Before you begin coding, you need to understand what a web application is, what Java technologies are available for use, and what development tools can save your time and make creating applications easier.
The number of technologies can appear overwhelming. Keep in mind that you will not need to use them all. In fact, a web application often consists of nothing more than one page created with the JavaServer Pages (JSP) technology. Sometimes you will combine three or more such technologies. No matter how many you end up using, it’s good to know what is available to you and how you can use each one in a web application.
Java Servlet API
The
Java Servlet API lets you define HTTP-specific classes. A servlet class extends the capabilities of servers that host applications that are 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. A servlet runs on the server side — without an application GUI or HTML user interface (UI) of its own. Java Servlet extensions make many web applications possible.
JavaServer Pages Technology
JavaServer Pages (JSP) technology provides a simplified, fast way to create dynamic web content. JSP technology enables rapid development of web-based applications that are server- and platform-independent. JSP technology lets you add snippets of servlet code directly into a text-based document. Typically, a JSP page is a text-based document that contains two types of text:
- Static data, which can be expressed in any text-based format, such as HTML, Wireless Markup Language (WML), or XML
- JSP technology elements, which determine how the page constructs dynamic content
The packages involved in creating JSP pages are
javax.el,
javax.servlet.jsp,
javax.servlet.jsp.el, and
javax.servlet.jsp.tagext, though you will rarely have to import these directly. A JSP page can be as simple as a bit of HTML with one snippet of JSP code and the
.jsp extension of the page name.
JavaServer Pages Standard Tag Library
The JavaServer Pages Standard Tag Library (JSTL) encapsulates core functionality common to many JSP technology-based applications. Instead of mixing tags from numerous vendors in your applications, you employ a single standard set of tags. This standardization allows you to deploy your applications on any JSP container that supports JSTL and makes it more likely that the implementation of the tags is optimized.
JavaServer Faces Technology
JavaServer Faces technology is a UI framework for building web applications. The main components of JavaServer Faces technology involve a GUI component framework, a flexible model for rendering components in various markup languages and technologies, and a standardRenderKit for generating HTML markup.
This functionality is available through standard Java APIs and XML-based configuration files.
Java Message Service API
Messaging is a method of communication between software components or applications. A messaging system is a peer-to-peer facility. In other words, a messaging client can send messages to and receive messages from any other client. Each client connects to a messaging agent that provides facilities for creating, sending, receiving, and reading messages. By combining Java technology with enterprise messaging, the Java Message Service (JMS) API provides a powerful tool for solving enterprise computing problems.
Enterprise messaging provides a reliable, flexible service for the exchange of business data throughout an enterprise. The JMS API adds to this a common API and provider framework that enables the development of portable message-based applications in the Java programming language.
JavaMail API and the JavaBeans Activation Framework
Web applications can use the JavaMail API to send email notifications. The API has two parts: an application-level interface that the application components use to send email and a service provider interface. Service providers implement particular email protocols, such as SMTP. Several service providers are included with the JavaMail API package, and others are available separately. The Java EE platform includes the JavaMail extension with a service provider that allows application components to send email.
Java API for XML Processing
The Java API for XML Processing (JAXP), part of the Java SE platform, supports the processing of XML documents using the Document Object Model (DOM), the Simple API for XML (SAX), and Extensible Stylesheet Language Transformations (XSLT). JAXP enables applications to parse and transform XML documents independent of a particular XML-processing implementation.
JAXP also provides namespace support, which lets you work with schemas that might otherwise have naming conflicts. Designed to be flexible,
JDBC API
The JDBC API allows you invoke database SQL commands from Java programming language methods. You can use the JDBC API in a servlet, JSP technology page, or an enterprise bean when you need to access the database.
Java Persistence API
The Java Persistence API is a Java technology standards-based solution for persistence. Persistence uses an object-relational mapping approach to bridge the gap between an object-oriented model and a relational database. Java technology persistence consists of three areas:
- The Java Persistence API
- The query language
- Object-relational mapping metadata
Java Naming and Directory Interface
The Java Naming and Directory Interface (JNDI) provides naming and directory functionality, enabling applications to access multiple naming and directory services. It provides applications with methods for performing standard directory operations, such as associating attributes with objects and searching for objects using their attributes.
Naming services provide application clients, enterprise beans, and web components with access to a JNDI naming environment. A naming environment allows the developer to customize a component without having to access or change the component’s source code.
