Reference Implementation Software
The J2EE SDK is a noncommercial operational definition of the J2EE platform and specification made freely available by Sun Microsystems for demonstrations, prototyping, and educational use. It comes with the J2EE application server, Web server, relational database, J2EE APIs, and complete set of development and deployment tools. You can download the J2EE SDK from the Webhttp://java.sun.com/j2ee/download.html#sdk
The purpose of the J2EE SDK is to allow product providers to determine what their implementations must do under a given set of application conditions, and to run the J2EE Compatibility Test Suite to test that their J2EE products fully comply with the specification. It also allows application component developers to run their J2EE applications on the J2EE SDK to verify that applications are fully portable across all J2EE products and tools.
The relational database provides persistent storage for application data. A J2EE implementation is not required to support a particular type of database, which means that the database supported by different J2EE products can vary. See the Release Notes included with the J2EE SDK download for a list of the databases currently supported by the reference implementation.
The Java 2 Platform, Standard Edition (J2SE) SDK is required to run the J2EE SDK and provides core APIs for writing J2EE components, core development tools, and the Java virtual machine. The J2EE SDK provides the following APIs to be used in J2EE applications.
Enterprise JavaBeans Technology 2.0
An enterprise bean is a body of code with fields and methods to implement modules of business logic. You can think of an enterprise bean as a building block that can be used alone or with other enterprise beans to execute business logic on the J2EE server.
There are three kinds of enterprise beans: session beans, entity beans, and message-driven beans. Enterprise beans often interact with databases. One of the benefits of entity beans is that you do not have to write any SQL code or use the JDBC API directly to perform database access operations; the EJB container handles this for you. However, if you override the default container-managed persistence for any reason, you will need to use the JDBC API. Also, if you choose to have a session bean access the database, you have to use the JDBC API.
JDBC API 2.0
The JDBC API lets you invoke SQL commands from Java programing language methods. You use the JDBC API in an enterprise bean when you override the default container-managed persistence or have a session bean access the database. With container-managed persistence, database access operations are handled by the container, and your enterprise bean implementation contains no JDBC code or SQL commands. You can also use the JDBC API from a servlet or JSP page to access the database directly without going through an enterprise bean.
The JDBC API has two parts: an application-level interface used by the application components to access a database, and a service provider interface to attach a JDBC driver to the J2EE platform.
Java Servlet Technology 2.3
Java Servlet technology lets you define HTTP-specific servlet classes. A servlet class extends the capabilities of servers that host applications accessed by way of a request-response programming model. Although servlets can respond to any type of request, they are commonly used to extend the applications hosted by Web servers.
JavaServer Pages Technology 1.2
JavaServer Pages technology lets you put snippets of servlet code directly into a text-based document. A JSP page is a text-based document that contains two types of text: static template data, which can be expressed in any text-based format such as HTML, WML, and XML, and JSP elements, which determine how the page constructs dynamic content.
Java Message Service 1.0
The JMS is a messaging standard that allows J2EE application components to create, send, receive, and read messages. It enables distributed communication that is loosely coupled, reliable, and asynchronous. For more information on JMS, see the online Java Message Service Tutorial:http://java.sun.com/products/jms/tutorial/index.html
Java Naming and Directory Interface 1.2
The JNDI provides naming and directory functionality. It provides applications with methods for performing standard directory operations, such as associating attributes with objects and searching for objects using their attributes. Using JNDI, a J2EE application can store and retrieve any type of named Java object.
Because JNDI is independent of any specific implementations, applications can use JNDI to access multiple naming and directory services, including existing naming and directory services such as LDAP, NDS, DNS, and NIS. This allows J2EE applications to coexist with legacy applications and systems. For more information on JNDI, see the online JNDI Tutorial:http://java.sun.com/products/jndi/tutorial/index.html
Java Transaction API 1.0
The Java Transaction API (JTA) provides a standard interface for demarcating transactions. The J2EE architecture provides a default auto commit to handle transaction commits and rollbacks. An auto commit means that any other applications viewing data will see the updated data after each database read or write operation. However, if your application performs two separate database access operations that depend on each other, you will want to use the JTA API to demarcate where the entire transaction, including both operations, begins, rolls back, and commits.
JavaMail API 1.2
J2EE applications can use the JavaMail API to send e-mail notifications. The JavaMail API has two parts: an application-level interface used by the application components to send mail, and a service provider interface. The J2EE platform includes JavaMail with a service provider that allows application components to send Internet mail.
JavaBeans Activation Framework 1.0
The JavaBeans Activation Framework (JAF) is included because JavaMail uses it. It provides standard services to determine the type of an arbitrary piece of data, encapsulate access to it, discover the operations available on it, and create the appropriate JavaBeans component to perform those operations.
Java API for XML Processing 1.1
XML is a language for representing text-based data so the data can be read and handled by any program or tool. Programs and tools can generate XML documents that other programs and tools can read and handle. Java API for XML Processing (JAXP) supports processing of XML documents using DOM, SAX, and XSLT. JAXP enables applications to parse and transform XML documents independent of a particular XML processing implementation.
For example, a J2EE application can use XML to produce reports, and different companies that receive the reports can handle the data in a way that best suits their needs. One company might put the XML data through a program to translate the XML to HTML so it can post the reports to the Web, another company might put the XML data through a tool to create a marketing presentation, and yet another company might read the XML data into its J2EE application for processing.
J2EE Connector Architecture 1.0
The J2EE Connector Architecture is used by J2EE tools vendors and system integrators to create resource adapters that support access to enterprise information systems that can be plugged into any J2EE product. A resource adapter is a software component that allows J2EE application components to access and interact with the underlying resource manager. Because a resource adapter is specific to its resource manager, there is typically a different resource adapter for each type of database or enterprise information system.
Java Authentication and Authorization Service 1.0
The Java Authentication and Authorization Service (JAAS) provides a way for a J2EE application to authenticate and authorize a specific user or group of users to run it.
JAAS is a Java programing language version of the standard Pluggable Authentication Module (PAM) framework that extends the Java 2 Platform security architecture to support user-based authorization.
Simplified Systems Integration
The J2EE platform is a platform-independent, full systems integration solution that creates an open marketplace in which every vendor can sell to every customer. Such a marketplace encourages vendors to compete, not by trying to lock customers into their technologies but by trying to outdo each other by providing products and services that benefit customers, such as better performance, better tools, or better customer support.
The J2EE APIs enable systems and applications integration through the following:
- Unified application model across tiers with enterprise beans
- Simplified response and request mechanism with JSP pages and servlets
- Reliable security model with JAAS
- XML-based data interchange integration with JAXP
- Simplified interoperability with the J2EE Connector Architecture
- Easy database connectivity with the JDBC API
- Enterprise application integration with message-driven beans and JMS, JTA, and JNDI
You can learn more about using the J2EE platform to build integrated business systems by reading J2EE Technology in Practice:http://java.sun.com/j2ee/inpractice/aboutthebook.html
The J2EE reference implementation provides an application deployment tool and an array of scripts for assembling, verifying, and deploying J2EE applications and managing your development and production environments. See Appendix B for a discussion of the tools.
Application Deployment Tool
The J2EE reference implementation provides an application deployment tool (
deploytool) for assembling, verifying, and deploying J2EE applications. There are two versions: command line and GUI.
The GUI tool includes wizards for
- Packaging, configuring, and deploying J2EE applications
- Packaging and configuring enterprise beans
- Packaging and configuring Web components
- Packaging and configuring application clients
- Packaging and configuring resource adaptors
In addition, configuration information can be set for each component and module type in the tabbed inspector panes.
Table 1-1 lists the scripts included with the J2EE reference implementation that let you perform operations from the command line.
Table 1-1 J2EE Scripts Script Description
Start and stop the J2EE server
Start and stop the default database
Add JDBC drivers, JMS destinations, and connection factories for various resources
Create public and private keys and generate X509 self-signed certificate.
Import certificate files. Add J2EE users to and remove J2EE users from the authentication and authorization list for a J2EE application
Package J2EE application components into EAR, EJB JAR, application client JAR, and WAR files
Verify that EAR, EJB JAR, application client JAR, and WAR files are well-formed and comply with the J2EE specification
Run a J2EE application client
Remove all deployed applications from the J2EE server