What is inter-servlet communication?

As the name says it, it is communication between servlets. Servlets talking to each other. There are many ways to communicate between servlets, including :       * Request Dispatching     * HTTP Redirect     * Servlet Chaining     * HTTP request (using sockets or the URLConnection class)     * Shared session, request, or application [...]

What is a WAR file and how do I create one?

WAR (or “web archive”) file is simply a packaged webapp directory. It is created using the standard Java jar tool.   For example: jar cf ../mywebapp.war *   How can I call a servlet from a JSP page? How can I pass variables from the JSP that the servlet can access? You can use <jsp:forward [...]

What is a web application (or “webapp”)?

A web application is a collection of servlets, html pages, classes, and other resources that can be bundled and run on multiple containers from multiple vendors. A web application is rooted at a specific path within a web server.   The contents of the WEB-INF directory are: /WEB-INF/web.xml deployment descriptor /WEB-INF/classes/* directory for servlet and [...]

What is a servlet bean?

A servlet bean is a serializable servlet that follows the JavaBeans component architecture, basically offering getter/setter methods.

How do I deal with multi-valued parameters in a servlet?

Instead of using getParameter() with the ServletRequest, as you would with single-valued parameters, use the getParameterValues() method. This returns a String array (or null) containing all the values of the parameter requested.

What is the difference between GenericServlet and HttpServlet?

GenericServlet is for servlets that might not use HTTP, like for instance FTP servlets. Of course, it turns out that there’s no such thing as FTP servlets, but they were trying to plan for future growth when they designed the spec. Maybe some day there will be another subclass, but for now always use HttpServlet. [...]

What is a servlet engine?

A “servlet engine” is a program that plugs in to a web server and runs servlets. The term is obsolete; the preferred term now is “servlet container” since that applies both to plug-in engines and to stand-alone web servers that support the Servlet API.

How can I download files from a URL using HTTP?

One way to do this is by using a URLConnection to open a stream to your desired URL, then copy the data out of the stream to a file on your local file system.

Can I invoke a JSP error page from a servlet?

Yes, you can invoke the JSP error page and pass the exception object to it from within a servlet. The trick is to create a request dispatcher for the JSP error page, and pass the exception object as a javax.servlet.jsp.jspException request attribute.   How can I download a file (for instance, a Microsoft Word document) [...]

What’s a better approach for enabling thread-safe servlets and JSPs? SingleThreadModel Interface or Synchronization?

Although the SingleThreadModel technique is easy to use, and works well for low volume sites, it does not scale well. If you anticipate your users to increase in the future, you may be better off implementing synchronization for your variables. The key however, is to effectively minimize the amount of code that is synchronized so [...]