L07 Frameworks
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This document discusses frameworks and design patterns used in frameworks. It introduces common framework patterns like inversion of control, dependency injection, template method, and strategy patterns. It provides examples of how these patterns are used in frameworks, including a sample framework that uses dependency injection and strategy patterns. The document also discusses benefits and drawbacks of using frameworks.
![▪ Fowler’s Naive Example
– MovieLister uses a finder class
– How can we separate the finder functionality?
class MovieLister...
public Movie[] moviesDirectedBy(String arg) {
List allMovies = finder.findAll();
for (Iterator it = allMovies.iterator(); it.hasNext();) {
Movie movie = (Movie) it.next();
if (!movie.getDirector().equals(arg)) it.remove();
}
return (Movie[])allMovies.toArray(new Movie[allMovies.size()]);
}
REMEMBER PROGRAM TO INTERFACES PRINCIPLE?
Dependency Injection
Separate
what
varies](https://image.slidesharecdn.com/l07frameworks-150907154905-lva1-app6891/85/L07-Frameworks-20-320.jpg)
![Template Method Pattern
public class AbstractOrderEJB
{
public final Invoice placeOrder(int customerId,
InvoiceItem[] items)
throws NoSuchCustomerException, SpendingLimitViolation
{
int total = 0;
for (int i=0; i < items.length; i++)
{
total += getItemPrice(items[i]) * items[i].getQuantity();
}
if (total >getSpendingLimit(customerId))
{
...
}
else if (total > DISCOUNT_THRESHOLD) ...
int invoiceId = placeOrder(customerId, total, items);
...
}
}](https://image.slidesharecdn.com/l07frameworks-150907154905-lva1-app6891/85/L07-Frameworks-32-320.jpg)
![public class MyOrderEJB extends AbstractOrderEJB
{
...
int getItemPrice(int[] i)
{
...
}
int getSpendingLimit(int customerId)
{
...
}
int placeOrder(int customerId, int total, int items)
{
...
}
}
Template Method Pattern](https://image.slidesharecdn.com/l07frameworks-150907154905-lva1-app6891/85/L07-Frameworks-34-320.jpg)
![Strategy Pattern
▪ Interface for specific functionality
▪ Generic class uses the interface
– Set method to inject the interface
public interface DataHelper
{
int getItemPrice(InvoiceItem item);
int getSpendingLimit(CustomerId) throws NoSuchCustomerException;
int palceOrder(int customerId, int total, InvoiceItem[] items);
}
private DataHelper dataHelper;
public void setDataHelper(DataHelper newDataHelper)
{
this.dataHelper = newDataHelper;
}
DEPENDENCY INJECTION](https://image.slidesharecdn.com/l07frameworks-150907154905-lva1-app6891/85/L07-Frameworks-39-320.jpg)
![Strategy Pattern
public class OrderEJB
{
public final Invoice placeOrder(int customerId, InvoiceItem[] items)
throws NoSuchCustomerException, SpendingLimitViolation
{
int total = 0;
for (int i=0; i < items.length; i++)
{
total += this.dataHelper.getItemPrice(items[i]) *
items[i].getQuantity();
}
if (total >this.dataHelper.getSpendingLimit(customerId))
{...
}
else if (total > DISCOUNT_THRESHOLD) ...
int invoiceId = this.dataHelper.placeOrder(customerId,
total, items);
...
}
}](https://image.slidesharecdn.com/l07frameworks-150907154905-lva1-app6891/85/L07-Frameworks-40-320.jpg)
![FileSystemXmlApplicationContext
▪ Loads the context from an XML file
▪ Application contexts are intended as central registries
– Support of hierarchical contexts (nested)
public class AppTest
{
public static void main(String[] args)
{
ApplicationContext ctx =
new FileSystemXmlApplicationContext("app.xml");
}
}](https://image.slidesharecdn.com/l07frameworks-150907154905-lva1-app6891/85/L07-Frameworks-50-320.jpg)
L07 Frameworks
- 1. HÖNNUN OG SMÍÐI HUGBÚNAÐAR 2015 L07 FRAMEWORKS
- 2. Agenda Why frameworks? Framework patterns •Inversion of Control and Dependency Injection •Template Method •Strategy From problems to patterns •Game Framework Spring framework •Bean containers •BeanFactory and ApplicationContext
- 3. Reading Dependency Injection Template Method Pattern Strategy Pattern Spring Framework (video) Article by Fowler Inversion of Control Containers and the Dependency Injection pattern
- 4. Resources ▪ Spring Framework homepage – http://www.springframework.org ▪ Reference Documentation – http://www.springframework.org/docs/reference/index.html – Also in PDF format
- 6. Why use Frameworks? ▪ Frameworks can increase productivity – We can create our own framework – We can use some third party framework ▪ Frameworks implement general functionality – We use the framework to implement our business logic
- 7. Framework design ▪ Inheritance of framework classes ▪ Composition of framework classes ▪ Implementation of framework interfaces ▪ Dependency Injection ?Your Domain Code Framework
- 8. Using Frameworks ▪ Frameworks are concrete, not abstract – Design patterns are conceptual, frameworks provide building blocks ▪ Frameworks are higher-level – Built on design patterns ▪ Frameworks are usually general or technology-specific ▪ Good frameworks are simple to use, yet powerful
- 9. Abstractions ▪ From API to Frameworks API Definition JEE/.NET API API Patterns JEE/.NET Patterns Framework Spring
- 10. Open Source Frameworks ▪ Web Frameworks – Jakarta Struts, WebWork, Maverick, Play! ▪ Database Frameworks – Hibernate, JDO, TopLink ▪ General Framework – Spring, Expresso, PicoContainer, Avalon ▪ Platform Frameworks – JEE
- 11. Where do Frameworks Come From? ▪ Who spends their time writing frameworks? ▪ If they give them away, how can anyone make money? ▪ Companies that use frameworks, have their developers work on them ▪ Give the code, sell the training and consulting
- 12. Write down the pros and cons (benefits and drawbacks) for frameworks. Use two columns, benefits on the left, drawbacks right EXERCISE
- 13. Pros and Cons ▪ Pros – Productivity – Well know application models and patterns – Tested functionality – Connection of different components – Use of open standards ▪ Cons – Can be complicated, learning curve – Dependant on frameworks, difficult to change – Difficult to debug and find bugs – Performance problems can be difficult – Can be bought by an evil company
- 15. Separation of Concerns ▪ One of the main challenge of frameworks is to provide separation of concerns – Frameworks deal with generic functionality – Layers of code ▪ Frameworks need patterns to combine generic and domain specific functionality
- 16. The Hollywood Principle ▪ “Don’t call us, we’ll call you” ▪ Your program does not call the framework, it’s the framework that controls the execution of your program TRADITIONAL HOLLYWOOD CALL Framework Handler Handler Framework Program Program
- 17. Inversion of Control (IoC) ▪ Your application runs in a container (framework) ▪ Container manages the life-cycle of your object and provides context ▪ The framework has the control
- 18. Framework Patterns ▪ Useful patterns when building a framework: – Dependency Injection: remove dependencies by injecting them (sometimes called Inversion of Control) – Template Method: extend a generic class and provide specific functionality – Strategy: Implement an interface to provide specific functionality
- 19. Dependency Injection Removes explicit dependence on specific application code by injecting depending classes into the framework ▪ Objects and interfaces are injected into the classes that to the work ▪ Two types of injection ▪ Setter injection: using set methods ▪ Constructor injection: using constructors
- 20. ▪ Fowler’s Naive Example – MovieLister uses a finder class – How can we separate the finder functionality? class MovieLister... public Movie[] moviesDirectedBy(String arg) { List allMovies = finder.findAll(); for (Iterator it = allMovies.iterator(); it.hasNext();) { Movie movie = (Movie) it.next(); if (!movie.getDirector().equals(arg)) it.remove(); } return (Movie[])allMovies.toArray(new Movie[allMovies.size()]); } REMEMBER PROGRAM TO INTERFACES PRINCIPLE? Dependency Injection Separate what varies
- 21. ▪ Fowler’s Naive Example – Let’s make an interface, MovieFinder – MovieLister is still dependent on particular MovieFinder implementation public interface MovieFinder { List findAll(); } class MovieLister... private MovieFinder finder; public MovieLister() { finder = new MovieFinderImpl("movies1.txt"); } Argh! Not cool. Dependency Injection
- 22. ▪ An assembler (or container) is used to create an implementation – Using constructor injection, the assembler will create a MovieLister and passing a MovieFinder interface in the contractor – Using setter injection, the assembler will create MovieLister and then all the setFinder setter method to provide the MovieFinder interface Dependency Injection
- 23. ▪ Example setter injection class MovieLister... private MovieFinder finder; public void setFinder(MovieFinder finder) { this.finder = finder; } class MovieFinderImpl... public void setFilename(String filename) this.filename = filename; } Dependency Injection
- 25. Example ▪ ContentLister public class ContentLister { private ContentFinder contentFinder; public void setContentFinder(ContentFinder contentFinder) { this.contentFinder = contentFinder; } public List<Content> find(String pattern) { return contentFinder.find(pattern); } }
- 26. Example ▪ ContentFinder interface public interface ContentFinder { List<Content> find(String pattern); }
- 27. Example ▪ SimpleContentFinder – implementation public class SimpleContentFinder implements ContentFinder { ... public List<Content> find(String pattern) { List<Content> contents = contentService.getContents(); List<Content> newList = new ArrayList<Content>(); for(Content c : contents) { if (c.getTitle().toLowerCase().contains(pattern)) { newList.add(c); } } return newList; } }
- 28. Example ▪ TestContentLister - Testcase public class TestContentLister extends TestCase { public void testContentLister () { ServiceFactoryserviceFactory = new ServiceFactory(); ContentServicecontentService = (ContentService) serviceFactory.getService("contentService"); contentService.addContent(new Content(1, ”The hundred-foot Journey", "", "", new Dat contentService.addContent(new Content(1, ”Life of Crime", "", "", new Date(), "")); contentService.addContent(new Content(1, ”The November Man", "", "", new Date(), "") ContentFindercontentFinder = new SimpleContentFinder(contentService); ContentListercontentLister = new ContentLister(); contentLister.setContentFinder(contentFinder); List<Content>searchResults = contentLister.find("simpsons"); for (Content c : searchResults) { System.out.println(c); } } } Magic stuff
- 29. Example
- 30. Template Method Pattern Create a template for steps of an algorithm and let subclasses extend to provide specific functionality ▪ We know the steps in an algorithm and the order – We don’t know specific functionality ▪ How it works – Create an abstract superclass that can be extended for the specific functionality – Superclass will call the abstract methods when needed
- 32. Template Method Pattern public class AbstractOrderEJB { public final Invoice placeOrder(int customerId, InvoiceItem[] items) throws NoSuchCustomerException, SpendingLimitViolation { int total = 0; for (int i=0; i < items.length; i++) { total += getItemPrice(items[i]) * items[i].getQuantity(); } if (total >getSpendingLimit(customerId)) { ... } else if (total > DISCOUNT_THRESHOLD) ... int invoiceId = placeOrder(customerId, total, items); ... } }
- 33. Template Method Pattern AbstractOrderEJB placeOrder () abstract getItemPrice() abstract getSpendingLimit() abstract placeOrder() MyOrderEJB getItemPrice() getSpendingLimit() placeOrder() extends Domain specific functionality Generic functionality
- 34. public class MyOrderEJB extends AbstractOrderEJB { ... int getItemPrice(int[] i) { ... } int getSpendingLimit(int customerId) { ... } int placeOrder(int customerId, int total, int items) { ... } } Template Method Pattern
- 35. ▪ When to Use it – For processes where steps are know but some steps need to be changed – Works if same team is doing the abstract and the concrete class ▪ When Not to Use it – The concrete class is forced to inherit, limits possibilities – Developer of the concrete class must understand the abstract calls – If another team is doing the concrete class as this creates too much communication load between teams Template Method Pattern
- 36. Create a template for the steps of an algorithm and inject the specific functionality ▪ Implement an interface to provide specific functionality ▪ Algorithms can be selected on-the-fly at runtime depending on conditions ▪ Similar as Template Method but uses interface inheritance Strategy Pattern
- 37. Strategy Pattern ▪ How it works ▪ Create an interface to use in the generic algorithm ▪ Implementation of the interface provides the specific functionality ▪ Framework class has reference to the interface an ▪ Setter method for the interface
- 38. Strategy Pattern
- 39. Strategy Pattern ▪ Interface for specific functionality ▪ Generic class uses the interface – Set method to inject the interface public interface DataHelper { int getItemPrice(InvoiceItem item); int getSpendingLimit(CustomerId) throws NoSuchCustomerException; int palceOrder(int customerId, int total, InvoiceItem[] items); } private DataHelper dataHelper; public void setDataHelper(DataHelper newDataHelper) { this.dataHelper = newDataHelper; } DEPENDENCY INJECTION
- 40. Strategy Pattern public class OrderEJB { public final Invoice placeOrder(int customerId, InvoiceItem[] items) throws NoSuchCustomerException, SpendingLimitViolation { int total = 0; for (int i=0; i < items.length; i++) { total += this.dataHelper.getItemPrice(items[i]) * items[i].getQuantity(); } if (total >this.dataHelper.getSpendingLimit(customerId)) {... } else if (total > DISCOUNT_THRESHOLD) ... int invoiceId = this.dataHelper.placeOrder(customerId, total, items); ... } }
- 41. We are building framework for games. It turns out that all the games are similar so we create an abstract class for basic functionality that does not change, and then extend that class for each game.What pattern is this? A) Layer Supertype B) Template Method C) Strategy D) Dependency Injection QUIZ
- 42. We are building framework for games. It turns out that all the games are similar so we create an abstract class for basic functionality that does not change, and then extend that class for each game.What pattern is this? A) Layered Supertype B) Template Method C) Strategy D) Dependency Injection QUIZ ✔
- 43. Spring Framework
- 44. Lightweight Containers ▪ Assemble components from different projects into a cohesive application – Wiring is done with “Inversion of Control” – Provide life-cycle management of objects – Provide context
- 45. Overview Spring 1 – Introduction
- 46. Lightweight Containers ▪ Manage objects ▪ Provide context
- 47. Spring Containers ▪ Lightweight containers – Provides life-cycle management and other services ▪ BeanFactory – Simple factory interface for creating beans ▪ ApplicationContext – Extends BeanFactory and adds some functionality for application context ▪ Packages – org.springframework.beans – org.springframework.context – Refer to Spring 3
- 48. Spring Containers ▪ The concept – Building applications from POJOs
- 49. Using BeanFactory BeanFactory <beans> <bean id="person" class="Person"> <property name="name"> <value>Olafur Andri</value> </property> <property name="email"> <value>[email protected]</value> </property> </bean> </beans> read, parse create Person The Bean Factory uses setter injection to create the person object
- 50. FileSystemXmlApplicationContext ▪ Loads the context from an XML file ▪ Application contexts are intended as central registries – Support of hierarchical contexts (nested) public class AppTest { public static void main(String[] args) { ApplicationContext ctx = new FileSystemXmlApplicationContext("app.xml"); } }
- 51. Summary ▪ Framework patterns – Inversion of Control and Dependency Injection – Template Method – Strategy ▪ From problems to patterns – Game Framework ▪ Spring framework – Bean containers – BeanFactory and ApplicationContext