Question

State whether each of the following is true or false. If false, explain why. a) The J2EE server uses port 8080 to await client requests. b) When deploying applications with the \(\mathrm{J} 2 \mathrm{EE}\) server, you can launch the Cloudscape and J2EE servers in any order. c) Initialcontext method 1ookup locates a resource with a JNDI name. d) Method lookup returns a connection object representing the connection to the database. e) The Java 2 Enterprise Edition 1.2.1 reference implementation includes the Apache Tomcat JSP and servlet container. P When RequestDispatcher method forward is called, processing of the request by the current servlet is temporarily suspended to wait for a response from the resource to which the request is forwarded. g) Both the ServletRequest and the Servletcontext getRequestDispatchex methods throw exceptions if the argument to getRequest Dispatcher is not a servlet. h) Each resource reference has a corresponding JNDI name that is used by the deployment tool to register the resource with the Java Naming and Directory Service. i) If you do not configure your data sources and other resources before deploying an Enterprise Java application, the \(\mathrm{J} 2 \mathrm{EE}\) server will search the application to determine the resources used and register those resources with the naming server. j) Not including the full package directory structure for a class in a package will prevent the application from loading the class and from executing properly.

Short answer

a) False, b) False, c) True, d) False, e) True, f) True, g) False, h) True, i) False, j) True.

Step-by-step solution

Analyzing Statement a

Statement a is false because by default, the J2EE server or more commonly, application servers often use port 8080 for HTTP connections. However, the actual port can vary depending on the server configuration and it's not exclusively set to port 8080 for J2EE servers.

Analyzing Statement b

Statement b is false. The J2EE server often requires that services like the database be available before it starts, in this case Cloudscape. Some dependencies might require a specific order of startup.

Analyzing Statement c

Statement c is true. The `Initialcontext.lookup` method is used to locate a resource using a JNDI name in the Java Naming and Directory Interface (JNDI) API.

Analyzing Statement d

Statement d is false. The `lookup` method typically returns an object reference from a naming service, but it does not specifically return a connection object. It can be anything as per what is bound with the JNDI name.

Analyzing Statement e

Statement e is true. The Java 2 Enterprise Edition 1.2.1 reference implementation includes Apache Tomcat as the JSP and servlet container.

Analyzing Statement f

Statement f is true. When the `RequestDispatcher` method `forward` is called, the control is transferred to another resource, and processing by the current servlet is suspended until the response is completed by the forwarded resource.

Analyzing Statement g

Statement g is false. The `getRequestDispatcher` method does not throw an exception if the argument is not a servlet. It returns null if the path does not correspond to any resource at all.

Analyzing Statement h

Statement h is true. Each resource reference does have a corresponding JNDI name that is used to register the resource with the Java Naming and Directory Service during deployment.

Analyzing Statement i

Statement i is false. If resources are not configured prior to deployment, the J2EE server does not automatically search the application and register resources; this configuration must be handled by the developer.

Analyzing Statement j

Statement j is true. Not including the full package directory structure in a Java application means the JVM cannot locate the class, and it will result in class not found errors, hindering the proper execution of the application.

Key concepts

Java Naming and Directory Interface (JNDI)

The Java Naming and Directory Interface, or JNDI, is an API for directory services that allows Java applications to discover and look up data and objects using names. JNDI plays a crucial role in Java applications that are distributed over a server environment. It acts as a bridge between Java programs and naming and directory services such as LDAP, DNS, and others.

JNDI is particularly important for Java EE applications, where resources such as databases, messaging systems, and EJBs must be dynamically located and accessed. By using JNDI names, these resources can be defined and accessed in a way that allows for more flexibility and less dependency on hard-coded values.

• The `InitialContext.lookup` method is typically used to retrieve resources by their JNDI names.
• This lookup mechanism allows for component decoupling and more dynamic configuration of Java applications.

Servlets

Servlets are server-side Java programs that handle client requests and generate dynamic web content. They are a key component of Java EE and are used to implement web applications efficiently. Servlets run on a web server, like Apache Tomcat, and act as a middle layer between client requests and server responses.

Servlets are designed to handle complex requests efficiently, providing a powerful way to extend the server's capabilities without a lot of overhead. They interact with the client through a request and response model and can interact with databases, invoke JavaBeans, and utilize other Java resources to generate dynamic content.

• Servlets are managed by the container, which handles loading, initialization, and invocation.
• They follow a lifecycle including `init()`, `service()` and `destroy()` methods.

Apache Tomcat

Apache Tomcat is an open-source implementation of the Java Servlet, JavaServer Pages (JSP), and other Java EE technologies. It provides a "pure Java" HTTP web server environment for running Java code and is a critical part of many enterprise applications that are deployed over the web.

Tomcat is widely used due to its simplicity and ability to easily manage the lifecycle and deployment of Java applications. It supports powerful configurations and is capable of handling a wide range of applications from simple JSP-based to large enterprise-grade applications.

• It operates on various platforms like Windows, Linus, and macOS.
• Tomcat also serves as a reference implementation for the Servlet and JSP specifications, making it a crucial tool for Java developers.
• It simplifies the deployment of web apps by providing an integrated environment with robust support and community contributions.

Enterprise Java applications

Enterprise Java applications harness the robust features of Java EE to provide scalable, secure, and well-supported applications tailored for enterprise environments. Java EE offers a comprehensive suite of tools and technologies designed to provide solutions to common problems faced by business applications.

Features of enterprise applications include support for scalability to accommodate growing amounts of load, transaction management for maintaining database integrity, and security features that ensure data and application safety. They are typically composed of numerous components such as servlets, JSPs, and Enterprise JavaBeans (EJBs), which work together to create a cohesive application.

• Java EE provides APIs like JNDI, JSP, and EJB which facilitate the design and deployment of these applications.
• Enterprise Java applications often require robust databases and messaging systems to handle the business logic and data processing needs efficiently.
• This ecosystem supports ease of integration with existing systems and technologies, allowing for extensive enterprise deployment.