javaee EJB begin

J2EEEJB 3.0 Overview5.1 Overviewl What plumbing do you need to build a robust distributed object deployment?l What is EJB, and what value does it add?5.1 Overviewl EJB is a server-side component framework¡simplifies the process of building enterprise-class distribute component application in Java5.1 Overviewl What is Software Component?¡A piece of code written to manifest the behavior of a corresponding abstract concept.¡Sounds like Objects, but it is differentl Self-contained Entity•Be used in a similar or completely different application•Can live an independent, reusable existence outside oforiginal application• A system can be designed to consist of reusablecomponents5.1 Overviewl The Need for Componentization ¡Lack of flexibility and interoperability¡Component Frameworkl Common Object Request Broker Architecture(CORBA)l ActiveX/COMl EJB5.1 Overview¡Remote methodinvocation¡Loading balancing¡Transparent failover¡Back-end integration¡Transaction¡Clustering¡Dynamicredeployment5.1 Overview¡Clean shutdown¡Logging and Auditing¡Systems management¡Threading¡Message-oriented middleware¡Component life cycle¡Resource pooling¡Security¡Caching¡And much…l Each of these aspects can be thought of as a service5.1 Overviewl Application Server-Class Software ¡Building Middleware Services from Scratch ¡Buying Middleware Services via Application Server Software5.1 Overviewl Standardization of Component Frameworks ¡More than 50 application servers on the market ¡Need an agreement to enable any componentto run within any application server5.1 Overview5.1 Overviewl E nterprise J ava B eans Technology ¡A standard for developing and deployingserver-side distribute components in Javal It is a ubiquitous industry standardl Portability is possiblel Rapid application development¡EJB is two things in onel Specificationl A set of Java Interfaces5.1 Overviewl Why Java¡Interface/implementation separation ¡Safe and securityl If a thread dies, the application stays upl No memory pointer in javal Memory leaks occur much less often ¡Cross-platform5.1 Overviewl EJB as a Business Tier Component ¡Presentation tier components deal directly with end user or end application¡Business tier components perform server-sideoperationl Such as executing complex algorithm or performingtransactional business operation5.1 Overview¡EJB components can perform following tasks l Performing business logicl Access a databasel Integrate with other systems¡Examples of EJB clientsl Application clientsl Dynamically generated Web pagesl Web service clients5.1 Overview5.1 Overviewl Distributed Computing: The Foundation of EJB5.0 (Java EE)5.0 (Java EE)l A uncompleted list of JavaEE Technologies¡Enterprise JavaBean(EJB)¡Java API for Web Services(JAX-WS)¡Java Remote Method Invocation (RMI) and RMI-IIOP¡Java Naming and Directory Interface (JNDI)¡Java Database Connectivity (JDBC)¡Java Transaction API(JTA) and Java Transaction Service(JTS) ¡Java Message Service (JMS)¡Java Servlets¡Java Server Pages (JSP)¡Java Server Faces (JSF)¡Java EE Connector Architecture (JCA)¡The Java API for XML Parsing (JAXP)¡The Java Architecture for XML Binding (JAXB)¡The Java Authentication and Authorization Service (JAAS)5.2 Pre-EJB 3.0: The World That Was l Briefly introduce the programming anddeployment model in EJB2.0l To realize the breadth and depth of enhancements made in EJB3.05.2 Pre-EJB 3.0: The World That Was5.2 Pre-EJB 3.0: The World That Was5.2 Pre-EJB 3.0: The World That Was5.2 Pre-EJB 3.0: The World That Was l Differences between the local and theremote interface¡The local interface extendsjavax.ejb.EJBLocalObject instead ofjavax.ejb.EJBObject¡The business method does not throw ajava.rmi.RemoteException5.2 Pre-EJB 3.0: The World That Was5.2 Pre-EJB 3.0: The World That Was5.2 Pre-EJB 3.0: The World That Wasl Differences between the local and the remote home interface¡The local home interface extendsjavax.ejb.EJBLocalHome instead ofjavax.ejb.EJBHome¡The local home interface methods do not throw java.rmi.RemoteException5.2 Pre-EJB 3.0: The World That Was5.2 Pre-EJB 3.0: The World That Wasl Dissect EJB 2.x¡Development Complexities¡Deployment Complexities¡Debugging and Testing Complexities5.3 The New Enterprise JavaBean5.3 The New Enterprise JavaBeanl EJB Container¡Responsible for managing enterprise bean l Transaction managementl Securityl Resource and life cycle managementl Remote accessibilityl Support for concurrent requestsl Clustering and load-balancing5.3 The New Enterprise JavaBeanl Type of Bean¡Session beansl model business processesl Stateful& Stateless session bean¡Message-driven beans (MDBs)l Similar to session beans, but driven by message ¡Entity beans (deprecated)l Model business data5.3 The New Enterprise JavaBean5.3 The New Enterprise JavaBeanl RMI-IIOP: The Protocol of Beanl EJB and Location Transparency¡JNDI is an enabler of location transparency l Provides a standard API to access different kinds ofnaming and directory services within a java programl Provides two API•Naming API•Directory API5.3 The New Enterprise JavaBeanl The EJB 3.0 Simplified API¡No home and object interfaces¡No component interface¡Use of Java metadata annotations¡Simplification of APIs for accessing bean’senvironment5.3 The New Enterprise JavaBeanl Elimination of Home and Object Interface ¡Pre EJB 3.0l The Home interface served as a factory for creatingreference to the EJB Object.l The EJB Object Interfaces was to provide client viewfor an EJB5.3 The New Enterprise JavaBeanl Elimination of Component Interface ¡Pre EJB 3.0l Components need to implementjavax.ejb.SessionBean orjavax.ejb.MessageDrivenBean•Carried the various life cycle method5.3 The New Enterprise JavaBeanl Use of Annotations¡Annotations are used to provide the additional context to program.¡Can be applied to various elements in Java l Methods, variables, constructors, packagedeclarations5.3 The New Enterprise JavaBean¡Annotations and Bean Developmentl EJB 3.0 is a mix of metadata tags and code structs5.3 The New Enterprise JavaBean¡Annotations and Deployment Descriptions l EJB 3.0 annotations can be used in lieu ofdeployment descriptors.¡Container Specific Deployment Description l Describe the value-added services of container5.3 The New Enterprise JavaBean l The Good, Bad and Ugly of DeploymentAnnotation¡Convenientl Place configuration along with the bean’s logic.¡Trickyl When the bean provider and deployer is not thesame person.l Simplified Access to environmentPackage and Deployment of the “New”Bean5.3 The New Enterprise JavaBeanl Example of EJB 3.0 Bean¡The Business Interface5.3 The New Enterprise JavaBean l The Bean Class5.3 The New Enterprise JavaBean l The Deployment Descriptor5.3 The New Enterprise JavaBeanl The ClientSummary of Terml The enterprise bean instance¡A POJO contains business method implementation of local/remote business interfacel The business interface¡A plain old java interface that enumerates the business methods exposed by the enterprise bean.l The deployment descriptor¡A XML file that specifies the middleware requirements of the beanl The Ejb-jar file¡The package unit for enterprise beanl The vendor-specific deployment descriptor¡Specify the bean’s need for proprietary container.。