深度探索 Axis2：AXIOM：
http://www.ibm.com/developerworks/cn/webservices/ws-java2/index.html
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Axis2是全新设计的，在2004年的“Axis峰会”上，大家决定采用新的架构来让Axis更加的富有弹性，更有效率，并且更加的可配置。Axis2现在具有的一些feature:
Speed
Low memory foot print
AXIOM - AXis Object Model
Hot Deployment
Asynchronous Web Services
MEP Support - Message Exchange Patterns
Flexibility
Stability
Component-oriented deployment
Transport framework
WSDL support
有些feature现在看不懂，还是先动手做一下，感性认识一下吧
第一步：下载AXIS2。http://ws.apache.org/axis2/download.cgi 。很有趣，在apache的Web Service 的Project目录下面还看不到AXIS2。要下那个binary的版本，因为里面有例程。
第二步：Copy axis2.war到$TOMCAT_HOME/webapps目录下面。Tomcat好像只能用JDK1.4，我在JDK1.5 用不出来。
第三步：打开 http://localhost:8080/axis2 ，就可以看到axis2的Welcome页面了。点一下Validate 和Services，看是不是都没有错误。都没有错误的话，就表示deploy成功了。那个adminstration页面可以通过上传文件来hot deploy Web service，可以用来remote deploy。
第四步：研究例程。先从"samples/userguide/src"目录下的例程看起。看到写一个web service很简单嘛:
public class MyService {
public OMElement echo(OMElement element) throws XMLStreamException {
//Praparing the OMElement so that it can be attached to another OM Tree.
//First the OMElement should be completely build in case it is not fully built and still
//some of the xml is in the stream.
element.build();
//Secondly the OMElement should be detached from the current OMTree so that it can be attached
//some other OM Tree. Once detached the OmTree will remove its connections to this OMElement.
element.detach();
return element;
}
public void ping(OMElement element) throws XMLStreamException {
//Do some processing
}
public void pingF(OMElement element) throws AxisFault{
throw new AxisFault("Fault being thrown");
}
}
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看得出来，函数统一使用OMElement作为参数。在META-INF目录下面有个services.xml文件：
<service name="MyService"> <description> This is a sample Web Service with two operations,echo and ping. </description> <parameter name="ServiceClass" locked="false">userguide.example1.MyService</parameter> <operation name="echo"> <messageReceiver class="org.apache.axis2.receivers.RawXMLINOutMessageReceiver"/> </operation> <operation name="ping"> <messageReceiver class="org.apache.axis2.receivers.RawXMLINOnlyMessageReceiver"/> </operation> </service>
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呵呵，也很简单嘛。有返回值的就用RawXMLINOutMessageReceiver，没返回值的就用RawXMLINOnlyMessageReceiver。把它们编译(要把axis2的jar写到classpath里去)打包压到 MyService.aar，包里文件目录如下：
./\META-INF/services.xml
./userguide/example1/MyService.class
把MyService.aar拷贝到$TOMCAT_HOME/webapps/axis2/WEB-INF/services，然后去点一下http://localhost:8080/axis2 页面上的Services，也就是http://localhost:8080/axis2/listServices.jsp ，就可以看到MyService已经被列出来了。
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客户端的调用
Web services提供的服务多种多样，有的可以马上获得结果，有的要消耗很长的时间。所以，如果我们需要多种调用方式来对付不同的情况。
大多数的Web services都提供阻塞(Blocking)和非阻塞(Non-Blocking)两种APIs.
这两个概念以前应该学过，简单说一下。
Blocking API - 调用端要等被调用的函数运行完毕才继续往下走。
Non-Bloking API - 调用端运行完调用函数以后就直接往下走了，调用端和被调用端是异步执行的。返回值是用回调函数来实现的。
这种异步叫做API层异步（API Level Asynchrony）。他们只用到一个连接来发送和接收消息，而且，如果是那种需要运行很长时间的函数，还会碰到Time Out 错误，如果用两个连接分别处理发送和接收消息，调用的时间就可以缩短，也可以解决Time Out 问题。用两个连接来分别处理发送和接收消息，叫做传输层异步（Transport Level Asynchrony）。
理论真无聊，还是来看实例吧。
打开 Eclipse, 创建一个新Project, 新建一个叫userguide.clients的包, 把"samples\userguide\src\userguide\clients" 下面的文件都copy到那个包下面, 把AXIS2的lib下面的jar都加到ilbrary里面去(应该不用全加,懒一点就全加了吧.) 发现了关于echo的调用的方式, 居然有五个:
EchoBlockingClient
EchoBlockingDualClient
EchoBlockingWsaBasedClient
EchoNonBlockingClient
EchoNonBlockingDualClient
一个一个看吧.
EchoBlockingClient.java
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();
Call call = new Call();
call.setTo(targetEPR);
call.setTransportInfo(Constants.TRANSPORT_HTTP,
Constants.TRANSPORT_HTTP,
false);
//Blocking invocation
OMElement result = call.invokeBlocking("echo",
payload);
StringWriter writer = new StringWriter();
result.serializeWithCache(XMLOutputFactory.newInstance()
.createXMLStreamWriter(writer));
writer.flush();
System.out.println(writer.toString());
} catch (AxisFault axisFault) {
axisFault.printStackTrace();
} catch (XMLStreamException e) {
e.printStackTrace();
}
}
}
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和一代几乎一样, 弄一个EndpointReference, 再弄一个call, 其他不一样,但是也很简单， 弄一个OMElement作为参数, 返回也是一个OMElement. 可惜运行居然有错.
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再来看双通道的版本
EchoBlockingDualClient.java
public class EchoBlockingDualClient {
private static EndpointReference targetEPR = new EndpointReference("http://127.0.0.1:8080/axis2/services/MyService");
public static void main(String[] args) {
try {
OMElement payload = ClientUtil.getEchoOMElement();
Call call = new Call();
call.setTo(targetEPR);
call.engageModule(new QName(Constants.MODULE_ADDRESSING));
call.setTransportInfo(Constants.TRANSPORT_HTTP,
Constants.TRANSPORT_HTTP,
true);
//Blocking Invocation
OMElement result = call.invokeBlocking("echo",
payload);
StringWriter writer = new StringWriter();
result.serializeWithCache(XMLOutputFactory.newInstance()
.createXMLStreamWriter(writer));
writer.flush();
System.out.println(writer.toString());
//Need to close the Client Side Listener.
call.close();
} catch (AxisFault axisFault) {
axisFault.printStackTrace();
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
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加了一句engageModule, 这句话好像没什么用，我删掉这句话也能运行的, 然后setTransportInfo最后一个参数改成了true. 关于setTransportInfo的三个参数, 第一个是发送的Transport, 第二个是接收的Transport, 第三个是"是否双通道", 支持的搭配形式如下:
http, http, true
http, http, false
http,smtp,true
smtp,http,true
smtp,smtp,true
看下一个吧，EchoNonBlockingClient，这个是单通道的非阻塞模式：
public class EchoNonBlockingClient {
private static EndpointReference targetEPR = new EndpointReference("http://127.0.0.1:8080/axis2/services/MyService");
public static void main(String[] args) {
try {
OMElement payload = ClientUtil.getEchoOMElement();
Call call = new Call();
call.setTo(targetEPR);
call.setTransportInfo(Constants.TRANSPORT_HTTP,
Constants.TRANSPORT_HTTP,
false);
//Callback to handle the response
Callback callback = new Callback() {
public void onComplete(AsyncResult result) {
try {
StringWriter writer = new StringWriter();
result.getResponseEnvelope().serializeWithCache(XMLOutputFactory.newInstance()
.createXMLStreamWriter(writer));
writer.flush();
System.out.println(writer.toString());
} catch (XMLStreamException e) {
reportError(e);
}
}
public void reportError(Exception e) {
e.printStackTrace();
}
};
//Non-Blocking Invocation
call.invokeNonBlocking("echo", 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();
}
}
}
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不同的地方，只是调用的方法从invokeBlocking变成了invokeNonBlocking，然后写了一个简单的匿名Callback类作为回调函数。关于这个Callback类，它是一个抽象类，其中有两个方法：onComplete和reportError，都是client端必须实现的，他还有一个Field，就是complete，可以用来设置和查询调用是否完成。可惜也不能运行，和上面的错误一样，是在createSOAPMessage的时候报null错误。
看下一个EchoNonBlockingDualClient，非阻塞的双通道：
public class EchoNonBlockingDualClient {
private static EndpointReference targetEPR = new EndpointReference("http://127.0.0.1:8080/axis2/services/MyService");
public static void main(String[] args) {
try {
OMElement payload = ClientUtil.getEchoOMElement();
Call call = new Call();
call.setTo(targetEPR);
//The boolean flag informs the axis2 engine to use two separate transport connection
//to retrieve the response.
call.engageModule(new QName(Constants.MODULE_ADDRESSING));
call.setTransportInfo(Constants.TRANSPORT_HTTP,
Constants.TRANSPORT_HTTP,
true);
//Callback to handle the response
Callback callback = new Callback() {
public void onComplete(AsyncResult result) {
try {
StringWriter writer = new StringWriter();
result.getResponseEnvelope().serializeWithCache(XMLOutputFactory.newInstance()
.createXMLStreamWriter(writer));
writer.flush();
System.out.println(writer.toString());
} catch (XMLStreamException e) {
reportError(e);
}
}
public void reportError(Exception e) {
e.printStackTrace();
}
};
//Non-Blocking Invocation
call.invokeNonBlocking("echo", payload, callback);
//Wait till the callback receives the response.
while (!callback.isComplete()) {
Thread.sleep(1000);
}
//Need to close the Client Side Listener.
call.close();
} catch (AxisFault axisFault) {
axisFault.printStackTrace();
} catch (Exception ex) {
ex.printStackTrace();
}
}
}
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