tu sca ny 1 Extending The Tuscany Java SCA Runtime 21 August 2006

tu sca ny 2 Agenda Overview Extension Types Creating a Binding Extension Advanced Tuscany Programming Model Creating a Component Type Extension

tu sca ny 3 Overview The Tuscany core was designed to be as simple and small as possible Focus on wiring/assembly Most capabilities provided as extensions Component implementation types, e.g. Spring Support for Bindings Support for Policy/Qualities of Sevice Loading of XML The basic extension model is SCA Extensions are “system services” which are SCA components

tu sca ny 4 Runtime Assembly The runtime is itself an SCA assembly Create Runtime Component Create Bootstrap Deployer Deploy System Assembly Locate Application Assemblies Locate System Assembly Deploy Application Assembly Start Server

tu sca ny 5 Component Tree Composites form a containment hierarchy The hierarchy may be arbitrarily deep The runtime itself, DefaultRuntime, is a composite There are two runtime hierarchies The application hierarchy End-user components The system hierarchy Runtime extensions

tu sca ny 6 The SPI Package A separate SPI project has been created for extending the runtime Extension code must never reference classes in core Besides being bad design, this type of code will break when deployed to hosts that enforce classloader isolation There is a test package for testcases to instantiate a few core implementation classes without directly referencing them (we should look to eliminate it if possible) tuscany-core is an implementation of spi core spi Extension

tu sca ny 7 Agenda Overview Extension Types Creating a Binding Extension Advanced Tuscany Programming Model Creating a Component Type Extension

tu sca ny 8 Base Extension Types Components Protocol Bindings Transport Bindings Data Bindings Policy Loaders Other types: Scope contexts Wires Proxy generation Anything people can think of and attach to the runtime…

tu sca ny 9 Extension Package spi contains an extension package with abstract classes for base extensions AtomicComponentExtension.java CompositeComponentExtension.java LoaderExtension.java ReferenceExtension.java ServiceExtension.java If extenders do not want to inherit from a base class, they can implement interfaces

tu sca ny 10 Extension Programming Model Extensions consist of a set of components that offer services Are POJOs that follow the SCA Java programming model Extensions are contributed as composite components to the runtime There are a few programming model extensions for logging and advanced wiring that we will discuss later

tu sca ny 11 Agenda Overview Extension Types Creating a Binding Extension Advanced Tuscany Programming Model Creating a Component Type Extension

tu sca ny 12 Binding Invocation Through a Reference When a message reaches the end of the outbound reference wire, the TargetInvoker dispatches over a transport OutboundInboundOutbound Invoke on transport AtomicComponentComposite Reference

tu sca ny 13 Binding Invocation Through a Service Invocation is deserialized from a transport and passed through the service invocationchain OutboundInbound Composite Service AtomicComponent Inbound Invoke Invoke from transport

tu sca ny 14 Creating a Binding Extension Bindings are used by Services and References Binding extensions produce either Services or References Must create a Loader and Builder For references the builder produces an implementation of org.apache.tuscany.spi.componen.Reference For services the builder produces an implemenation of org.apache.tuscany.spi.component.Service Services may register servlets for incoming requests through org.apache.tuscany.spi.host.ServletHost References responsible for creating instances TargetInvoker, Services do not need to loadbuild connect

tu sca ny 15 A Loader Is an SCA Component Extends org.apache.tuscany.spi.extension.LoaderExtension public class EchoBindingLoader extends LoaderExtension { public static final QName BINDING_ECHO = new QName(XML_NAMESPACE_1_0, public LoaderRegistry registry) { super(registry); } public QName getXMLType() { return BINDING_ECHO; } public EchoBinding load(CompositeComponent parent, XMLStreamReader reader, DeploymentContext context) throws XMLStreamException, LoaderException { return new EchoBinding(); } Returns the Binding model object Normally, XML would be parsed with the reader

tu sca ny 16 A Builder Is an SCA Component Extends org.apache.tuscany.spi.extension.BindingBuilderExtension public class EchoBuilder extends BindingBuilderExtension { public SCAObject build(CompositeComponent parent, BoundReferenceDefinition definition, DeploymentContext context) { Class interfaze = definition.getServiceContract().getInterfaceClass(); String name = definition.getName(); return new EchoReference(name, interfaze, parent, wireService); } public SCAObject build(CompositeComponent parent, BoundServiceDefinition definition, DeploymentContext context) { Class interfaze = definition.getServiceContract().getInterfaceClass(); return new EchoService(definition.getName(), interfaze, parent, wireService); } protected Class getBindingType() { return EchoBinding.class; } Describes to the runtime which binding type the class handles

tu sca ny 17 The TargetInvoker Returned by References public class EchoInvoker implements TargetInvoker { //… public Object invokeTarget(final Object payload) throws InvocationTargetException { // echo back the result, a real binding would invoke some API for flowing the request return ((Object[])payload)[0]; } public Message invoke(Message msg) throws InvocationRuntimeException { try { Object resp = invokeTarget(msg.getBody()); msg.setBody(resp); } catch (InvocationTargetException e) { msg.setBody(e.getCause()); } catch (Throwable e) { msg.setBody(e); } return msg; } public Object clone() throws CloneNotSupportedException { return super.clone(); } Describes to the runtime which binding type the class handles

tu sca ny 18 Agenda Overview Extension Types Creating a Binding Extension Advanced Tuscany Programming Model Creating a Component Type Extension

tu sca ny 19 The Extension Programming Model All components by default are module scoped (i.e. singletons within a composite) Wiring may be done directly as in SCA or through autowire (recommended) Wire by contract: runtime responsible for supplying an implementation of an interface Checks sibiling components, then recurses upward through the component hierarchy. If a sibling is a composite, only services exposed by it may be wired to. Virtually any type of extension can be supplied to the runtime this way

tu sca ny 20 An Example Component public abstract class BindingBuilderExtension implements BindingBuilder { protected BuilderRegistry builderRegistry; protected WireService public void setBuilderRegistry(BuilderRegistry registry) { this.builderRegistry = registry; public void setWireService(WireService wireService) { this.wireService = wireService; = true) public void init() { builderRegistry.register(getBindingType(), this); } //… }

tu sca ny 21 An Example SCDL <composite xmlns=" xmlns:system=" name=”BindingSCDL">

tu sca ny 22 Patterns: Monitor Logging is externalized Do not use commons-logging a.k.a. “clogging”, Log4J, JDK, etc. Instead, decorate a field, setter or constructor param Runtime will provide an implementation of the monitor interface. The implementation will delegate to a logging implementation Avoids memory leaks and allows for better public void setMyMonitor(MyMonitor){ //.. } public void someMethod(){ myMonitor.started(“Stated monitor”); }

tu sca ny 23 Patterns: Registry Often, a registry is used which is a component that other components register with Loaders and Builders register with a LoaderRegistry and BuilderRegistry. The latter dispatch to the right loader or builder when a SCDL or model is being evaluated Eager initialization is used to public void setBuilderRegistry(BuilderRegistry registry) { this.builderRegistry = registry; = true) public void init() { builderRegistry.register(getBindingType(), this); }

tu sca ny 24 Agenda Overview Extension Types Creating a Binding Extension Advanced Tuscany Programming Model Creating a Component Type Extension

tu sca ny 25 Creating an Atomic Component Implementation Type 1.Implement 1..n model POJOs 2.Implement Loader or extend LoaderExtension Reads a StAX stream and creates appropriate model objects 3.Implement AtomicComponent or extend AtomicComponentExtension Extension will be given InboundWires and OutboundWires corresponding to its services and references; it must decide how to inject those onto its implementation instances (e.g. create a proxy) A WireService will be provided to the extension, which it can use to generate proxies and WireInvocationHandlers The extension must implement createTargetInvoker(..) and instantiate TargetInvokers responsible for dispatching to target instances 4.Implement ComponentBuilder or extend ComponentBuilderExtension Implements build(..) which returns the AtomicComponent implementation 5.Write a simple SCDL file and deploy into the system composite hierarchy

tu sca ny 26 Creating a Composite Component Implementation Type 1.Implement 1..n model POJOs 2.Implement Loader or extend LoaderExtension Reads a StAX stream and creates appropriate model objects 3.Implement CompositeComponent or extend CompositeComponentExtension The extension must implement createTargetInvoker(..) and instantiate TargetInvokers responsible for dispatching to target child instances 4.Implement ComponentBuilder or extend ComponentBuilderExtension Implements build(..) which returns the AtomicComponent implementation 5.Write a simple SCDL file and deploy into the system composite hierarchy