javax.servlet

Class GenericServlet

public abstract class GenericServlet extends Object implements Servlet, ServletConfig, Serializable

Defines a generic, protocol-independent servlet. To write an HTTP servlet for use on the Web, extend HttpServlet instead.

GenericServlet implements the Servlet and ServletConfig interfaces. GenericServlet may be directly extended by a servlet, although it's more common to extend a protocol-specific subclass such as HttpServlet.

GenericServlet makes writing servlets easier. It provides simple versions of the lifecycle methods init and destroy and of the methods in the ServletConfig interface. GenericServlet also implements the log method, declared in the ServletContext interface.

To write a generic servlet, you need only override the abstract service method.

Version: $Version$

Author: Various

Constructor Summary
	GenericServlet() Does nothing.

Method Summary
void	destroy() Called by the servlet container to indicate to a servlet that the servlet is being taken out of service.
String	getInitParameter(String name) Returns a `String` containing the value of the named initialization parameter, or `null` if the parameter does not exist.
Enumeration	getInitParameterNames() Returns the names of the servlet's initialization parameters as an `Enumeration` of `String` objects, or an empty `Enumeration` if the servlet has no initialization parameters.
ServletConfig	getServletConfig() Returns this servlet's ServletConfig object.
ServletContext	getServletContext() Returns a reference to the ServletContext in which this servlet is running.
String	getServletInfo() Returns information about the servlet, such as author, version, and copyright.
String	getServletName() Returns the name of this servlet instance.
void	init(ServletConfig config) Called by the servlet container to indicate to a servlet that the servlet is being placed into service.
void	init() A convenience method which can be overridden so that there's no need to call `super.init(config)`.
void	log(String msg) Writes the specified message to a servlet log file, prepended by the servlet's name.
void	log(String message, Throwable t) Writes an explanatory message and a stack trace for a given `Throwable` exception to the servlet log file, prepended by the servlet's name.
abstract void	service(ServletRequest req, ServletResponse res) Called by the servlet container to allow the servlet to respond to a request.

Constructor Detail

GenericServlet

public GenericServlet()

Does nothing. All of the servlet initialization is done by one of the init methods.

Method Detail

destroy

public void destroy()

Called by the servlet container to indicate to a servlet that the servlet is being taken out of service. See Servlet.

getInitParameter

public String getInitParameter(String name)

Returns a String containing the value of the named initialization parameter, or null if the parameter does not exist. See ServletConfig.

This method is supplied for convenience. It gets the value of the named parameter from the servlet's ServletConfig object.

Parameters: name a String specifying the name of the initialization parameter

Returns: String a String containing the value of the initialization parameter

getInitParameterNames

public Enumeration getInitParameterNames()

Returns the names of the servlet's initialization parameters as an Enumeration of String objects, or an empty Enumeration if the servlet has no initialization parameters. See ServletConfig.

This method is supplied for convenience. It gets the parameter names from the servlet's ServletConfig object.

Returns: Enumeration an enumeration of String objects containing the names of the servlet's initialization parameters

getServletConfig

public ServletConfig getServletConfig()

Returns this servlet's ServletConfig object.

Returns: ServletConfig the ServletConfig object that initialized this servlet

getServletContext

public ServletContext getServletContext()

Returns a reference to the ServletContext in which this servlet is running. See ServletConfig.

This method is supplied for convenience. It gets the context from the servlet's ServletConfig object.

Returns: ServletContext the ServletContext object passed to this servlet by the init method

getServletInfo

public String getServletInfo()

Returns information about the servlet, such as author, version, and copyright. By default, this method returns an empty string. Override this method to have it return a meaningful value. See Servlet.

Returns: String information about this servlet, by default an empty string

getServletName

public String getServletName()

Returns the name of this servlet instance. See ServletConfig.

Returns: the name of this servlet instance

init

public void init(ServletConfig config)

Called by the servlet container to indicate to a servlet that the servlet is being placed into service. See Servlet.

This implementation stores the ServletConfig object it receives from the servlet container for later use. When overriding this form of the method, call super.init(config).

Parameters: config the ServletConfig object that contains configutation information for this servlet

Throws: ServletException if an exception occurs that interrupts the servlet's normal operation

init

public void init()

A convenience method which can be overridden so that there's no need to call super.init(config).

Instead of overriding init, simply override this method and it will be called by GenericServlet.init(ServletConfig config). The ServletConfig object can still be retrieved via GenericServlet.

Throws: ServletException if an exception occurs that interrupts the servlet's normal operation

log

public void log(String msg)

Writes the specified message to a servlet log file, prepended by the servlet's name. See log.

Parameters: msg a String specifying the message to be written to the log file

log

public void log(String message, Throwable t)

Writes an explanatory message and a stack trace for a given Throwable exception to the servlet log file, prepended by the servlet's name. See ServletContext.

Parameters: message a String that describes the error or exception t the java.lang.Throwable error or exception

service

public abstract void service(ServletRequest req, ServletResponse res)

Called by the servlet container to allow the servlet to respond to a request. See Servlet.

This method is declared abstract so subclasses, such as HttpServlet, must override it.

Parameters: req the ServletRequest object that contains the client's request res the ServletResponse object that will contain the servlet's response

Throws: ServletException if an exception occurs that interferes with the servlet's normal operation occurred IOException if an input or output exception occurs