Design patterns - Proxy & Composite
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The document discusses the composite and proxy design patterns. The composite pattern allows grouping objects into tree structures to represent part-whole hierarchies. It defines behaviors for primitive elements and composite elements that can have children. The proxy pattern provides a surrogate for another object to control access to it. A proxy acts as an interface to the real object and can perform additional tasks like access control and caching.
![/** Client */
public class Program {
public static void main(String[] args) {
//Initialize four ellipses
Ellipse ellipse1 = new Ellipse();
Ellipse ellipse2 = new Ellipse();
Ellipse ellipse3 = new Ellipse();
Ellipse ellipse4 = new Ellipse();](https://image.slidesharecdn.com/designpatterns-proxycomposite-140619034242-phpapp02/85/Design-patterns-Proxy-Composite-15-320.jpg)
![/** Client */
public class Program {
public static void main(String[] args) {
//Initialize four ellipses
Ellipse ellipse1 = new Ellipse();
Ellipse ellipse2 = new Ellipse();
Ellipse ellipse3 = new Ellipse();
Ellipse ellipse4 = new Ellipse();
!
//Initialize three composite graphics
CompositeGraphic graphic = new CompositeGraphic();
CompositeGraphic graphic1 = new CompositeGraphic();
CompositeGraphic graphic2 = new CompositeGraphic();](https://image.slidesharecdn.com/designpatterns-proxycomposite-140619034242-phpapp02/85/Design-patterns-Proxy-Composite-16-320.jpg)
![/** Client */
public class Program {
public static void main(String[] args) {
//Initialize four ellipses
Ellipse ellipse1 = new Ellipse();
Ellipse ellipse2 = new Ellipse();
Ellipse ellipse3 = new Ellipse();
Ellipse ellipse4 = new Ellipse();
!
//Initialize three composite graphics
CompositeGraphic graphic = new CompositeGraphic();
CompositeGraphic graphic1 = new CompositeGraphic();
CompositeGraphic graphic2 = new CompositeGraphic();
!
//Composes the graphics
graphic1.add(ellipse1);
graphic1.add(ellipse2);
graphic1.add(ellipse3);
graphic2.add(ellipse4);](https://image.slidesharecdn.com/designpatterns-proxycomposite-140619034242-phpapp02/85/Design-patterns-Proxy-Composite-17-320.jpg)
![/** Client */
public class Program {
public static void main(String[] args) {
//Initialize four ellipses
…
!
//Initialize three composite graphics
…
!
//Composes the graphics
graphic1.add(ellipse1);
graphic1.add(ellipse2);
graphic1.add(ellipse3);
graphic2.add(ellipse4);
graphic.add(graphic1);
graphic.add(graphic2);
!
graphic.add(graphic1);
graphic.add(graphic2);](https://image.slidesharecdn.com/designpatterns-proxycomposite-140619034242-phpapp02/85/Design-patterns-Proxy-Composite-18-320.jpg)
![/** Client */
public class Program {
public static void main(String[] args) {
//Initialize four ellipses
…
!
//Initialize three composite graphics
…
!
//Composes the graphics
…
…
!
…
!
//Prints the complete graphic (4 times "Ellipse").
graphic.print();
}](https://image.slidesharecdn.com/designpatterns-proxycomposite-140619034242-phpapp02/85/Design-patterns-Proxy-Composite-19-320.jpg)
Design patterns - Proxy & Composite
- 1. Design Patterns Proxy & Composite @sarat, architect Experion Technologies
- 3. is a structural pattern
- 4. Structural design patterns ease the design by identifying a simple way to realize relationships between entities
- 5. Compose objects into tree structures to represent part-whole hierarchies. ! describes that a group of objects are to be treated in the same way as a single instance of an object
- 6. Leaf (primitive element) • represents leaf objects in the composition. • A leaf has no children. • defines behavior for primitive objects in the composition
- 7. Composite • defines behavior for components having children. • stores child components. • implements child-related operations in the Component interface.
- 8. Client ! • manipulates objects in the composition through the Component interface.
- 10. /** "Component" */ interface Graphic { //Prints the graphic. public void print(); }
- 11. class CompositeGraphic implements Graphic { //Collection of child graphics. private List<Graphic> childGraphics = new ArrayList<Graphic>();
- 12. class CompositeGraphic implements Graphic { //Collection of child graphics. private List<Graphic> childGraphics = new ArrayList<Graphic>(); ! //Prints the graphic. public void print() { for (Graphic graphic : childGraphics) { graphic.print(); } }
- 13. class CompositeGraphic implements Graphic { //Collection of child graphics. private List<Graphic> childGraphics = new ArrayList<Graphic>(); ! //Prints the graphic. public void print() { for (Graphic graphic : childGraphics) { graphic.print(); } } ! //Adds the graphic to the composition. public void add(Graphic graphic) { childGraphics.add(graphic); } //Removes the graphic from the composition. public void remove(Graphic graphic) { childGraphics.remove(graphic); } }
- 14. /** "Leaf" */ class Ellipse implements Graphic { //Prints the graphic. public void print() { System.out.println("Ellipse"); } }
- 15. /** Client */ public class Program { public static void main(String[] args) { //Initialize four ellipses Ellipse ellipse1 = new Ellipse(); Ellipse ellipse2 = new Ellipse(); Ellipse ellipse3 = new Ellipse(); Ellipse ellipse4 = new Ellipse();
- 16. /** Client */ public class Program { public static void main(String[] args) { //Initialize four ellipses Ellipse ellipse1 = new Ellipse(); Ellipse ellipse2 = new Ellipse(); Ellipse ellipse3 = new Ellipse(); Ellipse ellipse4 = new Ellipse(); ! //Initialize three composite graphics CompositeGraphic graphic = new CompositeGraphic(); CompositeGraphic graphic1 = new CompositeGraphic(); CompositeGraphic graphic2 = new CompositeGraphic();
- 17. /** Client */ public class Program { public static void main(String[] args) { //Initialize four ellipses Ellipse ellipse1 = new Ellipse(); Ellipse ellipse2 = new Ellipse(); Ellipse ellipse3 = new Ellipse(); Ellipse ellipse4 = new Ellipse(); ! //Initialize three composite graphics CompositeGraphic graphic = new CompositeGraphic(); CompositeGraphic graphic1 = new CompositeGraphic(); CompositeGraphic graphic2 = new CompositeGraphic(); ! //Composes the graphics graphic1.add(ellipse1); graphic1.add(ellipse2); graphic1.add(ellipse3); graphic2.add(ellipse4);
- 18. /** Client */ public class Program { public static void main(String[] args) { //Initialize four ellipses … ! //Initialize three composite graphics … ! //Composes the graphics graphic1.add(ellipse1); graphic1.add(ellipse2); graphic1.add(ellipse3); graphic2.add(ellipse4); graphic.add(graphic1); graphic.add(graphic2); ! graphic.add(graphic1); graphic.add(graphic2);
- 19. /** Client */ public class Program { public static void main(String[] args) { //Initialize four ellipses … ! //Initialize three composite graphics … ! //Composes the graphics … … ! … ! //Prints the complete graphic (4 times "Ellipse"). graphic.print(); }
- 20. Questions?
- 22. it makes the clients of a component communicate with a representative rather than to the component Itself.
- 23. enables enhanced efficiency, easier access and protection from unauthorized access.
- 24. examples?
- 25. a network proxy
- 26. large object in memory
- 28. Context • A client needs access to the services of another component • Direct access is technically possible, but may not be the best approach
- 29. Problem • Often it’s inappropriate to access the component directly • Direct and unrestricted access can be insecure and inefficient
- 31. run-time efficient
- 32. cost effective
- 33. safe for both client and component
- 35. should be similar to component’s interface
- 37. solution
- 38. communicate to representative — proxy
- 39. proxy performs pre & post processing (e.g access control)
- 40. structure
- 41. uses proxy to fulfill it’s task Client
- 42. a common interface for proxy and original AbstractOriginal
- 43. provides interface of the original to clients proxy
- 44. ensures safe, efficient and correct access to the original proxy
- 48. dynamics
- 51. migrate all client responsibilities to proxy
- 52. remove all direct relationship with client and original
- 53. variants
- 54. To shield network addresses and inter-process communication protocols from clients Remote Proxy
- 55. Access authorization e.g network authorization to use Internet Protection Proxy
- 56. Multiple local components can share results from a remote proxy e.g. Cache server Cache Proxy
- 57. Provide synchronized access to services in a multi-access or multi- threaded environment Synchronization Proxy
- 58. Prevents accidental deletion of components or collects usage statistics e.g. reference counting objects Counting Proxy
- 59. Protects local clients from outside world Firewall proxy
- 60. benefits
- 61. enhanced efficiency and lower cost e.g. cache proxy
- 62. decouple clients from real objects
- 64. liabilities
- 65. less efficiency due to indirection
- 66. overkill using sophisticated strategies ! e.g. caching server in a dynamic environment
- 67. Questions?