JSP and Servlets - Glossary


A Servlet is a Java class in Java EE that conforms to the Java Servlet API, a protocol by which a Java class may respond to HTTP requests.
They are not tied to a specific client-server protocol, but are most often used with this protocol. The word Servlet is often used in the meaning of HTTP Servlet.
Thus, a software developer may use a servlet to add dynamic content to a Web server using the Java platform. The generated content is commonly HTML, but may be other data such as XML. Servlets are the Java counterpart to non-Java dynamic Web content technologies such as CGI and ASP.NET.
Servlets can maintain state in session variables across many server transactions by using HTTP cookies, or URL rewriting.
Action Parameter
The attribute on an HTML FORM tag that names the program to be run on the server when the form is submitted by the user.
Active Server Pages
A Microsoft server-side technology that uses VBScript or JavaScript on the server.
The knowledge that authorized users truly are the people you believe them to be.
A set of rules for calling a server-side program from a Web server.

Chaining servlet
A servlet that the Web server calls to process the output of another servlet.
An environment variable that the Java compiler and runner use to locate classes.
The knowledge that information you exchange with an authorized user is not copied by any other party.
A Data Source Name; used to identify an ODBC data source, such as an Access database.
An escape character is a way to write a symbol that can not normally be written.
For example, if you wish to create a string that contains a quote character, you can prevent the compiler from taking the quote as the end of the string by using n escape symbol before the quote, like this: .
Passing all output through a program that makes simple changes, such as changing a code name to a public name, or removing objectionable words.
HTTP authentication
A simple (and easy to break) login protection scheme used throughout the Web. The browser asks the user for a name and password, which it sends to the server.
The rules that cover how a browser asks for a resource from a server, and how a server tells the browser that resource is available or not.
HTTP response
The object that represents the information a servlet will send back to a browser, including the HTML that will be shown to the user.
HTTP request
The object that represents the information a browser has sent up to a servlet, including the values of any form fields that were submitted.
A scripting language that resembles Java in syntax, but is not compiled and cannot be used to write applets or servlets.
JDBC-ODBC bridge
A piece of software that allows Java programs, to use JDBC to read from and write to ODBC databases.
jv400 localhost A keyword to use in a browser; it always means the computer on which the browser is running.

Microsoft's Open Database Connectivity software, allowing simple access to a wide variety of databases.
Sending a browser to a Web page other than the one the user requested.
Restrictions on the actions a servlet or applet can take, in order to prevent security violations. For example, most applets and some servlets cannot access the local file system.
Security manager
An object provided by a Web server or browser that authorizes a servlet or applet, respectively, to perform a specific task such as reading a file.
Simple Mail Transfer Protocol, the rules for sending a mail message through an SMTP server.
SMTP Server
A program that accepts mail messages and holds them for a user.
Server Side Includes, a technique for including a file of HTML or the output of a server-side program within another file of HTML.
The opposite of stateless; describes a program that keeps track of things between separate requests from a user and can tell when two requests are from the same user.
Describes a program that treats all requests as being from complete strangers and does not keep track of any information about its users.
SQL Statement
A command, written in SQL, to retrieve or update values in a database. Some SQL statements can add or remove records from a table.
Structured Query Language; a way to make a specific request of a database.
A path of execution through a program. It's possible for two or more threads to run within a program, so that some processing can continue even while a time-consuming calculation is going on.
A method throws an exception to signal to the code that called it that something unexpected has gone wrong - for example an overflow error or a lack of memory. The throws list of a method is a list of all the exceptions it might throw.
A Universal Resource Locator, such as those typed into the address bar of a browser. Example: http://www.yahoo.com.
A scripting language that resembles Visual Basic in syntax, but is not compiled and cannot be used to write applications.
Web server
A program that accepts requests for resources such as HTML files or images, and returns them to browsers. Most Web servers can also launch programs on the server and return their output to the browser.
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