Spring intro classes-in-mumbai
- 1. Spring Framework Vibrant Technology & Computers 1
- 2. Vibrant Technology & Computers Vibrant Technology & Computers 2
- 3. Spring Overview • Spring is an open source layered Java/J2EE application framework • Created by Rod Johnson • Based on book “Expert one-on-one J2EE Design and Development” (October, 2002) • Current version 2.0.6 (released on 2007-06-18) • The Spring Framework is licensed under the terms of the Apache License, Version 2.0 and can be downloaded at: • http://www.springframework.org/download • Philosophy: J2EE should be easier to use, “Lightweight Container” concept A software framework is a re-usable design for a software system. Vibrant Technology & Computers 3
- 4. What are Lightweight Frameworks? • Non-intrusive • No container requirements • Simplify application development • Remove re-occurring pattern code • Productivity friendly • Unit test friendly • Very pluggable • Usually open source • Examples: • Spring, Pico, Hivemind • Hibernate, IBatis, Castor • WebWork • Quartz • Sitemesh Vibrant Technology & Computers 4
- 5. Spring Mission Statement • J2EE should be easier to use • It's best to program to interfaces, rather than classes. Spring reduces the complexity cost of using interfaces to zero. • JavaBeans offer a great way of configuring applications • OO design is more important than any implementation technology, such as J2EE • Checked exceptions are overused in Java. A framework shouldn't force you to catch exceptions you're unlikely to be able to recover from. • Testability is essential, and a framework such as Spring should help make your code easier to test • Spring should be a pleasure to use • Your application code should not depend on Spring APIs • Spring should not compete with good existing solutions, but should foster integration. (For example, JDO and Hibernate are great O/R mapping solutions. Don't need to develop another one). Vibrant Technology & Computers 5
- 6. Modules of the Spring Framework The Spring Framework can be considered as a collection of frameworks-in-the-framework: • Core - Inversion of Control (IoC) and Dependency Injection • AOP - Aspect-oriented programming • DAO - Data Access Object support, transaction management, JDBC-abstraction • ORM - Object Relational Mapping data access, integration layers for JPA, JDO, Hibernate, and iBatis • MVC - Model-View-Controller implementation for web- applications • Remote Access, Authentication and Authorization, Remote Management, Messaging Framework, Web Services, Email, Testing, … Vibrant Technology & Computers 6
- 7. Overview of the Spring Framework Very loosely coupled, components widely reusable and separately packaged. Vibrant Technology & Computers 7
- 8. Spring Details • Spring allows to decouple software layers by injecting a component’s dependencies at runtime rather than having them declared at compile time via importing and instantiating classes. • Spring provides integration for J2EE services such as EJB, JDBC, JNDI, JMS, JTA. It also integrates several popular ORM toolkits such as Hibernate and JDO and assorted other services as well. • One of the highly touted features is declarative transactions, which allows the developer to write transaction-unaware code and configure transactions in Spring config files. • Spring is built on the principle of unchecked exception handling. This also reduces code dependencies between layers. Spring provides a granular exception hierarchy for data access operations and maps JDBC, EJB, and ORM exceptions to Spring exceptions so that applications can get better information about the error condition. • With highly decoupled software layers and programming to interfaces, each layer is easier to test. Mock objects is a testing pattern that is very useful in this regard. Vibrant Technology & Computers 8
- 9. Advantages of Spring Architecture • Enable you to write powerful, scalable applications using POJOs • Lifecycle – responsible for managing all your application components, particularly those in the middle tier container sees components through well-defined lifecycle: init(), destroy() • Dependencies - Spring handles injecting dependent components without a component knowing where they came from (IoC) • Configuration information - Spring provides one consistent way of configuring everything, separate configuration from application logic, varying configuration • In J2EE (e.g. EJB) it is easy to become dependent on container and deployment environment, proliferation of pointless classes (locators/delegates); Spring eliminates them • Cross-cutting behavior (resource management is cross-cutting concern, easy to copy-and-paste everywhere) • Portable (can use server-side in web/ejb app, client-side in swing app, business logic is completely portable) Vibrant Technology & Computers 9
- 10. Spring Solutions • Solutions address major J2EE problem areas: • Web application development (MVC) • Enterprise Java Beans (EJB, JNDI) • Database access (JDBC, iBatis, ORM) • Transaction management (JTA, Hibernate, JDBC) • Remote access (Web Services, RMI) • Each solution builds on the core architecture • Solutions foster integration, they do not re-invent the wheel Vibrant Technology & Computers 10
- 11. How to Start Using Spring • Download Spring from www.springframework.org, e.g. spring-framework-2.0.6-with-dependencies.zip • Unzip to some location, e.g. C:toolsspring-framework-2.0.6 • Folder C:toolsspring-framework-2.0.6dist contains Spring distribution jar files • Add libraries to your application classpath and start programming with Spring Vibrant Technology & Computers 11
- 12. Inversion of Control (IoC) • Central in the Spring is its Inversion of Control container • Based on “Inversion of Control Containers and the Dependency Injection pattern” (Martin Fowler) • Provides centralized, automated configuration, managing and wiring of application Java objects • Container responsibilities: • creating objects, • configuring objects, • calling initialization methods • passing objects to registered callback objects • etc • All together form the object lifecycle which is one of the most important features Java objects that are managed by the Spring IoC container are referred to as beans Vibrant Technology & Computers 12
- 13. Dependency Injection – Non-IoC public class MainBookmarkProcessor implements BookmarkProcessor{ private PageDownloader pageDownloader; private RssParser rssParser; public List<Bookmark> loadBookmarks() { // direct initialization pageDownloader = new ApachePageDownloader(); rssParser = new JenaRssParser(); // or factory initialization // pageDownloader = PageDownloaderFactory.getPageDownloader(); // rssParser = RssParserFactory.getRssParser(); // use initialized objects pageDownloader.downloadPage(url); rssParser.extractBookmarks(fileName, resourceName); // ... } Vibrant Technology & Computers 13
- 14. Dependency Injection - IoC • Beans define their dependencies through constructor arguments or properties • Container resolves (injects) dependencies of components by setting implementation object during runtime • BeanFactory interface - the core that loads bean definitions and manages beans • Most commonly used implementation is the XmlBeanFactory class • Allows to express the objects that compose application, and the interdependencies between such objects, in terms of XML • The XmlBeanFactory takes this XML configuration metadata and uses it to create a fully configured system Vibrant Technology & Computers 14
- 15. Non-IoC versus IoC Non Inversion of Control approach Inversion of Control approach Vibrant Technology & Computers 15
- 16. IoC Basics • Basic JavaBean pattern: • include a “getter” and “setter” method for each field: • Rather than locating needed resources, application components provide setters through which resources are passed in during initialization • In Spring Framework, this pattern is used extensively, and initialization is usually done through configuration file rather than application code class MyBean { private int counter; public int getCounter() { return counter; } public void setCounter(int counter) { this.counter = counter; } } Vibrant Technology & Computers 16
- 17. IoC Java Bean public class MainBookmarkProcessor implements BookmarkProcessor{ private PageDownloader pageDownloader; private RssParser rssParser; public List<Bookmark> loadBookmarks() { pageDownloader.downloadPage(url); rssParser.extractBookmarks(fileName, resourceName); // ... } public void setPageDownloader(PageDownloader pageDownloader){ this.pageDownloader = pageDownloader; } public void setRssParser(RssParser rssParser){ this.rssParser = rssParser; } Vibrant Technology & Computers 17
- 18. References • Spring Home: http://www.springframework.org • Inversion of Control Containers and the Dependency Injection pattern http://www.martinfowler.com/articles/injection.html • Spring IoC Container: http://static.springframework.org/spring/docs/2.0.x/referenc e/beans.html • Introduction to the Spring Framework by Rod Johnson http://www.theserverside.com/tt/articles/article.tss? l=SpringFramework Vibrant Technology & Computers 18
- 19. Thank you… Vibrant Technology & Computers 19