Component-based Software Engineering

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Component-based Software Engineering
Component Model Comparison

• Marcello Bonsangue
• LIACS Leiden University
• Fall 2005

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Commercial Component Models

• Open standard
• CORBA
• Microsoft
• COM/DCOM
• .Net
• SUN
• JavaBeans
• Enterprise JavaBeans
• Philips,Nokia et al.
• RoboCop

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Comparison criteria (I)

• Components
• Abstract components (Interfaces)
• Concrete components (Implementations)
• Basic communication
• Composition of components
• Adaptation (external and internal)
• Reusability / Predefined services

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Abstract components

• Corba
• Interfaces generated from IDL
• Multiple inheritance
• DCOM
• Interfaces generated from MIDL
• Interfaces as first class objects
• Multiple inheritance
• Globally unique interfaces
• JavaBeans/EJB
• Defined by EJB designer
• Multiple inheritance
• .Net
• Interfaces generated from concrete components
• Multiple inheritance

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Concrete components

• Corba classes (objects)
• With reflection / transaction / persistency
  concept
• Language platform transparency
• Inheritance of the implementation language
• (D)COM objects and Interfaces
• With reflection / transaction / persistency
  concept
• Language transparency
• Inheritance of the implementation language
• JavaBeans, EJB
• With reflection / transaction / persistency
  concept
• Java but JNI
• Platform transparency
• Single inheritance of Java
• Different roles in EJB (stateless, session,
  entity, message-driven)
• .Net
• With reflection / transaction / persistency
  concept
• Language (but CLS) platform transparency
• Inheritance of the implementation language

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Basic communication

• Corba
• Object request broker ORB
• Remote procedure call (RPC)
• GIOP/IIOP (General/Internet Inter ORB Protocol)
• DCOM
• Object oriented (RPC)
• GUID (Globally Unique IDs)
• JavaBeans
• Asynchronous, Event based
• EJB
• EJB container and (web) server
• Synchronous Remote Method Invocation (RMI)
• Support for lease-based communication
• Migration of Java code
• .Net
• Synchronous Remote Method Invocation (RMI)
• Support for lease-based communication

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Composition of components
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Composition of components

• Corba
• Call via ORB
• Aggregation with pattern façade (also dynamic)
• DCOM
• Call via (D)COM library
• Delegation in components using wrappers
• Aggregation of classes with pattern façade (only
  static)
• Aggregation of interfaces
• EJB
• Call via container
• Java language concepts for delegation
• .Net
• Call via CLR
• Delegation

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Adaptation

• Aspect separation (all)
• Separation of interfaces and implementation
• Multiple interfaces per implementation
• Separation of persistency, transaction,
  distribution,
• External adaptation
• Bridges between the worlds
• EJB Corba
• Java DCOM
• Corba DCOM

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Internal adaptation

• Generation of glue code from interface
  descriptions
• Corba
• Stub-Skeleton generated from IDL
• DCOM
• Proxies and Interfaces generated from MIDL
• EJB
• Proxies generated from bean interfaces
• Reflection to adapt dynamically
• Corba,
• DCOM
• EJB
• .Net

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Reusability / Services

• Corba standardized
• general services (Facilities and Services)
• domain specific services (Vertical Facilities)
• DCOM
• quasi standardized general services
• Non-standard domain specific services
• Microsoft applications
• EJB
• quasi standardized general services
• quasi standardized domain specific services
• AWT and Swing (JavaBeans)
• Other Java libraries