Transcript Object Models for Distributed Systems

Presentation:
Advanced AXIS:
Deployment Descriptors and
Advanced Types
Outline
• So far with AXIS
– Installation of Apache Tomcat and AXIS
– Easy deployment of .java with .jws
– Using Dynamic Call Interface for the Client to .jws
• Rather tedious work – and pretty error-prone
– WSDL2Java Client generation
• This time
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Use of.wsdd deployment files in AXIS (server specific)
Types allowed in Java/WSDL mappings (client/server)
Use of Arrays and Objects (client/server)
Custom Objets (client/server)
Use of the WSDL2Java stubgeneration tool (client)
Scope (client/server)
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Using Axis Web Service Deployment
Descriptor
• Easy to use .jws
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But not nice deployment
How to undeploy
Problems with accessing outside classes
Not possible to use custom objects
• Alternative: Using the deployment tool in Axis
– % java org.apache.axis.client.AdminClient
deploy.wsdd
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Using Axis Web Service Deployment
Descriptor II
• Web Service Deployment Descriptor (.wsdd) is
XML for defining characteristics of a Web service
– The service name and the provider
<service name="HelloWorld" provider="java:RPC">
– The (packaged) class that provides the service
<parameter name="className" value=“hello.
HelloWorld"/>
– Which of the class methods are to be exposed (all or
limited)
<parameter name="allowedMethods" value="*"/>
<parameter name="allowedMethods"
value="getHelloWorldMessage
someOtherMethod"/>
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Using Axis Web Service Deployment
Descriptor III
• Web service scope specifies the lifetime/management of
the service class.
– Specify scope of the Web service (request, application or session)
in wsdd
<parameter name="scope" value="request"/>
– request - is the default scope; each request causes a new service
object to be created to handle the request
– session - conceptually, all requests by a single client are handled
by a single object (implemented with cookies)
– application - a singleton web service. A single object serves all
clients.
• More on scope later
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Parameter Types for Web Services and
Clients in AXIS
• The primitive types are mapped as shown below:
• XSD Type --> Java Type
xsd:base64Binary --> byte[]
xsd:boolean --> boolean
xsd:byte --> byte
xsd:dateTime --> java.util.Calendar
xsd:decimal --> java.math.BigDecimal
xsd:double --> double
xsd:float --> float
xsd:hexBinary --> byte[]
xsd:int --> int
xsd:integer --> java.math.BigInteger
xsd:long --> long
xsd:QName --> javax.xml.namespace.QName
xsd:short --> short
xsd:string --> java.lang.String
• These types can be used as either parameter or return types.
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Objects
• Allowed objects are:
– Objets listed above
– Objects that conforms to the Java Bean Standard
• Custom objects – rolling your own
– Normally one would like to use own objects as parameters and
return values
– This may be done using the BeanSerializer
– Beans MUST conform to the Java Bean Standard
• This means empty constructor and accessor (getter/setter) methods
– More on this later
• Collections SHOULD NOT BE USED if interoperability is
needed (e.g. with C# og C++)
– Instead use regular Arrays (Object[] and typecast)
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Using Custom Objects
• Axis supports passing user-defined class objects that are Java Beans
– get and set methods are defined for every class attribute
– the class is Serializable
• Marshalling and Unmarshalling parameters and returns
• Suppose a Web Service returns a user-defined SomeClass object.
– On the server, deploy with a wsdd element associating the user-defined
class (SomeClass ) with the Axis provided BeanService as:
– <beanMapping qname="msgNS:SomeClass"
xmlns:msgNS="urn:BeanService"
languageSpecificType="java:onk1Package.SomeClass"/>
• On the client side, WSDL2Java creates a BeanService. SomeObject
class
– The wsdl for the corresponding Web Service includes xml for SomeClass.
– The proxy unmarshals a returned Message object to a BeanService.
SomeClass object.
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Example WSDD
•TV-Program Web service (TVPSService.class):
•Java Server
•C# Client (Pocket PC .NET CF)
•Java Client (UNIX, LINUX, Windows)
<deployment xmlns="http://xml.apache.org/axis/wsdd/"
xmlns:java="http://xml.apache.org/axis/wsdd/providers/java">
<service name="TVPSService" provider="java:RPC">
<parameter name="className" value="tvps.TVPSService"/>
<parameter name="allowedMethods" value="*"/>
<beanMapping qname="myNS:Programme" xmlns:myNS="urn:BeanService"
languageSpecificType="java:tvps.Programme"/>
</service>
</deployment>
•Key elements:
•Package of service = tvps
•Class of service = tvps.TVPSService
•Allowed methods = all (*)
•Custom class (return parameter) = tvps.Programme
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Client side – using WSDL2Java
• The deployment is purely server side
• Lets now take a look at the client side
• If we would like to generate Client proxy stubs for
a WSDL service – we could use:
– C:\dev-axis\java org.apache.axis.wsdl.WSDL2Java
http://localhost:8080/axis/Calculator.jws?wsdl -p calc
• Which would generate a package ”calc”
containing all the Proxy code needed for building
a Client
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Result of WSDL2Java
WSDL clause
Java class(es) generated
For each entry in the type section
A java class
A holder if this type is used as an inout/out parameter
For each portType
A java interface
For each binding
A stub class
For each service
A service interface
A service implementation (the locator)
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Building a Client
•Lets start by generating the Clients stub given the WSDL (-p = destination package = hello):
•java org.apache.axis.wsdl.WSDL2Java http://localhost:8080/axis/HelloWorld.jws?wsdl –p hello
package hello;
public class HelloWorldClient {
public static void main (String args[]) throws Exception {
// Make a service
HelloWorldService service = new HelloWorldServiceLocator();
//Now use the service to get a stub which implements the SDI
HelloWorld stub = (HelloWorld) service.getHelloWorld();
String text = stub.getHelloWorldMessage("Test af OO indpakning");
System.out.println(”Recieved from server: "+text);
}
}
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Axis Life-Cycle Management for Web
Services
• Web service scope specifies the lifetime/management of
the service class.
– request - has the same effect as if a new service object is created
to handle each method call.
– Request is the default scope - provides scalability in highcapacity load-balanced applications. Connections and/or server
objects can be pooled.
– session - conceptually, all requests from a single client are
handled by a single object. Implemented with cookies, and
requires client support.
– application - a singleton web service. A single object serves all
clients.
• Using application scope for a Java Web Service and
Client
– The deploy.wsdd specifies application scope for the Web Service
<parameter name="scope" value="application"/>
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Using Session Scope with Axis
• Using the session scope for a Java Web Service and
Client
– For example, count all calls made to a service by a single client.
– Each client has its own call count -- in effect, has its own service
object.
– The deploy.wsdd specifies session scope for the Web Service
<parameter name="scope" value="session"/>
• For session scope to work, the web service client must
also specify a session mechanism
– In C# as: tcs.CookieContainer = new
System.Net.CookieContainer();
– Java Proxy as:
((MyWSServiceLocator)tcs).setMaintainSession(true);
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