1 / 60

Distributed Object-Oriented Programming (3) – Enterprise JavaBeans

Distributed Object-Oriented Programming (3) – Enterprise JavaBeans. SNU iDB Lab. Taewhi Lee. May 14th, 2007. Review – Distributed Programming Paradigm Shift. Service-Oriented Architecture. Distributed Computing  SOA DC – client/server are tightly coupled

berke
Download Presentation

Distributed Object-Oriented Programming (3) – Enterprise JavaBeans

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Distributed Object-Oriented Programming(3) – Enterprise JavaBeans SNU iDB Lab. Taewhi Lee May 14th, 2007

  2. Review – Distributed ProgrammingParadigm Shift Service-Oriented Architecture Distributed Computing  SOA DC – client/server are tightly coupled SOA – everything is decoupled Web Services Distributed Component Model OOP  CBD Object – limited reusability Component – independent service Several components are plugged in to a component architecture system CORBA Component Model EJB Distributed Object Model CORBA RMI Structured Programming  OOP SP – Complexity of system modeling Difficulty in code change/extension OOP – Natural object modeling Reusability by inheritance Flexibility by polymorphism Distributed Structural Model RPC Basic Inter-Process Communication Socket

  3. Outline Java EE EJB Overview Enterprise Beans EJB Programming Changes in EJB 3.0 References

  4. Java EE [1/5]Jave EE History 1995 1998 1998 2004~ Java J2SE J2EE Java SE Java EE For Distributed enterprise applications J2SE +Libraries(e.g. Security, Transaction) For Stand-alone applications Java 1.2 +Libraries(e.g. GUI, DB, networking) Object-oriented Platform-independent Garbage collection Since Java 1.5

  5. Java EE [2/5]What is Jave EE? • Java EE (Java Platform, Enterprise Edition) • The industry standard for developing enterprise applications • Portable, robust, scalable and secure server-side Java applications • Provides web services, component model, management, and communication APIs • Java EE goals • Highly available – to meet the needs of today’s global business environment • Secure – to protect the privacy of users and the integrity of enterprise data • Reliable and scalable – to insure that business transactions are accurately and promptly processed

  6. Java EE [3/5]Jave EE & EJB Java EE Web Services Technologies Web Application Technologies Enterprise Application Technologies Management & Security Technologies

  7. Java EE [4/5]Jave EE Technologies Web Services Technologies Implementing Enterprise Web Services Java API for XML-Based Web Services (JAX-WS) 2.0 Java API for XML-Based RPC (JAX-RPC) 1.1 Java Architecture for XML Binding (JAXB) 2.0 SOAP with Attachments API for Java (SAAJ) Streaming API for XML Web Service Metadata for the Java Platform Web Application Technologies Java Servlet 2.5 JavaServer Faces 1.2 JavaServer Pages 2.1 JavaServer Pages Standard Tag Library

  8. Java EE [5/5]Jave EE Technologies (cont’d) Enterprise Application Technologies Enterprise JavaBeans 3.0 J2EE Connector Architecture 1.5 Common Annotations for the Java Platform Java Message Service API The Java Database Connectivity API (JDBC) Java Persistence API Java Transaction API (JTA) JavaBeans Activation Framework (JAF) 1.1 JavaMail Management and Security Technologies J2EE Application Deployment J2EE Management Java Authorization Contract for Containers

  9. Outline Java EE EJB Overview Enterprise Beans EJB Programming Changes in EJB 3.0 References

  10. EJB Overview [1/11]What are Enterprise JavaBeans? • Enterprise JavaBeans (EJB) • A standard-based component model • APIs to implement business logics • EJB design goals • Common services • Multithreading • Transaction management • Resource management (e.g., connection pooling) • Persistence management • Security services • Distribution and scalability • “Throw money at it” solution

  11. EJB Overview [2/11]EJB Architecture EJB architecture Specifies the responsibilities and interactions among EJB entities Enterprise Bean Enterprise Bean Enterprise Bean Enterprise Bean Clients Clients EJB Client EJB Container EJB Container EJB Server EJB Server EJB Client

  12. EJB Overview [3/11]EJB Server EJB server Provides a run-time environment Provides system services and manages resources Process and thread management System resources management Database connection pooling and caching Management API Enterprise Bean Enterprise Bean Clients EJB Client EJB Container EJB Server

  13. EJB Overview [4/11]EJB Container EJB container Provides a run-time environment for an enterprise bean Likely provided by server vendor Hosts the EJBs and provides services to EJBs Naming Life cycle management Persistence (state management) Transaction Management Security Enterprise Bean Enterprise Bean Clients EJB Client EJB Container EJB Server

  14. EJB Overview [5/11]Enterprise Bean Enterprise Bean A specialized component for the real business logic Consists of several classes and interfaces Distributed over a network Server vendors provide tools that automatically generate distribution, transaction and security behavior Enterprise Bean Enterprise Bean Clients EJB Client EJB Container EJB Server

  15. EJB Overview [6/11]EJB Client Client access is controlled by the container in which the enterprise bean is deployed Clients locates an enterprise bean through Java Naming and Directory Interface (JNDI) RMI is the standard method for accessing a bean over a network Enterprise Bean Enterprise Bean Clients EJB Client EJB Container EJB Server

  16. EJB Overview [7/11]Pros and Cons of EJB Pros Component modularization Reusability ↑, maintenance cost ↓ Component portability “Write Once, Run Anywhere” (WORA) Development simplification A number of tricky middleware services are automatically managed Programmers can concentrate on writing business logic  Development speed ↑, code quality ↑ Cons Need to buy EJB container Implementation according to EJB specification

  17. EJB Overview [8/11]RMI vs. EJB

  18. EJB Overview [9/11]Code example: HelloWorld in RMI Remote interface Remote class public interface Hello extends Remote { public String sayHello(String name) throws RemoteException; } public class HelloImpl extends UnicastRemoteObject implements Hello { public HelloImpl() throws RemoteException { } public String sayHello(String name) throws RemoteException { return “Hello, ” + name; } }

  19. EJB Overview [10/11]Code example: HelloWorld in EJB Home interface Remote interface public interface HelloHomeextends EJBHome { public Hello create() throws RemoteException, CreateException; } public interface Hello extends EJBObject { public String sayHello(String name) throws RemoteException; }

  20. EJB Overview [11/11]Code example: HelloWorld in EJB (cont’d) Bean class public class HelloBeanimplements SessionBean { SessionContext ctx; // EJB container contract methods public void ejbCreate() { } public void ejbRemove() { } public void ejbActivate() { } public void ejbPassivate() { } public void setSessionContext(SessionContext ctx) { this.ctx = ctx; } // business method public String sayHello(String name) { return “Hello, ” + name; } }

  21. Outline Java EE EJB Overview Enterprise Beans EJB Programming Changes in EJB 3.0 References

  22. Enterprise Bean [1/7]Types of Enterprise Beans

  23. Session bean Implements some business logic Business process component e.g., order, payment in an online shopping mall Entity bean Object-oriented view of entities stored in persistent storage Normally, each instance represents a row in a RDB table e.g., product information, user information Enterprise Bean [2/7]Types of Enterprise Beans

  24. Stateful session bean Maintains a state The state is relevant only for a single client Cannot be seen by other clients Expires after a certain timeout e.g., shopping cart Enterprise Bean [3/7]Stateful Session Bean

  25. Stateless session bean No state Can have fields, but they are not unique to any client Since the container knows the bean has no state, it can: Use a single bean instance (while each client thinks it has its own copy) Destroy/re-instantiate on the fly Redirect requests to different instances (load balancing) e.g., currency conversion Enterprise Bean [4/7]Stateless Session Bean

  26. CMP(Container-Managed Persistence) entity bean Container is responsible for saving the persistent state DB-related classes are auto-generated You specify the container-managed attributes Persistence is independent of the data source The mapping can be applied to other DBs  very portable Container can manage caching, locking strategies Can only be used with data sources supported by JDBC Enterprise Bean [5/7]CMP Entity Bean

  27. BMP(Bean-Managed Persistence) entity bean The bean writer must provide code for storing/restoring persistent state Less portable Can exploit any persistence framework Not limited to databases Manual tuning can result in performance benefits At the price of portability and hard work Enterprise Bean [6/7]BMP Entity Bean

  28. Deployment Process to plug-in enterprise beans to EJB container Jar packaging + plug-in Class files are auto-generated Deployment Descriptor XML file Additional information to run enterprise beans e.g., transaction type, security information Makes it possible to use enterprise beans which are developed by other developers Enterprise Bean [7/7]Deployment Descriptor

  29. Outline Java EE EJB Overview Enterprise Beans EJB Programming Changes in EJB 3.0 References

  30. Choice of the bean type Session bean? Entity bean? Session bean – Stateful? Stateless? Entity bean – CMP? BMP? Code writing Home interface Remote interface Bean class Primary key class (entity bean only) Deployment descriptor EJB Programming [1/25]EJB Programming

  31. Template Example EJB Programming [2/25]Stateful Session Bean (1/6) Code Example: Shopping Cart – Home Interface public interface <BeanName>Homeextends javax.ejb.EJBHome { public <BeanName> create(<rmiParams>) throws [<otherException>, …] javax.ejb.CreateException, java.rmi.RemoteException; } public interface CartHome extends EJBHome { public Cart create(String customerName, String account) throws BadAccountException, CreateException, RemoteException; }

  32. Template Example EJB Programming [3/25]Stateful Session Bean (2/6) Code Example: Shopping Cart – Remote Interface public interface <BeanName> extends javax.ejb.EJBObject { public <rmiReturnType> <businessMethod> (<rmiParams>) throws [<otherException>, …], java.rmi.RemoteException; } public interface Cart extends EJBObject { public void addItem(int item) throws RemoteException; public void purchase() throws RemoteException; }

  33. Template EJB Programming [4/25]Stateful Session Bean (3/6) Code Example: Shopping Cart – Bean Class public class <BeanName>Beanimplements javax.ejb.SessionBean { public <rmiReturnType> <businessMethod> (<rmiParams>) throws [<otherException>, …], java.rmi.RemoteException { { /* implementation */ } // … other business methods // EJB container contract methods public void ejbCreate (<rmiParams>) … { /* implementation */ } private SessionContext _context; public void setSessionContext(SessionContext ctx) { _context = ctx; } public void ejbRemove() { /* implementation */ } public void ejbActivate() { } public void ejbPassivate() { } }

  34. Example EJB Programming [5/25]Stateful Session Bean (4/6) Code Example: Shopping Cart – Bean Class (cont’d) public class CartBeanimplements SessionBean { private SessionContext _context; private String customerName, account; // to maintain state information public void setSessionContext(SessionContext ctx) { _context = ctx; } public void ejbCreate (String customerName, String account) { this.customerName = customerName; this.account = account; } public void ejbRemove() { } public void ejbActivate() { /* implementation for activation */ } public void ejbPassivate() { /* implementation for de-activation */ } public void addItem(int item) { /* implementation */ } public void purchase() { /* implementation */ } }

  35. EJB Programming [6/25]Stateful Session Bean (5/6) Deployment Descriptor – Shopping Cart <session id=“Cart"> <ejb-name>Cart</ejb-name> <home>demo.j2ee. CartHome</home> <remote>demo.j2ee. Cart</remote> <ejb-class>demo.j2ee.CartBean</ejb-class> <session-type>Stateful</session-type> <transaction-type>Container</transaction-type> </session>

  36. EJB Programming [7/25]Stateful Session Bean (6/6) Code Example: Shopping Cart – Client code Context initialContext = new InitialContext(); // Get the reference of the home object using JNDI CartHome cartHome = (CartHome)PortableRemoteObject.narrow( initialContext.lookup(“java:comp/env/ejb/cart”), CartHome.class); // Create EJB object Cart cart = cartHome.create(“John”, “7506”); cart.addItem(96); // business method call cart.purchase();

  37. Template Example EJB Programming [8/25]Stateless Session Bean (1/5) Code Example: Currency Converter – Home Interface public interface <BeanName>Homeextends javax.ejb.EJBHome { public <BeanName> create()throws javax.ejb.CreateException, java.rmi.RemoteException; } public interface CurrencyConverterHome extends EJBHome { public CurrencyConverter create() throws CreateException, RemoteException; }

  38. Template Example EJB Programming [9/25]Stateless Session Bean (2/5) Code Example: Currency Converter – Remote Interface public interface <BeanName> extends javax.ejb.EJBObject { public <rmiReturnType> <businessMethod> (<rmiParams>) throws [<otherException>, …], java.rmi.RemoteException; } public interface CurrencyConverter extends EJBObject { public double convertUsdToWon(double usd) throws RemoteException; }

  39. Template EJB Programming [10/25]Stateless Session Bean (3/5) Code Example: Currency Converter – Bean Class public class <BeanName>Beanimplements javax.ejb.SessionBean { public <rmiReturnType> <businessMethod> (<rmiParams>) throws [<otherException>, …], java.rmi.RemoteException { { /* implementation */ } // … other business methods // EJB container contract methods public void ejbCreate() … { /* implementation */ } private SessionContext _context; public void setSessionContext(SessionContext ctx) { _context = ctx; } public void ejbRemove() { /* implementation */ } public void ejbActivate() { } public void ejbPassivate() { } }

  40. Example EJB Programming [11/25]Stateless Session Bean (4/5) Code Example: Currency Converter – Bean Class (cont’d) public class CurrencyConverterBeanimplements SessionObject { private SessionContext _context; private static final double WON_PER_USD = 950; public void setSessionContext(SessionContext ctx) { _context = ctx; } public void ejbCreate () { } public void ejbRemove() { } public void ejbActivate() { } public void ejbPassivate() { } public double convertUsdToNis(double usd) { return usd * WON_PER_USD; } }

  41. EJB Programming [12/25]Stateless Session Bean (5/5) Deployment Descriptor – Currency Converter <session id="CurrencyConverter"> <ejb-name>CurrencyConverter</ejb-name> <home>demo.CurrencyConverterHome</home> <remote>demo.CurrencyConverter</remote> <ejb-class>demo.CurrencyConverterBean</ejb-class> <session-type>Stateless</session-type> <transaction-type>Container</transaction-type> </session>

  42. EJB Programming [13/25]Session Bean Lifecycle

  43. Template EJB Programming [14/25]CMP Entity Bean (1/6) Code Example: Product – Home Interface public interface <BeanName>Homeextends javax.ejb.EJBHome { public <BeanName> create(<rmiParams>) throws [<otherException>, …] javax.ejb.CreateException, java.rmi.RemoteException; public <BeanName> findByPrimaryKey(<PrimaryKey>) throws [<otherException>, …] javax.ejb.CreateException, java.rmi.RemoteException; public Collection findXXX(<rmiParams>) throws [<otherException>, …] javax.ejb.CreateException, java.rmi.RemoteException; }

  44. Example EJB Programming [15/25]CMP Entity Bean (2/6) Code Example: Product – Home Interface public interface ProductHome extends EJBHome { public Product create(String productId, String description, double price) throws CreateException, RemoteException; public ProductfindByPrimaryKey(String productId) throws RemoteException, FinderException; public CollectionfindByPriceRange(double low, double high) throws RemoteException, FinderException; }

  45. Example EJB Programming [16/25]CMP Entity Bean (3/6) Code Example: Product – Remote Interface public interface Product extends EJBObject { public void setPrice(double price) throws RemoteException; public double getPrice() throws RemoteException; public String getDescription() throws RemoteException; }

  46. Example EJB Programming [17/25]CMP Entity Bean (4/6) Code Example: Product – Bean Class public class ProductBeanimplements EntityBean { public String productId, description; public double price; private EntityContext context; public ejbCreate(String productId, String description, double price) throws CreateException { if (productId == null) throw new CreateException(“productId required.”); this.productId = productId; this.description = description; this.price = price; return null; }

  47. Example (cont’d) EJB Programming [18/25]CMP Entity Bean (5/6) Code Example: Product – Bean Class (cont’d) public void setPrice(double price) { this.price = price; } public double getPrice() { return price; } public String getDescription() { return description; } public void setEntityContext(EntityContext ctx) { this.context = ctx; } public void ejbActivate() { productId = (String)context.getPrimaryKey(); } public void ejbPassivate() { productId = null; description = null; } public void ejbRemove() { } public void ejbLoad() { } public void ejbStore() { } public void unsetEntityContext() { } public void ejbPostCreate(String productId, String description, double price) { } }

  48. EJB Programming [19/25]CMP Entity Bean (6/6) Deployment Descriptor – Product <entity id="Account"> <persistence-type>Container</persistence-type> <ejb-name>Product</ejb-name> <home>demo.ProductHome</home> <remote>demo.Product</remote> <ejb-class>demo.ProductBean</ejb-class> <prim-key-class>java.lang.String</prim-key-class> <abstract-schema-name>Product</abstract-schema-name> <cmp-field><field-name>productId</field-name></cmp-field> <cmp-field><field-name>description</field-name></cmp-field> <cmp-field><field-name>price</field-name></cmp-field> <primkey-field>productId</primkey-field> <query> <query-method> <method-name>findByPriceRange</method-name> </query-method> <ejb-ql>select object(o) from Product o where o.price >= ?1 and o.price <= ?2</ejb-ql> </query> </entity>

  49. Example EJB Programming [20/25]BMP Entity Bean (1/5) Code Example: Product – Bean Class … // Not to locate the record, but to verify that the record exists public StringejbFindByPrimaryKey(String primaryKey) throws FinderException { boolean result; try { result = selectByPrimaryKey(primaryKey) } catch (Exception e) { } if (result) return primaryKey; else throw new ObjectNotFoundException(“Row for ” + primaryKey + “ not found”); } …

  50. Example EJB Programming [21/25]BMP Entity Bean (2/5) Code Example: Product – Bean Class … public boolean selectByPrimaryKey(String primaryKey) throws SQLException { String selectStmt = “select productId ” + “from product where productId = ?”; PreparedStatement prepStmt = _conn.prepareStatement(selectStmt); prepStmt.setString(1, primaryKey); ResultSet rs = prepStmt.executeQuery(); boolean result = rs.next(); prepStmt.close(); return result; } …

More Related