Java
JavaBeans
Java Server Page (JSP)
JavaScript
JDBC

Java is a programming language expressly designed for use in the distributed environment of the Internet. It was designed to have the "look and feel" of the C++ language, but it is simpler to use than C++ and enforces a completely object-oriented view of programming. Java can be used to create complete applications that may run on a single computer or be distributed among servers and clients in a network. It can also be used to build small application modules or applets for use as part of a Web page. Applets make it possible for a Web page user to interact with the page.

The major characteristics of Java are:

• The programs you create are portable in a network. Your program is compiled into Java bytecode that can be run anywhere in a network on a server or client that has a Java virtual machine. The Java virtual machine interprets the bytecode into code that will run on the real computer hardware. This means that individual computer platform differences such as instruction lengths can be recognized and accommodated locally just as the program is being executed. Platform-specific versions of your program are no longer needed.
• The code is "robust," here meaning that, unlike programs written in C++ and perhaps someother languages, the Java objects can contain no references to data external to themselves or other known objects. This ensures that an instruction can not contain the address of data storage in another application or in the operating system itself, either of which would cause the program and perhaps the operating system itself to terminate or "crash." The Java virtual machine makes a number of checks on each object to ensure integrity.
• Java is object-oriented, which means that, among other characteristics, similar objects can take advantage of being part of the same class and inherit common code. Objects are thought of as "nouns" that a user might relate to rather than the traditional procedural "verbs." A method can be thought of as one of the object's capabilities or behaviors.
• In addition to being executed at the client rather than the server, a Java applet has other characteristics designed to make it run fast.
• Relative to C++, Java is easier to learn. (However, it is not a language you'll pick up in an evening!)

JavaScript should not be confused with Java. JavaScript, which originated at Netscape, is interpreted at a higher level, is easier to learn than Java, but lacks some of the portability of Java and the speed of bytecode. Because Java applets will run on almost any operating system without requiring recompilation and because Java has no operating system-unique extensions or variations, Java is generally regarded as the most strategic language in which to develop applications for the Web. (However, JavaScript can be useful for very small applications that run on the Web client or server.)

JavaBeans is an object-oriented programming interface from Sun Microsystems that lets you build re-useable applications or program building blocks called components that can be deployed in a network on any major operating system platform. Like Java applets, JavaBeans components (or "Beans) can be used to give World Wide Web pages (or other applications) interactive capabilities such as computing interest rates or varying page content based on user or browser characteristics.

From a user's point-of-view, a component can be a button that you interact with or a small calculating program that gets initiated when you press the button. From a developer's point-of-view, the button component and the calculator component are created separately and can then be used together or in different combinations with other components in different applications or situations.

When the components or Beans are in use, the properties of a Bean (for example, the background color of a window) are visible to other Beans and Beans that haven't "met" before can learn each other's properties dynamically and interact accordingly.

Beans are developed with a Beans Development Kit (BDK) from Sun and can be run on any major operating system platform (Windows 95, UNIX, Mac) inside a number of application environments (known as containers), including browsers, word processors, and other applications.

To build a component with JavaBeans, you write language statements using Sun's Java programming language and include JavaBeans statements that describe component properties such as user interface characteristics and events that trigger a bean to communicate with other beans in the same container or elsewhere in the network.

Beans also have persistence, which is a mechanism for storing the state of a component in a safe
place. This would allow, for example, a component (bean) to "remember" data that a particular user had already entered in an earlier user session.

JavaBeans gives Java applications the compound document capability that the OpenDoc and ActiveX interfaces already provide.

Java Server Page (JSP) is a technology for controlling the content or appearance of Web pages through the use of servlets, small programs that are specified in the Web page and run on the Web server to modify the Web page before it is sent to the user who requested it. Sun Microsystems, the developer of Java, also refers to the JSP technology as the Servlet API (Application Program Interface). JSP is comparable to Microsoft's Active Server Page (ASP) technology. Whereas a Java Server Page calls a Java program that is executed by the Web server, an Active Server Page contains a script that is interpreted by a script interpreter (such as VBScript or JScript) before the page is sent to the user.

An HTML page that contains a link to a Java servlet is sometimes given the file name suffix of .JSP.

JavaScript is an interpreted programming or script language from Netscape. It is somewhat similar in capability to Microsoft's Visual Basic, Sun's Tcl, the UNIX-derived Perl, and IBM's REXX. In general, script languages are easier and faster to code in than the more structured and compiled languages such as C and C++ and are ideal for programs of limited capability or that can reuse and tie together existing compiled programs.

JavaScript is used in Web site development to do such things as:

• Automatically change a formatted date on a Web page (see our "Today" page)
• Cause a linked-to page to appear in a popup window (see our "Make a WordPop!" page)
• Cause text or a graphic image to change during a mouse rollover (put your mouse over our menu page)

JDBC (Java Database Connectivity) is an application program interface (API) specification for connecting programs written in Java to the data in popular databases. The application program interface lets you encode access request statements in structured query language (SQL) that are then passed to the program that manages the database. It returns the results through a similar interface. JDBC is very similar to Microsoft's Open Database Connectivity (ODBC) and, with a small "bridge" program, you can use the JDBC interface to access databases through Microsoft's ODBC interface. For example, you could write a program designed to access many popular database products on a number of operating system platforms. When accessing a database on a PC running Microsoft's Windows 95 and, for example, a Microsoft Access database, your program with JDBC statements would be able to access the Microsoft Access database.

JDBC actually has two levels of interface. In addition to the main interface, there is also an API from a JDBC "manager" that in turn communicates with individual database product "drivers", the JDBC-ODBC bridge if necessary, and a JDBC network driver when the Java program is running in a network environment (that is, accessing a remote database).

When accessing a remote database, JDBC takes advantage of the Internet's file addressing scheme and a file name looks much like a Web page address (or URL). For example, a Java SQL statement might identify the database as:

jdbc:odbc://www.somecompany.com:400/databasefile

JDBC specifies a set of object-orient programming classes for the programmer to use in building SQL requests. An additional set of classes describes the JDBC driver API. The most common SQL data types, mapped to Java data types, are supported. The API provides for implementation-specific support for transactional requests and the ability to commit or roll back to
the beginning of a transaction. 

More on JDBC from the Java Site....