知Axis2引擎停用客户端的用于接收response的listener。
    在我们运行客户端的例程之前，我们还有一件事情要做。如前面提到的，Axis2使用基于地址的关联机制，因此我们必须在服务器端和客户端“搭建”寻址模块。

结果：
<?xml version='1.0' encoding='utf-8'?>
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:wsa="http://www.w3.org/2005/08/addressing">
<soapenv:Header>
<wsa:To>http://59.14.131.187:6060/axis2/services/__ANONYMOUS_SERVICE__/__OPERATION_OUT_IN__
</wsa:To>
<wsa:ReplyTo>
<wsa:Address>
http://www.w3.org/2005/08/addressing/anonymous
</wsa:Address>
</wsa:ReplyTo>
<wsa:From>
<wsa:Address>
http://127.0.0.1:8080/axis2/services/MyService
</wsa:Address>
</wsa:From>
<wsa:FaultTo>
<wsa:Address>
http://127.0.0.1:8080/axis2/services/MyService
</wsa:Address>
</wsa:FaultTo>
<wsa:MessageID>
urn:uuid:B087CBB98F1B51A24711742241136206
</wsa:MessageID>
<wsa:Action>urn:echo</wsa:Action>
<wsa:RelatesTo wsa:RelationshipType="wsa:Reply">
urn:uuid:CA4B9513377E6E9E1511742241130391
</wsa:RelatesTo>
</soapenv:Header>
<soapenv:Body>
<example1:echo xmlns:example1="http://example1.org/example1" xmlns:tns="http://ws.apache.org/axis2">
<example1:Text>
Axis2 Echo String
</example1:Text>
</example1:echo>
</soapenv:Body>
</soapenv:Envelope>
[SimpleHTTPServer] Stop called

2.6 实现服务器端的寻址
    根据Axis2的结构，寻址模块在"pre-dispatch"阶段已经给出它的句柄。因此，所谓的“搭建”仅仅是在”axis2.xml”（注意不是services.xml）增加一个模块的引用。现在将下面这行字加入到axis2.xml，该文件在"/webapps/axis2/WEB-INF/conf"目录下。
<module ref="addressing"/>
注： 一旦你改变了axis2.xml，你必须重启这个servlet容器，改变才能生效。

2.7 实现客户端的寻址
    有两种方式。
    一种方法是在%Axis2_HOME%\axis2-std-1.0-bin\modules目录下得到addressing-<version>.mar。并且在你的classpath中对其可见。（此种方法目前，我还没有调试成功，具体见注解①。下面的第二种方法可用）
    另一种方法是创建一个ConfigurationContext，指定一个repository位置。Axis2支持repository的方式来保存服务和模块。
    你可以使用二进制distribution作为repository，只要它含有一个Axis2 repository认可的repository结构（其中应包含services和modules目录）。ConfigurationContext 中含有Axis2体系的运行时的上下文信息。
    如果你解压一个标准的二进制distribution到目录（譬如）$user_home/axis2/dist, 那么在 sender = new ServiceClient();之前加入（具体见EchoNonBlockingDualClient.java）：
new ServiceClient();之前加入（具体见EchoNonBlockingDualClient.java）：
ConfigurationContext configContext =
ConfigurationContextFactory.createConfigurationContextFromFileSystem(< Axis2RepositoryLocation >, null);
    用"sender = new ServiceClient(configContext, null);" 替换 "sender = new ServiceClient();"
这样可以在客户端和服务器端都实现寻址。

2.8 EchoBlockingDualClient
    这又是一个两路的传输的request/response客户端，但这次，我们使用一个Blocking API。实现机制和EchoNonBlockingDualClient差不多，唯一的不同是，这里不需要使用一个callback对象来处理response。
EchoBlockingDualClient.java
package userguide.clients;
import org.apache.axiom.om.OMElement;
import org.apache.axis2.AxisFault;
import org.apache.axis2.Constants;
import org.apache.axis2.addressing.EndpointReference;
import org.apache.axis2.client.Options;
import org.apache.axis2.client.ServiceClient;
import javax.xml.namespace.QName;
import javax.xml.stream.XMLOutputFactory;
import java.io.StringWriter;
/**
* Sample for synchronous dual channel blocking service invocation.
* Message Exchage Pattern IN-OUT
*/
public class EchoBlockingDualClient {
private static EndpointReference targetEPR =
new EndpointReference("http://127.0.0.1:8080/axis2/services/MyService");
    public static void main(String[] args) {
        ServiceClient sender = null;
        try {
            OMElement payload = ClientUtil.getEchoOMElement();
            Options options = new Options();
            options.setTo(targetEPR);
            options.setAction("urn:echo");
            //The boolean flag informs the axis2 engine to use two separate transport connection
            //to retrieve the response.
            options.setTransportInProtocol(Constants.TRANSPORT_HTTP);
            options.setUseSeparateListener(true);
            //Blocking Invocation
            ConfigurationContext sysContext = ConfigurationContextFactory
            .createConfigurationContextFromFileSystem(
             "D:\\Dvp\\Axis2\\axis2\\WEB-INF", null);
            sender = new ServiceClient(sysContext, null);
            sender.engageModule(new QName(Constants.MODULE_ADDRESSING));
            sender.setOptions(options);
            OMElement result = sender.sendReceive(payload);
            StringWriter writer = new StringWriter();
           result.serialize(XMLOutputFactory.newInstance().createXMLStreamWriter(writer));
            writer.flush();
            System.out.println(writer.toString());
            //Need to close the Client Side Listener.
        } catch (AxisFault axisFault) {
            axisFault.printStackTrace();
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally{
            try {
                sender.finalizeInvoke();
            } catch (AxisFault axisFault) {
                //
            }
        }
    }
}
结果：
<example1:echo xmlns:example1="http://example1.org/example1" xmlns:tns="http://ws.apache.org/axis2">
<example1:Text>Axis2 Echo String </example1:Text>
</example1:echo>
[SimpleHTTPServer] Stop called

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