+ * A servlet is a small Java program that runs within a Web server. Servlets + * receive and respond to requests from Web clients, usually across HTTP, the + * HyperText Transfer Protocol. + * + *
+ * To implement this interface, you can write a generic servlet that extends
+ * javax.servlet.GenericServlet or an HTTP servlet that extends
+ * javax.servlet.http.HttpServlet.
+ *
+ *
+ * This interface defines methods to initialize a servlet, to service requests, + * and to remove a servlet from the server. These are known as life-cycle + * methods and are called in the following sequence: + *
init
+ * method.
+ * service method are handled.
+ * destroy method, then garbage collected and finalized.
+ *
+ * In addition to the life-cycle methods, this interface provides the
+ * getServletConfig method, which the servlet can use to get any
+ * startup information, and the getServletInfo method, which allows
+ * the servlet to return basic information about itself, such as author,
+ * version, and copyright.
+ *
+ * @see GenericServlet
+ * @see javax.servlet.http.HttpServlet
+ */
+public interface Servlet {
+
+ /**
+ * Called by the servlet container to indicate to a servlet that the servlet
+ * is being placed into service.
+ *
+ *
+ * The servlet container calls the init method exactly once
+ * after instantiating the servlet. The init method must
+ * complete successfully before the servlet can receive any requests.
+ *
+ *
+ * The servlet container cannot place the servlet into service if the
+ * init method
+ *
ServletException
+ * ServletConfig object containing the servlet's
+ * configuration and initialization parameters
+ *
+ * @exception ServletException
+ * if an exception has occurred that interferes with the
+ * servlet's normal operation
+ *
+ * @see UnavailableException
+ * @see #getServletConfig
+ */
+ public void init(ServletConfig config) throws ServletException;
+
+ /**
+ *
+ * Returns a {@link ServletConfig} object, which contains initialization and
+ * startup parameters for this servlet. The ServletConfig
+ * object returned is the one passed to the init method.
+ *
+ *
+ * Implementations of this interface are responsible for storing the
+ * ServletConfig object so that this method can return it. The
+ * {@link GenericServlet} class, which implements this interface, already
+ * does this.
+ *
+ * @return the ServletConfig object that initializes this
+ * servlet
+ *
+ * @see #init
+ */
+ public ServletConfig getServletConfig();
+
+ /**
+ * Called by the servlet container to allow the servlet to respond to a
+ * request.
+ *
+ *
+ * This method is only called after the servlet's init() method
+ * has completed successfully.
+ *
+ *
+ * The status code of the response always should be set for a servlet that + * throws or sends an error. + * + * + *
+ * Servlets typically run inside multithreaded servlet containers that can
+ * handle multiple requests concurrently. Developers must be aware to
+ * synchronize access to any shared resources such as files, network
+ * connections, and as well as the servlet's class and instance variables.
+ * More information on multithreaded programming in Java is available in
+ * the Java tutorial on multi-threaded programming.
+ *
+ *
+ * @param req
+ * the ServletRequest object that contains the
+ * client's request
+ *
+ * @param res
+ * the ServletResponse object that contains the
+ * servlet's response
+ *
+ * @exception ServletException
+ * if an exception occurs that interferes with the servlet's
+ * normal operation
+ *
+ * @exception IOException
+ * if an input or output exception occurs
+ */
+ public void service(ServletRequest req, ServletResponse res)
+ throws ServletException, IOException;
+
+ /**
+ * Returns information about the servlet, such as author, version, and
+ * copyright.
+ *
+ *
+ * The string that this method returns should be plain text and not markup
+ * of any kind (such as HTML, XML, etc.).
+ *
+ * @return a String containing servlet information
+ */
+ public String getServletInfo();
+
+ /**
+ * Called by the servlet container to indicate to a servlet that the servlet
+ * is being taken out of service. This method is only called once all
+ * threads within the servlet's service method have exited or
+ * after a timeout period has passed. After the servlet container calls this
+ * method, it will not call the service method again on this
+ * servlet.
+ *
+ *
+ * This method gives the servlet an opportunity to clean up any resources + * that are being held (for example, memory, file handles, threads) and make + * sure that any persistent state is synchronized with the servlet's current + * state in memory. + */ + public void destroy(); +}