Component Models and Technology Component-based Software Engineering Ivica Crnkovic ivica.crnkovic@mdh.se Page 1 Overview Introduction ACME Architectural Description Language Java Bean Component Model COM, DCOM, MTS and COM+ CORBA Component Model (CCM).NET Component Model OSGI Component Model Page 2
Architecture Definition Languages ADLs primarily address the issues related to the early phases of software engineering: Design Analysis They identify a number of concepts, such as: Architecture, configurations, connectors, bindings, properties, hierarchical models, style, static analysis and behavior. Page 3 ACME Architectural Description Language Components and Ports Connectors and Roles Systems and Attachments Representations and Bindings Properties, Constraints, Types and Styles Page 4
Components and Ports Components Represent the computational elements and data stores of a system. Ports Are the points of interaction between a component and its environment. Component Port Page 5 Connectors and Roles Connectors Represent interactions between components such as method calls or an SQL connection between a client and a database server. The interface of a connector is defined as a set of roles Connector Role Page 6
Systems and Attachments The structure of a system is specified by a set of components, a set of connectors, and a set of attachments. Attachment Links a component port to a connector role. Attachement Page 7 Representations and Bindings Component Connector Port Role Attachement Binding Page 8
Component Interactions Interactions with other components Iteractions with traditional software entities Interactions with component infrastructure Interactions with other components Traditional software entities Components Component Infrastructure Page 9 Java Bean Component Model Page 10
Key Features "A Java Bean is a reusable software component that can be manipulated visually in a builder tool. The Java Bean was designed for the construction of graphical user interface (GUI). Explicitly tailored to interact in two different contexts: At composition time, within the builder tool. At execution time, with the runtime environment. Any Java class that adheres to certain conventions regarding property and event interface definitions can be a JavaBean. Beans are Java classes that can be manipulated in a visual builder tool and composed into applications. Page 11 Interface of a Component This model defines four types of port: methods, properties, event sources (generate an event) event sinks called listeners (they receive event) Property Method Event source Event sink(listener) Bounded property v Vetoable property ro wo 1 Read-only property Write-onlyproperty Unicast event source Ports Page 12
Implementation of a Component Most bean components are implemented by a simple Java object by naming convention Object Method A simple implementation Page 13 Components Assembly Assembly is one of the key features of Java Bean though no not specific solution is provided. Composition tools (Bean Box) No composition language Different ways of assembling components are supplied. Component-based assembly Heterogeneous assembly Page 14
Packaging and Deployment Java Beans define a model for packaging components into archives. Includes the definition of dependency relationships between the package items. Each package item can be marked "Design Only", so that they can be removed in a final application. Page 15 Enterprise JavaBeans Architecture for distributed applications Framework for creating middleware EJB client EJB Server EJB Container Enterprise bean Clients accesses JBs via containers Page 16
EJB Servers Analogous to CORBA ORB Naming and directory interface (JNDI) Client finds EJB via JNDI JTS Java Transaction Services Page 17 COM/DCOM Page 18
Interfaces and Assembly A COM interface is seen as a C++ virtual class and takes the form of a list of data and function declarations without associated code. All interfaces are descendants of the IUnknown interface. Interface Component interface Component implementation Page 19 Implementation COM defines a binary standard for interfaces Language independent implementation of the interfaces Interfaces are defined in Interface Definition Language (IDL) An interface has an GUID as an identifier IUnknown IDispatch Page 20
Composition Two type of explicit composition Delegation Aggregation For aggregation source code is needed Page 21 CORBA Component Model (CCM) Page 22
OMA Overview OMA Object Management Architecture CORBAapps CORBAdomains CORBAfacilities CORBA (Common Object Request Broker Architecture) Transactions Event Security Naming CORBAservices Page 23 Interface and Assembly A component interface is made of ports divided into: Facets - for interaction with clients Receptacles references o external code Event sources Event sinks Attribute Facet Receptacle Event source Event sink Segment Component interface Ports Component implementation Page 24
Framework : The Container Approach Framework a set of containers. Containers contains components and provides a set of standard services (security, events, persistence, life -cycle support) container CCM run-time infrastrucure Page 25 :NET Page 26
What is.net? NET is a platform that enables: Software as services, especially over the web Distributed computing Componentization Enterprise services Page 27.NET Platform VB C++ C# JScript Common Language Specification ASP.NET Windows Forms ADO.NET and XML Base Class Library Common Language Runtime Visual Studio.NET Operating Systems Page 28
.NET Framework Components Common Language Runtime (CLR) Common type system for all languages Runtime environment Class libraries (.NET Framework) Base class libraries, ADO.NET and XML Windows Forms for, Win32 applications Web application platform ASP.NET Interactive pages Web services that are SOAP enabled Page 29.NET Component Model - Implementation A component (assembly) is made of modules, which are traditional executable files (DLL). Modules cannot be assemblies, thus the.net model is not hierarchical. Attribute Method Event source Modules Component interface Ports Component implementation Page 30
Framework.NET relies on the traditional programming approach : the framework is seen as the language run-time support. MISL Microsoft Intermediate language (similar to Java Byte code) Common Runtime Language (similar to Java Virtual Machine) Transaction control relies on MTS. Page 31 Lifecycle Assemblies (and their modules) are local to an application, and thus different DLLs with same name can run simultaneously. Each assembly has a versioning information about itself and about the assemblies it depends on. Version control is delegated to the dynamic loader, which selects the right version. Significantly improve the application packaging and deployment. Page 32
Other component models OSGI Component Model KOALA component model IEC 61131-3 standard languages (functional blocks) Real-time components Page 33 A Koala Component Subcomponent Interfaces A switch C C C 1 s m C 2 C 3 A module Page 34
OSGI Component Model Components Interface of a Bundle Component Assembly of Bundle Components Implementation of a Bundle Component Page 35 Components A bundle use three kinds of ports to express its interactions with Traditional technology Other components The run-time environment Bundles may listen to events published by the framework such as the insertion of a new component in a system. Page 36
Interface of a Bundle Component Package export Package import Service interface Service use static dynamic Interface of a bundle component Ports Page 37 Assembly of Bundle Components A system is an evolving set of bundle components. A bundle component publishes a service interface It can attach to it a set of properties describing its characteristics. A component requires an interface for its use, It will select one via a query expression based on these properties. This flexibility also has its counterpart There is no guarantee than the service will continue to be available Page 38
Implementation of a Bundle Component JAR archive containing: Service components Java packages Other resources files Package Resource Service component Activator Page 39