In Axis2 there are three kinds of configuration files to configure the system. First one configuration file is to configure whole system, second one is to configure a service and the third one is to configure a module.

Global Configuration

All the configuration that requires starting axis2 is obtained from axis2.xml. The way of specifying them is very simple and easy. The document is all about the proper way of specifying the configurations in axis2.xml. There are six top level elements that can be seen in the configuration file and those can be listed as follows;

Parameter
In axis2 a parameter is nothing but name value pair, each and every top level parameter available in the axis2.xml (direct sub elements of root element) will be transformed into properties in AxisConfiguration. Therefore the top level parameters in configuration document can be accessed via AxisConfiguration in the running system. The correct way of defining a parameter looks like what is shown below;

 
  <parameter name="name of the parameter" >parameter value </parameter>

Transport Receiver
Depending on the underline transport that axis going to be run , need to have different transport receivers so the way of adding them to the system can be done as follows;

 
<transportReceiver name="http" class="org.apache.axis2.transport.http.SimpleHTTPServer">
        <parameter name="port" >6060</parameter>
 </transportReceiver>
The above elements shows the way of defining transport receivers in axis2.xml , here name attribute of the 'transportReceiver' element is the name of transport it can be http, tcp , smtp , commonshttp stc , and when the system starts up or when setting transport at the client side one can use these transport names to load the appropriate transport. Class attribute is to specify actual java class which implements required interfaces for the transport. Any transport can have zero or more parameters, and if there are any, then those parameters can be accessed via the corresponding transport receiver.

Transport Senders
As same as transport receivers it is possible to register transport senders in the system, and latter at the run time those senders can be used to send the messages. As an example consider Axis2 running under tomcat, then axis can use TCP transport senders to send message rather than HTTP. The way of specifying transport senders is as follows:

 
<transportSender name="http" class="org.apache.axis2.transport.http.CommonsHTTPTransportSender">
        <parameter name="PROTOCOL" locked="xsd:false">HTTP/1.0</parameter>
 </transportSender>
name: Name of the transport (it is possible to have http and http1 as transport name) Class: Implementation class of the corresponding transport. As same as transport receivers, transport senders can have zero or more parameters, and if there is any then it can be accessed via corresponding transport sender.

Phase Order
The specifying order of phases in execution chain has to be done using phase order element and it will be look like below;

<phaseOrder type="inflow">
         <phase name="TransportIn"/>
         .
         .
</phaseOrder>
The most interesting thing is that you can add handlers here as well , if you want to add a handler which should go in to that phase you can directly do that by adding a handler element into it . In addition to that there is no any hard coding stuffs for handler chain in anywhere in Axis2 (at any Axis*) , so all those configuration are also done here in phase order element. The complete configuration will look like as follows; 
<phaseOrder type="inflow"">
        <!--  System pre defined phases       --">
        <phase name="TransportIn"/">
        <phase name="PreDispatch"/">
        <phase name="Dispatch" class="org.apache.axis2.engine.DispatchPhase">
            <handler name="AddressingBasedDispatcher"
                     class="org.apache.axis2.engine.AddressingBasedDispatcher"">
                <order phase="Dispatch"/">
            </handler">
             <handler name="RequestURIBasedDispatcher"
                     class="org.apache.axis2.engine.RequestURIBasedDispatcher"">
                <order phase="Dispatch"/">
            </handler">
             <handler name="SOAPActionBasedDispatcher"
                     class="org.apache.axis2.engine.SOAPActionBasedDispatcher"">
                <order phase="Dispatch"/">
            </handler">
             <handler name="SOAPMessageBodyBasedDispatcher"
                     class="org.apache.axis2.engine.SOAPMessageBodyBasedDispatcher"">
                <order phase="Dispatch"/">
            </handler">
            <handler name="InstanceDispatcher"
                     class="org.apache.axis2.engine.InstanceDispatcher"">
                <order phase="Dispatch"/">
            </handler">
        </phase">
        <!--  Sysem pre defined phases       --">
        <!--   After Postdispatch phase module author or or service author can add any phase he want      --">
        <phase name="OperationInPhase"/">
    </phaseOrder">
    <phaseOrder type="outflow"">
        <!--      user can add his own phases to this area  --">
        <phase name="OperationOutPhase"/">
        <!--system predefined phase--">
        <!--these phase will run irrespective of the service--">
        <phase name="PolicyDetermination"/">
        <phase name="MessageOut"/">
    </phaseOrder">
    <phaseOrder type="INfaultflow"">
        <!--      user can add his own phases to this area  --">
        <phase name="OperationInFaultPhase"/">
    </phaseOrder">
    <phaseOrder type="Outfaultflow"">
        <!--      user can add his own phases to this area  --">
        <phase name="OperationOutFaultPhase"/">
        <phase name="PolicyDetermination"/">
        <phase name="MessageOut"/">
    </phaseOrder">
type: the attribute represent type of the flow and which can only be one of the following

In addition to that only child element allowed inside pahseOrder is phase element, which represents available phases in the execution chain. The way of specifying phase inside phaseOrder has to be done as follows;

 <phase name="TransportIn"/>
name: Name of the phase.
There are number of things that one has to keep in mind when changing pahseOrder,
    there are phases called system pre-defined phases in all four flows;
    You are not allowed change those , and you can add new phase after system pre-defined phase
    If you closely look at the default axis2.xml can clearly identify that.

Module References
If you want to engage a module system wide you can do it by adding top level module element in axis2.xml. It should be look like following:

<module ref="addressing"/>
ref: the module name which is going to be engage, system wide.

Listeners (Observers)

In Axis2 AxisConfiguration is observable so that one can register observers into that, and they will be automatically informed whenever a change occurs in AxisConfiuration. In the current implementation the observers are informed of the following events

Registering Observers is very useful for additional features such as RSS feed generation which will provide service information to subscribers. The correct way of registering observers should be like below; 
<listener class="org.apache.axis2.ObserverIMPL">
    <parameter name="RSS_URL" >http://127.0.0.1/rss</parameter>
  </listener>
class: Represent an Implementation class of observer, and it should be note that the implementation class should implement AxisObserver interface, and the class has to be available in the classpath.

Service Configuration

The description of service is specified using services.xml, each service archive file need to have services.xml in order to be a valid service. And which has to be available in META-INF directory of the archive file.
A very simple services.xml is shown below:

<service name="name of the service" scope="name of the scope" targetNamespace="target namespase for the service">
    <description> The description of the service  </description>  

    <transports> 
       <transport>HTTP</transport>
    </transports>
    
    <schema schemaNamespace="schema namespace"/> 
     
    <messageReceivers>
            <messageReceiver mep="http://www.w3.org/2004/08/wsdl/in-out"
                             class="org.apache.axis2.rpc.receivers.RPCMessageReceiver"/>
    </messageReceivers>
     
     <parameter name="ServiceClass"     locked="xsd:false">org.apache.axis2.sample.echo.EchoImpl</parameter>
    
    <operation name="echoString" mep="operation MEP"> 
        <actionMapping>Mapping to action</actionMapping>
        <module ref=" a module name "/>
        <messageReceiver class="org.apache.axis2.receivers.RawXMLINOutMessageReceiver"/>
    </operation>
  </service>
name: the service name will be the name of the archive file if the .aar file contains only one service else name of the service will be the name given by the name attribute

scope : Scope that the service need to be deployed and scope can be one of "Application","SOAPSession","TransportSession","Request";

targetNamespace : Targtet name space of the service , and this value will be used when generation wsdl

description: This is an optional element if you want to display any description about the service via Axis2 web-admin module then the description can be specified here.

transports : The transports that the service is going to be exposed , this is an optional element . If the transports element is not present then the service will be exposed in every transports available in the system. The transport child element is to specify the transport prefix (the name of the transport specified in axis2.xml)

Parameter:
services.xml can have any number of top level parameters and all the specified parameters will be transformed into service properties in corresponding AxisService. There is a compulsory parameter in a services.xml called ServiceClass which specify the java class which really does the job and the class will be loaded by MessageReceiver.

Operations
If the service impl class is java then all the public methods in that service will be exposed and if user wnats to override then he has to add operation tag and override that . In the case of Non-Java case or if you does no thave service class then all the operations user wants to expose by the service has to be indicated in the services.xml and the correct way of specifying that should be as follows:

    <operation name="echoString">
        <module ref=" a module name "/>
        <messageReceiver class="org.apache.axis2.receivers.RawXMLINOutMessageReceiver"/>
    </operation>
Only compulsory attribute here is name, which represent the operation name that is going to be exposed. Any operation can contains module references, any number of parameters. The most interesting is that one can register custom message receiver per operation, then the registered message receiver will be the message receiver for the corresponding operation. If one does not specify the message receiver then the default message receiver will do the job.

Module Configuration

The description of module is specified using module.xml, each module archive file need to have module.xml in order to be a valid module. And which has to be available in META-INF directory of the archive file.
A very simple module.xml is shown below:

<module class="org.apache.module.Module1Impl">
    <inflow>
        .
        .
    </inflow>
    <outflow>
        .
        .
    </outflow>

    <Outfaultflow>
        .   
        .
    </Outfaultflow>

    <INfaultflow>
        .         
        .
    </INfaultflow>

    <operation name="creatSeq" mep="MEP_URI_IN_OUT">
        <messageReceiver class="org.apache.axis2.receivers.RawXMLINOutMessageReceiver"/>
        <parameter name="para1" locked="xsd:true">10</parameter>
    </operation>
</module>
class: This is an optional attribute which indicate module implementation class, a module may or may not contain module implementation class since the module can also be a collection of handlers. If a module contains an implementation class which implements the org.apache.axis2.modules.Module inteface where at the deployment time its init(); method will be called.

parameter: Module can contains any number of parameters and all the listed parameters in the module.xml will be transformed into corresponding AxisModule of the module.

Flow :

Defining of handlers in a module has to done inside Flows , and there are four types of flows as listed below.

It is possible to add any number of handlers into a flow and those handlers will be available in corresponding chains at the runtime when they engaged .

operations If a module wants to add an operation when it is engaged into a service it can be done by adding operation tag in module.xml and the way of specifying the operation is same as operation in services.xml.

Handler
Handler element consists of compulsory and optional attribute and the way of defining a handler will be look like follows;

<handler name="handler1" class="handlerClass ">
            <order phase="userphase1" />
 </handler>

Compulsory attributes
name: name of the handler
nlass: handler implementation class
phase: name of the phase that the handler should stay in the execution chain

Optional attributes :
phaseLast: to indicate the handler is last handler of the phase
phaseFirst: to indicate the handler is first handler of the phase.
before : the handler should be invoked before the handler specified by before handler
after: the handler should be invoked after the handler specified by after handler